Showing papers in "Agronomy for Sustainable Development in 2008"

Soil-Erosion and Runoff Prevention by Plant Covers: A Review

Abstract: Soil erosion is a critical environmental problem throughout the world’s terrestrial ecosystems. Erosion inflicts multiple, serious damages in managed ecosystems such as crops, pastures, or forests as well as in natural ecosystems. In particular, erosion reduces the water-holding capacity because of rapid water runoff, and reduces soil organic matter. As a result, nutrients and valuable soil biota are transported. At the same time, species diversity of plants, animals, and microbes is significantly reduced. One of the most effective measures for erosion control and regeneration the degraded former soil is the establishment of plant covers. Indeed, achieving future of safe environment depends on conserving soil, water, energy, and biological resources. Soil erosion can be controlled through a process of assessment at regional scales for the development and restoration of the plant cover, and the introduction of conservation measures in the areas at greatest risk. Thus, conservation of these vital resources needs to receive high priority to ensure the effective protection of managed and natural ecosystems. This review article highlights three majors topics: (1) the impact of erosion of soil productivity with particular focus on climate and soil erosion; soil seal and crust development; and C losses from soils; (2) land use and soil erosion with particular focus on soil loss in agricultural lands; shrub and forest lands; and the impact of erosion in the Mediterranean terraced lands; and (3) the impact of plant covers on soil erosion with particular focus on Mediterranean factors affecting vegetation; plant roots and erosion control; and plant cover and biodiversity.

Role of Nutrients in Controlling Plant Diseases in Sustainable Agriculture: A Review

Abstract: In recent years the importance of sustainable agriculture has risen to become one of the most important issues in agriculture. In addition, plant diseases continue to play a major limiting role in agricultural production. The control of plant diseases using classical pesticides raises serious concerns about food safety, environmental quality and pesticide resistance, which have dictated the need for alternative pest management techniques. In particular, nutrients could affect the disease tolerance or resistance of plants to pathogens. However, there are contradictory reports about the effect of nutrients on plant diseases and many factors that influence this response are not well understood. This review article summarizes the most recent information regarding the effect of nutrients, such as N, K, P, Mn, Zn, B, Cl and Si, on disease resistance and tolerance and their use in sustainable agriculture. There is a difference in the response of obligate parasites to N supply, as when there is a high N level there is an increase in severity of the infection. In contrast, in facultative parasites at high N supply there is a decrease in the severity of the infection. K decreases the susceptibility of host plants up to the optimal level for growth and beyond this point there is no further increase in resistance. In contrast to K, the role of P in resistance is variable and seemingly inconsistent. Among the micronutrients, Mn can control a number of diseases as Mn has an important role in lignin biosynthesis, phenol biosynthesis, photosynthesis and several other functions. Zn was found to have a number of different effects as in some cases it decreased, in others increased, and in others had no effect on plant susceptibility to disease. B was found to reduce the severity of many diseases because of the function that B has on cell wall structure, plant membranes and plant metabolism. Cl application can enhance host plants’ resistance to disease. Si has been shown to control a number of diseases and it is believed that Si creates a physical barrier which can restrict fungal hyphae penetration, or it may induce accumulation of antifungal compounds. Integrative plant nutrition is an essential component in sustainable agriculture, because in most cases it is more cost-effective and also environmentally friendly to control plant disease with the adequate amount of nutrients and with no pesticides. Nutrients can reduce disease to an acceptable level, or at least to a level at which further control by other cultural practices or conventional organic biocides are more successful and less expensive.

Soils and sustainable agriculture. A review.

Abstract: Enhancing food production and supporting civil/engineering structures have been the principal foci of soil science research during most of the 19th and the first seven or eight decades of the 20th century. Demands on soil resources during the 21st century and beyond include: (i) increasing agronomic production to meet the food needs of additional 3.5 billion people that will reside in developing countries along with likely shift in food habits from plant-based to animal-based diet, (ii) producing ligno-cellulosic biomass through establishment of energy plantations on agriculturally surplus/marginal soils or other specifically identified lands, (iii) converting degraded/desertified soils to restorative land use for enhancing biodiversity and improving the environment, (iv) sequestering carbon in terrestrial (soil and trees) and aquatic ecosystems to off-set industrial emissions and stabilize the atmospheric abundance of CO2 and other greenhouse gases, (v) developing farming/cropping systems which improve water use efficiency and minimize risks of water pollution, contamination and eutrophication, and (vi) creating reserves for species preservation, recreation and enhancing aesthetic value of soil resources. Realization of these multifarious soil functions necessitate establishment of inter-disciplinary approach with close linkages between soil scientists and chemists, physicists, geologists, hydrologists, climatologists, biologists, system engineers (nano technologists), computer scientists and information technologists, economists, social scientists and molecular geneticists dealing with human, animal and microbial processes. While advancing the study of basic principles and processes, soil scientists must also reach out to other disciplines to address the global issues of the 21st century and beyond.

Agri-environmental indicators to assess cropping and farming systems. A review

Abstract: Environmental impacts of agriculture cannot be always assessed by using direct measurements. Since the 1990s, numerous agri-environmental indicators were developed to assess the adverse effects of cropping and farming systems in the environment, such as water pollution, soil erosion, and emission of greenhouse gases. Here we present the different types of indicators developed during the last decade and review the progress of the methods used for their development. The application of different groups of indicators is discussed and illustrated by examples in the fields of nitrogen losses and pesticide risk: (1) indicators based on a single or a combination of variables related to farmer practices, (2) indicators derived from operational or more complex simulation models assessing emissions of pollutants, and (3) measured indicators linked directly to environmental impacts. The nitrogen indicator (IN) of the INDIGO method and the MERLIN indicator will be presented and used to illustrate the methodological discussion. We show that a good identification of the end-users, of the practical objectives of the indicator, and of the spatial and temporal scales is essential and should be done at a preliminary step before designing the indicator itself. The possibilities of deriving an indicator from a model and of setting a reference value are discussed. Several methods are also presented to study the sensitivity and the validity of agri-environmental indicators. Finally, several practical recommendations are made. As only few data are usually available at the regional level, several simple indicators should be used for assessing a given impact at this level. When more detailed information is available, indicators based on operational models can be useful to analyse the effects of several factors related to soil, climate, and cropping system on an environmental impact. In experimental studies, we suggest using both measured indicators and model-based indicators.

