• Authors:
    • Weeks, C.
    • Robertson, M.
    • Oliver, Y.
  • Source: Agricultural Water Management
  • Volume: 98
  • Issue: 2
  • Year: 2010
  • Summary: The practice of long fallowing, by omitting a year of cropping, is gaining renewed focus in the low rainfall zone of the northern agriculture region of Western Australia. The impetus behind this practice change has been a reduced use of pasture breaks in cereal crop rotations, and the belief that a fallow can improve soil water accumulation and thus buffer the negative effects of dry seasons on crop yields. We evaluated the benefits of long fallowing (full stubble retention, no weed growth allowed) in a continuous wheat sequence via simulation modelling with APSIM at two rainfall locations and five soil types. The simulated benefits to long fallowing were attributable to soil water accumulation only, as the effects on soil nitrogen, diseases or weeds were not evaluated. The long-term (100 years) mean wheat yield benefit to fallowing was 0.36-0.43 t/ha in clay, 0.20-0.23 t/ha in sand and loam, and 0-0.03 t/ha in shallow sand and shallow loams. Over the range of seasons simulated the response varied from -0.20 to 3.87 t/ha in the clay and -0.48 to 2.0 t/ha for the other soils. The accumulation of soil water and associated yield benefits occurred in 30-40% of years on better soils and only 10-20% on poorer soils. For the loam soil, the majority of the yield increases occurred when the growing-season (May-September) rainfall following the fallow was low (30 mm), although yield increase did occur with other combinations of growing-season rainfall and soil water. Over several years of a crop sequence involving fallow and wheat, the benefits from long fallowing due to greater soil water accumulation did not offset yield lost from omitting years from crop production, although the coefficient of variation for inter-annual farm grain production was reduced, particularly on clay soils during the 1998-2007 decade of below-average rainfall. We conclude that under future drying climates in Western Australia, fallowing may have a role to play in buffering the effects of enhanced inter-annual variability in rainfall. Investigations are required on the management of fallows, and management of subsequent crops (i.e. sowing earlier and crop density) so as to maximise yield benefits to subsequent crops while maintaining groundcover to prevent soil erosion.
  • Authors:
    • Bradford, S.
    • Crohn, D.
    • Poss, J.
    • Shouse, P.
    • Segal, E.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 3/4
  • Year: 2010
  • Summary: A nutrient management plan (NMP) field experiment was conducted to investigate the fate of nitrogen (N), phosphorus (P), potassium (K) and salts in a semi-arid environment (San Jacinto, CA). Our mechanistic approach to study NMP performance was based on comprehensive measurements of water and N mass balance in the root zone. A cereal crop rotation (wheat-rye hybrid to sorghum, Triticum aestivum L.- Secale cereale L. to Sorghum bicolor L. Moench) that does not fix atmospheric N was employed during 2007, whereas a legume crop (alfalfa, Medicago sativa L.) that forms nodules to fix N was used in 2008. Blending (2007 and 2008) and cyclic (2007) dairy wastewater (DWW) application strategies (no statistical difference in 2007) were implemented to meet crop water and N uptake. The high content of salts in DWW and accurate application of water to meet evapotranspiration ( ET) yielded salt accumulation in the root zone. Leaching these salts after the fallow period resulted in the flushing of nitrate that had accumulated in the root zone due to continuous mineralization of soil organic N. This observation suggested that a conservative NMP should account for mineralization of organic N by (i) leaching salts following harvests rather than prior to planting and (ii) maintaining soils with low values of organic N. For the wheat-rye hybrid-sorghum rotation, losses of nitrate below the root zone were minimal and the soil organic N reservoir and P were depleted over time by applying only a fraction of the plant N uptake with DWW (28-48%) and using DWW that was treated to reduce the fraction of organic N (3-10%), whereas K accumulated similar to other salts. Conversely, with alfalfa approximately 15% of the applied N was leached below the root zone and the soil organic N increased during the growing season. These observations were attributed to fixation of atmospheric N, increased root density, and applying a higher fraction of plant N uptake with DWW (76%). Collectively, our results indicate that NMPs should accurately account for water and nutrient mass balances, and salt accumulation to be protective of the environment.
  • Authors:
    • Mohd, M.
    • Tahir, S.
  • Source: Agricultural and Biological Research
  • Volume: 26
  • Issue: 2
  • Year: 2010
  • Summary: The experiment on intercropping of potato with turnip, radish, rutabaga and kale was carried out at Regional Agricultural Research Sub-Station SKUAST-K Kargil during 2006-2007 to study the agronomic and economic productivity as well as advantages of intercropping as compared to sole crops. The potato equivalent yield was found to be significantly higher when potato was intercropped with Kale (279 q/ha.) while as potato equivalent yields of all other intercrop combinations was considerably lower compared to sole potato crop (248 q/ha.). Economic analysis of sole and intercrop association indicated that potato in combination with Kale gave higher economic returns (Rs. 191500) than other intercrop combinations and sole crops.
