Showing papers in "The Journal of Agricultural Science in 2013"

Farmers’ Perceptions and Adaptations to Climate Change in Sub-Sahara Africa: A Synthesis of Empirical Studies and Implications for Public Policy in African Agriculture

Abstract: The problem of climate change in Africa has the potential of undermining sustainable development efforts if steps are not taken to respond to its adverse consequences. This study reviews existing and available literature on farmers’ perceptions and adaptations to climate change in sub-Sahara Africa. It is evident that the majority of farmers in sub-Sahara Africa are aware of warmer temperatures and changes in precipitation patterns. To respond to these changes, farmers have adopted crop diversification, planting different crop varieties, changing planting and harvesting dates to correspond to the changing pattern of precipitation, irrigation, planting tree crops,water and soil conservation techniques, and switching to non-farm income activities. Years of farming experience, household size, years of education, access to credit facilities, access to extension services and off-farm income are among the signicant determinants of adopting climate change adaptation measures. To enable sub-Sahara African farmers to develop more effective climate change adaptationstrategies,there is the need for African governments to support farmers by providing the necessary resources such as credit, information and extension workers to train farmers on climate change adaptation strategies and technologies, and investing in climate resilient projects like, improving on existing or building new water infrastructure and building climate change monitoring and reporting stations.

Farmers’ Perception of and Coping Strategies to Climate Change: Evidence From Six Agro-Ecological Zones of Uganda

Abstract: In Uganda, weather-related events such as prolonged dry seasons, floods, storms, mudslides, extreme rainfall, and delayed/early rains have become more frequent and/or intense. This has left most of the rural poor farmers’ food insecure and their livelihoods threatened. A total of 192 sweetpotato farmer households distributed in six agro-ecological zones were interviewed to assess how farmers perceive the effects of changes in climatic variables, and how they have adjusted their farming practices to cope with the changes in climate. Gender of the household head and size of land owned significantly affected adaptation. Ninety nine percent of all households interviewed had observed a change in the climate in the last 10 years. Drought and floods had the highest impact on crop production across agro-ecological zones. Coping strategies towards extreme events included storing food, income diversification and digging drainage channels. Other strategies were planting trees; high-yielding, early-maturing, drought-tolerant, disease and/or pest-resistant varieties; planting at onset of rains; increased pesticide/fungicide application among others. The smallholder farmer households studied have a high awareness of changes in rainfall and temperature and have taken measures to cope with effects of a changing climate.

Marginal Lands: Concept, Assessment and Management

Abstract: Marginal lands have received wide attention for their potential to improve food security and support bioenergy production. However, environmental issues, ecosystem services, and sustainability have been widely raised over the use of marginal land. Knowledge of the extent, location, and quality of marginal lands as well as their assessment and management are limited and diverse. There are many perceptions about what constitutes marginal lands and so clear definitions are needed. This paper provides a review of the historical development of marginal concept, its application and assessment. Challenges and priority research needs of marginal land assessment and management were also discussed.

Genetic improvement of bread wheat yield and associated traits in Spain during the 20th century

Abstract: A collection of 26 wheat genotypes widely grown in Spain during the 20th century was evaluated in eight contrasting environments in order to quantify breeding achievements in yield and associated traits. From 1930 to 2000, yield increased at a rate of 35·1 kg/ha/yr or 0·88%/yr, but estimations of relative genetic gain (RGG) were environment-dependent. RGG estimated for yield were positively associated with the average minimum daily temperatures from sowing to heading in the testing environments (R2 = 0·81; P < 0·01). The number of grains/spike and the number of spikes/m2 increased at a rate of 0·60%/yr and 0·30%/yr, respectively, while grain weight remained unchanged. The present study detected two main episodes of yield improvement during the century. The first one coincided with the introduction, during the 1950s, of the first improved cultivars derived from intra-specific crosses, which increased the yield of landraces by 30% due to an increase of c. 58% in the number of grains/spike, accompanied by a 16% reduction in grain weight. These initial cultivars (termed ‘old-bred’ in a previous study by Sanchez-Garcia et al. 2012) exhibited a higher harvest index (HI), increased from 0·25 to 0·40, but maintained the same aboveground biomass at maturity as the landraces (despite reducing both plant height and the number of tillers/plant) due to increases in the proportion of tillers bearing spikes. The second yield gain occurred after the introduction, in the early 1970s, of semi-dwarf germplasm from CIMMYT (International Maize and Wheat Improvement Centre) and some French cultivars. This new germplasm further reduced plant height, improved HI up to 0·45 and increased the number of tillers/plant while maintaining their rate of fertility, thus resulting in a yield gain of c. 37%. The cultivars released during the last decade of the century did not contribute to significant yield improvements.

A review of factors influencing milk urea concentration and its relationship with urinary urea excretion in lactating dairy cattle

Abstract: Milk urea nitrogen (MUN) concentration in dairy cows may serve as an on-farm indicator to guide nutritional strategies and to help reduce emissions of nitrogen (N) to the environment. Excretion of urinary urea nitrogen (UUN) is positively related to MUN, but the relationship is highly variable. The accuracy of MUN as a predictor of UUN may improve when various factors that affect this relationship can be taken into account. The current review discusses the impact of a number of UUN : MUN ratio influencing factors related to: physiological mechanisms in the dairy cow, farm management, differences between individual cows, nutrition and analysis methods for MUN. Factors related to variation in water intake, urine production, dietary protein level, body weight (BW) and time and frequency of feeding and milking are shown to affect MUN and its relationship with UUN. In addition, a number of factors are discussed that are likely to affect this relationship such as biological rhythm, renal reabsorption of urea during periods of protein deficiency and breeding value for MUN. Accounting for these above-mentioned factors in the relationship between MUN and UUN might substantially improve the applicability and accuracy of MUN as a predictor of protein utilization efficiency and UUN.