MOTIFS: a monitoring tool for integrated farm sustainability

Abstract: Indicator-based monitoring tools are frequently applied for sustainability assessments, also in agriculture. However, many indicators focus on a rather restricted number of sustainability aspects such as economy or ecology. Moreover the choice of the indicator is rarely explained. The aim of our study was to develop an indicator-based monitoring tool for integrated farm sustainability - i.e. taking into account economic and ecological and social aspects - based on a supported vision of sustainable agriculture and using a set of relevant indicators. Hereby, specific attention was paid to aspects of communication and user-friendliness. Four methodological steps were considered: (i) translating the major principles of a supported vision of sustainable Flemish agriculture into concrete and relevant themes; (ii) designing indicators to monitor progress towards sustainability for each of those themes; (iii) aggregating the indicators into an integrated farm sustainability monitoring tool and (iv) applying the monitoring tool on a practical farm, as a first attempt at end-use validation. Stakeholder participation and expert consulting played an important part in each of these methodological steps. As a case study, the methodology was applied to Flemish dairy farms. As a result, we developed MOTIFS, a user-friendly and strongly communicative indicator-based monitoring tool that allows the measurement of progress towards integrated sustainable dairy farming systems and fits within a well-founded methodological framework. MOTIFS is based on the equality of the economic, ecological and social sustainability dimensions, and this equality is inherently built into the system. Through the applied methodology, we founded the selected themes and indicators and we avoided using indicators that are not relevant to the problem at hand.

Ex ante Assessment of the Sustainability of Alternative Cropping Systems: Implications for Using Multi-criteria Decision-Aid Methods - A Review

Abstract: Sustainability is a holistic and complex multi-dimensional concept encompassing economic, social and environmental issues, and its assessment is a key step in the implementation of sustainable agricultural systems. Realistic assessments of sustainability require: (1) the integration of diverse information concerning economic, social and environmental objectives; and (2) the handling of conflicting aspects of these objectives as a function of the views and opinions of the individuals involved in the assessment process. The assessment of sustainability is therefore increasingly regarded as a typical decision-making problem that could be handled by multi-criteria decision-aid (MCDA) methods. However, the number and variability of MCDA methods are continually increasing, and these methods are not all equally relevant for sustainability assessment. The demands for such approaches are also rapidly changing, and faster ex ante assessment approaches are required, to address scales currently insufficiently dealt with, such as cropping system level. Researchers regularly carry out comparative analyses of MCDA methods and propose guidelines for the selection of a priori relevant methods for the assessment problem considered. However, many of the selection criteria used are based on technical/operational assumptions that have little to do with the specificities of ex ante sustainability assessment of alternative cropping systems. We attempt here to provide a reasoned comparative review of the main groups of MCDA methods, based on considerations related to those specificities. The following main guidelines emerge from our discussion of these methods: (1) decision rule-based and outranking qualitative MCDA methods should be preferred; (2) different MCDA tools should be used simultaneously, making it possible to evaluate and compare the results obtained; and (3) a relevantly structured group of decision-makers should be established for the selection of tool variants of the choosen MCDA methods, the design/choice of sustainability criteria, and the analysis and interpretation of the evaluation results.

Saffron, An Alternative Crop for Sustainable Agricultural Systems: A Review

Abstract: Saffron (Crocus sativus L.) is an autumnal flowering geophite whose dried stigmas, well known for their aromatic and colouring power, have been used since immemorial time as a spice in human nutrition, for medicinal purposes and as a dye. Many doubts remain on its origin; it was probably selected and domesticated in Crete during the Late Bronze Age. Saffron is an autotriploid geophyte species, self- and out-sterile and mostly male-sterile and therefore unable to produce seed, that reproduces by means of corms. Furthermore, it has a reverse biological cycle compared with the majority of cultivated and spontaneous plants: flowering first in October–November, then vegetative development until May, which means that the vegetative development is not directly important for production of stigmas, but for the production of new corms. Due to its unique biological, physiological and agronomic traits, saffron is able to exploit marginal land and to be included in low-input cropping systems, representing an alternative viable crop for sustainable agriculture. Notwithstanding this great potential and the considerable increase in new generation consumer demand for saffron, the future of the plant is still uncertain. Indeed, the main obstacles to saffron production are: (1) the limited areas of cultivation in countries where it is traditionally grown, (2) the great amount of sophisticated spice, (3) management techniques executed by hand, and (4) the very high price of the spice. Here we review the main biological, genetic and ecological traits associated with agronomic management techniques of saffron in relation to environmental conditions. Colour, taste and aroma are the essential features on which the quality of saffron stigmas is founded. In turn, these aspects are strictly connected with the biomolecular composition of the stigmas, namely, the carotenoids and their derivatives. With this in mind, the biosynthetic pathway that leads to the formation of saffron secondary metabolites and their abundance in the spice is presented, together with the biomedical properties commonly associated with saffron. Furthermore, a detailed overview of the more recent instrumental methods to assess the quality of saffron, strictly from a chemical point of view, will be discussed.

Yield potential and land-use efficiency of wheat and faba bean mixed intercropping

Abstract: In Ethiopia, food production for a rapidly growing population from a continually shrinking farm size is a prime developmental challenge. Rising input costs, decline in soil quality, and buildup of insect pests, diseases and weeds have threatened the ecological and economic sustainability of crop production. To address those issues, intercropping of cereals with pulse crops could increase total grain production, provide diversity of products, stabilize yield over seasons, reduce economic and environmental risks common in monoculture systems, and thereby enhance sustainability. Here, mixed intercropping of wheat (Triticum aestivum L.) with faba bean (Vicia faba L.) was compared with sole culture of each species in 2002 and 2003 at Holetta Agricultural Research Center, in the central highlands of Ethiopia. The treatments were sole wheat at a seed rate of 175 kg ha −1 , sole faba bean at a seed rate of 200 kg ha −1 , and an additive series of 12.5, 25, 37.5, 50 and 62.5% of the sole faba bean seed rate mixed with the full sole wheat seed rate. Our results showed that mixed intercropping increased the land equivalent ratio by +3% to +22% over sole cropping. Increasing the faba bean seed rate in the mixture from 12.5 to 62.5% reduced wheat grain yield from 3601 kg ha −1 to 3039 kg ha −1 but increased faba bean grain yield from 141 kg ha −1 to 667 kg ha −1 . Sole culture grain yield exceeded mixed culture grain yield by + 5t o+25% for wheat and by +172 to +1190% for faba bean. Nonetheless, we obtained the highest total grain yield of 4031 kg ha −1 , gross monetary value of US$ 823, system productivity index of 4629 and crowding coefficient of 4.70 when wheat at its full seed rate was intercropped with faba bean at a rate of 37.5%. On average, weed biomass was reduced from 40.4 g m −2 in sole wheat to 31.1 g m −2 in mixed culture and the chocolate spot disease score was reduced from 5.1 in sole faba bean to 3.4 in mixed culture. In conclusion, intercropping of wheat with faba bean may increase total yield and revenue, reduce weed and disease pressure, increase land-use efficiency, and thereby enhance sustainability of crop production in Ethiopian highlands. aggressivity / crowding coefficient / faba bean / land-use efficiency / intercropping / wheat

