• Authors:
    • Joshi, A. K.
    • Dixon, J.
    • Waddington, S. R.
    • Li, X.Y.
    • Vicente, M. C. de
  • Source: Food Security
  • Volume: 3
  • Issue: 1
  • Year: 2011
  • Summary: Variation in water availability is a major source of risk for agricultural productivity and food security in South Asia. Three hundred and thirty expert informants were surveyed during 2008-09 to determine the relative importance of drought and water-related constraints compared with other constraints limiting the production of four major food crops (wheat, rice, sorghum, chickpea) in five broad-based South Asian farming systems. Respondents considered drought an important constraint to crop yield in those farming systems that are predominantly rainfed, but associated it with low yield losses (well below 10% of all reported losses) for crops in farming systems with well-developed irrigation. In these systems, other water-related constraints (including difficult access to sufficient irrigation water, the high cost of irrigation, poor water management, waterlogging and flooding of low-lying fields) were more important. While confirming the importance of drought and water constraints for major food crops and farming systems in South Asia, this study also indicated they may contribute to no more than 20-30% of current yield gaps. Other types of constraint, particularly soil infertility and the poor management of fertilizer and weeds for the cereals, and pests and diseases for chickpea, contributed most yield losses in the systems. Respondents proposed a wide range of interventions to address these constraints. Continued investments in crop-based genetic solutions to alleviate drought may be justified for food crops grown in those South Asian farming systems that are predominantly rainfed. However, to provide the substantial production, sustainability and food security benefits that the region will need in coming decades, the study proposed that these be complemented by other water interventions, and by improvements to soil fertility for the cereals and plant protection with chickpea.
  • Authors:
    • Knies, A. E.
    • Streck, N. A.
    • Radons, S. Z.
    • Martins, J. D.
    • Carlesso, R.
  • Source: Ciência Rural
  • Volume: 41
  • Issue: 6
  • Year: 2011
  • Summary: The plastochron, which is the time interval between the appearance of two successive nodes and the final node number (FNN) are important variables of the vegetative development in soybean. The objective of this study was to determine the plastochron and the FNN of soybean ( Glycine max (L.) Merrill) cultivars sown in different dates under irrigated conditions in a subtropical location. A field experiment was carried out in Santa Maria, RS, Brazil during 2005/2006 growing season, with three sowing dates (09/11/2005, 09/12/2005 and 28/01/2006). It was used 15 soybean cultivars recommended for the Central and North Argentina, and South and Southeast Brazil. The variables measured were the number of nodes (NN) and the (FNN) on the main stem. The plastochron was estimated by the inverse of the slope of the linear regression between NN and the thermal time (base temperature=10degreesC) accumulated since plant emergence. The late sowing resulted in lower plastochron and FNN, probably because of the lower photoperiod under which the plants were submitted in the node phase, a typical response of short day plants.
  • Authors:
    • Mapurazi, S.
    • Mapfaire, L.
    • Masona, C.
    • Makanda, R.
  • Source: Journal of Sustainable Development
  • Volume: 4
  • Issue: 6
  • Year: 2011
  • Summary: A study was carried out in March 2010 at Firle Sewage Works in Harare, Zimbabwe to determine the effects of long term wastewater irrigation on the concentrations of heavy metals (Zn, Cu, Mn, Cd, Pb, Ni, Fe and Cr) in soil, and their subsequent accumulation in maize plants. The study revealed that long term wastewater use for irrigation results in heavy metal accumulation in soils and bioaccumulation in plants beyond maximum permissible limits (MPL) for both humans and livestock consumption. Lead had highest transfer factor and iron had the least transfer factor. The soil pH was found to be less acidic (pH=5.6) in soils exposed to waste water than in soils where no wastewater had been applied (pH=5). As a recommendation there is need for phytoextraction of heavy metals by intercropping maize plants with local agro forestry shrubs to reduce amount of heavy metals in the soil.
  • Authors:
    • da Silva Matos, E.
    • de Lima, P. C.
    • Souto, R. L.
    • Cardoso, . M.