  • Authors:
    • Towett, B. K.
    • Ogola, J. B. O.
    • Kinyua, M. G.
    • Gottschalk, K.
    • Kimurto, P. K.
  • Source: Agricultural Engineering International: CIGR Journal
  • Volume: 12
  • Issue: 3/4
  • Year: 2010
  • Summary: Carrying out field trial-research in dryland areas is usually expensive and costly for most national breeding programmes; hence development of simple crop simulation models for predicting crop performance in actual semi-arid and arid lands (ASALS) would reduce the number of field evaluation trials. This is especially critical in developing countries like Kenya where dry areas is approximately 83% of total land area and annual rainfall in these area is low, unreliable and highly erratic, causing frequent crop failures, food insecurity and famine. This paper used data generated from the rain shelter by measurement of evapotranspiration together with weather variables in Katumani to predict wheat yields in that site. Maximum yield of the wheat genotype considered for genotype Chozi under ideal conditions was 5 t/ha. Total above-ground biomass was obtained and grain yield was to be predicted by the model. Transpiration was estimated from the relationship between total dry matter production and normalised TE (7.8 Pa). The results presented are based on the assumption that all agronomic conditions were optimal and drought stress was the major limiting factor. Predicted grain yield obtained from the conceptual model compares very well with realised yields from actual field experiments with variances of 14%-43% depending on watering regime. This study showed that it is possible to develop simple conceptual model to predict productivity in wheat in semi-arid areas of Kenya to supplement complicated and more sophisticated models like CERES-maize and ECHAM models earlier used in Kenya. The presence of uncontrolled factors in the simulation not accounted for in the estimation and could have contributed to decrease in observed yield need to be included in the model, hence modulation of the equations by introducing these factors may be necessary to reduce variances; thus need to be quantified. To improve the accuracy of prediction and increase wheat production in these areas measures that conserve water and/or make more water available to the crop such as prevention or minimisation of run-off, and rain water harvesting for supplemental irrigation are necessary.
  • Authors:
    • Kheira, A. A. A.
    • Lamm, F. R.
    • Trooien, T. P.
  • Source: Applied Engineering in Agriculture
  • Volume: 26
  • Issue: 5
  • Year: 2010
  • Summary: A 5-year field study (2004-2008) using irrigation water from an unlined surface reservoir was conducted to examine the effect of dripline depth (0.2, 0.3, 0.4, 0.5, or 0.6 m) on subsurface drip-irrigated rotational crop production of sunflower, soybean, and grain sorghum on a deep silt loam soil in western Kansas. Additional years (1999-2003) of data were included in the analysis of long-term dripline flowrates as affected by dripline depth. Crop seed germination and plant establishment with the subsurface drip irrigation system was not examined in this field study. There were no significant differences in crop yields or yield components in any year of the study with the exception of the number of soybean pods/plant in 2007. In that year, the number of pods/plant was significantly greater for the deeper dripline depths, but this improvement was not reflected in significantly greater soybean yield due to compensation from the other yield components. Measured crop water use and calculated water productivity (yield/water use) also were not significantly affected by dripline depth for any crop in any year. Crop water use varied less than 4% and water productivity varied less than 8% with dripline depth from the mean values for a given crop within a given year, but water productivity tended to be greater for the intermediate 0.4 m dripline depth. There was a tendency for the deeper dripline depths to have greater amounts of plant available soil water and this tendency was stronger as the crop season progressed and for deeper portions of the crop root zone. However, there were neither significant differences in plant available soil water in the upper (0 to 0.9 m) and lower root zones (0.9 to 2.4 m) at physiological maturity of the crop in any year, nor in the total 2.4 m soil profile. The lack of significant differences in crop yields, water use, water productivity and plant available soil water at physiological maturity suggests that dripline depths ranging from 0.2 to 0.6 m are acceptable for crop production of these three crops on the silt loam soils of the region. Measurements of plot dripline flowrates during the period 1999 through 2008 indicated a tendency for deeper disciplines to have reduced flowrates and these flowrate reductions were statistically significant in 2001, 2006, 2007, and 2008. Although the reason for these plot flowrate reductions cannot be fully ascertained, it seems likely they were caused by emitter clogging related to an interaction between dripline depth and irrigation water quality for which the rationale was not determined.
  • Authors:
    • Delve, R. J.
    • Zingore, S.
    • Nyawasha, R. W.