Economic and agronomic impact of commercialized GM crops: a meta-analysis

Abstract: The present paper presents a meta-analysis of the economic and agronomic performance of genetically modified (GM) crops worldwide. Bayesian, classical and non-parametric approaches were used to evaluate the performance of GM crops v. their conventional counterparts. The two main GM crop traits (herbicide tolerant (HT) and insect resistant (Bt)) and three of the main GM crops produced worldwide (Bt cotton, HT soybean and Bt maize) were analysed in terms of yield, production cost and gross margin. The scope of the analysis covers developing and developed countries, six world regions, and all countries combined. Results from the statistical analyses indicate that GM crops perform better than their conventional counterparts in agronomic and economic (gross margin) terms. Regarding countries’ level of development, GM crops tend to perform better in developing countries than in developed countries, with Bt cotton being the most profitable crop grown.

Effect of Agricultural Extension Program on Smallholders' Farm Productivity: Evidence from Three Peasant Associations in the Highlands of Ethiopia

Abstract: This study evaluates the effect of agricultural extension program participation on farm productivity taking three case study kebeles (peasant associations) in Ethiopia. A total of 1112 plot-level data collected from 300 selected farm households, comprising of extension participants and non-participants, were used in the study. The study begins the estimation with simple Ordinary Least Square (OLS) method. To deal with the potential bias due to the existence of observed and unobserved characteristics, we employed Heckman Treatment Effect Model (HTEM) and Propensity Score Matching (PSM). The OLS result shows that extension participation increases farm productivity by about 6%. However, both HTEM and PSM clearly reveal the presence of selection bias in extension program participation which leads to underestimation of the OLS estimates. The participation could have increased farm productivity by up to 20% had it not been to the serious selection bias related to non-farming factors such as involvement in kebele administration, and wealth status of the participants observed during program placement. Our PSM analysis also verifies the positive effect of extension program participation on farm productivity. In conclusion, the extension program has a positive effect on farm productivity in the study area. However, its effect with its current structure and input could have tripled had there been no bias related to extension program participation. This result provides a valuable policy insight in which improving access to diversified and quality agricultural inputs are critically necessary for the participants on top of expanding the program to less resourceful farmers by avoiding any entry barriers in the future.

Physicochemical Parameters, Phytochemical Composition and Antioxidant Activity of the Algarvian Avocado (Persea americana Mill.)

Abstract: The physical, chemical and nutritional properties of Persea americana fruits variety ‘Hass’ produced in the Algarve region were studied. Edible and non-edible parts of the fruits (pulp, seeds and peel) were compared considering their possible contribution to improve the sustainability of the food and pharmaceutical industries. The nutritional contents evaluated were moisture, ash, proteins, fat, total soluble solids and acidity. It were also evaluated the contents of bioactive compounds (phenolics, flavonoids, carotenoids, ascorbic acid and vitamin E) and their influence in the antioxidant activity exhibited by the fruit material. The results of the analysis demonstrated that the Algarvian avocado has physical and chemical characteristics comparable or superior to avocados from other growing regions around the world namely, Mexico and California. With regard to the contents of bioactive compounds, the pulp of the Algarvian avocado proved to be rich in carotenoids (0.815±0.201 mg/100g), phenolic compounds (410.2±69.0 mg/100g) and flavonoids (21.9±1.0 mg/100g). The skin was superior to the pulp in the contents of all these compounds with 2.585±0.117 mg/100g of carotenoids, 679.0±117.0 mg/100g of total phenolics and 44.3±3.1 mg/100g of flavonoids. The seed, in turn, was the part of the fruit with the highest total phenolic content (704.0±130.0 mg/100g) and flavonoids (47.97±2.69 mg/100g). Regarding the concentration of vitamins C and E, the highest values were found in the pulp (5.36±1.77 mg/100g of vitamin E) and skin (4.1±2.7 mg/100g of vitamin C). The extracts obtained from the seeds demonstrated higher in vitro DPPH· assay antioxidant activity (43%) than those obtained from the skin (35%) and the fruit pulp (23%). The contents of carotenoids, phenolic compounds and flavonoids found in the non-edible parts of the Algarvian avocado demonstrated that these byproducts could be an interesting inexpensive raw material for the food and cosmetic industries.