    • de Sá Mendonça, E.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 42
  • Issue: 5
  • Year: 2011
  • Summary: We investigated the chemical and biochemical composition, residue decomposition, and mineralization rate of leguminous (Cajanus cajan, Crotalaria spectabilis, and Lablab purpureus) and spontaneous vegetation in two experimental coffee systems in southeast Brazil. The nitrogen (N) content of the shoot biomass varied from 19.3 to 45.7 g kg-1, and phosphorus (P) content ranged from 1.6 to 3.8 g kg-1. C. cajan contained the greatest values of N and P, whereas spontaneous plants had the lowest values. In both areas, spontaneous vegetation had the greatest values of carbon (C) / P, C/N, polyphenol/N, and (lignin + polyphenol) / N ratios. Decomposition rate increased in the order C. cajan C. spectabilis L. purpureus spontaneous vegetation. There was no correlation between the chemical and biochemical composition and the decomposition rate under field conditions. However, the cumulative carbon dioxide (C-CO2) produced by the residues under laboratory conditions was correlated positively with initial contents of N and P and negatively with polyphenol/N and (lignin + polyphenol) / N ratio (P 0.01) throughout the sampling period. The low nutrient content, especially for N, of spontaneous vegetation is compensated by the greater decomposition rate under natural conditions than that of introduced species. Management of the spontaneous plants is therefore an attractive alternative for sustainable agriculture.
  • Authors:
    • Ralish, R.
    • de Lima, G. P.
    • Rosa, D. M.
    • Pereira Nóbrega, L. H.
    • Mauli, M. M.
  • Source: Brazilian Archives of Biology and Technology
  • Volume: 54
  • Issue: 4
  • Year: 2011
  • Summary: This study analyzed possible interferences associated to the amount of crop residues produced by the black oats and the consortium of black oats, common vetch and forage turnip on weeds incidence and soil seed bank. It was a field trial with seven treatments and five replications. The cover crop was sown at throwing, cut at 100 days and residues were put on each respective plot, using a proportion of normal amount of produced straw, either its half and double. The heaviest weights were obtained from cover crop consortium and their application decreased weeds incidence in such area. The seeds bank and other analyzed parameters did not show statistical differences. According to these results, it was concluded that winter cover crop could be used in crops rotation with soybean.
  • Authors:
    • McSorley, R.
  • Source: Nematropica
  • Volume: 41
  • Issue: 2
  • Year: 2011
  • Summary: Studies that utilized rotation crops for management of root-knot nematodes in the southeastern United States were examined to evaluate the overall performance of rotation crops. In general, nematode-susceptible crops that followed effective rotation crops produced yields and supported nematode numbers similar to those obtained on crops treated with most standard nematicides. Fumigation with methyl bromide was an exception, and resulted in low nematode numbers up to the end of the susceptible target crop, whereas nematode numbers recovered following rotation crops. Performance of rotation crops was similar to clean fallow in most studies, and there was little evidence that rotation crops could suppress nematode numbers below levels obtained after clean fallow. Large reductions in nematode numbers often were achieved following rotation crops. In sites with relatively low initial population levels before rotation crops were used, effective rotation crops sometimes maintained relatively low nematode numbers through the following susceptible target crop, and nematode recovery was not observed until the second year of the rotation sequences. Where practical, very long rotations such as bahiagrass pastures were often effective in preventing increase in nematode numbers on subsequent susceptible crops. Rehabilitation of heavily infested sites is difficult, could require several years of rotation crops, and the benefit gained may last only through one susceptible crop.
  • Authors:
    • Lopez, C.
    • Suarez, P.
    • Gonzalez Anta, G.
    • Luca, M. J. de
    • Melchiorre, M.
    • Lascano, R.
    • Racca, R. W.
  • Source: Biology and Fertility of Soils
  • Volume: 47
  • Issue: 1
  • Year: 2011
  • Summary: Bradyrhizobium strains were isolated from nodules obtained from field-grown soybean plants sampled in 12 soybean production locations in Argentina. These fields had been annually cropped with soybean and did not show decreases in yields even though they had been neither N-fertilized nor inoculated for at least the last 5 years. We hypothesized that the isolated strains maintained high competitiveness and efficiency in fixing adequate N 2 levels. A set of strains that showed the highest nodular occupancy in each sampling location were assayed for symbiotic performance under greenhouse and field conditions and comparatively evaluated with Bradyrhizobium japonicum E109, the strain officially recommended for inoculant formulation in Argentina. An inoculant pool, formed by four strains obtained from nodules collected from Canada Rica, developed higher nodular biomass than B. japonicum E 109 in assays carried out in greenhouses under well irrigated conditions. Additionally, neither nodule production nor specific nitrogenase activity decreased with respect to B. japonicum E 109 when plants were drought stressed during 7 days from sowing. The mean yields obtained under field conditions and plotted against the principal component one (CP1) obtained with an additive main effect and multiplicative interaction (AMMI) model showed that the inoculant pool from Canada Rica had higher contribution to yield than strain E 109, although with lower environmental stability. The inoculant pool from Canada Rica could be considered an improved inoculant and be used for preliminary assays, to formulate inoculants in Argentina.
