• Authors:
    • Tiefenthaler, A. E.
    • Goldman, I. L.
    • Tracy, W. F.
    • Schaber, M. A.
  • Source: Plant Breeding Reviews: Long-term Selection: Crops, Animals, and Bacteria
  • Volume: 24
  • Issue: 2
  • Year: 2004
  • Summary: This review covers some long-term trends of the Illinois Long-term Selection Experiment and offers some perspectives on the impact of long-term selection on productivity of crops (lucerne, oats, rye, barley, winter wheat, spring wheat, soyabeans, groundnuts, sweetcorn, sweet potato, cotton, green peas, sorghum, maize, rice and potato) in the USA. Discussions on the crop productivity, variability of crop productivity and causes of increased productivity, are provided.
  • Authors:
    • Varlev, I.
  • Source: Bulgarian Journal of Agricultural Science
  • Volume: 10
  • Issue: 1
  • Year: 2004
  • Summary: Long-term data (13-18 years) from 15 experimental farms were used to evaluate quantitatively the risk of maize cultivation on drylands in different regions of Bulgaria. Results established that the risk of maize cultivation on drylands in north Bulgaria seldom surpasses 10% of the years. Losses in south Bulgaria cover 20-70% of the years. Only on soils of high water-holding capacity is the risk close to 20%.
  • Authors:
    • Bunce, J. A.
  • Source: Oecologia
  • Volume: 140
  • Issue: 1
  • Year: 2004
  • Summary: Reductions in leaf stomatal conductance with rising atmospheric carbon dioxide concentration ([CO 2]) could reduce water use by vegetation and potentially alter climate. Crop plants have among the largest reductions in stomatal conductance at elevated [CO 2]. The relative reduction in stomatal conductance caused by a given increase in [CO 2] is often not constant within a day nor between days, but may vary considerably with light, temperature and humidity. Species also differ in response, with a doubling of [CO 2] reducing mean midday conductances by 50% in others. Elevated [CO 2] increases leaf area index throughout the growing season in some species. Simulations, and measurements in free air carbon dioxide enrichment systems both indicate that the relatively large reductions in stomatal conductance in crops would translate into reductions of
  • Authors:
    • Schimmelpfennig, D. E.
    • McCarl, B. A.
    • Chen, C. C.
  • Source: Climatic Change
  • Volume: 66
  • Issue: 1/2
  • Year: 2004
  • Summary: One of the issues with respect to climate change involves its influence on the distribution of future crop yields. Many studies have been done regarding the effect on the mean of such distributions but few have addressed the effect on variance. Furthermore, those that have been done generally report the variance from crop simulators, not from observations. This paper examines the potential effects of climate change on crop yield variance in the context of current observed yields and then extrapolates to the effects under projected climate change. In particular, maximum likelihood panel data estimates of the impacts of climate on year-to-year yield variability are constructed for the major U.S. agricultural crops. The panel data technique used embodies a variance estimate developed along the lines of the stochastic production function approach suggested by Just and Pope. The estimation results indicate that changes in climate modify crop yield levels and variances in a crop-specific fashion. For sorghum, rainfall and temperature increases are found to increase yield level and variability. On the other hand, precipitation and temperature are individually found to have opposite effects on corn yield levels and variability.
  • Authors:
    • Porter, G. A.
    • Griffin, T. S.
  • Source: Biology and Fertility of Soils
  • Volume: 39
  • Issue: 5
  • Year: 2004
  • Summary: Information is needed on the ability of different crop management factors to maintain or increase soil C and N pools, especially in intensively tilled short crop rotations. Soil samples from field experiments in Maine were used to assess the effect of cover crop, green manure (GM) crop, and intermittent or annual amendment on soil C and N pools. These field experiments, of 6-13 years' duration, were all characterized by a 2-year rotation with either sweet corn (Zea mays L.) or potato (Solanum tuberosum L.), and primary tillage each year. Total, particulate organic matter (POM), and soil microbial biomass (SMB)-C and -N pools were assessed for each experiment. Total C and N stocks were not affected by red clover (Trifolium pratense L.) cover crop or legume GM, but were increased by 25-53% via a single application of papermill sludge or an annual manure and/or compost amendment. With the exception of continuous potato production which dramatically reduced the SMB-C and SMB-N concentration, SMB-C and -N were minimally affected by changes in cropping sequence, but were quite sensitive to amendments, even those that were primarily C. POM-C and -N, associated with the coarse mineral fraction (53-2,000 mum), were more responsive to management factors compared to total C and N in soil. The change in soil C fractions was a linear function of increasing C supply, across all experiments and treatments. Within these intensively tilled, 2-year crop rotations, substantial C and N inputs from amendments are needed to significantly alter soil C and N pools, although cropping sequence changes can influence more labile pools responsible for nutrient cycling.
  • Authors:
    • Grzebisz, W.
  • Source: Journal of Elementology
  • Volume: 9
  • Issue: 4(Supplement)
  • Year: 2004
  • Summary: Natural availability of potassium in Polish soils and its uptake by various crops are examined on a regional basis. Potassium requirements of the main agricultural crops (wheat, rye, barley, oats, triticale, maize, potato, sugar beet, oilseed rape and grass for haymaking) are considered in view of the element's content both in farmyard manure and in chemical fertilisers; their use and the overall balance of potassium available for plant uptake in individual regions are shown in maps.
