• 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:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 26
  • Issue: 1-2
  • Year: 1995
  • Summary: Legumes provide benefit in crop rotations, but data are limited on soil inorganic nitrogen (N) and soil strength responses to spring- or fall-seeded legumes as green manures for grain sorghum [Sorghum bicolor (L.) Moench] production on the prairie soils of the eastern Great Plains of the United States. With increased emphasis on conservation tillage, information is also needed on combining conservation tillage with the use of legume cover crops. This experiment was established to examine the effects of i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth.) as previous crops to grain sorghum compared with continuous grain sorghum, ii) reduced or no-tillage, and iii) fertilizer N rate on changes in soil inorganic N and soil strength. At two adjacent sites (Parsons silt loam; fine, mixed thermic Mollic Albaqualf) differing in initial pH and phosphorus (P) and potassium (K) fertility, soil nitrate-nitrogen (NO3-N) was as much as fourfold higher following kill-down of red clover or hairy vetch than following continuous grain sorghum. At the higher fertility site, soil total inorganic N [TIN: sum of ammonium-nitrogen (NH4-N) and NO3-N] shortly following kill-down of red clover exceeded TIN following hairy vetch by more than 35% and that with continuous grain sorghum by 110%; however, at the lower fertility site, the trend for soil TIN to be higher following legumes was not significant. Tillage did not affect soil NO3-N levels in the spring following legume kill-down. However, subsequent soil NO3-N levels under no-tillage tended to be higher in the spring, but lower in the fall than with reduced tillage. Increases in soil TIN by legumes and fertilizer were related to grain sorghum yield, but likely were not the only factors affecting yield. Legumes and tillage used in grain sorghum production may also provide other non-N benefits as suggested by soil penetration resistance measured at the end of the study.
  • 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:
    • Martin, R. J.
    • Marcellos, H.
    • Felton, W. L.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 35
  • Issue: 7
  • Year: 1995
  • Summary: Four experiments were commenced after a 1980 wheat crop, and a fifth after the 1981 crop, at different sites representing the major soil types of northern New South Wales in the 550-700 mm rainfall zone, to examine the influence of 3 fallow management practices [no tillage (NT); stubble retention after harvest, cultivation (SM); stubble burning after harvest, cultivation (SB)] on wheat production. Data considered in this paper cover the continuous wheat subtreatments of the 5 experiments (1981-90). Nitrogen applied at 50 kg N/ha in addition to the basal treatment was included as a treatment from 1986 to 1988. Across all sites and seasons, grain yields were in the order SB>SM approximate to NT, stubble retention having a greater effect than tillage. In some years at some sites, differences in grain yield and grain N yield were not significant. In others, when significant yield differences occurred, variations in grain yield and grain N yield were highly correlated with differences in soil N available for the crop. The data show that the influence of fallow management interacted with season and crop nutrition, and required long-term study for proper assessment.
  • Authors:
    • Ghaffarzadeh, M.
    • Cruse, R. M.
    • Robinson, C. A.
  • Source: Soil Science Society of America Journal
  • Volume: 60
  • Issue: 1
  • Year: 1994
  • Summary: Time, fertilizer, tillage, and cropping systems may alter soil organic carbon (SOC) levels. Our objective was to determine the effect of long-term cropping systems and fertility treatments on SOC. Five rotations and two N fertility levels at three Iowa sites (Kanawha, Nashua, and Sutherland) maintained for 12 to 36 yr were evaluated. A 75-yr continuous corn (Zea mays L.) site (Ames) with a 40-yr N-P-K rate study also was evaluated. Soils were Typic and Aquic Hapludolls and Typic Haplaquolls. Four-year rotations consisting of corn, oat (Avena sativa L.), and meadow (alfalfa [Medicago sativa L.], or alfalfa and red clover [Trifolium pratense L.]) had the highest SOC (Kanawha, 32.1 g/kg; Nashua, 21.9 g/kg; Sutherland, 27.9 g/kg). Corn silage treatments (Nashua, [≤] 18.9 g/kg; Sutherland, [≤]23.2 g/kg) and no-fertilizer treatments (Kanawha, 25.3 g/kg; Nashua, [≤]20.9 g/kg; Sutherland, [≤]23.5 g/kg) had the lowest SOC. A corn-oat-meadow-meadow rotation maintained initial SOC (27.9 g/kg) after 34 yr at Sutherland. Continuous corn resulted in loss of 30% of SOC during 35 yr of manure and lime treatments. SOC increased 22% when N-P-K treatments were imposed. Fertilizer N, initial SOC levels, and previous management affected current SOC levels. Residue additions were linearly related to SOC (Ames, r2 = 0.40; Nashua, r2 = 0.82; Sutherland, r2 = 0.89). All systems had 22 to 49% less SOC than adjacent fence rows. Changing cropping systems to those that conserve SOC could sequester as much as 30% of C released since cropping began, thereby increasing SOC.