  • Authors:
    • Canaday, C. H.
    • Little, C. R.
    • Chen, P.
    • Rupe, . B.
    • Wrather, A. J.
    • Shannon, G. J.
    • Bond, J. P.
    • Arelli, P. A.
    • Mengistu, A.
    • Newman, M. A.
    • Pantalone, V. R.
  • Source: Plant Health Progress
  • Issue: September
  • Year: 2011
  • Summary: Charcoal rot, caused by Macrophomina phaseolina, significantly reduces yield in soybean more than most other diseases in the midsouthern United States. There are no commercial genotypes marketed as resistant to charcoal rot. Reactions of 27 maturity group (MG) III, 29 Early MG IV, 34 Late MG IV, and 59 MG V genotypes were evaluated for M. phaseolina between 2006 and 2008 in a non-irrigated, no-till field that had been artificially infested for three years. There was significant variation in root colonization among genotypes and years, indicating the value of screening genotypes over multiple years. Based on CFUI there was no genotype that was consistently immune to charcoal rot each year. However, there were a total of six genotypes (one genotype in MG III, one in Late MG IV, and four in MG V) that were identified as moderately resistant. Some of the commercial and public genotypes were resistant to M. phaseolina at levels equal to or greater than the standard DT97-4290, a moderately resistant cultivar. The genotypes identified as having moderate resistance across the three years could be useful as sources for developing resistant soybean genotypes.
  • Authors:
    • Mengistu, A.
    • Bellaloui, N.
    • Ray, J. D.
    • Smith, J. R.
  • Source: Plant Disease
  • Volume: 95
  • Issue: 9
  • Year: 2011
  • Summary: The seasonal progress of charcoal rot (caused by Macrophomina phaseolina) was measured over two growing seasons in four separate experiments: irrigated infested, irrigated non-infested, non-irrigated infested, and non-irrigated noninfested. Disease was assessed at V5, R1, R3, R5, R6, and R7 growth stages based on colony forming units (CFU) of M. phaseolina recovered from the lower stem and root tissues and the area under the disease progress curve (AUDPC). The population density of M. phaseolina increased slowly from the V5 to R6 growth stages and then rapidly from the R6 to R7 growth stages for all genotypes in all four experiments. Yield loss due to charcoal rot ranged from 6 to 33% in irrigated environments. The extent of yield loss was affected by severity of charcoal rot, which in turn was affected by year. Yield loss due to charcoal rot was consistently measured in all paired comparisons in irrigated environments, suggesting that charcoal rot can be an important disease in irrigated environments. Disease severity based on CFU accounted for more yield loss variation (42%) than did the AUDPC (36%) when used to assess disease. Growth stage R7 was found to be the optimum stage for assessing disease using CFU. In addition, screening soybean genotypes under irrigation environment may have utility in breeding programs where there is a need for evaluating soybean genotypes for both disease resistance and yield.
  • Authors:
    • Muthukrishnan, P.
    • Fanish, S. A.
  • Source: Madras Agricultural Journal
  • Volume: 98
  • Issue: 7/9
  • Year: 2011
  • Summary: Field experiment was conducted at farmer's field at Palani taluk of Dindigul district in Tamil Nadu during kharif 2008 with the objective of evaluating the drip fertigation on water saving and Water Use Efficiency (WUE) in intensive maize based intercropping system. The experiment was laid out in strip plot design with three replications. The experiment consisted of 9 fertigation levels in main plot and 4 intercrops in sub plot. Among the different fertigation levels, higher maize grain yield of 7300 kg ha-1 was recorded under drip fertigation of 100 per cent RDF with 50 per cent P and K through water soluble fertilizer (WSF) followed by application of 150 per cent RDF through drip (7050 kg ha -1). The yield increase over drip irrigation with soil application of fertilizer was 39 per cent. Drip irrigation helped to save water up to 43.65 per cent compared to surface irrigation method. Among the different intercrops tested, higher WUE of 21.0 kg ha -1 mm -1 was observed under maize+vegetable coriander intercropping system.