Showing papers in "Journal of Agronomy and Crop Science in 2005"

The Exploitation of Crop Allelopathy in Sustainable Agricultural Production

Abstract: Crop allelopathy may be useful to minimize serious problems in the present agricultural production such as environmental pollution, unsafe products, human health concerns, depletion of crop diversity, soil sickness and reduction of crop productivity. Several crops including alfalfa, buckwheat, maize, rice, rye, sorghum, sunflower, wheat, etc. are affected either by their own toxicity or phytotoxin exudates when their residues decompose in the soil, that show strong suppression on weed emergences. Allelopathic crops when used as cover crop, mulch, smother crops, green manures, or grown in rotational sequences are helpful in reducing noxious weeds and plant pathogen, improve soil quality and crop yield. Those crop plants, particularly the legumes, incorporated at 1-2 tons ha -1 (alfalfa, buckwheat, rice byproducts), which can give weed reduction and increase of rice yield by 70 and 20 %, respectively, are suggested for use as natural herbicides. Allelochemicals from allelopathic crops may aid in the development of biological herbicides and pesticides. Cultivating a system with allelopathic crops plays an important role in the establishment of sustainable agriculture. The introduction of allelopathic traits from accessions with strong allelopathic potential to the target crops will enhance the efficacy of crop allelopathy in future agricultural production.

Jasmonic Acid Differentially Affects Growth, Ion Uptake and Abscisic Acid Concentration in Salt-tolerant and Salt-sensitive Rice Cultivars

Abstract: Phytohormones play critical roles in regulating plant responses to stress. Here, we investigated the effects of salt stress and stress recovery by applying jasmonate to the two different rice (Oryza saliva L.) cultivars Dongjinchalbyeo (DJC, salt-tolerant) and Dongjinbyeo (DJ, salt-sensitive). Salt stress remarkably decreased the root length of plants even at low NaCI concentration (20 mM). Salt stress led to a sharp increase in the concentrations of abscisic acid (ABA) in 20 and 40 mM NaCl, when compared with the control values. The concentrations of ABA in the salt-tolerant cultivar DJC plants progressively increased with increasing NaCI levels, whereas in the salt-sensitive cultivar DJ, they sharply decreased in all three parts of rice plants at 80 mM NaCI treatment. The decrease of jasmonic acid (JA) concentrations in salt-tolerant cultivar DJC was lesser than in the salt-sensitive cultivar DJ plants in the shoot. Post-application in the stressed plants with 30 μM JA at 24 and 48 h after NaCI treatment, recovered salt inhibition on dry mass production more effectively than application of JA at 48 and 24 h before salt stress, and during salt stress simultaneously. The uptake of Na decreased especially in the salt-sensitive cultivar DJ plants, whereas there was an increase in Ca and Mg levels and slight increase of K by JA application. Leaf water potential, leaf photosynthetic rate, and maximum quantum yield of photosystem II (PSII) also remarkably recovered when 30 μM JA was applied 24 h after the salt stress compared with the 40 mM NaCl-treated plants. These results clearly indicate that post-application with exogenous JA can ameliorate salt-stressed rice seedlings, especially the salt-sensitive cultivar rather than the salt-tolerant cultivar. This may change the balance of other endogenous plant hormones.

Remobilization of Nitrogen and Carbohydrate from Stems of Bread Wheat in Response to Heat Stress during Grain Filling

Abstract: When wheat (Triticum aestivum L.) is grown under heat-stress conditions during grain filling, preanthesis stored total non-structural carbohydrates (TNC) and nitrogen (N) could serve as alternative source of assimilates. This study was performed to evaluate wheat genotypes for their ability to accumulate and remobilize TNC and N stored in their stem to support grain filling under heat stress. Eighteen genotypes were used for N remobilization study while nine of them were used for TNC remobilization study. They were grown in pots and placed in a vinyl house with the maximum temperature kept below 30 °C. Five days after anthesis (5DAA), half of the pots were taken to phytotrons where temperature was gradually increased and the maximum was set at 38 °C. Grain yield and grain weight decreased by about 35 % under heat stress. Significant differences were found among genotypes in percentage reduction in grain yield, grain weight, grain filling duration and harvest index because of heat stress. The N and TNC concentrations of the stem at 5DAA were significantly different among genotypes. Heat stress significantly reduced the N remobilization efficiency of most of genotypes. However, heat stress significantly increased TNC remobilization efficiency and significant variation were observed among genotypes. N remobilization efficiency across treatments significantly correlated with grain yield, grain weight, harvest index and grain filling duration. TNC at 5DAA negatively correlated with N at 5DAA and harvest index, but the TNC remobilization efficiency under heat stress positively correlated with mainstem grain yield, grain weight and harvest index. The rate of chlorophyll loss from flag leaf positively correlated with N and TNC remobilization efficiencies under heat stress suggesting a link between leaf senescence and remobilization efficiency. The results indicate that heat stress negatively affected grain yield, its components and N remobilization while it increased TNC remobilization because of the increasing demand for resources.