  • Authors:
    • Lindwall, C. W.
    • Roman, E. S.
    • Moyer, J. R.
    • Blackshaw, R. E.
  • Source: Crop Protection
  • Volume: 13
  • Issue: 4
  • Year: 1994
  • Summary: Soil erosion by wind or water is a serious problem in North and South America. When no-till or reduced tillage is used to control erosion, the density of certain annual and perennial weeds can increase and new weed control techniques are usually required. The effects of conservation tillage on annual and perennial weeds, weeds that are spread by wind, plants from rangelands and pasture as weeds and volunteer plants as weeds arc reviewed. Current weed control methods with minimum tillage, herbicides, cover crops and other cultural practices in conservation tillage systems in North and South America are described. Some producers are successfully controlling weeds in continuous summer cropping systems in North America and in double cropping systems that include wheat in the winter and soybean or corn in the summer in Brazil, Argentina and southeastern United States. Successful conservation tillage systems usually involve cropping sequences of three or more crop types and several herbicides. In these cropping sequences, the ground is covered with a crop during most of the period in which the climate is favourable for weed growth. Perennial weeds are a problem in all tillage systems and there is a general dependence on glyphosate for perennial weed control. In successful conservation tillage systems, the amount and cost of herbicides used is similar to that for herbicides used in conventional tillage systems.
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Soil Science Society of America Journal
  • Volume: 58
  • Issue: 5
  • Year: 1994
  • Summary: With increased emphasis on conservation tillage, information is needed on the use of spring- or fall-seeded legumes as green manures for eastern Great Plains grain sorghum [Sorghum bicolor (L.) Moench] production. This study was conducted to determine whether legumes can be beneficial to subsequent grain sorghum crops grown in conservation tillage systems on prairie soil. Comparisons included the effects of (i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) before grain sorghum vs. continuous grain sorghum, (ii) reduced or no-tillage, and (iii) fertilizer N rates on grain sorghum grown on two sites of a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf). Surface soil at Site 1 was higher in pH (7.2 vs. 6.2), P (12 vs. 4 mg kg(-1)), and K (80 vs. 60 mg kg(-1)) than at Site 2. Yield of the first sorghum crop after legume kill-down in 1987 ranged from 79 to 131% more than for continuous grain sorghum. At the higher fertility Site 1, red clover residual increased yields to 3.7 from 2.7 Mg ha(-1) with continuous grain sorghum in the third year; at the lower fertility Site 2, the legume residual did not influence yield after the first year. First-year grain sorghum yielded 1.1 to 1.6 Mg ha(-1) more with reduced tillage than with no-tillage, but the difference was less in subsequent years. In 1987, yield was not affected by fertilizer N even following grain sorghum, but the response was significant in subsequent years. Low N response on this high organic matter prairie soil contributed to uncertain fertilizer N equivalencies and suggested other non-N benefits from the legumes.
  • Authors:
    • Hernandez, C. F.
    • Casanova, M. R.