Bacillus thuringiensis: applications in agriculture and insect resistance management. A review

Abstract: Bacillus thuringiensis (Bt) is a sporulating, Gram-positive facultative-aerobic soil bacterium. Its principal characteristic is the synthesis, during sporulation, of a crystalline inclusion containing proteins known as δ-endotoxins or Cry proteins. These proteins have insecticidal properties. The considerable diversity of these toxins, their efficacy and their relatively cheap production have made Bt the most widely used biopesticide in the world. It is used in the fight against many agricultural crop pests – mostly lepidopteran and coleopteran larvae – notably in the creation of new plant varieties expressing Bt cry genes. For human health, Bt can be used for the effective control of populations of several dipteran disease vectors. The aim of this review is to provide an overview of the use of Bt for crop protection and to deal with the problem of the emergence of insects resistant to this biopesticide. We will begin by presenting various aspects of the biology of this entomopathogenic micro-organism, focusing on the diversity and mode of action of the insecticidal toxins it produces. We will then present several examples of utilization of commercially available Bt products used as sprays or as transgenic crops. Finally, we will describe the principal strategy for the use of Bt transgenic plants, developed so as to prevent or delay the emergence of resistance in target insect populations.

Genetically Modified Glyphosate-Tolerant Soybean in the USA: Adoption Factors, Impacts and Prospects - A Review

Abstract: Transgenic crops are the subject of lively debate and controversy. Despite such controversy, transgenic soybean has undergone a rapid expansion. Among various types of transgenic crops, herbicide-tolerant crops appear to many to be of limited interest, especially in Europe. Nonetheless, herbicide-tolerant crops are the most widely spread in the world. Indeed, glyphosate-tolerant soybean was notably the most cultivated transgenic plant in the world in 2006. In the USA 91% of soybean was transgenic in 2007. How can this particularly significant diffusion in the USA be explained, and what are its impacts? Such issues are addressed in this article, using surveys, studies of numerous statistical data and literature analysis. A first section underlines the importance of soybean in the current development of transgenic crops in the world, and the favourable context for their expansion in the USA. Then follows an analysis of the advantages and drawbacks of transgenic soybean for American farmers. Factors explaining the rapid diffusion of transgenic soybean are also analysed. A comparison of transgenic versus conventional soybean reveals that transgenic glyphosate-tolerant soybean allows both the simplification of weed control and greater work flexibility. Cropping transgenic soybean also fits well with conservation tillage. Transgenic soybean has an economic margin similar to conventional soybean, despite a higher seed cost. The next section describes the evolution of the use of herbicides with transgenic soybean, and some issues linked to the rapid increase in the use of glyphosate. At the beginning a smaller amount of herbicides was used, but this amount increased from 2002, though not steadily. Nonetheless, the environmental and toxicological impacts of pesticides do not only depend on the amounts applied. They also depend on the conditions of use and the levels of toxicity and ecotoxicity. The levels of ecotoxicity seem to have somewhat decreased. The success of transgenic soybeans for farmers has led to a higher use of glyphosate as a replacement for other herbicides, which has in turn led to a decline in its effectiveness. However, the issue here is not only genetic engineering in itself, but rather the management and governance of this innovation. Finally, the prospects of transgenic soybean are addressed. Transgenic soybean with new traits should be placed on the market. The conclusion describes economic context of the development of the first transgenic crops.

Sustainable Pest Management for Cotton Production: A Review

Abstract: Cotton cultivation, often highlighted for its excessive consumption of plant protection products, is taken as a model to illustrate the development of the ideas and practices of crop protection over the last 50 years. Cotton is grown in 69 countries on 30–35 million hectares and the production exceeded 20 million tones of lint in recent years. Despite the continual improvement in the performance of chemical control strategies, harvest losses remain very high, of about 30%. The largest consumer of pesticides in the world, the cotton production system has the advantage of having been an experimental model for many crop protection programmes under various agronomic conditions and in the presence of diverse pest complexes. Without attempting an exhaustive bibliography, this review explores how and why the ideas underlying crop protection have significantly evolved since the advent of synthetic pesticides. After a spectacular demonstration of yield growth through the application of chemical control, cotton production was rapidly confronted by the secondary effects of this control. These included the appearance of evolved insecticide resistance and the appearance of new damage caused by pests considered up to then as of only secondary importance. In extreme cases, the economic viability of the production systems themselves have been compromised following increases in the application rate and frequency of insecticidal treatments. In general, harvest losses have remained high despite the constantly improving technical performance of pest control chemicals. Two models of the future of crop protection can be drawn: total pest management which involves the eradication of pests, and integrated pest management (IPM), which aims at the management of pest populations below economic thresholds by a mixture of chemical control and a suite of alternative control measures. The first method, total pest management is limited in agricultural systems to particular cases in which the pest in question has no significant alternate hosts in the vicinity of the crop system. On the other hand, the application of IPM is constrained both by the difficulties in exploiting the concept of an ‘intervention threshold’ and by the limitations of many of the specific non-chemical techniques proposed, but does have the advantage of taking into consideration the full pest complex in a cropping system. In practice, it has been a calendar schedule, largely of insecticidal treatments, established on the basis of earlier local observations which has been most widely adopted by growers. This strategy has produced significant improvements in production in the cotton producing countries of francophone Africa and elsewhere. This has led to area-wide integrated pest management which takes into account the potential for natural factors to regulate populations in a specific region. In cotton production, biological control by introduction and acclimation of beneficial arthropods has not been notably successful because of the difficulty of developing a suite of beneficial organisms capable of responding effectively to the diversity of pests in the system, the annual nature of the crop, and the disrupting effects of chemical control measures directed against the remaining pests. Only inundative biological control has had significant success and then in particular cases where the pressure of chemical insecticides has been reduced. More benefit is to be obtained from the active conservation of the indigenous fauna of beneficial organisms. In spite of an increased general environmental awareness, in practice it has been the growth of evolved resistance to pesticides which has had the dominant role in constraining the growers to a more rational use of control strategies. These can be illustrated by the development of window strategies for control measures across the growing season, initially in Australia. The reduction in chemical control treatments made possible by the efficacy of genetically modified cotton has shown the positive role that indigenous natural enemies can play. At the same time, however, there has been a growth in the importance of pest species which are unaffected by Bt toxins. For example, the sucking pests are progressively coming to displace the vegetative and fruit feeding caterpillars as key pests of Bt cotton. Taking into account the spatio-temporal dimension of natural population regulatory factors has led to changes in agricultural practices and production systems. In cotton, for example, production systems maintaining permanent ground cover, are having increasing success. Intercropping and trap cropping have been favourable to the maintenance of beneficial arthropod complexes and unfavourable to the growth of pest populations. This new design context for crop protection in general and for cotton in particular, in applying the principles of agroecology, moves towards the concept of a truly sustainable agriculture. This implies a change of strategy towards a total systems approach to sustainable pest management, characterised by a movement from a paradigm of pest control field-by-field, through farm-by-farm and agroecosystem-by-agroecosystem, to a landscape by landscape approach.