Seed Priming Increases Crop Yield Possibly by Modulating Enzymes of Sucrose Metabolism in Chickpea

Abstract: The number of seeds and seed yield per plant were higher in chickpea crops raised from water and mannitol (4 %) primed seeds in comparison with the control non-primed crops. In primed plants, an enhanced acid invertase activity in the apical part of the main stem and the part immediately below it at 100 and 130 days after sowing (DAS) might result in an increased availability of hexoses to these plant parts. In addition, decreased acid invertase activity at the point of initiation of branches and in the internodes of stem observed in primed plants indicated restricted hydrolysis of sucrose during its transport through the stem, resulting in its more supply to the actively growing sinks. The activities of sucrose-cleaving enzymes, i.e. invertase and sucrose synthase (SS) in podwall of primed plants were higher at 110 DAS. At 140 DAS, a stage of rapid seed filling, increased activities of SS and sucrose phosphate synthase (SPS) were observed in seeds of primed plants. Increased SPS activity in seeds of primed crop could meet the increased assimilate requirements of the developing seeds. Higher activity of SS in seeds of primed crop may facilitate seed filling. These data suggest that enzymes of sucrose metabolism play an important role in increasing the yield of chickpea crops raised from primed seeds.

Analysis of unbalanced data by mixed linear models using the MIXED procedure of the SAS System

Abstract: Unbalanced data are a common problem in plant research based on designed experiments. Such data are often conveniently analysed using linear mixed models. Recent developments in mixed model theory have been implemented in major packages. This paper describes the use of the mixed procedure of the SAS System for the analysis of designed experiments. Special emphasis is given to the specification of options as depending on the assumed mixed model and on the unbalancedness in the data. In addition, we consider a compact representation of multiple comparisons for unbalanced data (letter display). Two small data sets are used to exemplify the methods.

Decomposition of Allelopathic Plants in Soil

Abstract: Higher plants with strong allelopathic properties are commonly incorporated into soil for weed-control purposes. To understand the phytotoxic variation in the soil, which can be utilized for weed control through the use of allelopathic plants, the decomposition of alfalfa (Medicago sativa L. cv. Rasen) and kava (Piper methysticum L.) after soil amendment were evaluated. Both alfalfa and kava strongly inhibited barnyardgrass and monochoria growth for up to 10 days (80-100 % weed control). After 20-25 days, the magnitude of inhibition was drastically reduced, but was still effective (50 % weed control). A number of phenolic acids were detected in the soil even 50 days after incorporation in low concentration, but their concentrations reached a maximum after 10-15 days and were efficacious until 20-25 days. Phenolic acids varied between alfalfa and kava. The variations in electrical conductivity (EC) and osmotic pressure (OP) were strongly related to chemicals and toxic compounds exuded into the soil during decomposition and were proportional to the magnitude of inhibition observed, whereas pH did not appear to be correlated with inhibition. The decomposition of several unknown inhibitors present in kava was also analysed and assessed. Our findings indicate that these growth inhibitors were almost disintegrated in soil after 10 days, but strong inhibition was detected until 25 days after amendment. Results from this study demonstrate that chemicals released from allelopathic plants incorporated into soil are toxic and cause inhibition of certain species and could be exploited as a biological tool for weed management.

Alternate Row Spacing and Plant Density Effects on Forage and Dry Matter Yield of Corn Hybrids (Zea mays L.)

Abstract: Irrigated field experiments were conducted in the Marmara region of Turkey in 2002 and 2003 to compare alternate 40 : 25 cm row spacings and conventional 65 cm with four different plant densities (65 000, 85 000, 105 000 and 125 000 plants ha -1 ) of three corn hybrids (DK-585, ADA 95-10 and C-955) in some morphological traits and forage and dry matter yield. Morphological traits such as plant height, leaf per plant. stem diameter, ear per plant and ear percentage were measured, forage and dry matter yield was also determined in this study. Hybrids, row spacings and plant densities significantly affected some morphological traits, forage and dry matter yield at 0.01 level. Later maturing hybrids tended to produce taller and thicker stemmed plants. Row spacings and plant densities did not affect plant height. Average stem diameter increased significantly with population density. Row spacings did not influence leaf number, whereas leaf number increased slightly with plant density. On average, all corn plants had slightly more than 1.0 ear per plant in our experiment. Row spacings and plant densities did not affect significantly number of ear per plant. Early maturing DK-585 had the highest ear percentage whilst late maturing C-955 lowest. Yields usually increased with hybrid maturity. When averaged across years, row spacings and plant densities, late maturing C-955 performed significantly better in forage and dry matter yield in all experimental years and combined years. The studies showed favourable advantage for alternate 40 : 25 cm rows over conventional 65 cm row spacings at all plant densities. Average forage and dry matter yields were greater for alternate 40 : 25 cm row spacings than for 65 cm row spacings. However, strong hybrid x row spacing interactions for both forage and dry matter yield were detected.

Suppressing Weeds in Direct‐seeded Lowland Rice: Effects of Methods and Rates of Seeding

Abstract: High weed infestation is a major constraint to widespread adoption of direct seeding of rice (Oryza sativa L.) The experiments were conducted in 1998 wet and 1999 dry seasons in the Philippines to examine the effects of seeding methods and rates on suppressing weeds in direct-seeded lowland rice. Treatments consisted of four seeding methods: conventional and modified broadcast seeding, drill seeding with east–west and north–south row orientations; three seeding rates: 40, 80 and 160 kg seed ha−1 as well as two weed control levels: weed control with herbicide and no weed control. Among the seeding methods drill seeding with east–west row orientation had the lowest rice grain yield loss caused by weeds (38 % in the wet and 20 % in the dry season), whereas the highest losses because of weeds were observed with conventional broadcast seeding (59 % in the wet and 27 % in the dry season). Seeding rate was inversely correlated to weed interference. Severe rice yield reduction (71 %) caused by weeds was found at a seeding rate of 40 kg seed ha−1 in the wet season. Using seeding rates of 80 and 160 kg seed ha−1, respectively, lowered yield loss to 47 and 26 % in the wet season, 32 and 18 % in the dry season. Therefore suitable method and/or rate of seeding can significantly suppress weeds in direct-seeded lowland rice.

