• Authors:
    • Iraj Eskandari
    • Abbas Hemmat
  • Source: Aktualni zadaci mehanizacije poljoprivrede. Zbornik radova, 31. međunarodnog simpozija iz područja mehanizacije poljoprivrede, Opatija, Hrvatska, 24-28 veljač 2003
  • Year: 2003
  • Authors:
    • Flury, M.
    • Huggins, D. R.
    • Bezdicek, D. F.
    • Fuentes, J. P.
  • Source: Soil & Tillage Research
  • Volume: 71
  • Issue: 1
  • Year: 2003
  • Summary: Understanding the fate of soil water and nitrogen (N) is essential for improving crop yield and optimizing the management of water and N in dryland cropping systems. The objective of this study was to evaluate how conventional (CT) and no-till (NT) cropping systems affect soil water and N dynamics. Soil water and N were monitored in 30 cm increments to a depth of 1.5 m for 2 years at growers' fields in two different agroclimatic zones of Washington State (USA): (1) the annual cropping region with a mean annual precipitation of more than 500 rum (Palouse site) and (2) the grain-fallow cropping region with mean precipitation below 350 mm (Touchet site). In each zone, a CT and a NT cropping system were chosen. All sites had an annual cropping system, except for the CT site in the drier area, which was under a traditional winter wheat/fallow rotation previous to the study. At Palouse, the volumetric water content in the top 1.5 m of the soil throughout the year was about 0.05-0.1 m(3) m(-3) less under CT as compared to NT, indicating improved seasonal accumulation and distribution of soil water under NT. Cropping systems modeling indicated, that during winter, surface runoff occurred in the CT system, but not under NT. The differences in soil water dynamics between CT and NT were mainly caused by differences in surface residues. Dynamics of NO3--N at Palouse were similar for NT and CT. At Touchet, differences in soil moisture between NT and CT were less than 0.05 m(3) m(-3). Under NT, high levels of NO3--N, up to 92 kg NO3-N ha(-1), were found after harvest below the root zone between 1.5 and 2.5 m, and were attributed to inefficient use or over-application of fertilizer. In both climatic zones, grain yield was positively correlated with evapotranspiration.
  • Authors:
    • Paustian, K.
    • Elliott, E.
    • Mooney, S.
    • Capalbo, S. M.
    • Antle, J. M.
  • Source: Journal of Environmental Economics and Management
  • Volume: 46
  • Issue: 2
  • Year: 2003
  • Summary: In this paper we develop methods to investigate the efficiency of alternative contracts for Carbon (C) sequestration in cropland soils, taking into account the spatial heterogeneity of agricultural production systems and the costs of implementing more efficient contracts. We describe contracts being proposed for implementation in the United States and other countries that would pay farmers for adoption of specified practices (per-hectare contracts). We also describe more efficient contracts that would pay farmers per tonne of soil C sequestered, and we show how to estimate the costs of implementing these more efficient contracts. In a case study of a major agricultural region in the United States, we confirm that the relative inefficiency of per-hectare contracts varies spatially and increases with the degree of spatial heterogeneity. The results also show that per-hectare contracts are as much as five times more costly than per-tonne contracts--a degree of inefficiency similar to that found in assessments of command-and-control industrial emissions regulations. Measurement costs to implement the per-tonne contracts are found to be positively related to spatial heterogeneity but are estimated to be at least an order of magnitude smaller than the efficiency losses of the per-hectare contract for reasonable error levels. This finding implies that contracting parties could afford to bear a significant cost to implement per-tonne contracts and achieve a lower total cost than would be possible with the less efficient per-hectare contracts.
  • Authors:
    • Jacobsen, J. S.
    • Jones, C. A.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 34
  • Issue: 13/14
  • Year: 2003
  • Summary: Granular phosphorus (P) fertilizers are often treated with coatings, such as oil or wax, to decrease dust production during packaging, shipping, storage, and spreading. Unconfirmed reports from the field suggest these coatings may negatively impact plant response to applied P fertilizers. A three-phase study was conducted in Montana, USA to determine if these coatings significantly affect P dissolution rates, soil P test levels, P uptake, or yield. Coated and uncoated monoammonium phosphate granules were obtained from two fertilizer manufacturers. In Phase I, fertilizer dissolution rates in water were measured for fertilizer application rates representing both irrigated and dryland conditions. In Phase II, dissolution rates were evaluated in an acid-washed sand at two moisture contents. In Phase III, Olsen P, P uptake, and dry biomass in maize ( Zea mays) were measured in a low pH and high pH soil for both broadcast and incorporated fertilizer applications. Dust control coatings did not significantly decrease dissolution rates, Olsen P levels, P uptake amounts, or biomass for any of the treatments or at any time. In a small percentage of comparisons, coatings significantly increased solubility, Olsen P levels, P uptake, or biomass; although, in general, coatings caused no significant differences in these parameters.
  • Authors:
    • Thornton, P. K.
    • Jones, P. G.