Effect of cadmium on photosynthesis, nutrition and growth of mungbean

Abstract: Contamination of soils with cadmium is a major threat to ecosystems. Root uptake of cadmium from contaminated soils induces physiological changes such as a decrease in plant growth. Plant species and varieties show differential physiological mechanisms of cadmium tolerance. Here, we studied the effect of cadmium chloride on leaf chlorosis, gas exchange attributes and some essential nutrients in the shoots of selected tolerant and sensitive mungbean (Vigna radiata) varieties at the seedling, vegetative and reproductive growth stages. Our results show that elevated concentrations of cadmium led to accumulation of cadmium in the shoot and roots, intervein chlorosis of leaves and loss of pigments. Tolerant mungbean showed steady-state contents of potassium, magnesium, manganese and iron, and photosynthetic pigments at all growth stages. A decrease in the net photosynthesis, increase in substomatal CO2 level and a decline in the ratio of net photosynthesis and substomatal CO2 level revealed that cadmium prevented CO2 fixation by Rubisco. Correlations of shoot cadmium concentration and chlorosis with its nutrient and pigment content, although negative in both varieties, were closer in the tolerant but absent, or weaker if present, in the sensitive mungbean. Most nutrients had close association with the content of photosynthetic pigments of tolerant mungbean, which indicated their involvement in maintaining steady levels of pigments. This finding indicates the involvement of nutrients and pigments in cadmium tolerance. In conclusion, cadmium tolerance in mungbean was attributed to low cadmium uptake and its accumulation in the shoot, leaf chlorosis, improved pigment, nutrient levels and carboxylation efficiency of Rubisco throughout the mungbean phenology. Based on these findings the tolerant mungbean can be grown in moderately cadmium-contaminated soils.

Alternative weed control using the allelopathic effect of natural benzoxazinoids from rye mulch

Abstract: In conventional agriculture, weed control by herbicides is an expensive practice and can also have a negative effect on the environment. Allelopathy permits sustainable weed management while reducing the impact of agriculture on the environment. We studied the content of 2,4-dihydroxy-1,4 (2H)-benzoxazin-3-one (DIBOA) and benzoxazolin-2(3H)-one (BOA), indicated as benzoxazinoids and considered effective for weed control, in 8 cultivars of rye and 1 of triticale grown in a greenhouse. We also tested the ability of mulches to inhibit the germination of four warm-season weeds. Our results show that all rye cultivars produced DIBOA, while BOA was found only in four of them. Benzoxazinoids were absent in triticale. Total benzoxazinoid content ranged from 177 to 545 μg g−1 and was statistically different among cultivars. Rye mulches were not able to suppress velvetleaf and common lambsquarters seedlings, while redroot pigweed and common purslane were significantly affected. Weed suppression ranged from 40% to 52% for redroot pigweed and from 40% to 74% for common purslane. The inhibitory activity of triticale mulch was observed only for common purslane, with a suppression percentage of 33%. No correlation was found between total benzoxazinoid content and the number of weed seedlings suppressed, with R2 of 0.076 for redroot pigweed and R2 of 0.003 for common purslane, indicating that benzoxazinoids are not the only source of phytotoxicity.

Potential of Miscanthus grasses to provide energy and hence reduce greenhouse gas emissions.

Abstract: Using bio-fuels, such as bio-ethanol or bio-diesel in transportation, or biomass in power generation reduces CO2 emissions as the carbon is fixed by the plants from the atmosphere and saves the equivalent fossil fuel. The perennial rhizomatous C4 grass Miscanthus has one of the highest energy intensities per hectare of land in Europe. Here we model the future potential of Europe to produce Miscanthus with four different future land use and climate change scenarios and conclude that up to 17% of Europe’s current primary energy consumption could be provided by this bio-energy crop by the year 2080 but that inter-annual variation of crop yield can be more than 20%. We conclude that that the highest greenhouse gas mitigation from bio-energy can be achieved by growing a Miscanthus crop on existing fertile and degraded arable land and not on land with a currently undisturbed ecosystem.

Effect of catch crops on N dynamics and following crops in organic farming

Abstract: Green manure catch crops promote the sustainability of agricultural systems by reducing soil erodibility and by nutrient uptake and transfer to the following main crops. This effect efficiently reduces the risk of nitrate leaching. Biological nitrogen fixation by legume catch crops is an additional benefit, mainly in organic farming. Such crops may, however, reduce nitrogen uptake from the soil and increase nitrate leaching. Additionally, under drought conditions, their extra water consumption may outweigh the beneficial effects. To determine the best catch crop management in stockless organic farming under dry, Pannonian site conditions in eastern Austria, four treatments were compared in 2002 and 2004: (1) legumes: field pea, common vetch and chickling vetch, (2) non-legumes: phacelia, oil radish and turnip, (3) a legume and non-legume mixture (all mentioned components), and (4) a bare fallow control. Our results show that catch crop biomass and N yield, biological N fixation, and crop N uptake from the soil were about 4 times higher under moderately dry conditions in 2002 than under drought conditions in summer and autumn 2004. In 2002, the legume/non-legume mixture had the highest biomass and N yield and the highest biological N fixation. Both the legume/non-legume mixture and the non-legumes were more efficient than legumes in N uptake from the soil (+32 kg N ha−1); and in reducing both soil inorganic N contents by −45 kg N ha−1 and nitrate concentrations in soil solution by −20 mg N L−. These findings show that the legume/non-legume mixture combined the positive effects of non-legumes and legumes. In 2004, catch crop effects did not differ except for their above-mentioned effect on inorganic N contents. The only pre-crop effect was that of legumes compared with non-legumes on spring barley grain dry matter of +0.6 Mg DM ha−1 and grain N yield of +17 kg N ha−1 in 2005. The water consumption of catch crops never adversely affected the following crops.