  • Authors:
    • Nelson, L. A.
    • Baltensperger, D. D.
    • Eskridge, K. M.
    • Russell, W. K.
    • Guillen-Portal, F. R.
    • D'Croz-Mason, N. E.
    • Johnson, B. E.
  • Source: Crop Science
  • Volume: 44
  • Issue: 5
  • Year: 2004
  • Summary: Dryland maize ( Zea mays L.) production in the U.S. western High Plains is hampered by variable yields because of substantial environmental variation in this region. This study was conducted to determine the degree to which the ranking of superior maize hybrids for dryland production in the western High Plains was predictable from performance of the same hybrids in highly productive, irrigated environments in the same region. Forty-five maize hybrids were evaluated for grain yield performance under different water regimes in western Nebraska, eastern Wyoming, and northeastern Colorado in 1998 and 1999. The value of genotypic variance was by far larger in fully irrigated test environments (0.70) than in nonirrigated test environments (0.01-0.17). The genotypic mean repeatability in fully irrigated test environments (0.63) compared with that in nonirrigated test environments (0.18-0.69, respectively), and it showed correspondence with yield performance. The genetic correlation between fully and nonirrigated environments (0.72) was lower than that observed between all-nonirrigated environments (0.78-1.02). Thus, the proportion of direct advance in the former case (0.63) was generally lower than in the latter (0.41-0.97). However, an environmental similarity ratio (ESR) derived from crossover interaction indicated that water-contrasting environments were as similar (ESR=0.53) as nonirrigated environments (ESR=0.49) in ranking the maize hybrids. Selective identification of maize hybrids in irrigated environments for production under nonirrigated environments in the western High Plains might be a useful surrogate to direct selection in the latter environments.
  • Authors:
    • Australia, Australian Bureau of Agricultural and Resource Economics
  • Source: Australian Bureau of Agricultural and Resource Economics
  • Issue: 132
  • Year: 2004
  • Summary: An overview of crop production in Australia in 2004 is presented. The crop conditions in New South Wales, Victoria, Queensland, Western Australia and South Australia are described. Cropping areas and yields of winter crops (wheat, barley, oats, rape, lupins, field peas, chickpea, faba beans, lentils, triticale, safflower and vetch) and summer crops (cottonseed, sorghum, rice, maize, sunflowers, soyabeans, groundnuts, mung beans and navy beans) are compared with previous years. Various crop production, precipitation and pricing data are also tabulated.
  • Authors:
    • Australian Bureau of Agricultural and Resource Economics
  • Source: Australian Bureau of Agricultural and Resource Economics
  • Issue: 132
  • Year: 2004
  • Summary: An overview of crop production in Australia in 2004 is presented. The crop conditions in New South Wales, Victoria, Queensland, Western Australia and South Australia are described. Cropping areas and yields of winter crops (wheat, barley, oats, rape, lupins, field peas, chickpea, faba beans, lentils, triticale, safflower and vetch) and summer crops (cottonseed, sorghum, rice, maize, sunflowers, soyabeans, groundnuts, mung beans and navy beans) are compared with previous years. Various crop production, precipitation and pricing data are also tabulated.
  • Authors:
    • Sherrod,L. A.
    • Shaver,T. M.
    • Peterson,G. A.
  • Source: Geoderma
  • Volume: 116
  • Issue: 1-2
  • Year: 2003
  • Summary: Great Plains dryland agriculture is a risky venture because of large annual fluctuations in precipitation and high evaporation potentials. Water capture is limited by low water infiltration rates because many of our soils have relatively small aggregate size distributions, which limit infiltration, and are also susceptible to crusting and sealing. No-till management has permitted cropping intensification, which via improved water storage, has increased crop residue returned to the soil, decreased surface bulk density, and increased surface soil porosity. Our objective was to quantify the relationship between crop residue biomass generated by cropping system intensification and the physical properties of the surface soil (0-2.5-cm depth). This study was conducted within an existing long-term dryland experiment consisting of three sites in eastern Colorado that transect an evapotranspiration gradient. Each site transects a soil catena with three distinct soils arranged along a slope gradient. Only soils at the summit and toe slopes were sampled for this study. Soils are Argiustolls and Ustochrepts. Three no-till cropping systems, Wheat-Fallow (WF), Wheat-Corn-Fallow (WCF), and Continuous Cropping (CC), were sampled in the summer of 1998 after the cropping systems had been in place for 12 years. Bulk density, effective porosity, aggregate size distribution, sorptivity, and soil aggregate organic C content were measured at the surface 2.5 cm of the soil in each cropping system at the two soil positions at each site. Bulk density was reduced by 0.01 g cm(-3) for each 1000 kg ha(-1) of residue addition over the 12-year period. Each 1000 kg ha(-1) of residue addition increased effective porosity by 0.3%. Increases in macroaggregation were associated with linear increases in the C content of the aggregates; each g kg(-1) of organic C in the macroaggregates increased the proportion of macroaggregates by 4.4%. Implementation of no-till intensive cropping systems under this semiarid environment increased, residue biomass, which has ultimately increased effective porosity, and thus water capture potential was increased.