The Deterioration of Eating and Cooking Quality Caused by High Temperature During Grain Filling in Early-Season indica Rice Cultivars

Abstract: The effect of temperature during grain filling on eating and cooking quality of early-season indica rice was investigated by using four cultivars with different amylose content. Starting from flowering stage until maturity, the plants of all cultivars were subjected to two temperature treatments, referred as optimum (mean daily air temperature, 22 � C) and high (32 � C) temperature regimes. The results showed that the effect of high temperature on apparent amylose content and gel consistency in milled rice was cultivardependent. Under high temperature, amylose content increased for cv. Jiayu353 and remained little changed for cv. Guangluai4, which had intrinsically higher amylose content, and decreased for cv. Zhefu49 and cv. Jiazao935, which had lower amylose content. By contrast, high temperature reduced or kept stable gel consistency values for cultivars with higher amylose content and increased gel consistency values for those with lower amylose content. Moreover, high temperature significantly increased the gelatinization temperature of all cultivars. Pasting profiles and X-ray diffraction pattern of rice were also affected by temperature. The results suggest that high temperature during grain filling change the component and crystalline structure of starch and result in deterioration of eating and cooking quality for early-season indica rice.

Flowering, Pod Set and Reproductive Success in Soya Bean

Abstract: Much of the variation in yield of soya bean [Glycine max (L.) Merrill] and other grain crops is associated with changes in the number of pods and seeds per unit area. Photosynthesis and seed characteristics are the primary determinants of pod and seed number, but recent research suggests that the temporal distribution of flower production may also play an important role. Soya bean has a long flowering period (up to 40 days or more), but most of the flowers are produced in a much shorter time. The length of the period varies among cultivars, growth habits (indeterminate and determinate) and environments. The reproductive success of flowers produced early in the period is usually greater than those produced later. Little is known, however, of the regulation of the temporal distribution of flower production or its potential role in determining pod and seed number at maturity. Research is needed to determine first, if the temporal distribution can be manipulated to increase pod and seed set and secondly, if such increases would result in higher yields.

Nitrogen Accumulation and Translocation for Winter Wheat under Different Irrigation Regimes

Abstract: The translocation of pre-anthesis nitrogen to the grain is an important source for winter wheat. The relation between the nitrogen translocation and irrigation regime was studied in the field under a rain-proof trough shelter. Nitrogen (N) translocation amount, N translocation efficiency decreased with a decline in irrigation amount or by excessive irrigation. Compared with different organs, the leaf and stem had higher N translocation amounts, and contributions to grain for both cultivars - Jinan 17 and Lumai 21, indicating that stem also is a major N source for grain development. The contribution of pre-anthesis total above ground N to grain N ranged from 57 to 76 %, indicating the importance of pre-anthesis storage of N for achieving high grain N concentrations. Grain nitrogen and yield (kg ha -1 ) were positively and significantly correlated with the N translocation amounts and contributions, respectively, suggesting that the sink strength may be involved in the translocation of N from a vegetative organ to the grain. N harvest index (NHI) was significantly correlated with N translocation efficiency, suggesting that the latter is a prerequisite for increasing grain N and improving grain quality. The experiment showed that N translocation status is enhanced by better irrigation practices, but limited by severely deficient or excessive irrigation.

Slow Export of Photoassimilate from Stay‐green Leaves during Late Grain‐Filling Stage in Hybrid Winter Wheat (Triticum aestivum L.)

Abstract: Hybrid winter wheat (cv. XN901) shows a strong hybrid vigor in terms of yield potential and its leaves and stems stay green when its kernels reach maturity. Much of its pre-stored carbon reserve is left unused in its stems and leaves. In this study, photosynthesis and translocation of carbon assimilates of the hybrid wheat were investigated at its late grain-filling stage. Feeding labelled 14 CO 2 to flag leaves of XN901 showed that its export to grains was much slower than that of an ordinary cultivar (Shaan 229) that is currently used in production. Within 24 h of labelling, Shaan 229 and XN901 exported 59 % and 40 %, respectively, of the 14 C from their flag leaves. At the sink side, 52.1 % of the fed 14 C in Shaan 229 was exported to its grains within the first 24 h while XN901 deposited only 15.8 % of the fed 14 C in the grains at the same period. Photosynthetic rates and chlorophyll contents in the flag leaves declined much more slowly in XN901 than in Shaan 229 during the late grain-filling stage. Hybrid wheat XN901 also had a longer grain-filling period (6 days longer), higher grain yield (15 % more), but lower harvest index (19 % less) than Shaan 229. Its grain-filling rate was lower but declined more slowly at the late grain-filling stage than that of Shaan 229. Results indicate that the strong hybrid vigour of XN901 leads to an unfavourably delayed senescence which results in the much unused carbon reserve in its straws. Raising harvest index should be the key aim to materialize its yield potential.