Sorption and leaching of 14 C-glyphosate in agricultural soils

Abstract: Glyphosate (N-(phosphonomethyl)glycine) is one of the most widely used herbicides in the world to control weeds in agricultural and urban areas. Its increasing use requires special attention to its transfer from terrestrial to aquatic environments. However, knowledge on the leaching of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) is scarce. Here we aimed to assess the dynamic interactions between glyphosate sorption and leaching; and to identify the main factors that influence the two processes in three undisturbed agricultural soils using microlysimeters under outdoor conditions. We studied the sorption, desorption and leaching of 14C-labelled glyphosate on three soils using batch experiments in the laboratory and lysimeters under natural conditions for 11 months. The laboratory results showed that glyphosate was strongly adsorbed, yielding empirical constants of Freundlich sorption isotherms (Kf) of 16.6 for the clay loam soil, 33.6 for the silt clay loam soil and 34.5 for the sandy loam soil, with nf close to 1 in all three cases. Glyphosate was also weakly desorbed, i.e. 5 to 24% (w) of initially sorbed glyphosate. Sorption and desorption were only pH-dependent. The outdoor results showed that nearly 70% of the initial glyphosate was present in the soil in a non-extractable form at the beginning of the experiment. Conversely, only less than 20% of the initial glyphosate is present in the soil in a non-extractable form after 11 months. These findings suggest that the non-extractable residues become available and take part in biodegradation and leaching. The amounts of 14C-glyphosate derivatives leached were less than 0.28% of the initially applied glyphosate. HPLC analyses showed that the AMPA metabolite generally represented up to 100% of the residues present in the leachates. The results of leaching were highly influenced by the hydrodynamic properties and the biodegradation capacities of the soils. Although glyphosate residues were found in low concentrations in the leachates for almost a year, the contamination of groundwater does not seem to be a concern, regardless of the soil type, if the herbicide is used in accordance with good agricultural practice.

Methodological progress in on-farm regional agronomic diagnosis. A review

Abstract: The development of sustainable cropping systems is a key priority for agronomists and crop scientists. A first step involves understanding the relationship between cropping system performance and farmers’ practices. To complete this step, a methodological framework entitled Regional Agronomic Diagnosis (RAD) has been developed. During the last ten years, the scope of the regional agronomic diagnosis has been enlarged to include several factors describing crop quality and the environmental impact of cropping systems. Regional agronomic diagnosis has led to several major advances such as (1) the assessment of the effect of preceding crop and soil structure on malting barley quality in France and (2) the assessment of the effects of ploughing, nematicide use and fertilisers on soil properties in intensive banana plantations in the West Indies. Improvements have also been gained in methodology, particularly by the selection of indicators for assessing the effects of crop management, soil and weather conditions, and data analysis. Finally, regional agronomic diagnosis has been integrated into more general approaches of agricultural development. We review here this methodological progress.

A study of 15 N transfer between legumes and grasses

Abstract: The overuse of classical N fertilisers contributes substantially to environmental degradation by pollution of groundwater by nitrates. This leaching of N in waters is also an economic flaw for farmers because only a part of the fertiliser is used by the plants. Here, systems involving mixtures of legumes and grasses represent a sustainable alternative because legumes can fix atmospheric N2 using symbiotic microbes. N transfer in those mixtures has been thoroughly investigated but little is known concerning the effect of N fertiliser on N transfer between N-fixing legumes and companion grasses. In white clover (Trifolium repens L.) — perennial ryegrass (Lolium perenne L.) associations, N is transferred mostly through rhizodeposition into the soil by clover followed by re-uptake by ryegrass. Rhizodeposition of N occurs through senescence and decomposition of legume tissue or through exudation of N compounds by living cells. Ammonium and amino acids are the main compounds exuded and their exudation is thought to occur by passive diffusion attributed to a concentration gradient from root to soil. In this study, we test the hypothesis that greater N transfer from clover to grass, as seen in N-rich soils or nutrient solutions, is due to greater N rhizodeposition brought about by higher ammonium and amino acid content of roots. The relations between N input, root N content, N net exudation and N transfer between legumes and grasses were investigated using 15N by growing white clover and perennial ryegrass with increasing N application in axenic microlysimeters or in pots. Ammonium and amino acid concentrations were measured in root tissues, in root bathing solutions and in soils. We found that mineral N application strongly reduced atmospheric N fixation by clover, from 3.0 to 0.9 mg per plant, and root amino acid content, from 164 to 49 nmoles per g dry weight, but had no effect on ammonium and amino acid concentrations in sterile exudates, showing for the first time that amino acid net exudation is independent of root content. In contrast, ammonium and amino acid concentrations in clover soils increased with N fixation, showing the link between N fixation and N rhizodeposition in soils. Nitrate application increased ryegrass root growth by 7–8 times, and transfer of N between clover and ryegrass (by 3 times). It is concluded that N fertiliser does not modify N exudation but decreases N fixation and ammonium rhizodeposition in soil by clover. N fertiliser increases N transfer between clover and ryegrass by increasing soil exploration by ryegrass and giving a better access to different available N sources, including the N compounds exuded from clover.

