• Authors:
    • Gracia, R.
    • Moret, D.
    • Arrúe, J. L.
    • López, M. V.
  • Source: Soil & Tillage Research
  • Volume: 72
  • Issue: 1
  • Year: 2003
  • Summary: Maintenance of crop residues on the soil surface is considered the most effective method to control wind erosion. In semiarid Aragon (NE Spain), where the risk of wind erosion can be high, the adoption of conservation tillage systems has been encouraged as a fallow management alternative. However, little information concerning the dynamics of residue cover during fallow is available for this area. We report here results on the evolution of barley residues during two fallow periods under conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). The three tillage treatments were compared under both continuous cropping (CC) and cereal-fallow (CF) rotation. The CC system involves a summer fallow period of 5-6 months and the CF rotation a long-fallow of 17-18 months. Effects of specific tillage operations on soil cover are also presented and discussed in relation to wind erosion control during the long-fallow period. Average dry mass of barley residues at harvest was 1395 and 729 kg ha(-1) in the first and second year of the study, respectively. In general, crop residues at harvest were not significantly affected by tillage or cropping system. Primary tillage operations had the major influence on residue incorporation with reduction percentages of residue cover of 90-100% in CT (mouldboard ploughing) and 50-70% in RT (chiselling). During the two long-fallow periods, large clods (4-10 cm diameter) produced by mouldboard ploughing did not fully compensate for the complete burial of residues and the soil surface was insufficiently protected against wind erosion (soil covers
  • Authors:
    • Blumenthal, J. M.
    • McLean, G. B.
    • Hammer, G. L.
    • Lyon, D. J.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 4
  • Year: 2003
  • Summary: In a 2-yr multiple-site field study conducted in western Nebraska during 1999 and 2000, optimum dryland corn ( Zea mays L.) population varied from less than 1.7 to more than 5.6 plants m -2, depending largely on available water resources. The objective of this study was to use a modelling approach to investigate corn population recommendations for a wide range of seasonal variation. A corn growth simulation model (APSIM-maize) was coupled to long-term sequences of historical climatic data from western Nebraska to provide probabilistic estimates of dryland yield for a range of corn populations. Simulated populations ranged from 2 to 5 plants m -2. Simulations began with one of three levels of available soil water at planting, either 80, 160, or 240 mm in the surface 1.5 m of a loam soil. Gross margins were maximized at 3 plants m -2 when starting available water was 160 or 240 mm, and the expected probability of a financial loss at this population was reduced from about 10% at 160 mm to 0% at 240 mm. When starting available water was 80 mm, average gross margins were less than $15 ha -1, and risk of financial loss exceeded 40%. Median yields were greatest when starting available soil water was 240 mm. However, perhaps the greater benefit of additional soil water at planting was reduction in the risk of making a financial loss. Dryland corn growers in western Nebraska are advised to use a population of 3 plants m -2 as a base recommendation.
  • Authors:
    • Hubbard, K. G.
    • Mahmood, R.
  • Source: Journal of Hydrology
  • Volume: 280
  • Issue: 1/4
  • Year: 2003
  • Summary: Soil moisture (SM) plays an important role in land surface and atmospheric interactions. It modifies energy balance at the surface and the rate of water cycling between the land and atmosphere. In this paper we provide a sensitivity assessment of SM and ET for heterogeneous soil physical properties and for three land uses including irrigated maize, rainfed maize, and grass at a climatological time-scale by using a water balance model. Not surprisingly, the study finds increased soil water content in the root zone throughout the year under irrigated farming. Soil water depletes to its lowest level under rainfed maize cultivation. We find a 'land use' effect as high as 36 percent of annual total evapotranspiration, under irrigated maize compared to rainfed maize and grass, respectively. Sensitivity analyses consisting of comparative simulations using the model show that soil characteristics, like water holding capacity, influence SM in the root zone and affect seasonal total ET estimates at the climatological time-scale. This 'soils' effect is smaller than the 'land use' effect associated with irrigation but, it is a source of consistent bias for both SM and ET estimates. The 'climate' effect basically masks the 'soils' effect under wet conditions. These results lead us to conclude that appropriate representation of land use, soils, and climate are necessary to accurately represent the water and energy balance in real landscapes.
  • Authors:
    • Tope, K. L.
    • Gaddis, S. E.
    • Petersen, B. E.
    • Sterner, R. T.
    • Poss, D. J.
  • Source: Crop Protection
  • Volume: 22
  • Issue: 4
  • Year: 2003
  • Summary: During 2000-2001, small mammals, birds, and potential corn/soybean damage were studied at a low-tillage, non-irrigated agricultural research site in the Colorado Piedmont. A small mammal survey involved four trapping sessions and 18, 12-live-trap grids each. Within years, two grids each were placed at random, fixed locations in experimental corn, fallow, millet, pea, soyabean, sunflower, and wheat plots at the site; two off-plot grids each were set at random, fixed locations
  • Authors:
    • Sadras, V. O.