    • Nyamangara, J.
    • Masvaya, E. N.
    • Giller, K. E.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 88
  • Issue: 1
  • Year: 2010
  • Summary: This paper examines a number of agronomic field experiments in different regions of sub-Saharan Africa to assess the associated variability in the efficiencies with which applied and available nutrients are taken up by crops under a wide range of management and environmental conditions. We consider N and P capture efficiencies (NCE and PCE, kg uptake kg(-1) nutrient availability), and N and P recovery efficiencies (NRE and PRE, kg uptake kg(-1) nutrient added). The analyzed cropping systems employed different soil fertility management practices that included (1) N and P mineral fertilizers (as sole or their combinations) (2) cattle manure composted then applied or applied directly to fields through animal corralling, and legume based systems separated into (3) improved fallows/cover crops-cereal sequences, and (4) grain legume-cereal rotations. Crop responses to added nutrients varied widely, which is a logical consequence of the wide diversity in the balance of production resources across regions from arid through wet tropics, coupled with an equally large array of management practices and inter-season variability. The NCE ranged from 0.05 to 0.98 kg kg(-1) for the different systems (NP fertilizers, 0.16-0.98; fallow/cover crops, 0.05-0.75; animal manure, 0.10-0.74 kg kg(-1)), while PCE ranged from 0.09 to 0.71 kg kg(-1), depending on soil conditions. The respective NREs averaged 0.38, 0.23 and 0.25 kg kg(-1). Cases were found where NREs were > 1 for mineral fertilizers or negative when poor quality manure immobilized soil N, while response to P was in many cases poor due to P fixation by soils. Other than good agronomy, it was apparent that flexible systems of fertilization that vary N input according to the current seasonal rainfall pattern offer opportunities for high resource capture and recovery efficiencies in semi-arid areas. We suggest the use of cropping systems modeling approaches to hasten the understanding of Africa's complex cropping systems.
  • Authors:
    • Holzapfel, C. B.
    • Kutcher, H. R.
    • Gan, Y.
    • Brandt, S. A.
    • May, W. E.
    • Lafond, G. P.
  • Source: Canadian Journal of Plant Science
  • Volume: 90
  • Issue: 5
  • Year: 2010
  • Summary: Differences in response to nitrogen (N) fertilizer will affect the production economics of field crops. Currently, there is limited information comparing the agronomic and economic performance of juncea canola (Brassica juncea L.) and sunflower (Helianthus annuus L.) to napus canola (Brassica napus L.) and flax (Limon ustitatissimum L.) in Saskatchewan under no-till practices. A study of these species was carried out at five Saskatchewan locations over 3 yr and included eight nitrogen rates. All four species had a curvilinear increase in grain yield as N rate increased with the largest yield response observed in napus canola to as much as 200 kg N ha I. The majority of the increase in flax grain yield occurred as the N rate increased from 10 to 90 kg ha(-1), while most of the increase in grain yield of juncea canola and sunflower occurred as N increased from 10 to 70 kg ha(-1). Biplot analysis indicated that grain yield variation was reduced at and above 50 kg N ha(-1) in flax, napus canola and juncea canola, but not in sunflower. Analysis indicated that a wide range of N rates would provide a similar adjusted gross return within each crop with the exact N range being determined by crop price and nitrogen cost. The N rate affected the kernel weight of sunflower but not the kernel weight of other crops. The protein concentration of all the species increased as N rate increased. Seed oil concentration tended to decrease as the N rate increased, but this was not consistent. In conclusion, higher yielding cultivars of sunflower and juncea canola are needed before they will replace a large acreage of flax or napus canola; however, in the drier regions of the Saskatchewan there is potential to expand sunflower production.
  • Authors:
    • Vigil, M. F.
    • Benjamin, J. G.
    • Mikha, M. M.
    • Nielson, D. C.
  • Source: Soil Science Society of America journal
  • Volume: 74
  • Issue: 5
  • Year: 2010
  • Summary: The predominant cropping system in the Central Great Plains is conventional tillage (CT) winter wheat ( Triticum aestivum L.)-summer fallow. We investigated the effect of 15 yr of cropping intensities, fallow frequencies, and tillage (CT and no-till [NT]) practices on soil organic C (SOC) sequestration, particulate organic matter (POM), and wet aggregate-size distribution. A crop rotation study was initiated in 1990 at Akron, CO, on a silt loam. In 2005, soil samples were collected from the 0- to 5- and 5- to 15-cm depths in permanent grass, native prairie, and cropping intensities (CI) that included winter wheat, corn ( Zea mays L.), proso millet ( Panicum miliaceum L.), dry pea ( Pisum sativum L.), and summer fallow. The native prairie was sampled to provide a reference point for changes in soil parameters. The most intensive crop rotation significantly increased C sequestration compared with the other CIs where fallow occurred once every 2 or 3 yr. Legume presence in the rotation did not improve SOC sequestration relative to summer fallow. Significant amounts of macroaggregates were associated with grass and intensive cropping compared with the rotations that included fallow. Reduced fallow frequency and continuous cropping significantly increased soil POM near the surface compared with NT wheat-fallow. Macroaggregates exhibited a significant positive relationship with SOC and POM. A significant negative correlation was observed between microaggregates and POM, especially at 0- to 5-cm depth. Overall, a positive effect of continuous cropping and NT was observed on macroaggregate formation and stabilization as well as SOC and POM.