Sensitivities of crop models to extreme weather conditions during flowering period demonstrated for maize and winter wheat in Austria

Abstract: The objective of the present study was to compare the performance of seven different, widely applied crop models in predicting heat and drought stress effects. The study was part of a recent suite of model inter-comparisons initiated at European level and constitutes a component that has been lacking in the analysis of sources of uncertainties in crop models used to study the impacts of climate change. There was a specific focus on the sensitivity of models for winter wheat and maize to extreme weather conditions (heat and drought) during the short but critical period of 2 weeks after the start of flowering. Two locations in Austria, representing different agro-climatic zones and soil conditions, were included in the simulations over 2 years, 2003 and 2004, exhibiting contrasting weather conditions. In addition, soil management was modified at both sites by following either ploughing or minimum tillage. Since no comprehensive field experimental data sets were available, a relative comparison of simulated grain yields and soil moisture contents under defined weather scenarios with modified temperatures and precipitation was performed for a 2-week period after flowering. The results may help to reduce the uncertainty of simulated crop yields to extreme weather conditions through better understanding of the models’ behaviour. Although the crop models considered (DSSAT, EPIC, WOFOST, AQUACROP, FASSET, HERMES and CROPSYST) mostly showed similar trends in simulated grain yields for the different weather scenarios, it was obvious that heat and drought stress caused by changes in temperature and/or precipitation for a short period of 2 weeks resulted in different grain yields simulated by different models. The present study also revealed that the models responded differently to changes in soil tillage practices, which affected soil water storage capacity.

Plant pathogens, insect pests and weeds in a changing global climate: a review of approaches, challenges, research gaps, key studies and concepts

Abstract: Climate change biology is witnessing a significant quantity of new publications each year, which compromises efforts to keep up-to-date on the rapidly growing body of climate change biology literature. The present paper provides an overview on research approaches and challenges in climate change biology with respect to plant pathogens, insect pests and weeds (collectively termed ‘pests’ here). It also summarizes the suggestions of researchers about how to conceptualize and prioritize future research strategies. Recently published key studies demonstrate that climate change research is qualitatively advancing and that the interactions among environmental and biotic factors which have been found are complex. This complexity hinders attempts to generalize responses of pests to changes in climate. The challenge remains to identify the most significant causal relationships and to separate them from other factors such as crop management practices, which may also influence the observed changes in pest distribution and prevalence in managed ecosystems. In addition, the present overview shows that there are still gaps in many research areas, while other fields have been intensively investigated. For example, the identification of potential benefits in plant protection that may emerge from future climate change has not been explored as extensively as the potential threats. However, encouraging developments can be observed in recent climate change research, for instance the increased number of studies performed under subtropical and tropical climatic conditions, the increased availability of results from multi-factorial field experiments and modelling studies do consider increasingly pest–crop–climate interactions. Further progress can be expected, provided that researchers, sponsors and other stakeholders maintain their interest in climate change biology research.

Grazing behaviour, herbage intake and animal performance of beef cattle heifers on marandu palisade grass subjected to intensities of continuous stocking management

Abstract: The ability to adapt to a range of edaphic conditions favours the widespread use of marandu palisade grass in high as well as low input systems of animal production in Brazil. However, little information exists regarding the influence of grazing management practices on sward structure and the carry-over effects on animal responses. The present experiment was planned to evaluate animal behaviour, herbage intake (HI) and nutritive value, herbage accumulation and body weight gain (BWG) of beef cattle heifers grazing marandu palisade grass subjected to intensities of continuous stocking management. Treatments corresponded to four sward surface heights (SSH: 100, 200, 300 and 400 mm) and were allocated to experimental units (1200 m 2 paddocks) according to a randomized complete block design with four replications. Herbage accumulation rate (HAR) varied with season of the year and SSH, with highest and lowest values recorded during summer and winter, respectively. During the summer, herbage accumulation was larger on swards managed at 200, 300 and 400 mm, with the opposite occurring during winter/early spring. Stocking rate (SR) and number of grazing days (GD) followed a similar seasonal pattern of variation, with values decreasing as SSH increased. Crude protein (CP) and in vitro organic matter digestibility (IVOMD) of hand-plucked herbage decreased as SSH increased from 100 to 400 mm, while the inverse happened with BWG (from 0·190 to 0·930 kg/day, respectively). Bite mass (BM) increased and rate of biting and grazing time (GT) decreased as SSH increased, with daily HI being larger on tall (300 and 400 mm) relative to short (100 and 200 mm) swards. Grazing management affected the nutritive value and the amount of herbage consumed, particularly through changes in BM. However, variations in intake were relatively more important than variations in nutritive value in influencing animal performance, highlighting the importance of providing favourable harvest conditions for grazing animals by establishing adequate sward targets for management.

Potato Production in Kenya: Farming Systems and Production Constraints

Abstract: Potato (Solanum tuberosum L.) is a major food and cash crop in the Kenyan highlands, widely grown by small-scale farmers. Farmer practices and constraints in potato production differ from region to region. A survey was conducted in three major potato producing districts namely Bomet, Molo and Meru Central with the following objectives: 1) to document farmers’ practices, key potato production and marketing constraints, 2) to determine farmers’ potato cultivar and trait preferences and 3) to assess the prevalence and farmers’ management of bacterial wilt. The survey was carried out between November 2011 and March 2012. During the survey, a semi-structured questionnaire was administered to 253 individual farmers. The results show that the average household farm sizes are less than 2.4 hectares in all the districts. Majority of farmers allocate more than 25% of their farms to potatoes. Potato is produced both for food and cash by 90% of respondents in all districts. In Bomet district the red-skinned Dutch Robyjn is widely grown. In Molo district, the white- skinned Cangi is prominent while in Meru Central, the red-skinned Asante is predominantly grown by farmers. Cultivar preferences are mostly dictated by availability of markets, yield potential and taste. The major potato production constraints are diseases with bacterial wilt being the most prominent.