  • Source: Conservation Ecology
  • Volume: 5
  • Issue: 2
  • Year: 2003
  • Summary: Making decisions in natural resource management involves an understanding of the risk and uncertainty of the outcomes, such as crop failure or cattle starvation, and of the normal spread of the expected production. Hedging against poor outcomes often means lack of investment and slow adoption of new methods. At the household level, production instability can have serious effects on income and food security. At the national level, it can have social and economic impacts that may affect all sectors of society. Crop models such as CERES-Maize are excellent tools for assessing weather-related production variability. WATBAL is a water balance model that can provide robust estimates of the potential growing days for a pasture. These models require large quantities of daily weather data that are rarely available. MarkSim is an application for generating synthetic daily weather files by estimating the third-order Markov model parameters from interpolated climate surfaces. The models can then be run for each distinct point on the map. This paper examines the growth of maize and pasture in dryland agriculture in southern Africa (includes the southern part of Tanzania, Malawi, much of Mozambique, and all of Zimbabwe, and extends west from the Indian Ocean to include Zambia, the southeastern part of the Democratic Republic of Congo and small portions of Angola). Weather simulators produce independent estimates for each point on the map; however, we know that a spatial coherence of weather exists. We investigated a method of incorporating spatial coherence into MarkSim and show that it increases the variance of production. This means that all of the farmers in a coherent area share poor yields, with important consequences for food security, markets, transport, and shared grazing lands. The long-term aspects of risk are associated with global climate change. We used the results of a global circulation model to extrapolate to the year 2055. We found that low maize yields would become more likely in the marginal areas, whereas they may actually increase in some areas. The same trend was found with pasture growth. We outline areas where further work is required before these tools and methods can address natural resource management problems in a comprehensive manner at local community and policy levels.
  • 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:
    • Norman, J. M.
    • Morgan, C. L. S.
    • Lowery, B.
  • Source: Soil Science Society of America Journal
  • Volume: 67
  • Issue: 2
  • Year: 2003
  • Summary: The variability of crop yield in dryland production is primarily affected by the spatial distribution of plant-available water even for seemingly uniform fields. The most productive midwestern soils, which are loess caps over glacial till or outwash, can have a wide range of water-holding capacities in individual fields because of landscape processes and management. An inverse yield model was created as a robust method to quantify the spatial and temporal role of plant-available water on large agricultural fields to improve management options in precision agriculture. Plant-available water maps for a field were estimated from yield maps using inverse water-budget modeling based on measurements of solar radiation, temperature, precipitation, and vapor pressure deficit. The model presented in this paper was applied to 5 yr of corn ( Zea mays L.) yield-monitor data from a field in Waunakee, WI, having three soil mapping units, Plano silt loam (fine-silty, mixed, mesic Typic Argiudoll), St. Charles silt loam (fine-silty, mixed, mesic Typic Hapludalf), and Griswold loam (Fine-loamy, mixed, mesic Typic Argiudoll). The comparison of measured and inverse-modeled plant-available water suggests that the simple inverse yield model produces reasonable results in drier years with uncertainties of about 28 mm of plant-available water. The model helped to quantify the role of plant-available water in determining crop yield. Because of limited input requirements, the model shows promise as a practical tool for using precision farming to improve management decisions, and as a tool to obtain input for landscape-based models.
  • Authors:
    • Counce, P. C.
    • Gordon, E. C.
    • Keisling, T. C.
    • Oliver, L. R.
    • Manning, P. M.
    • Popp, M. P.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 34
  • Issue: 19/20
  • Year: 2003
  • Summary: Clay soils are difficult to manage to obtain a soyabean [ Glycine max (L.) Merr.] stand, especially when dry. A novel production system, recently observed on several farms in Arkansas, consists of bedding the dry clayey soil with disk-bedders, broadcasting the soyabean seed over the surface, re-bedding the seedbed to cover the seed, rolling the beds to flatten the tops and finally furrow irrigating immediately thereafter. Typically this planting system provides a stand of soyabean within 4 to 6 days after irrigation and is designated as "hipped" after the common reference of a disk-bedder as a hipper. Studies were conducted on Sharkey soil at Keiser, AR from 1998 to 2000 for comparing this "hipped" system to more widely used planting methods. On dry clayey soils, a randomized complete block design with three replications was used to compare full-season soyabean under a conventional 96-cm row system, drilled-planting into a stale seedbed, and the "hipped" system. A similar study for double-cropped wheat-soybean involved straw management (burn or leave) coupled with no-till drill, tilled drill, and "hipped" systems. Other small studies on the "hipped" system were conducted to investigate the sensitivity to planting depth, soyabean plant population, and suitability for obtaining a stand on other crops such as cotton [ Gossypium hirsutum (L.)] and grain sorghum [ Sorghum bicolor (L.) Moench]. The "hipped" system worked well for obtaining stands of soyabean, cotton, and grain sorghum. In essence the "hipped" system (1) provides insurance against poor planting conditions; (2) allows for a reduction in the uncertainty of planting and stand establishment time required; (3) can be used to achieve high plant populations; (4) requires a relatively higher seeding rate in double-crop than full-season systems; (5) shows promise for situations when wheat stubble burning becomes curtailed especially if planting can occur early to lead to improved canopy coverage and (6) leads to yield reductions in fields where depth of seed placement cannot be controlled easily.