Analysis of Soil Fertility and Management Effects on Yields of Wheat and Corn in the Rolling Pampa of Argentina

Abstract: The Rolling Pampa is the most productive region of the Argentine Humid Pampa comprising around 10 Mha Wheat (Triticum aestivum L), corn (Zea mays L), and soya bean [Glycine max (L) Merr] are the main grain crops produced To develop sound cropping strategies, a better understanding of the impact of soil fertility and management on crops is needed The objective of this study was to develop models for estimating the effects of growing season precipitation, soil fertility and management on wheat and corn yields Data from 347 wheat and 323 corn field experiments and production fields over six growing seasons were used Soil, management and weather characteristics were determined and yields were then evaluated Data were analysed using linear and quadratic models and a quadratic polynomial surface model Soil fertility, management and rainfall and interactions were analysed Growing season precipitation correlated with wheat (R 2 = 042) and corn (R 2 = 025) yield Maximum wheat yield was achieved with 350-400 mm rainfall and corn yield reached a plateau around 700 mm Soil fertility accounted for 33 % of wheat yield variability and 5 % of corn yield variability Management accounted for 48 and 9 % respectively Whole polynomial models integrating rainfall, fertilizer N and P rates, soil N and P, previous crop and tillage system accounted for 67 % of wheat yield variability and 51 % of corn yield variability Soil organic matter was not included in the models but an indirect effect on yield was detected as organic matter correlated with initial soil N levels for both crops Soya bean as a previous crop had a positive effect on wheat and corn yields Wheat was insensitive to tillage system but corn yield was higher under no till N and P fertilization had a two- to three-fold greater impact on yield than soil nutrient levels As this region is considered to be of high soil fertility and has a history of very low fertilizer consumption, adequate use of N and P fertilization will be essential to maintaining high wheat and corn yields

Deferred Seeding of Blackgram (Phaseolus mungo L.) in Rice (Oryza sativa L.) Field on Yield Advantages and Smothering of Weeds

Abstract: Field experiments were conducted at Agricultural Experimental Farm, Giridih, Jharkhand, during the kharif (wet) seasons of consecutive four years (1998-2001) to study the effect of staggered seeding of blackgram (Phaseolus mungo L.) in rice field as a cereal-legume intercropping system and to minimize the degree of competition between the crop species to avoid yield damage, and at the same time to create a high level of competition by the intercrops to suppress the weeds. Intercropping systems were assessed on the basis of land equivalent ratio, relative crowding coefficient, aggressivity, actual yield loss, monetary advantage, etc. Intercropping reduced the yield of component crops when compared with respective pure stands. However, deferred seeding of blackgram in rice (30 cm) after one weeding was most remunerative system and registered maximum rice-equivalent yield (2711 kg ha -1 ). Rice-black-gram (20 cm) intercropping system was very effective for weed smothering among unweeded intercropping treatments. In conclusion, deferred seeding of blackgram in rice field (30 cm) with one weeding may be recommended for better yield, weed suppression and better economics in the eastern plateau region of India.

Effect of Water Stress on the Yield of Cowpea (Vigna unguiculata L. Walp.) Genotypes in the Delmarva Region of the United States

Abstract: Drought is an important yield-reducing factor for corn and soya bean which are the two major crops in the Delaware, Maryland and Virginia (Delmarva) region of the United States. Cowpea (Vigna unguiculata L. Walp.) is primarily grown in drier regions of the world where it is one of the most drought-resistant food legumes. Field experiments were conducted in which 10 genetically diverse cowpea genotypes were evaluated for adaptability to the Delmarva area. The cowpea genotypes were grown in rain-out shelters under non-water-stressed and water-stressed conditions. The results showed that under non-water-stressed conditions cowpea genotypes California Blackeye 5, Champion and Mississippi Silver gave higher seed yields, while genotypes White Acre, Six Week Browneye and Texas Cream 8 provided lower seed yields. Genotypes California Blackeye 5 and Champion gave comparatively better seed yields under water-stressed conditions. California Blackeye 5 was the highest seed-yielding genotype under both water-stressed and non-water-stressed conditions. The highest biological yield under non-water-stressed conditions was given by genotypes Two Crop Brown, White Acre and Elite, whereas under the water-stressed condition genotypes Texas Cream 8, California Blackeye 5, and Mississippi Silver gave higher biological yield. Genotypes Quickpick Pinkeye and Elite were identified as early maturing genotypes. The harvest index (HI) varied significantly among genotypes, with Texas Cream 8 having the lowest HI. Cowpea genotypes which gave higher seed yield under water-stressed conditions could play an important role in sustaining crop production in the Delmarva region.

Increased Yield and Revenue with a Seedling Transplanting System for Hybrid Seed Production in Bt Cotton

Abstract: Rapid adoption of Bacillus thuringiensis (Bt) transgenic hybrid cotton (Gossypium hirsutum L.) in China is greatly attributed to high-quality hybrid seed produced in northern Shandong cotton production area; however, seed yield has reached a plateau in this area in recent years. Shifting the growing season earlier in the year by planting earlier in a greenhouse-like hut and transplanting the raised seedlings to the open fields later may allow the crop to produce more seeds. Four-year consecutive experiments conducted in Huimin County (northern Shandong, China) showed that early-season chilling stress on seedlings was avoided in such a hut, and that the blooming period was extended by about 1 week longer and the peak blooming occurred 5 days earlier in the year in the transplanting system than in the normal planting system. The number of early-season blooms and the number of bolls retained per unit area in transplanting system were significantly higher than those in normal planting system, but there were no significant differences in boll size and lint percentage between the two planting systems. Seed yield and quality parameters were significantly improved in the transplanting system through the increased number of bolls per square metre and earlier blooming respectively. As a result of improvement in seed yield and quality, the net revenue for seed producers with the transplanting system was increased by 20.8 and 22.5 % in 2002 and 2003, respectively, compared with the corresponding net revenue in the normal planting system. Seedling transplanting is a potent way to enhance hybrid seed production in Bt transgenic cotton.