  • Authors:
    • Brennan, J. P.
    • Murray, G. M.
  • Source: Australasian Plant Pathology
  • Volume: 39
  • Issue: 1
  • Year: 2010
  • Summary: The incidence, severity and yield loss caused by 40 pathogens associated with 41 diseases of barley were assessed from a survey of 15 barley pathologists covering the winter cereal growing areas of Australia. The survey provided data on the frequency of years that each pathogen developed to its maximum extent, the proportion of the crop then affected in each growing area, and the yield loss that resulted in the affected crops with and without current control measures. These data were combined with crop production and grain quality data to estimate the value of the losses aggregated to the Northern, Southern and Western production regions. Pathogens were estimated to cause a current average loss of $252 x 10(6)/year or 19.6% of the average annual value of the barley crop in the decade 1998-99 to 2007-08. Nationally, the three most important pathogens are Pyrenophora teres f. maculata, Blumeria graminis f. sp. hordei and Heterodera avenae with current average annual losses of $43 x 10(6), $39 x 10(6) and $26 x 10(6), respectively. If current controls were not used, losses would be far higher with potential average annual losses from the three most important pathogens, P. teres f. maculata, H. avenae and P. teres f. teres, being $192 x 10(6), $153 x 10(6) and $117 x 10(6), respectively. The average value of control practices exceeded $50 x 10(6)/year for nine pathogens. Cultural methods (rotation, field preparation) were the only controls used for 14 pathogens and contributed more than 50% of the control for a further 13 pathogens. Breeding and the use of resistant cultivars contributed more than 50% of control for five pathogens and pesticides for four pathogens. The relative importance of pathogens varied between regions and zones.
  • Authors:
    • Bengtson, L. E.
    • Fagre, D.
    • Pederson, G.
    • Zeyuan, Q.
    • Prato, T.
    • Williams, J. R.
  • Source: Environmental Management
  • Volume: 45
  • Issue: 3
  • Year: 2010
  • Summary: Potential economic impacts of future climate change on crop enterprise net returns and annual net farm income (NFI) are evaluated for small and large representative farms in Flathead Valley in Northwest Montana. Crop enterprise net returns and NFI in an historical climate period (1960-2005) and future climate period (2006-2050) are compared when agricultural production systems (APSs) are adapted to future climate change. Climate conditions in the future climate period are based on the A1B, B1, and A2 CO(2) emission scenarios from the Intergovernmental Panel on Climate Change Fourth Assessment Report. Steps in the evaluation include: (1) specifying crop enterprises and APSs (i.e., combinations of crop enterprises) in consultation with locals producers; (2) simulating crop yields for two soils, crop prices, crop enterprises costs, and NFIs for APSs; (3) determining the dominant APS in the historical and future climate periods in terms of NFI; and (4) determining whether NFI for the dominant APS in the historical climate period is superior to NFI for the dominant APS in the future climate period. Crop yields are simulated using the Environmental/Policy Integrated Climate (EPIC) model and dominance comparisons for NFI are based on the stochastic efficiency with respect to a function (SERF) criterion. Probability distributions that best fit the EPIC-simulated crop yields are used to simulate 100 values for crop yields for the two soils in the historical and future climate periods. Best-fitting probability distributions for historical inflation-adjusted crop prices and specified triangular probability distributions for crop enterprise costs are used to simulate 100 values for crop prices and crop enterprise costs. Averaged over all crop enterprises, farm sizes, and soil types, simulated net return per ha averaged over all crop enterprises decreased 24% and simulated mean NFI for APSs decreased 57% between the historical and future climate periods. Although adapting APSs to future climate change is advantageous (i.e., NFI with adaptation is superior to NFI without adaptation based on SERF), in six of the nine cases in which adaptation is advantageous, NFI with adaptation in the future climate period is inferior to NFI in the historical climate period. Therefore, adaptation of APSs to future climate change in Flathead Valley is insufficient to offset the adverse impacts on NFI of such change.