Effects of elevated CO2 and temperature on seed quality

Abstract: Successful crop production depends initially on the availability of high-quality seed. By 2050 global climate change will have influenced crop yields, but will these changes affect seed quality? The present review examines the effects of elevated carbon dioxide (CO2) and temperature during seed production on three seed quality components: seed mass, germination and seed vigour. In response to elevated CO2, seed mass has been reported to both increase and decrease in C3 plants, but not change in C4 plants. Increases are greater in legumes than non-legumes, and there is considerable variation among species. Seed mass increases may result in a decrease of seed nitrogen (N) concentration in non-legumes. Increasing temperature may decrease seed mass because of an accelerated growth rate and reduced seed filling duration, but lower seed mass does not necessarily reduce seed germination or vigour. Like seed mass, reported seed germination responses to elevated CO2 have been variable. The reported changes in seed C/N ratio can decrease seed protein content which may eventually lead to reduced viability. Conversely, increased ethylene production may stimulate germination in some species. High-temperature stress before developing seeds reach physiological maturity (PM) can reduce germination by inhibiting the ability of the plant to supply the assimilates necessary to synthesize the storage compounds required for germination. Nothing is known concerning the effects of elevated CO2 on seed vigour. However, seed vigour can be reduced by high-temperature stress both before and after PM. High temperatures induce or increase the physiological deterioration of seeds. Limited evidence suggests that only short periods of high-temperature stress at critical seed development stages are required to reduce seed vigour, but further research is required. The predicted environmental changes will lead to losses of seed quality, particularly for seed vigour and possibly germination. The seed industry will need to consider management changes to minimize the risk of this occurring.

Soil Properties and Crop Yields along the Terraces and Toposequece of Anjeni Watershed, Central Highlands of Ethiopia

Abstract: In the Highlands of Ethiopia, soil erosion is a pressing challenge causing deterioration of soil quality including soil fertility. To overcome this problem, the government has been taking various sustainable land management (SLM) measures. This study was conducted in 2011 to investigate the long-term impacts of soil conservation on soil qualities and crop performance at Anjeni watershed in the central highlands of Ethiopia. Soil and crop samples were collected from the lower (deposition), middle and upper (loss) zones of the terraces at a depth of 30cm.The test crops were maize (Zea mays) and bread wheat (Triticum aestivum). Soil samples were also taken at toe slope, foot slope, back slope, shoulder slope and crest positions of the watershed from 0-30 cm soil depth to evaluate the status of soil qualities along the catena. Results of the study showed that soil pH, exchangeable cations, available phosphorus, sum of exchangeable bases and percent base saturation showed non-significant difference between the loss zone and deposition zones, whereas higher mean value of organic carbon, and total nitrogen were obtained at the deposition zone than the loss zone. For both testing crops, higher mean yields were found at deposition zones followed by the middle zones while the lowest value was obtained from the loss zones. Soil pH, exchangeable cations, available phosphorus, sum of exchangeable bases, percent base saturation, organic carbon and total nitrogen showed significant variation due to slope position differences. Toe slope position followed by crest slope position showed higher mean value of the parameters. The shoulder slope position had the lowest mean value for all parameters. From the results of the study, it was possible to conclude that soil conservation measures implemented at Anjeni watershed reduced soils erosion, improved soil qualities and increased crop yield. It is, therefore, possible to recommend the need for scaling up of results obtained from learning watersheds on soil conservation activities to the highlands of Ethiopia to improve the soil quality and livelihoods’ of the society.

Regional climate change impacts on agricultural crop production in Central and Eastern Europe – hotspots, regional differences and common trends

Abstract: The present study investigates regional climate change impacts on agricultural crop production in Central and Eastern Europe, including local case studies with different focuses in Austria, the Czech Republic and Slovakia. The area studied experiences a continental European climate and is characterized by strong climatic gradients, which may foster regional differences or trends in the impacts of climate change on agriculture. To study the regional aspects and variabilities of climate change impacts on agriculture, the effect of climate change on selected future agroclimatic conditions, crop yield and variability (including the effect of higher ambient CO2 concentrations) and the most important yield limiting factors, such as water availability, nitrogen balance and the infestation risks posed by selected pests were studied. In general, the results predicted significant agroclimatic changes over the entire area during the 21st century, affecting agricultural crop production through various pathways. Simulated crop yield trends confirmed past regional studies but also revealed that yield-limiting factors may change from region to region. For example, pest pressures, as demonstrated by examining two pests, are likely to increase due to warmer conditions. In general, higher potentials for cereal yield increase are seen for wetter and cooler regions (i.e. uplands) than for the drier and warmer lowlands, where yield potentials will be increasingly limited by decreasing crop water availability and heat under most scenarios. In addition, yield variability will increase during the coming decades, but this may decrease towards the end of the 21st century. The present study contributes to the interpretation of previously conducted climate change impact and adaptation studies for agriculture and may prove useful in proposing future research in this field.