Can Leaf Chlorophyll Measures at Differing Growth Stages be used as an Indicator of Winter Wheat and Spring Barley Nitrogen Requirements in Eastern Canada

Abstract: Plant need-based N management approaches may increase the efficiency of N fertilizer application in wheat (Triticum aestivum L) and barley (Hordeum vulgare L) The leaf chlorophyll concentration estimated through the SPAD-502 meter gives a relative assessment of N status in crop Field trials were conducted near St John's, Newfoundland, between 1997 and 2000 to describe the relationship between winter wheat and spring barley grain yield, protein content, protein yield and SPAD measurements, as affected by differential stage of crop growth, seeding rate and topdress N fertilizer Grain yield, protein content, and protein yield of winter wheat and spring barley exhibited linear responses to increasing N topdress application rate SPAD-502 values were moderately to highly positively correlated with grain yield, protein content, and protein yield as a result of increasing topdress N fertilization, and moderately negatively correlated as a result of increasing seeding rate It may be difficult to make an N-application rate recommendation based on SPAD measurements, as a critical SPAD value may vary among years, locations, cultivars and soil characters

A comparison of methods used to determine biomass on naturalized swards

Abstract: An experiment was conducted in 2000 to compare simple visual estimate, sward height and rising plate meter (RPM) methods for determining forage biomass in mixed-species, naturalized, rotationally grazed dairy and beef pastures. Measurements were taken pre- and post-grazing on 10 sampling dates at the dairy pasture, and post-grazing at 13 sampling dates at the beef pasture. For each sampling date, the effectiveness of each method for estimating the actual biomass from a quadrat was evaluated using regression analysis. The results for the visual estimate method were not consistent, with non-linear relationships occurring early and late in the season. While the meter stick was most effective in the dairy pasture, the RPM was most effective in the beef pasture. Species composition and structural characteristics of the stand were important factors affecting accuracy of biomass estimation. Equations developed for each method and site using data from all dates had low R 2 -adjusted values, and were unreliable predictors of biomass. The results from individual sites and dates were extremely variable, with no single method effective in all circumstances. To estimate forage biomass in mixed-species, naturalized pastures, standard quadrat harvesting remains the most reliable method, provided that enough quadrats are clipped to adequately represent a given area.

Water use efficiency, carbon isotope discrimination and biomass production of two sugar beet varieties under well-watered and dry conditions

Abstract: Two sugar beet (Beta vulgaris sp.) varieties, which were supposed to differ in drought tolerance, were exposed to drought stress in a growth chamber and a container experiment in field. The aim was to test for (i) differences between the varieties in water use efficiency (WUE), biomass production and distribution and (ii) the relationship between WUE and carbon isotope discrimination (A). and between biomass production and A. Significant differences in WUE were detected between plants of well-watered and drought treatments in both experiments, but not between the varieties. Production losses due to drought were large for both varieties in both experiments. Losses in the growth chamber were up to 50 % of plant dry weight and the corresponding value in the field was 24 %, when plants were given 60 and 30 %, respectively, of the full-watered treatments. Significant negative correlations between WUE and A were found, but not between biomass production and A, when both varieties were included. Negative correlations between WUE and A were also found for each variety separately. The results suggest that A estimates from leaf tissue of sugar beet may provide a useful tool for genetic selection of drought-tolerant sugar beet varieties.

Putrescine Increases Floral Retention, Pod Set and Seed Yield in Cold Stressed Chickpea

Abstract: Chickpea (Cicer arietinum L.) is sensitive to cold stress (< 8 °C) at its reproductive phase that results in flower abortion, poor pod set and thus reduced yield. Early maturing genotypes are especially more sensitive. In this crop, the metabolic causes underlying cold injury that are imperative to induce cold tolerance are not known. In the present study, the endogenous levels of putrescine (diamine), spermidine (triamine) and spermine (tetramine) were examined in early maturing chickpea genotype ICCV 96029, subjected to chilling temperatures of field (12-15/ 4-6 °C; average maximum and minimum temperature respectively), at flowering or early podding stage. These were compared with controls growing in warmer conditions (28/12 °C) of the glasshouse. The polyamine levels increased six to nine times because of stress. Relatively, putrescine (PUT) elevation was the highest but short-lived and its decrease appeared to match with the onset of flower and pod abscission in stressed plants. Compared with controls, chilling injury, observed as electrolyte leakage (EL), increased by 60 % while cellular respiration declined by 68 % in stressed plants. Exogenous application of 10 mM PUT to stressed plants reduced the EL by 29 % and elevated the cellular respiration by 40 %. PUT application at flowering stage resulted in increase of 30, 31, 23 and 25 % in floral retention, pod set. pod retention and fertile pods respectively. At the early podding stage, PUT treatment increased the seed yield per plant, seed number per 100 pods and individual seed weight by 50, 17 and 19 % respectively. The number of single-seeded pods per plant increased from 4.4 in stressed plants to 12.2 in PUT-treated plants while the number of double-seeded pods reduced from 6.2 to 4.3. The number of infertile pods declined from 8.2 in stressed plants to 3.1 in PUT-treated plants.

Seasonal development of genotypic differences in sugar beet (Beta vulgaris L.) and their interaction with water supply.

