19662015
  • Authors:
    • Avci, M.
  • Source: Efficient soil water use: the key to sustainable crop production in the dry areas of West Asia, and North and Sub-Saharan Africa. Proceedings of the workshops organized by the Optimizing Soil Water Use Consortium, Niamey, Niger, 26-30 April, 1998, Amman, J
  • Year: 1999
  • Summary: Semi-arid areas cover about 55% of Turkey and are mainly found in the Central Anatolian Plateau. The main crop production systems are fallow/wheat and legume/wheat. Wheat is generally prone to droughts, which severely affect the yields. Research on soil moisture use in fallow-wheat systems started in the 1930s. Its focus was on water interception and conservation techniques, and detailed research on rainfall interception led to practices which have been adopted by most of the plateau farmers. In the 1980s research focused on the replacement of fallow by a crop in the rotation systems. In most areas, fallow can best be replaced in terms of yield by forage crops and economically by edible legumes. Characterization of the other regions will identify fallow or continuous cropping target areas, and extrapolation of research results to them. Regarding technologies, the importance of terracing for moisture conservation increases with the degree of slope and the occurrence of erosive rainfall. Contour tillage and sowing were effective only on steep slopes. Future research is needed on supplemental irrigation to increase the water-use efficiencies of the wheat and barley varieties especially developed for irrigation.
  • Authors:
    • Camp, C. R.
  • Source: Transactions of the ASAE
  • Volume: 41
  • Issue: 5
  • Year: 1998
  • Summary: A comprehensive review of published information on subsurface drip irrigation was performed to determine the state of the art on the subject. Subsurface drip irrigation has been a part of drip irrigation development in the USA since its beginning about 1960, but interest has escalated since the early 1980s. Yield response for over 30 crops indicated that crop yield for subsurface drip was greater than or equal to that for other irrigation methods, including surface drip, and required less water in most cases. Lateral depths ranged from 0.02 to 0.70 m and lateral spacings ranged from 0.25 to 5.0 m. Several irrigation scheduling techniques, management strategies, crop water requirements, and water use efficiencies were discussed. Injection of nutrients, pesticides, and other chemicals to modify water and soil conditions is an important component of subsurface drip irrigation. Some mathematical models that simulate water movement in subsurface drip systems were included Uniformity measurements and methods, a limited assessment of root intrusion into emitters, and estimates of overall system longevity were also discussed. Sufficient information exists to provide general guidance with regard to design, installation, and management of subsurface drip irrigation systems. A significant body of information is available to assist in determining relative advantages and disadvantages of this technology in comparison with other irrigation types. Subsurface drip provides a more efficient delivery system if water and nutrient applications are managed properly. Waste water application, especially for turf and landscape plants, offers great potential Profitability and economic aspects have not been determined conclusively and will depend greatly on local conditions and constraints, especially availability and cost of water.
  • Authors:
    • Singh, B.
    • Aulakh, M. S.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 47
  • Issue: 3
  • Year: 1997
  • Summary: Porous soils are characterized by high infiltration, low moisture retention and poor fertility due to limitation of organic matter and nitrogen (N). However, wherever irrigated and properly managed, these are among the most productive soils in the world. For sustained productivity and prevention of N related pollution problems, fertilizer N management in porous soils needs to be improved by reducing losses of N via different mechanisms. Losses of N through ammonia volatilization are not favoured in porous soils provided fertilizer N is applied before an irrigation or rainfall event. Ammonium N transported to depth along with percolating water cannot move back to soil surface where it is prone to be lost as NH3. Under upland conditions nitrification proceeds rapidly in porous soils. Due to high water percolation rates in porous soils, continuous flooding for rice production usually cannot be maintained and alternate flood and drained conditions are created. Nitrification proceeds rapidly during drained conditions and nitrates thus produced are subsequently reduced to N-2 and N2O through denitrification upon reflooding. Indirect N-budget estimates show that up to 50% of the applied N may be lost via nitrification-denitrification in irrigated porous soils under wetland rice. High soil nitrate N levels and sufficient downward movement of rain water to move nitrate N below the rooting depth are often encountered in soils of humid and subhumid zones, to a lesser extent in soils of semiarid zone and quite infrequently, if at all in arid zone soils. The few investigations carried out with irrigated porous soils do not show substantial leaching losses of N beyond potential rooting zone even under wetland rice. However, inefficient management of irrigation water and fertilizer N particularly with shallow rooted crops may lead to pollution of groundwater due to nitrate leaching. At a number of locations, groundwater beneath irrigated porous soils is showing increased nitrate N concentrations. Efficient management of N for any cropping system in irrigated porous soils can be achieved by plugging losses of N via different mechanisms leading to both high crop production and minimal pollution of the environment.
  • Authors:
    • Walters, D. T.
    • Kessavalou, A.