Yield and grain quality of wheat in response to increased temperatures at key periods for grain number and grain weight determination: considerations for the climatic change scenarios of Chile

Abstract: Agricultural systems are challenged by global climatic change in a scenario of increasing food demand by a growing population. The increase in average temperature will be the main environmental factor affecting the crop development and productivity worldwide, although changes in carbon dioxide (CO 2 ) concentration and rainfall are also expected. Global warming in the range of moderately high temperatures (15–32°C) is projected for temperate environments such as that of central-southern Chile, where grain crops such as wheat are widely grown. The present study assessed the impact of moderately high temperatures on both yield and quality traits of wheat during key stages for grain number and grain weight determination. Two cultivars of spring wheat (Pandora INIA and Huayun INIA) were grown under field conditions during two cropping seasons (2006/07 and 2007/08) under different thermal regimes, consisting of a combination of three temperatures (a control at ambient temperature and two increased temperature treatments, ranging from 2·6 to 11·7°C above the control) and two (3–15 and 20–32 days after anthesis) or three (booting to anthesis (Bo-At), 3–15 and 20–32 days after anthesis) timing regimes. The data recorded showed that the extent of yield reduction was strongly dependent on the timing of the heat treatments. Increased temperature at pre- (Bo-At) or early post-anthesis (3–15 days after anthesis) affected grain yield the most (reducing it by 8–30%). In light of these results, yield reductions of up to 18% can be expected when the crop undergoes average temperature increase of 2·8°C at Bo-At. In this study, the negative effect of increasing temperature on grain yield was associated with both grain number and grain weight reductions; however, different sensitivities to higher temperatures were found between cultivars. Although protein concentration of grains was not affected by higher temperatures, other negative effects on industrial quality traits are important, considering the impact of thermal treatments on grain size of both cultivars.

The Role of Spirulina platensis (Arthrospira platensis) in Growth and Immunity of Nile Tilapia (Oreochromis niloticus) and Its Resistance to Bacterial Infection

Abstract: The current study was designed to optimize the dietary levels of Spirulina platensis in Oreochromis niloticus; this was tested via graded levels. Six isonitrogenous and isocaloric rations containing graded levels of dried spirulina 0, 5, 7.5, 10, 15 and 20 g/kg diet were fed separately to six equal groups of O. niloticus fingerlings for 3 months. Growth performance, non-specific immune parameters, tissue reactions and resistance of tilapias post challenge infection with Pseudomonas fluorescens were estimated monthly. There were significant increase in growth performance parameters and survival rates in spirulina-supplemented groups at concentration level of 10 g/kg for 2 months. Significant increases in hematocrit, nitroblue tetrazolium and lysozyme activity were observed in most of the supplemented groups. Bacterial challenge infections resulted in significantly lower mortality rate in all Spirulina groups with remarkable increase in protection of fish received 10 g/kg. In sum, it advisable to incorporate 10 g/kg diet of spirulina for 2 months for maximum growth performance, immunity and disease resistance in O. niloticus.

Influence of Tyre Inflation Pressure and Wheel Load on the Traction Performance of a 65 kW MFWD Tractor on a Cohesive Soil

Abstract: The choice of tractor configuration is of primary importance in tillage operations for the optimisation of traction performance, i.e. for limiting slip which involves energy loss. To a great extent, this aspect affects the fuel consumption and the time required for soil tillage. Tyre inflation pressure and wheel load are both easily managed parameters which play a significant role in controlling the traction performance of a tractor. The present study aimed to investigate the influence of tyre inflation pressure and wheel load on the traction performance of a mechanical front wheel drive MFWD tractor (65 kW engine power) on an agricultural clay (C) Vertic Cambisol on the basis of results of traction tests and simulations with a semi-empirical soil-tyre interaction model adapted for MFWD vehicles. The traction tests were carried out using four tractor configurations with two tractor weights (40.8 kN and 50.2 kN) and two tyre inflation pressures (60 kPa and 160 kPa). Traction performance was considered in terms of drawbar pull, traction coefficient, tractive efficiency, power delivery efficiency and specific fuel consumption in relation to wheel slip. A decrease in tyre pressure and an increase in wheel load resulted in higher drawbar pull however, only the former produced improvements in terms of coefficient of traction, tractive efficiency, power delivery efficiency and specific fuel consumption, while the only significant benefit resulting from the latter was a reduction in specific fuel consumption at a tyre pressure of 160 kPa and a slip of under 15%.

Effects of Different Land Use Systems on Selected Physico-Chemical Properties of Soils in Northwestern Ethiopia

Abstract: Information about effects of different land use systems on soil physico-chemical properties is crucial for best land management practices. This study was, therefore, conducted to evaluate the same on Nitosols of Achefer District, Northwestern Ethiopia. The landuse systems studied included grassland, cultivated land, plantation forest and natural forest. The research was superimposed on land use systems that were located nearby on similar soil, contour line and slope classes. Undisturbed core and disturbed composite soil samples were collected randomly from two sites with three replications for each landuse system at two varying depths (0-15 cm and 15-30 cm). The undisturbed soil samples were analysed for bulk density, particle density, porosity and moisture content at different pressures; while the composite soil samples were analyzed for pH, organic carbon, total N and available P. Results of the study indicated that the lowest bulk and particle densities, the highest total porosity, and higher moisture content at both field capacity and permanent wilting percentage were found under natural forest land use system. In contrast, the highest bulk and particle densities, the lowest total porosity and lower water contents at both field capacity and permanent wilting percentage were obtained under the cultivated landuse system. Soil pH was moderately acidic under all landuse systems. The lowest organic carbon, total N, and C:N ratio were recorded under cultivated land; whereas the highest values of the same parameters were found under natural forest. In all landuse systems, organic carbon and total N decreased with soil depth. The highest and lowest available P contents were recorded under natural forest and grassland, respectively. From the results of the study it was possible to conclude that conversion of forest lands to cultivated and grasslands had detrimental effects on the soil physico-chemical properties under subsistance farming systems of the study area. It is, therefore, recommended that appropriate and integrated land management options for different land use syetems are required to sustain agricultural productivity while protecting the environment.