Abstract: Depending on genotype, sugar beet can differ considerably in yield and quality characteristics. These are additionally modified by environmental conditions with drought stress recently gaining in importance, restricting growth and altering the chemical composition of the beet. The occurrence and development of these genotypic differences during the vegetation period and their possible interaction with environmental conditions were investigated. In 2002 and 2003, four sugar beet genotypes differing in yield and quality and putative different with regard to drought tolerance were tested in field trials, partly under irrigated conditions, in a total of 10 environments with consecutive harvests starting in early summer. In 2 years of stress and non-stress conditions they exhibited significant differences for taproot and leaf dry matter and the concentration of sucrose, K, Na and α-amino nitrogen in the taproot. These differences existed already in mid-June and virtually did not change any more from this time on. Accordingly, interactions between genotype and harvest date did not occur. For sugar beet, genotype by environment interactions generally do not exist. Water supply, as an important single determinant of the effect of the environment, was studied separately analysing data from selected locations. Under drought conditions, withholding irrigation reduced leaf and taproot growth and root-to-leaf ratio, decreased the percentage of sucrose in dry matter and resulted in an accumulation of α-amino N. Interactions between genotype and water supply did not occur for any of the parameters under study. A genotype-specific high α-amino N content, which might be of advantage for osmoregulation, did not improve the adaptation to drought. Differences in leaf maintenance or taproot-to-leaf ratio during drought also did not affect yield response. Due to the lack of interaction between genotype and harvest date as well as between genotype and irrigation it is concluded that harvest date or climatic factors of the growing region do not have to be taken into consideration when choosing a variety.

Water Stress-induced Injury to Reproductive Phase in Chickpea: Evaluation of Stress Sensitivity in Wild and Cultivated Species in Relation to Abscisic Acid and Polyamines

Abstract: Chickpea (Cicer arietinum L.) is more sensitive to water stress during its reproductive growth and consequently experiences substantial yield loss. Wild species being relatively tolerant to abiotic stresses offer a potential gene source for incorporation of drought tolerance in cultivated species. In the present study, the differential stress sensitivity of wild (Cicer reticulatum Ladiz.) and cultivated species (C. arietinum) was evaluated by subjecting the plants of both the species to water stress for 14 days during the reproductive phase and examined for stress injury, endogenous status of polyamines (PA) and abscisic acid (ABA). Comparatively, the cultivated species experienced higher stress injury (assessed as electrolyte leakage, 2,3,5-triphenyl tetra/olium chloride reduction ability, chlorophyll loss) as well as decreased leaf water potential (Φ w ; -2.48 MPa) than the wild species (-1.98 MPa). The stressed plants of cultivated species lost more number of flowers (62 %) and pods (65 %) when compared with the unstressed ones while those of wild species showed 30 % and 44 % loss, respectively. The number of infertile pods was significantly more in stressed plants of cultivated species than in those of wild species. The endogenous status of PA revealed that putrescine (PUT), spermidine (SPD) and spermine (SPM) levels accumulated to a higher extent in the cultivated species relative to the wild species until the eighth day of stress, and thereafter, the wild species had significantly higher levels of PA. In contrast, ABA levels increased to a higher extent in the wild species until the eighth day of stress and declined subsequently to a greater degree than the cultivated species. The injury to reproductive growth appeared to accentuate with reduction in leaf Φ w that was coupled with depletion of PA in both the species, especially in the cultivated one. Exogenous application of 10 mM PUT partially alleviated the damage to reproductive growth by increasing the leaf water status and chlorophyll content while decreasing the ABA content, which resulted in improvement of retention of flowers and pods, particularly in the cultivated species.

Influence of water stress on the chemical composition of seeds of two lupins (Lupinus albus and Lupinus mutabilis)

Abstract: We have performed chemical proximate analysis and determined the carbohydrate profile of mature seeds of Lupinus albus, cv. Rio Maior and Lupinus mutabilis. cv. Potosi plants, either well watered (ww) or subjected to a water-stress period (imposed from the 15th to 35th day after anthesis). Protein content from lupin seeds was 450 and 320 g kg -1 of seed on dry weight basis, for ww plants, respectively, of L. albus and L. muabilis. Water stress did not affect protein content. The oil content of ww plants was about 120 g kg -1 of seed dry weight for L. albus and 180 g kg -1 of seed dry weight for L. mutabilis. Water stress reduced those values of half. The sugar content was about 90 g kg -1 for L. albus and 50 g kg -1 of seed dry weight for L. mutabilis, in ww plants. Water stress led to an increase in sugar content to 200 and 130 g kg -1 of seed dry weight, respectively, for L. albus and L. mutabilis. The «-galactosides amounted to 70 % of the total sugars (raffinose being 30 % and stachyose, 40 %) and sucrose was about 20 % of the total sugars. Water stress increased total carbohydrates and increased the sucrose/α-galactoside ratio, although reducing raffinose content and increasing sucrose content.