    • Andrade, F. H.
    • Calvino, P. A.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 2
  • Year: 2003
  • Summary: The aim of this study was to investigate the influence of rainfall, soil depth, and crop management practices on the yield of dryland maize ( Zea mays L.) crops of the Argentine Pampas. We were concerned with the relevance of known physiological mechanisms in commercial crops and with developing a framework to quantify the impact of improved management practices on crop yield. Our approach included three steps. First, baseline functions were developed to quantify the relationship between yield and water availability (W) during the critical period for kernel set. Second, baseline functions were tested using an independent data set. Third, using the baseline functions as benchmarks, the effects on yield of soil depth and crop management practices were evaluated. Yield varied between 4.2 and 10 t ha -1, and most of this variation (>84%) was accounted for by W during the period bracketing flowering. Shallow soils presented lower yield than deep soils at a given rainfall. Using yield vs. W functions to account for the effect of variation in W, we quantified the impact of crop management on productivity. Technology-related yield increases were (a) 2.3 t ha -1 from the late 1980s to the mid-1990s, mainly explained by P fertilization, better and earlier weed control, and improved hybrids; (b) 0.9 t ha -1 from the mid-1990s to 1996-1998, related to no-till and higher plant density; and (c) 0.8 t ha -1 from 1996-1998 to 1999-2000, mainly explained by enhanced rates of N fertilization.
  • Authors:
    • Felton, W.
    • Haigh, B.
  • Source: Update of research in progress at the Tamworth Agricultural Institute 2002
  • Year: 2003
  • Summary: Crop growth rate and weed competition were studied in New South Wales, Australia during 2002 using reflectance sensors. Seeds of wheat cv. Sunstate, chickpea cv. Howzat, faba bean cv. Fiord and rape cv. Oscar were sown at 40, 70, 100 and 3 kg/ha, respectively. Two reflectance sensors mounted on a small tractor were used to collect data across each plot every two weeks (45-129 days after sowing). Wheat recorded the greatest biomass, yield and water consumption, whereas chickpea recorded the highest harvest index and lowest water consumption. The rate of crop development was greatest in wheat and lowest in chickpea. The number of days required to produce 1000 kg/ha of shoot dry matter was 92, 100, 102 and 11 days after sowing for wheat, faba bean, rape and chickpea, respectively. Reflectance measurements were also used to evaluate the potential of wheat, triticale and barley as 'mimic weeds' against wild oat [ Avena fatua] in chickpea. Reflectance estimates were made at 51, 62, 84, 100 and 120 days after sowing. The 'mimic weeds' established faster than wild oat. The density of wild oat was lower than that of the mimic weeds, although none of the weeds achieved the target density of 81 weeds/m 2. The similar linear relationships with regard to the effects of weed biomass on crop yield for wild oat and 'mimic weeds' indicated that the latter can be used in weed studies instead of the actual weed. At low densities, wheat and barley were the most competitive. Triticale and wild oat exhibited similar competitive ability.
  • Authors:
    • Crawford, M.
    • Ransom, K.
    • Hirth, J.
    • Harris, R.
    • Naji, R.
  • Source: Solutions for a better environment: Proceedings of the 11th Australian Agronomy Conference, Geelong, Victoria, Australia, 2-6 February 2003
  • Year: 2003
  • Summary: Companion cropping (also known as intercropping) of lucerne involves sowing an annual crop into an existing lucerne stand. A sample of eight farmers from north central Victoria, Australia, who currently companion crop, were interviewed to document the impact of this practice on grain production, and to determine why and how they used this approach in their farming system. All eight farmers companion cropped lucerne to produce grain for either human or livestock consumption. Wheat, barley, oat and triticale were most commonly sown into lucerne stands, with rape less frequently companion cropped. Most companion-cropped stands of lucerne were either winter-active or highly winter-active cultivars and most had densities of 10-30 plants/m 2. They were commonly 9-12 months old, although some stands up to 10 years old were successfully companion cropped. Sowing rates of the annual crop were generally greater than those used in conventional monoculture cropping, and most farmers sowed diagonally across existing lucerne rows. Most interviewed farmers adopted companion cropping because of perceived better economic returns from cropping rather than grazing their second-year stands of lucerne, which then became more persistent and productive stands for future grazing. Farmers who companion cropped into mature stands aimed to maintain year-round plant transpiration to minimize the impact of their cropping practices on local groundwater systems, through a better hydrologic balance between the rainfall and their vegetation. Decreased grain yields from companion-cropped crops were common, and were estimated to be 10 to 80% of those obtained in the absence of lucerne. The magnitude of the yield decreases appeared to be most strongly influenced by seasonal conditions. The use of herbicides for in-crop lucerne suppression was perceived to enhance grain quality by slowing lucerne growth over the late winter-spring period, thereby reducing lucerne seed and herbage contamination at harvest. As seasonal and soil water conditions critically influenced the success of herbicide applications, specialist advice was often sought.