Grasslands for Bioenergy Production: A Review

Abstract: The promise of low-input high-diversity prairies to provide sustainable bioenergy production has recently been emphasized. This review article presents a critical discussion of some controversial points of using grasslands to produce bioenergy. The following issues are addressed: proteins vs. biofuels; reactive nitrogen emissions; biodiversity; and effective land use. Two major disadvantages in deriving bioenergy from grasslands are identified: (1) marginal lands are displaced from their fundamental role of producing meat and milk foods, in contrast with the rising worldwide demand for high-quality food; and (2) the combustion of N-rich grassland biomass, or by-products, results in emission of reactive N into the atmosphere and dramatically reduces the residence time of biologically-fixed nitrogen in the ecosystems. Nitrogen oxides, released during atmospheric combustion of fossil fuels and biomass, have a detrimental effect on global warming. Since intensively managed crops on fertile soils need to be cultivated to fulfil the dietary needs of populations, the potential role of inedible cereal crop residues in providing bioenergy merits consideration. This might spare more marginal land area for forage production or even for full natural use, in order to sustain high levels of biodiversity. Owing to the complexity of terrestrial systems, and the complexity of interactions, a modeling effort is needed in order to predict and quantify outcomes of specific combination of land use at higher integration levels.

Impact of zinc-tolerant plant growth-promoting rhizobacteria on lentil grown in zinc-amended soil

Abstract: Though zinc is a plant nutrient at low levels, Zn ions can be highly phytotoxic at higher concentrations found in contaminated soils. Plant growth-promoting rhizobacteria can be used to decrease this toxicity. Indeed, in addition to their role in plant-growth promotion, rhizobacteria also reduce the toxicity of heavy metals. In turn, they can be effective for crops grown in metal-contaminated soils. Here, we isolated a zinc-tolerant plant growth-promoting rhizobacterium, Rhizobium species RL9, from a zinc-contaminated soil and assayed its plant growth-promoting activities in vitro. We found that the rhizobacterium strain RL9 tolerated zinc up to a concentration of 400 μg mL−1 on yeast extract mannitol agar medium. It produced 33 μg mL−1 of indole acetic acid in Luria Bertani broth at 100 μg mL−1 of tryptophan and was positive for siderophore, hydrogen cyanide and ammonia. Such phytohormones released by this strain could help in promoting the growth of legumes. We further tested the effect of rhizobacterium strain RL9 on lentils grown in zinc-amended soil. We found that when the rhizobacterium strain RL9 was added to soil contaminated with Zn at 4890 mg/kg, lentil dry matter increased by 150%, nodule numbers by 15%, nodule dry mass by 27%, leghaemogloblin by 30%, seed yield by 10% and grain protein by 8%, compared with uninoculated plants. We also found that the concentration of zinc was higher in uninoculated plant organs than in the inoculated counterpart. Our findings thus suggest that rhizobacterium strain RL9 could be exploited for bacteria-assisted reduction of zinc toxicity in zinc-contaminated soils due to its intrinsic abilities of expressing growth-promoting substances and reduction of the toxic effects of zinc.

Genotypic variation for drought tolerance in cotton

Abstract: Increasing scarcity of irrigational water is a major threat to sustainable production of cotton (Gossypium hirsutum L.). It could be resolved by developing drought-tolerant cultivars. Osmotic adjustment and cellular membrane stability are well-documented traits that help to sustain yield under drought in cereals. However, their utility in cotton is not well established. Here, we studied genotypic variability and relationships among osmotic adjustment, cell membrane stability and productivity traits under field-induced water stress at the flowering stage. We evaluated a set of cotton germplasm comprising 32 cotton genotypes under contrasting water regimes for measurements of productivity including seedcotton yield, number of bolls per plant and boll weight, and physiological attributes such as osmotic adjustment and cell membrane stability in two field trials. The mean reduction in seedcotton yield due to water deficit was 20 and 43% in 2003 and 2004, respectively. Genotypes differed considerably for relative yield losses due to water stress ranging from 20 to 74%. Significant association between number of bolls and seedcotton yield under a water-limited regime suggests boll retention as the principal determinant of yield in a water-deficit-stress environment. Cell membrane stability varied significantly among the cotton genotypes; however, its association with productivity measurements was not significant in the water-limited regime. The significant positive correlation found between cell membrane stability and osmotic adjustment implicates the role of osmolytes in the protection of various cellular functions, including those associated with cellular membranes. Moderate but significant differences for osmotic adjustment were found among the genotypes in both years. Osmotic adjustment was positively associated with seedcotton yield under the water-limited regime and inversely correlated with the drought susceptibility index. These results demonstrated the contribution of osmotic adjustment in sustaining yield under water-deficit stress in cotton. Thus, like cereals, osmotic adjustment may be useful as a selection criterion in breeding programs with the objective of improving drought tolerance and yield in cotton under water-limited environments; however, the role of cell membrane stability as a drought-tolerant trait requires further investigation.

High decrease in nitrate leaching by lower N input without reducing greenhouse tomato yield

Abstract: Nitrate pollution due to excessive N fertirrigation in greenhouse tomato production is a persisting environmental concern in the Mediterranean region. Driven by productivity rather than sustainability, growers continue to use very high N concentrations of more than 11 mM in greenhouse tomato production. A greenhouse study was conducted in Barcelona, Spain, over two growing seasons to analyze the effect of N concentrations from 5 mM to 11 mM (control) on tomato yield and physical quality. The relative environmental impact was calculated by using the life cycle assessment method (LCA). Our results show that N concentration in the nutrient solution can be reduced from 11 mM (control) to 7 mM under a daily mean drainage volume of 30%. This finding implies a 70% decrease in nitrate leaching without reducing tomato yield or quality. According to life cycle assessment, a reduction of 36% in N fertilizers leads to a 60% decrease in the potential impact of eutrophication, 50% decrease in the potential impact of climate change, and 45% decrease in the potential impact of photochemical oxidants.

Organic and conventional management of mixtures of wheat and spring cereals

Abstract: Cereal mixtures may provide both organic and conventional producers with a more sustainable approach in reducing weed pressure, crop rotation flexibility, improved yield stability, buffering against pests and diseases, minimizing soil variability and increasing animal feed value. We examined the response of small grain mixtures containing wheat, oats, barley and triticale to varying degrees of natural competition and environmental stress at three locations in central Alberta, Canada. One modern and one heritage hard-red spring wheat cultivar, along with one cultivar each of oats, barley and triticale and eighteen two-way mixtures, were planted on organic and conventional land at seven location-years between 2003 and 2005. Average yields were 30% to 70% lower on organically managed sites. Monocrop barley yielded 43% and 16% higher than the site average at two organic locations. Our results suggest two main conclusions: (1) on conventionally managed land, wheat-barley mixtures exhibited potential for yield maintenance and weed suppression, and; (2) on organically managed land, competition with weeds had a large negative effect on yield (>30%). The 25:75 mixtures of wheat and oats, and all mixtures of Park (a heritage) wheat and Manny barley exhibited yield potential similar to or (up to 1.0 t ha−1) greater than monocrop yield. Manny barley mixtures exhibited weed suppressive capabilities.