Competition and Productivity in Mixture of Oats and Wheat

Abstract: The research assesses the productivity of mixture of oats (Avena saliva) and wheat (Triticum aestivum), and compares two different approaches used in plant competition studies: replacement (substitutive) designs and additive designs. The experiment was carried out on sandy loam soil at the Experimental Station of Agricultural University of Wroclaw (Poland). Oats and wheat were grown for grain as sole crops and in 1: 1 replacement mixtures at three rates of seeding: 150, 300 and 600 viable seeds m -2 . These designs allowed mixtures seeded at a rate of 300 and 600 seeds m -2 to be analysed according to either a replacement or an additive approach. In 1999, pure stand wheat and oats-wheat mixture yielded significantly more grain than oats grown alone but in 2000 there was no difference in yield. Wheat outcompeted oats in mixture but the relative competitive ability of the two species changed little with increasing seeding density. Relative yield total (RYT) for grain was significantly > 1.0 (RYT = 1.07) in 1999 for the lowest seeding density, showing partial complementarity in use of limiting resources by the species in mixture. Based on grain yields, the results obtained from substitutive and additive mixtures were similar with respect to the relative yields and relative competitive ability of the two species concerned.

Regional yield forecasts of malting barley (Hordeum vulgare L.) by NOAA-AVHRR remote sensing data and ancillary data

Abstract: Yield forecasts are of major interest to the malting and brewing industry in order to allow the most convenient organization of the respective policy of raw materials. As malting barley is predominantly cultivated in a limited set of growing regions because of its special requirements, yield predictions can be limited to these regions of interest. Within this investigation, malting barley yield forecasts (Hordeum vulgare L.) are performed for typical growing regions in southwestern Germany. Multitemporal remote sensing data on the one hand and ancillary data such as meteorological, phenological, pedological, agro statistical and administrative data on the other hand are used as input data for two versions of prediction models, which are both based on an empirical–statistical modelling approach. The basic version of the yield estimation model is conducted by means of linear correlation of remote sensing data [national oceanic and atmospheric administration-advanced very high resolution radiometer (NOAA-AUHRR) normalized difference vegetation index (NDVI) maximum value composites], CORINE land cover data and agro statistical data. In an extended version, meteorological data (temperature and evapotranspiration) and soil data are incorporated. Yield predictions are significantly influenced by the selected time span for NDVI integration. For NDVI time-integration across the grain-filling period, the mean deviation of reported and simulated yield is 7.0 and 6.4 %, respectively, for the basic and extended yield estimation model.

Comparison of Sugar Beet Cropping Systems with Dead and Living Mulch using a Glyphosate‐resistant Hybrid

Abstract: The aim of this study was to evaluate new options for sugar beet mulch systems, using a glyphosate-resistant hybrid. In four field trials - conducted in 2002 and 2003 at two sites in a major sugar beet-growing region in the central Germany - three different mulch systems (straw, non-winterhardy and winterhardy cover crop) and an alternative seedbed preparation method (rotary band tillage) have been tested in comparison with a control treatment (plough, no mulch, broadcast seedbed preparation) representing the common German practice. In all systems, a set of eight different weed control programmes, including two reference treatments, one with selective conventional herbicides and five exclusively using glyphosate, has been evaluated for efficacy. It could be shown that the integration of winterhardy cover crops into sugar beet mulch systems reduced the risk of nitrogen loss by leaching. The changes in the nitrogen dynamics neither influence the yield nor the technical quality of the sugar beet. The field emergence of sugar beet decreased while using a winterhardy cover crop, but was not altered by the seedbed preparation method. Compared with the conventional broadcast seedbed preparation, the rotary band tillage did reduce the weed density. The lowest weed density was observed in the straw mulch system. It was not possible to control the remaining plants of the winterhardy cover crops completely with selective herbicides. If glyphosate was used until the four-leaf stage of the sugar beet, a regulation of the winterhardy cover crop was achievable. With glyphosate it was also feasible to control older weeds together with the newly emerging ones with post-emergence applications only. For most of the mulch systems tested, the sugar beet was very sensitive to weed competition between the four- and 10-leaf stage. If the weeds within the sugar beet rows were controlled during this sensitive period with an early glyphosate band application, the remaining weeds between the rows could be left uncontrolled until the 10-leaf stage of the sugar beet without any yield loss. Only in the combination of winterhardy cover crop x rotary band seedbed preparation, the weeds and cover crop had to be controlled directly after emergence of the sugar beet.

Effect of N Fertilization Rate on Sugar Yield and Non-Sugar Impurities of Sugar Beets (Beta vulgaris) Grown Under Mediterranean Conditions

Abstract: For three successive growing seasons (1999-2001), a completely randomized block design experiment was established at the surrounding area of each of four sugar beet processing plants of Hellenic Sugar Industry SA, Greece (a total of 12 experiments) Nitrogen was applied at five rates (0, 60, 120, 180 and 240 kg N ha -1 ) and six replications per rate Nitrogen fertilization had site-specific effects on quantitative (fresh root and sugar yields) and qualitative (sucrose content, K, Na, α-amino N) traits When data were combined over years and sites, fresh root and sugar yields were maximized at high N rates (33075 and 295 kg N ha -1 respectively), as derived from quadratic functions fitted to data In three trials, increased N rates had negative effects on root and sugar yield These sites were characterized by high yield in control plots, light soil texture (sand > 50 %) and low CEC values When data were converted into relative values (the ratio of the trait values to the control mean of each experiment), root and sugar yield was found to be maximized at higher N rates (350 and 316 kg N ha -1 , respectively) Sucrose content was strongly and linearly reduced by the increased N rates when data were combined but a significant reduction with increasing N rates was found in only two sites Non-sugar impurities (K, Na, α-amino N) were positively related to the increased N rates when data were combined Sodium and α-amino N showed to be most affected by N fertilization as positive relationships were found in six and eight of 12 locations, respectively Increased N supply resulted in higher soil NO 3 -N concentrations (0-90 cm depth) at harvest which were related with amino N contents in sugar beet roots (in 1999 and 2001)