  • Authors:
    • Featherstone, A. M.
    • Langemeier, M. R.
    • Abdulkadri, A. O.
  • Source: Applied Economics
  • Volume: 35
  • Issue: 7
  • Year: 2003
  • Summary: The risk attitudes of dryland wheat, irrigated maize, and dairy producers in Kansas, USA, are examined using the nonlinear mean-standard deviation approach. Observations on farm characteristics, obtained from 1993-97, and the statewide market year average prices for wheat and maize from 1950-97, are used. Results of analyses indicated that dryland wheat and dairy producers are characterized by increasing absolute and increasing relative risk aversion while irrigated maize producers are characterized by constant absolute and increasing relative risk aversion. Both crop enterprises exhibited constant returns to scale technology while the dairy enterprise exhibited decreasing returns to scale. Gross farm income was significant and positively related to relative risk aversion.
  • Authors:
    • Kirkland, K. J.
    • Beckie, H. J.
  • Source: Weed Technology
  • Volume: 17
  • Issue: 1
  • Year: 2003
  • Summary: Model simulations predict that lowering herbicide efficacy by reducing the application rate would slow the rate of enrichment of herbicide-resistant individuals in a weed population, but the resulting increase in density of susceptible plants would reduce crop yield and increase the weed seed bank. A study was conducted at three sites in Saskatchewan, Canada, from 1997 to 2000 to examine the implication of reduced rates of acetyl-CoA carboxylase (ACCase) inhibitors in a diverse 4-yr crop rotation, in conjunction with variable crop seeding rates, on the enrichment of resistant wild oat in a mixed (resistant and susceptible) population. Main-plot treatments were crop (barley, canola, field pea, and spring wheat), subplot treatments were crop seeding rate (recommended and high), and sub-subplot treatments were ACCase inhibitor rate (0, 0.33, 0.67, and 1.0 times the recommended rate). Herbicide rate frequently interacted with seeding rate in affecting wild oat seedling density, seed return, the viable fraction of the weed seed bank, and crop seed yield. As simulation models predict, reduced herbicide efficacy decreased the proportion of resistant individuals in the population. The high crop seeding rate compensated for a one-third reduction in herbicide rate by limiting total wild oat seed return and by reducing the number of resistant seedlings recruited from the seed bank. The level of resistance in the seed bank can be reduced without increasing the total (resistant plus susceptible) seed bank population by manipulating agronomic practices to increase crop competitiveness against wild oat when ACCase inhibitor rates are reduced to a maximum of two-thirds of that recommended.
  • Authors:
    • Lyon, D. J.
    • Blumenthal, J. M.
    • Stroup, W. W.
  • Source: Agronomy Journal
  • Volume: 95
  • Issue: 4
  • Year: 2003
  • Summary: Dryland corn ( Zea mays L.) production increased more than 10-fold from 1995 through 2000 in semiarid western Nebraska. Corn population and N fertilizer management recommendations are needed for this area. The objectives of this study were to determine the influence of plant population and N fertility on corn yields in semiarid western Nebraska. In 1999 and 2000, experiments were conducted each year at four sites. Factorial experimental treatments were five plant populations (17 300, 27 200, 37 100, 46 900, and 56 800 plants ha -1) and five N fertilizer rates (0, 34, 67, 101, and 134 kg N ha -1) arranged in a randomized complete block with five blocks. Corn yields ranged from less than 100 kg ha -1 to more than 5550 kg ha -1. Overall, grain yield increased 353 kg ha -1 with increasing population from 17 300 to 27 200 plants ha -1. Population increases above 27 200 plants ha -1 resulted in inconsistent yield results. Nitrogen fertilization and plant population effects did not interact. Yields were maximized by 202 kg N ha -1 in the form of soil NO 3-N and fertilizer N available before crop emergence. Growers are advised to use a plant population of 27 200 plants ha -1. Economic optimal fertilizer rate can be estimated using the equation: Nfert.=(10.6 * Pcorn- Pfert.)/(0.0526 * Pcorn)- Nsoil, where Pcorn and Pfert. are corn and fertilizer price ($ kg -1), respectively, Nsoil is soil test NO 3-N (kg ha -1) as determined by preplant soil test in a 0- to 120-cm soil sample, and Nfert. is economic optimal fertilizer rate (kg ha -1).