Impact of organic amendments and compost extracts on tomato production and storability in agroecological systems

Abstract: The sustainability of a farm system greatly relies on fertilizers and other inputs. Soil factors such as texture and local rainfall, along with management-related factors such as soil organic matter, aggregate stability and agronomic practices, have much greater influence on the sustainability of any given farm than do the type or amount of soil amendments. Growers use a wide variety of practices to maintain or improve soil health in organic vegetable production systems. These practices generally are part of long-term, site-specific management programs that aim at developing fertile and biologically active soils that readily capture and store water and nutrients, have good tilth, and suppress plant diseases. Field experiments were conducted in 2005 and 2006 in Mashhad, Iran, to study the effects of organic amendments, synthetic fertilizers and compost extracts on crop health, productivity and storability of tomato (Lycopersicon esculentum Mill.). Treatments included different fertilizers of cattle, sheep and poultry manures, green-waste and household composts and chemical fertilizers of urea and superphosphate; and five aqueous extracts from cattle manure, poultry manures, green-waste, and household composts plus water as control. Our results show that application of poultry manure showed lower disease incidence, as shown by 80% healthy tomato, compared with the other fertilizers. However, the organic fertilizers used did not give higher yields compared with chemical fertilizers. Sheep manure and chemical fertilizers led to the highest total tomato yield. Marketable yield was highest in poultry manures, of 16 t/ha, and lowest in chemical fertilizer, of 7 t/ha, 6 weeks after storage. The effect of aqueous extracts was not significant on either crop health or tomato yield and the results were inconsistent. The compost made of poultry manure therefore appears to be a promising ecological alternative to classical fertilizers.

Sweet corn production and efficiency of nitrogen use in high cover crop residue

Abstract: In the humid, temperate mid-Atlantic area of the USA, crop production that leaves the soil uncovered can lead to undesirable soil and nutrient losses to the surrounding Chesapeake Bay watershed. To cope with this issue, winter annual cover crops could provide soil cover both during winter months and, as surface residue in no-tillage cropping systems, during summer months. Legume cover crops such as hairy vetch can produce abundant biomass and N by the time summer crops are planted in spring. Although N mineralized from a legume cover crop can contribute to meeting the N requirement of crops such as corn, it also may not be used efficiently by crops and could be lost into the local environment. This research was conducted to determine whether hairy vetch or a hairy vetch-rye mixture that was allowed to produce high levels of biomass with a high N content (200 to 250 kg/ha) could meet the N requirements of no-tillage sweet corn and to determine the efficiency of N use relative to that of fertilizer N. Our results show that marketable yield of sweet corn was approximately doubled by hairy vetch in 2 of 3 years compared to an unfertilized, no-cover crop control. However, in 2 of 3 years, hairy vetch and the vetch-rye mix reduced yield by 19 and 34%, respectively, compared to a no-cover crop control with fertilizer N. Reduced plant population that reduced the number of ears per ha accounted for the yield reduction by these cover crops compared to the fertilized no-cover crop control. Fertilizer N was 1.5 to 2 times more efficient than hairy vetch at producing sweet corn ear mass per unit of N input but combinations of fertilizer N with cover crops were less efficient than either alone. Results suggest that growing sweet corn without tillage in high biomass levels of cover crops can interfere with crop establishment, reduce the efficiency of crop production, and allow for potentially high N losses into the environment.

Transfer of iodine from soil to vegetables by applying exogenous iodine

Abstract: Iodine deficiency disorders are one of the commonest preventable human health problems. Producing iodine-enriched crops could be an effective way to reduce their epidemicity in many regions. However, the actual knowledge on this issue is limited mostly to studies involving grain crops and inorganic iodine fertilizers such as I− and IO 3 − . Moreover, the translocation, transformation and distribution of iodine from soil to plants are not well understood. Here, we studied iodine transfer from soil to vegetables using both inorganic iodine (KI) and organic, seaweed iodine. Greenhouse culture experiments were undertaken to assess the absorption and accumulation of iodine by four vegetables: Chinese cabbage, lettuce, tomato and carrot. We also investigated the dynamic variation of exogenous iodine in soil by applying KI and a composite of seaweed and diatomite. Our results show first that iodine levels in vegetables increase with the increasing addition of iodine. Second, the iodine content in the edible portion ranks as follows: Chinese cabbage (high I) > lettuce > carrot > tomato (low I). The iodine accumulation in the edible portion of the cabbage is thus 2.25 and 4.45 times higher than that of lettuce and carrot, respectively, and 19.67 times higher than that of tomato. In vegetable tissues the iodine distribution is ranked as: root (high I) > leaf > stem > fruit (low I), except for carrot, where the average iodine level in the rhizome is 50% of the shoot. Third, vegetable growth is inhibited when the added iodine concentration is higher than 50 mg kg−1. The order of tolerance against iodine toxicity is ranked as: carrot (high tolerance) > Chinese cabbage > lettuce > tomato (low tolerance). Fourth, the seaweed composite iodine fertilizer demonstrates more potential of durability than KI. Indeed, when KI is added to the soil at 150 mg kg−, the biomass of cabbage, lettuce, tomato and carrot decreases by 34.8%, 41.3%, 46.8% and 17.9%, respectively. By comparison, the biomass decreases are lower, 16.6%, 22.9%, 23.4% and 9.7%, respectively, when applying the seaweed composite. Fifth, after harvest, the residual iodine in soil fertilized with KI is only 56% of the initial addition, which is less than that for seaweed composite. This study is of theoretical importance to understand iodine biogeochemistry and its transfer behavior, and also has practical implications for seeking effective alternatives of iodine biofortification to prevent iodine deficiency disorders.