Analysis of genotype x environment interaction for grain yield in Maize hybrids

Abstract: Maize is an important staple crop for millions of people in Sub-Saharan Africa. The crop grows in a wide range of environmental conditions. The present study was performed to analyze the genotype-by-environment (G×E) interaction for grain yield of fourty two single cross hybrids grown in three environments located at different agro-ecological zones of Kenya. The maize genotypes were grown in randomized complete block design with three replicates in 2006 and 2007. Grain yield data of the single cross hybrids was analysed using the additive main effects and multiplicative interaction (AMMI) and GGE biplot methods. The additive main effects and multiplicative interaction model (AMMI) analysis of variance (additive main effects) showed significant effects for genotypes, environment and the genotype by environment interaction. The total proportion contributed by environment and G x E interaction accounted for 78% and 10% of the total variation. The results also showed that 64.5% of the total variation was contributed by the environment while the genotype and interaction was associated with 20.7% and 10.3% of the total variation, respectively. The most stable genotype in the high yielding group in this study was CML312/TZMI 711 (X20), followed by genotypes TZMI 102/CML384 (designated as X33), and CML312/TZMI 712 (X21). The genotype CML312/TZMI 711 (designated as X20) could be used for broad selection since it was found to be the most ideal genotypes with both high mean yield and high stability. In the biplot analysis, X20 was also close to the origin, had the shortest vector from the ATC and with large PC1 scores (high mean yield) and small (absolute) PC2 scores (high stability) implying it had the least contribution to genotype by environment interaction (GEI). Through the stability analysis, the superior genotypes identified could also be used as references for genotype evaluation and also included in further testing in both early and later stages of selection.

A method of screening for spike fertility in wheat

Abstract: Wheat grain yield is often associated with grain number/m 2 . Spike fertility (SF), i.e. the quotient between grain number and spike chaff dry weight, is a major component of grain number/m 2 determination. Several methodologies have been proposed in the literature for field determination of SF, but they are tedious and expensive. Also, no comparison between methodologies has been done. The feasibility of using wheat SF as a selection criterion in a breeding programme or as a variable of interest in crop physiology studies depends largely upon the availability of a simpler and faster method for collecting and processing samples. Thus, the objective of the present study was to determine: (1) the association between SF calculated with the non-grain spike dry weight at anthesis (reference method) or at crop maturity, (2) the association between SF evaluated at the plot level (i.e. both non-grain spike dry weight and grain number determined as per area unit) and at the individual spike level and (3) the minimum number of individual spikes that should be sampled for the development of a screening method that can be applied in wheat breeding programmes or in crop physiology studies. Associations between variables were determined by correlation analysis of treatment means, and by a test of agreement for categorical rating (low, medium and high SF) between individual data of each variable. Four experiments (BY95, BC96, BC97 and ML07) were performed with five, ten, eight and eight wheat cultivars, respectively, under no environmental limitations, except for experiment ML07 which was not irrigated. In the first three experiments, SF was determined both at the beginning of grain filling and at maturity, in plot-size samples (0·8 m 2 /plot). In experiments BC96 and BC97, SF was determined both in plot-size samples and in individual spikes (five spikes per plot), at the beginning of grain filling. In experiment ML07, increasing numbers of individual spikes were sampled at maturity to assess SF. As a result: (1) a significant association ( R 2 =0·78; P d.f .=20) was detected between SF determined at the beginning of grain filling and at maturity, and the test of agreement for categorical rating showed that the classification of data into categories of SF was equivalent between methods ( P >0·05); (2) when comparing SF determined in large plot-size samples v. in small samples of individual spikes, a good adjustment ( R 2 =0·77; P d.f .=6) was also observed, with no significant cultivar×experiment interaction and a good agreement between methods in the classification of data into categories of SF ( P >0·05); and (3) increasing sample size from 5 to 40 spikes gradually decreased the average relative standard error of the mean (from 0·034 to 0·012, respectively). In conclusion, wheat SF can be determined in a fairly accurate way by sampling a small group of individual spikes at crop maturity, thereby allowing the evaluation of a large number of treatments in a timely fashion and the screening of breeding material from early generations.

The Role of Biochar on Acid Soil Reclamation and Yield of Teff (Eragrostis tef [Zucc] Trotter) in Northwestern Ethiopia

Abstract: The study was conducted to investigate the effect of biochar on soil properties and teff yield at Koga watershed, West Gojam Zone, Amhara National Regional State, Ethiopia. Five rates of amendments including three rates of biochar (4, 8, 12 t ha-1), one rate of lime (2 t ha-1) and no amendment were combined in a factorial design with full, half and zero rates of the recommended N & P fertilizer rates. A randomized complete block design with three replications was used. Composite soil samples were taken from the experimental sites using soil auger at 0-20 cm soil depth before treatment application; and treatment based soil sampling was made after harvest. Soil pH, organic carbon, CEC, total N and available P were analyzed using standard laboratory procedures. Grain yield and biomass data were also collected and analyzed. Results of the study indicated that application of biochar increased soil pH, CEC, available P and organic carbon and significantly increased yield. Using 12 t ha-1, 8 t ha-1 biochar, and 2 t ha-1 lime rates of biochar, 2.67, 1.98 and 2.45 t ha-1, respectively teff grain yield was harvested while the lowest grain yield (1.44 t ha-1) was found from treatment with no lime or biochar. Biochar combined with NP fertilizers increased yield significantly compared to plots that received fertilizer or lime alone; suggesting that biochar improved fertilizer use efficiency.