  • Source: Agronomy Journal
  • Volume: 89
  • Issue: 1
  • Year: 1997
  • Summary: Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] provides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promote potentially excessive soil erosion following soybean harvest. An irrigated field experiment was conducted in eastern Nebraska for 4 yr (1990-1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybean on (i) rye dry matter yield, (ii) surface residue cover for erosion protection, and (iii) corn establishment and production. The soil was a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls). Treatments were (i) no-tillage and disk tillage; (ii) corn following soybean with a winter rye cover crop (CBR), corn following soybean without rye (CB) and corn following corn (CC); and (iii) 0, 50, 100, 150, and 300 kg N ha(-1) (applied to corn). Rye aboveground dry matter yield, surface residue cover, and corn yield parameters were estimated. Rye dry matter yield ranged from 0.25 to 2.9 Mg ha(-1) and was influenced by tillage, N rate, and weather conditions in different years. During the years of high rye dry matter yield, presence of rye in the corn-soybean system gave approximately 16% additional surface residue cover prior to planting through cultivation, compared with soybean residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no-till management. In 1 of the 3 yr, corn plant population and grain yield were reduced following rye (CBR) compared with the no rye system (CB), possibly due to apparent allelopathic effects related to the age of rye. No significant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without rye) resulted in an increase of approximately 27% in corn grain yield and N uptake over continuous corn. During the years of high rye dry matter production, rye accumulated approximately 45 kg N ha(-1) through aboveground dry matter. Overall, including a winter rye cover crop in the corn-soybean rotation system was beneficial.
  • Authors:
    • Schulbach, K. F.
    • Jackson, L. E.
    • Wyland, L. J.
  • Source: The Journal of Agricultural Science
  • Volume: 124
  • Year: 1995
  • Summary: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A N-15 experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg N-15/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the N-15 was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and N-15 content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied N-15 was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.
  • Authors:
    • Coady, S. A.
    • Clark, R. T.
    • Schneekloth, J. P.
    • Klocke, N. L.
    • Hergert, G. W.
  • Source: Journal of Production Agriculture
  • Volume: 8
  • Issue: 3
  • Year: 1995
  • Summary: Declining groundwater levels in parts of the Great Plains could lead to reduced irrigation and a decline in the economies of those areas. Improved irrigation efficiency has helped slow the rate of decline in aquifer levels but adoption of limited irrigation and water conserving rotations could slow the decline even more. The objective was to estimate the riskiness and profitability of these alternatives with and without farm commodity programs. Three water levels-rainfed, limited irrigation (6 in./yr water allocation) and full irrigation (meet crop evapotranspiration demands) were established for continuous corn (Zea mays L.), winter wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.], and corn-soybean rotations. The profitability of each rotation under each water level was estimated using results of field experiments conducted since 1981 in west central Nebraska and cost estimates based on a typical center pivot irrigation system covering 126 acres. Stochastic dominance techniques were then applied to the data by using combinations of prices for corn, wheat, and soybean to generate cumulative distribution functions. Profitability and riskiness were estimated with and without participation in the wheat and feed grain programs and with alternate acreage conservation reserve (ACR) levels. Results showed that the government program improved income levels and reduced income variation for each water level and all rotations. Program participation did encourage monoculture corn under full irrigation and under limited irrigation with low ACR requirements. Under rainfed conditions the relative ranking of the three rotations was not changed by program participation.
  • Authors:
    • Unger, P. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 50
  • Issue: 3
  • Year: 1995
  • Summary: Crop residue management was chosen as a key practice to help control erosion on nearly 75% of the highly erodible land covered by conservation plans. This study determined the effects of treatments that involved retaining all residues on the surface (NT+Res), removing some residues at harvest (NT-ResH) or at planting (NT-ResP), and conventional tillage (ConvT) on soil water storage and use, and yields of continuous winter wheat (Triticum aestivum L.) produced with limited irrigation. Water storage between crops was greater with NT+Res (95 mm) and NT-ResH (100 mm) than with ConvT (79 mm), but soil water depletion was not affected by treatments. Grain yield was greater with NT+Res (4.56 Mg ha(-1)), than with ConvT (4.26 Mg ha(-1)) and NT-ResH (4.18 Mg ha(-1)), but straw yield was not affected by treatments. Grain and straw yield differed among crops. Continuous wheat production with limited irrigation resulted in an estimated 2.2 Mg ha(-1) of residues on the surface at planting with the NT-ResH and NT-ResP treatments. The initial amount was 9.0 Mg ha(-1) with the NT+Res treatment, and much of this remained on the surface at planting of the next crop. In all cases, the residue amounts provided considerably more (a minimum of about 70%) than the 30% surface cover usually required to control erosion on highly erodible land. Hence, use of limited irrigation and no-tillage can help producers meet the surface residue requirements established for their conservation plans for highly erodible lands in the southern Great Plains.
  • Authors:
    • Copeland, S. M.
    • Tanaka, D. L.
    • Power, J. F.
    • Allmaras, R. R.
  • Source: Conservation Tillage in Temperate Agroecosystems
  • Year: 1994
  • Authors:
    • Raun, W. R.
    • Sander, D. H.
    • Olson, R. A.
  • Source: Agronomy Journal
  • Volume: 81
  • Issue: 2
  • Year: 1989
  • Authors:
    • Raun, W. R.
    • Sander, D. H.
    • Olson, R.A.
  • Source: Soil Science Society of America Journal
  • Volume: 51
  • Issue: 4
  • Year: 1987