Weed control strategies for grain legumes

Abstract: There has been increasing interest in sustainable weed management in low-input farming systems. In an integrated approach, the development of cropping systems such as appropriate spatial arrangement and efficient tillage will help crops themselves to compete with weeds. With this aim, we investigated the strategic use of plant lodging combined with mechanical weed treatment to improve crop competitiveness and reduce the use of herbicides. We studied weed infestation and grain yield of three grain legumes, field bean, chickpea and field pea, grown according to different plant lodgings (narrow, wide and twin rows) and weed suppression methods: untreated, chemical and mechanical control. In the two years of the trial, two different weed infestation levels were observed due to different meteorological conditions. Our results show that the different crops showed different competitive behaviours, especially in weedy conditions. Indeed, in the bean plots, weed infestation was decreased from 70% in wide rows to 30% in narrow rows. Mechanical treatment produced weed levels similar to those in narrow rows (27%). Mechanical treatment gave grain yields of 2.3 t ha −1 , that are comparable with chemically treated plots (2.7 t ha −1 ). For chickpea, mechanical treatment combined with wide rows proved effective in fighting weeds at a similar level to chemical treatment. Moreover, the yield using mechanical treatment, of 1.6 t ha −1 , was only slightly lower than the yield using chemical treatment (2.3 t ha −1 ). For field peas, mechanical and cropping weed control can limit herbicides, but they are unable to control weed infestation on their own. Vicia faba L. / Cicer arietinum L. / Pisum sativum L. / weed control / plant lodging / integrated weed management

Sustainable production of fennel and dill by intercropping

Abstract: Intercropping is claimed to be one of the most significant cropping techniques in sustainable agriculture, and much research and many reviews attribute to its utilization a number of environmental benefits, from promoting land biodiversity to diversifying agricultural outcome. In this sense, intercropping is thought to be a useful means of minimizing the risks of agricultural production in many environments, including those typical of under-developed or marginal areas. In order to validate this hypothesis in a representative area of the semiarid Mediterranean environment, we evaluated the possibility of growing dill and fennel, both belonging to the family Apiaceae, in temporary intercropping. Our trial was performed in Sicily in 2000–01 and 2001–02; in the first year, fennel and dill were cultivated in a mixture using a substitution scheme, whereas in 2001–02 we evaluated the bio-agronomical and chemical features of fennel alone. The biological efficiency of the intercropping system was evaluated by using the Land Equivalent Ratio and the Competitive Ratio, and an estimate of the interaction effects of both crops was performed by analyzing the major vegetative and yield traits of plants, along with the chemical profile of volatiles of the fruits. Both in grain yield and in biomass yield, the most efficient cropping system was the intercropping ratio with a higher proportion of fennel, in which the competitive ratio values calculated for dill reached 1.90 for grain and 2.59 for biomass. Our results also indicate that the presence of dill exerted a clear stabilizing effect on fennel seed yield of the following year: whereas no difference in fennel seed yield was detected from one year to the following on the previously intercropped plots, in the repeated pure stand a 50% yield reduction was recorded. In the trial environment, the technique showed a good potential to improve the efficiency of resource utilization; further long-term experiments will be necessary in order to demonstrate the application of such a technique to other medicinal and aromatic plant mixtures.

Categorising farming practices to design sustainable land-use management in mountain areas

Abstract: In European mountain areas, shrub encroachment resulting from farmland abandonment is most often managed by mechanical operations such as roller chopping or controlled burning, which have proved to be ineffective and unsustainable. Recent agroecological findings highlight the potential impact of grazing on long-term shrub dynamics. We thus explored the potential contribution of livestock farms to the management of shrub encroachment. We studied the diversity of livestock practices and strategies on the scale of a small mountain valley in France where a land-use management plan was initiated. We interviewed 33 livestock farmers with a comprehensive approach and analysed the data in partnership with local land-use managers. To categorise farming practices, we used an innovative constructivist method based on knowledge engineering techniques and tools such as repertory grids. Our results show that the diversity of land-use practices can be summed up by ten practices related to three management domains: (i) livestock management, that is, splitting herds into batches, leading animals to pasture and breeding choices; (ii) the feeding system, including indoor feeding during the year, the hierarchy between haymaking and grazing in spring and the system’s forage autonomy; and (iii) farmland utilisation and maintenance, which comprises hillside use, spatial configuration of grazed areas, maintenance practices and technical choices to cut meadows. We also show that farmers combine these practices within six types of strategies: ensuring feeding security and simplifying labour (type A), maintaining farmland heritage (type B), taking advantage of hillsides (type C), focusing on animal care (type D), combining areas, periods and batches (type E), or selling on local markets (type F). This makes it possible to identify: (1) farmers’ strategies that have the greatest impact on shrub encroachment; and (2) practices that may develop into more sustainable management of shrub encroachment. Our work is thus a first step in developing sustainable land-use management plans in rural areas threatened by shrub encroachment. In return, this deep understanding of farmers’ strategies allowed us to address socially pertinent scientific issues related to the dynamics of grazed plant communities.

Effect of compost enriched with N and L-tryptophan on soil and maize

Abstract: Composting provides an excellent way to manage the huge volume of organic waste and convert it into a useful soil amendment. The effectiveness of composted organic waste can be further improved by enriching and blending it with nutrients and biologically active substances. The resulting value-added composts can be used at substantially low rates such as a few hundred kg per ha compared with conventional use of organic wastes in tons per ha. This approach could have practical significance in reducing the use of chemical fertilizer for sustainable agriculture and the environment. L-tryptophan is a precursor of the growth hormone indole acetic acid and is known to stimulate plant growth at extremely low concentrations. Here, we studied the effect of composted fruit and vegetable wastes, enriched with N at 133 g kg−1 compost, with or without L-tryptophan at 10 mg kg−1 compost, on soil and maize crops. The enriched compost was applied at 300 kg ha−1 to a sandy clay loam soil either by mixing with the top 15-cm soil layer in pots or as a band placement along the maize plants grown in the field. The compost was applied alone and in combination with 40 or 80 kg ha−1 urea N and compared with a treatment containing 160 kg N ha−1, a full dose of N fertilizer alone, while P and K fertilizers were applied in all the treatments. Our results show that application of the enriched compost to soil increased aggregate stability by up to 24.8% and water retention by up to 43.1% compared with untreated control. A gradual increase in the concentration of indole acetic acid in compost, ranging from 1.02 to 3.34 mg kg−1, was observed when compost was treated with its precursor L-tryptophan. The results of pot and field experiments revealed that compost enriched with N and L-tryptophan in the presence of 80 kg N fertilizer significantly increased cob and grain yields, by up to 19.8 and 21.4%, respectively, compared with a full dose of N fertilizer. These findings suggest that enrichment of composted organic wastes with N and L-tryptophan can change them into a value-added organic product that could be used as a soil amendment at rates as low as 300 kg ha−1 to increase crop production on a sustainable basis.