Expansion of Eucalyptus Woodlots in the Fertile Soils of the Highlands of Ethiopia: Could It Be a Treat on Future Cropland Use?

Abstract: A study was conducted to assess the effect of land use change from eucalyptus to cropland on soil physico-chemical properties and perceptions of farmers in Koga irrigation area, Amhara Region. Soil samples were taken from 4 sites of three land uses (eucalyptus woodlots, cropland, and eucalyptus land use changed to cropping) and at 0-20, 20-40 and 40-60 cm depths. The three depths were used for analysis of soil chemical properties, whereas the first two depths for physical properties. Furthermore, randomly selected 15 farmers were interviewed for their perception on the state of soil fertility and crop yield conditions on lands that were recently changed from eucalyptus to cropland. The result showed that except for available P, sampled plots that were changed from eucalyptus to cropland were found better in soil chemical properties (pH, N, CEC) and SOM contents as compared to croplands. As compared to the other two land uses, total N was found larger at eucalyptus woodlots. Regarding soil physical properties (bulk density and texture), little or no difference was recorded among the different land use types. On top of that, farmers perceived that plots that were under eucalyptus have better fertility, require less nitrogen fertilizer and crops perform well compared to plots that are contineously under cropping. Thus, results of this study confirmed that changing land use from eucalyptus to cropland is possible without detrimental effect on soil properties and without affecting productivity of lands to raise crops.

The Impact of Soil Erosion on Agricultural Potential and Performance of Sheshegu Community Farmers in the Eastern Cape of South Africa

Abstract: Soil erosion is one of the unresolved problems of rural agriculture. This study investigates the impact of soil erosion on the agricultural potential and performance of Sheshegu community farmers in the Eastern Cape of South Africa. Structured interview scheduled was used to collect data from 50 respondents using simple random sampling. Findings revealed that most (62%) respondents are male, who are above 46 years old (68%). Most of whom (72%) had education above grade 7. Further, the majority of them (50.8%) depend on social grants as sources of income. Most respondents confirmed that erosion occurred naturally through heavy rainfall and persistent drought while human causes that facilitated erosion include farming activities, deforestation and indiscriminate bush burning that expose soil to impact of rain drop. Respondents affirmed that erosion contributed to poor health of livestocks due to lack of pasture grass to feed on, loss of grazing land and poor bush regrowth. It is recommended that awareness on the negative effect of human causes of erosion should be created while simple technologies on soil erosion control should be pushed to the farmers. Finally, edict on bush burning should be enforced to check indiscriminate bush burning.

A review of the impact of charcoal rot ( Macrophomina phaseolina ) on sunflower

Abstract: Charcoal rot, caused by Macrophomina phaseolina, is the most prevalent and important disease of crop plants such as sunflower. Although it is monotypic and no physiological races have been reported, it has high genetic variability resulting in a wide host range, which in turn means that crop rotation is not an effective strategy to combat the disease. The current paper reviews the adverse effects of this disease and summarizes the present state of knowledge about charcoal rot severity and its impact on crop production.

Seasonal Vegetative Growth in Genotypes of Coffea canephora, as Related to Climatic Factors

Abstract: Knowledge about the seasonality of different genotypes of Coffea canephora is an important tool for this crop management, particularly with regard to irrigation and fertilisation issues. This study was conducted in Espirito Santo, Brazil and aimed at to evaluate the seasonal vegetative growth in genotypes of C. canephora, as related to climatic factors, based on the growth of groups of orthotropic and plagiotropic branches with different ages. Three groups of plagiotropic branches and one group of orthotropic branches of 14 genotypes (Ipiranga and 13 that belonged to the variety Vitoria) were selected and marked to followed along the one-year experiment. Three-year-old plants were cultivated under full-sun conditions, with a spacing of 3 m between rows and 1 m between plants. The growth rates of the orthotropic and plagiotropic branches differed among the genotypes and underwent seasonal variation during the entire year, with high correlations to the air temperature. Under the natural experimental conditions, the growth rate of the branches decreased when the minimum air temperatures were below 17.2oC for most of the genotypes studied. The plagiotropic branches presented lower vegetative growth, mainly for the coffee berries, compared to the younger branches. Presumably, the genotypes of C. canephora demanded more nutrients for growth between mid-September and the second week of May.