  • Source: Avance Agroindustrial
  • Volume: 14
  • Issue: 57
  • Year: 1994
  • Summary: In field trials on degraded or fertile soils at 2 sites in Tucuman in 1991-93, maize was sown directly or following a range of cultivations as part of a rotation with wheat and soyabeans, or in a system of continuous cultivation, and with or without application of N and P. Application of 60-80 kg N as urea was recommended under trial conditions; P had no further beneficial effect. The importance is stressed of maintaining the water balance by reducing disturbance of the soil and of increasing N use efficiency through management of stubble and cover crops. Production systems based on direct sowing, rotations, green manures, and sowing into stubble with application of complementary fertilizer were recommended to give the highest grain yields.
  • Authors:
    • Hipp, B. W.
    • Graff, P. S.
    • Marshall, D. S.
    • Knowles, T. C.
  • Source: Agronomy Journal
  • Volume: 85
  • Issue: 4
  • Year: 1993
  • Summary: Decomposition of sorghum [Sorghum bicolor (L.) Moench] and wheat (Triticum aestivum L.) plant residues can immobilize enough surface-applied N to cause a deficiency in successive winter wheat crops. This experiment examined the effects of conventional and no-till grain sorghum and wheat residues on N requirements of dryland winter wheat. Field experiments conducted from 1987-1991 on an Austin silty clay (fine-silty, carbonatic, thermic Udorthentic Haplustoll) soil included sorghum and wheat residue treatments with conventional till (CT), no-till (NT), and residue removal (RR). All residue plots received four preplant N rates (0, 45, 90, and 135 kg N ha-1), with subplots planted to three winter wheat cultivars in 1988 and 1989, and two cultivars in 1990 and 1991. Grain and stover yields were significantly lower when wheat followed sorghum than under continuous wheat. Wheat grain yields at N application rates < 90 kg ha-1 were 39% lower in NT plots vs. CT plots, 5% lower in CT plots compared with yields in RR plots, and 39% lower in sorghum-wheat rotation compared with continuous wheat. Wheat N uptake at N application rates < 90 kg ha-1 was 41% lower in NT plots vs. N uptake in CT plots, 10% lower in CT plots vs. N uptake in RR plots, and 36% lower in sorghum-wheat rotation vs. continuous wheat. Grain yield and N uptake of wheat at the 135 kg N ha-1 rate were not significantly different in NT and CT plots. Preplant soil NO3-N analysis indicated a need for the application of N fertilizer at planting in CT and NT sorghum residues, and basal stem NO3-N analysis showed wheat growing in NT residues and sorghum-wheat rotations had higher N fertilizer requirements than continuous CT wheat. Microbial immobilization of surface-applied N was responsible for N deficiencies observed in NT winter wheat, while a decrease in fallow time between sorghum harvest and wheat planting dates was the primary cause for reduced mineralization rates of residue-derived and indigenous soil N in sorghum-wheat rotations. A fallow period following grain sorghum and/or band application of fertilizer N could alleviate N deficiencies observed in this study.
  • Authors:
    • Maule, C.
    • Reed, W.
  • Source: Canadian Agricultural Engineering
  • Volume: 35
  • Issue: 3
  • Year: 1993
  • Summary: The effects of no-till and conventional tillage systems on water infiltration and related soil parameters were investigated in five fields under dryland farming in southern Saskatchewan. A rainfall simulator was used for the infiltration measurements. Three fields were under a no-till system for different lengths of time ranging from 5 years to 13 years. A heavy duty cultivator was used in both fields under conventional tillage; one field was under continuous cropping, and the other under a traditional wheat-fallow rotation. Fields under the no-till system had higher organic matter contents, higher macroporosities, and higher saturated hydraulic conductivities than the fields with the conventional tillage. Organic matter in the no-till and conventional continuously cropped fields increased approximately 0.2% for every year since the last conventional fallow-crop rotation. The field in conventional fallow had the lowest infiltration rates, while the conventional continuously cropped field had the highest infiltration rates, although not significantly different than those from the 13 year old no-till field. Cumulative infiltration at 60 minutes was most highly correlated with organic matter content; for every 1 percentage point increase in organic matter, cumulative infiltration increased by 9 mm.