Changes in N Composition of Sugar Beet Varieties in Response to Increasing N Supply

Abstract: The soluble nitrogen (N) components in sugar beet seriously impair sugar recovery. The only N component determined routinely in the sugar factory is amino N (the sum of amino acids in the beet), which is assumed to reflect all the other N components. Amino N is affected by N supply and variety, but only little is known about the other N components such as total soluble N, betaine and nitrate. This study aimed at investigating the effect of N supply on the N composition of sugar beet varieties with special emphasis on N supply by variety interactions. In 2001 and 2002, field trials with four varieties and four N treatments were carried out at six sites in Germany. Storage root yield and the concentrations of sucrose, sodium, amino N, betaine, nitrate and total soluble N in the beet were determined. With increasing N supply, the concentration of amino N increased considerably and that of nitrate slightly, whereas that of betaine remained rather constant. Thus, the N composition of sugar beet changed with increasing N supply and the percentage of amino N of total soluble N increased. Although amino N has the closest correlation with total soluble N, for quality assessment it may overestimate the effect of N supply on other N components. Varieties clearly differed in root yield and quality as well as in all N components. The variety with the lowest amino N had the highest betaine concentration. However, as related to the concentration of total soluble N in the beet, for all varieties amino N as well as betaine showed the same response pattern. This indicates that the N composition of sugar beet is determined by the level of total soluble N, irrespective of variety or N supply. All varieties required the same N supply for obtaining maximum yield or quality. N supply did not affect the ranking of the varieties for all parameters studied, consequently it need not be considered for variety choice.

Barley Autotoxicity as Influenced by Varietal and Seasonal Variation

Abstract: Barley (Hordeum vulgare L.) is widely cultivated in the semi-arid region of Tunisia for grain production and grazing, which often occurs during the same season. We previously demonstrated autotoxic effects of barley among varieties. The present study was conducted to test the effects of barley variety and seasonal variation on the expression of autotoxicity by barley. Four barley varieties were grown in a field experiment over three growing seasons (1999–2000, 2000–01, 2001–02). In the laboratory, germination and seedling growth bioassays were used to assess autotoxicity potential of field-harvested barley. Barley autotoxicity was fully expressed based on inhibition of radicle growth detected in seedling bioassays. Stems were often the most allelopathic plant component. Allelopathic activity of the barley varieties differed across growing seasons suggesting the influence of a seasonal effect due to the extent of water deficit during the dry season and monthly rainfall variability. The results suggest that when planning to integrate barley within cropping sequences, barley producers should carefully select appropriate barley varieties to minimize autotoxicity, which can be more severe under drought conditions.

Irrigation and Nutrient Effects on Growth and Water–Yield Relationship of Wheat (Triticum aestivum L.) in Central India

Abstract: Increasing production of wheat from a limited water supply can result from efficient irrigation and nutrient management. A 3-year field experiment was conducted at the Indian Institute of Soil Science, Bhopal, to study the growth, yield, seasonal evapotranspiration (ET) and water use efficiency (WUE), and the water-yield relationship of wheat in a soybean-wheat cropping system on vertisols. Three levels of irrigation, viz. I 0 , no post-sowing irrigation; I 1 , two irrigations [crown root initiation (CRI) and flowering stage]; and I 2 , three irrigations (CRI, maximum tillering and flowering stage) and three nutrient management treatments, viz. F 0 , control (without fertilizer manure); F 1 , 100 % NPK (100-21.5-24.9 kg ha -1 ); and F 2 , 100 % NPK + farmyard manure (FYM-10 t ha -1 ) were tested in a split-plot design with three replication. It has been established (through ANOVA) that the year effect was rather negligible and the interaction effects of irrigation and nutrient management on the growth parameters, ET. yield components, yield and WUE were significant. Plant height, progressive leaf area index, dry matter accumulation and crop growth rate were higher in I 2 F 2 , and I 2 F 1 and I 1 F 2 were statistically at par. The seasonal ET increased significantly with the increase in water supply in every nutrient treatment and it was highest in I 2 F 2 and lowest in I 0 F 0 . The highest grain yield was obtained in I 2 F 2 ; and a similar yield was recorded in I 3 F 1 and I 2 F 2 . This shows a strong interaction effect between irrigation and nutrients. Yield components, viz. number of ears m -2 , number of grains ear -1 and 1000-grain weight were significant. The higher number of ears m -2 containing greater number of grains with relatively heavier weights appeared to have contributed to the higher yield in I 1 F 2 , I 2 F 1 and I 2 F 2 . The highest WUE obtained in I 0 F 2 did not correspond to the highest yield and maximum ET, but a WUE of 10.43 kg ha -1 mm -1 in the I 2 F 2 combination corresponded with the highest yield and the seasonal ET requirement was 391.8. which was 137 % greater than the water use at maximum WUE. The ET-grain yield relationship was linear, with a lowest regression slope (i.e. marginal WUE) and elasticity of water production (E wp ) in F 0 and a considerably higher slope and E wp in F 1 and F 2 . As the E wp is positive and close to one in 100 % NPK treatment, the scope of improving WUE and yield with only inorganic fertilizer is very little. and relatively greater scope exists in the integrated management of organic manure and inorganic fertilizer. The results suggest that integrated nutrient management (100 % NPK + FYM) in conjunction with three irrigations maximized yield of wheat with concomitant improvement in ET and WUE under limited water availability.