Chemical Composition of Four Cultivated Tropical Bamboo in Genus Gigantochloa

Abstract: The chemical compositions of cultivated 3 year-old bamboo culms of Gigantochloa brang, G. levis, G. scortechinii and G. wrayi were studied. The culms exhibited different chemical composition in extractives, α-cellulose, lignin and ash contents between the bamboo species, location in the culms and position at the nodes and internodes. The extractive content in four species ranged from 8.30 to 9.23%. The extractive content of G.brang, G.levis, G.scortechinii and G.wrayi were 8.30%, 9:23%, 8:00% and 8.62% respectively. The holocellulose content for G. levis were 85.08%, G. wrayi 84.53%, G. brang 79.94% and G. scortechinii 74.62%. The holocellulose content for the cultivated bamboo genus Gigantochloa were 74% to 85%. The α- cellulose is the chemical constituents in the holocellulose. The highest was G.brang (51.58%) followed by G. scortechinii (46.87%), G. wrayi (37.66%) and G. levis (33.80%). The lignin content ranged between 24.84 to 32.65%. The highest were obtained in G. scortechinii (32.55%), G. wrayi (30.04%), G. levis (26.50%) and lowest in G. brang (24.83%). The ash content in four species of Gigantochloa bamboo ranged between 0.88 to 2.86%. The ash content is the highest in G. scortechinii (2.83%) follow by G. levis (1.29%), G. brang (1.25%) and the lowest in G. wrayi (0.88%).

Determinants of Farm-Level Adoption of Cultural Practices for Banana Xanthomonas Wilt Control in Uganda

Abstract: Understanding the factors influencing farmers’ adoption decisions of the disseminated Banana Xanthomonas wilt (BXW) control package is critical for successful management of the disease. This paper analysed the determinants of farmers’ decisions to adopt the control package by smallholder banana farmers in Uganda. A binomial Logit model is applied to household survey data collected from 350 households. Results from the study show that household labour availability, technology package attributes such as labour demand and perceived effectiveness of the practices in managing the disease; and agro-ecological location and banana production system significantly influence adoption decisions. These results suggest the need for adaptation of the technology package to better suit the needs and socio-economic conditions of smallholder farmers through a farmer participatory technology development approach that takes into account research findings, farmers’ indigenous knowledge and resource constraints to enhance adoption.

Effect of Different Levels of Nanoparticles Chromium Picolinate Supplementation on Performance, Egg Quality, Mineral Retention, and Tissues Minerals Accumulation in Layer Chickens

Abstract: This study was conducted to investigate the effects of various levels of nanoparticles chromium picolinate on performance, egg quality, minerals retention, and tissues accumulation of layer chickens This study used 54 seventy-week old post-molt laying hens randomly allocated into 0 (control), 500 ppb (µg kg-1) Cr and 3000 ppb Cr groups for a 60-day experiment The chromium was nanosize (808 ± 27 nm) chromium picolinate (NanoCrPic) and each treatment was undertaken with six replicates In the meantime, a total of 18 birds (1 bird/replicate) were used for metabolic experimentation The results of the experiment indicated that there were no significant effects on body weight, feed intake, feed efficiency, and egg production of layers Supplemental NanoCrPic could significantly (p < 005) improve egg quality, or retention of chromium and zinc, but decrease shell ratio in the 60th day eggs The addition of NanoCrPic resulted in increased minerals accumulation in tissues such as Cr, Ca, and P concentration in the liver, Cr concentration in the yolk and Ca concentration in the eggshell In conclusion, supplemental NanoCrPic improved Cr and Ca accumulation in the liver and egg, improved Zn and Mn retention in layer chickens

Genetic diversity assessment of extra­early maturing yellow maize inbreds and hybrid performance in Striga­infested and Striga­free environments

Abstract: Maize (Zea mays L.), a major staple food crop in West and Central Africa (WCA), is adapted to all agro-ecologies in the sub-region. Its production in the sub-region is greatly constrained by infestation of Striga hermonthica (Del.) Benth. The performance and stability of the extra-early maturing hybrids, which are particularly adapted to areas with short growing seasons, were assessed under Striga-infested and Striga-free conditions. A total of 120 extra-early hybrids and an open-pollinated variety (OPV) 2008 Syn EE-Y DT STR used as a control were evaluated at two locations each under Striga-infested (Mokwa and Abuja) and Striga-free (Ikenne and Mokwa) conditions in 2010/11. The Striga-resistant hybrids were characterized by higher grain yield, shorter anthesis–silking interval (ASI), better ear aspect, higher numbers of ears per plant (EPP), lower Striga damage rating, and lower number of emerged Striga plants at 8 and 10 weeks after planting (WAP) compared with the susceptible inbreds. Under Striga infestation, mean grain yield ranged from 0·71 to 3·18 t/ha and 1·19 to 3·94 t/ha under Striga-free conditions. The highest yielding hybrid, TZEEI 83×TZEEI 79, out-yielded the OPV control by 157% under Striga infestation. The hybrids TZEEI 83×TZEEI 79 and TZEEI 67×TZEEI 63 were the highest yielding under both Striga-infested and Striga-free conditions. The genotype main effect plus genotype×environment interaction (GGE) biplot analysis identified TZEEI 88×TZEEI 79 and TZEEI 81×TZEEI 95 as the ideal hybrids across research environments. Twenty-three pairs of simple sequence repeat (SSR) markers were used to assess the genetic diversity among the inbred lines. The correlations between the SSR-based genetic distance (GD) estimates of parental lines and the means observed in F1 hybrid under Striga infestation and optimum growing conditions were not significant for grain yield and other traits except ASI under optimum conditions. Grain yield of inbreds was not significantly correlated with that of F1 hybrids. However, a significant correlation existed between F1 hybrid grain yield and heterosis under Striga infestation (r=0·72, P<0·01). These hybrids have the potential for increasing maize production in Striga endemic areas in WCA.