• Authors:
    • Bendotti, S.
    • Proffitt, A. P. B.
    • Riethmuller, G. P.
  • Source: Soil & Tillage Research
  • Volume: 35
  • Issue: 4
  • Year: 1995
  • Summary: The effects of past grazing management practice on subsequent seedbed condition, draft requirements, fuel consumption, crop establishment and growth, and grain yield and quality were examined using three tillage systems on two sowing dates. The crop was wheat (Triticum aestivum), sown on a fragile sandy clay loam (red duplex soil) in a dryland agricultural area (307 mm average annual rainfall) of Western Australia. The three tillage-sowing systems investigated were: (i) scarifying followed by sowing with wide (180 mm) points; (ii) direct drilling with wide (180 mm) points; (iii) direct drilling with narrow (50 mm) inverted 'T'-shaped Super-Seeder points. The two sowing dates provided differences in seedbed water content at sowing time. The three grazing management strategies practised in the previous pasture year were: (i) traditional set-stocking (where sheep were grazed continuously for 17 weeks, beginning soon after the start of the early winter rains); (ii) controlled grazing (where sheep were temporarily removed from the enclosure when the topsoil was close to its plastic limit); (iii) no grazing (where the pasture was mown to simulate grazing without trampling). Tillage prior to sowing with wide points reduced the mechanical impedance of the soil following set-stocking and provided a good seedbed for successful crop establishment and growth. In both the controlled-grazing management treatment and the treatment where the pasture had been mown the soil was suitable for direct drilling with both wide and narrow points (i.e. no pre-sowing tillage was required). The use of narrow points had the added advantage of requiring less fuel, but the need for a suitable implement to cover seeds was more critical than for wider sowing points. There were no advantages with respect to grain yield from adopting a controlled-grazing management practice owing to the lack of finishing rainfall. However, grain protein levels were higher in both the controlled and ungrazed treatments compared with the set-stocking treatment.
  • 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:
    • 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:
    • Zuberer, D. A.
    • Hons, F. M.
    • Franzluebbers, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 58
  • Issue: 6
  • Year: 1994
  • Summary: Crop management strategies that alter the timing, placement, quantity, and quality of crop residue input can affect the size, turnover, and vertical distribution of the active and passive pools of soil organic matter (SOM). Our objectives were to quantify long-term changes in soil organic, soil microbial biomass (SMB), and mineralizable C and N in continuous wheat (Triticum aestivum L.), continuous wheat/soybean [Glycine max (L.) Merr.], and wheat/soybean-sorghum [Sorghum bicolor (L.) Moench.] sequences under conventional tillage (CT) and no tillage (NT) with and without N fertilizer. A Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas was collected from a 9-yr field study. Soil microbial biomass C (SMBC) and N (SMBN) were determined with the chloroform fumigation-incubation method and mineralizable C and N were determined from 10-d aerobic incubations at 25{degrees}C. More crop residue C input was retained as soil organic C (SOC), SMBC, and mineralizable C under NT than under CT. Soil organic C, SMBC, and mineralizable C at a depth of 0 to 50 mm were 33 to 125% greater under NT than under CT. Increasing cropping intensity increased SOC up to 22%, SMBC up to 31%, and mineralizable C up to 27% under NT. Differences in crop management systems significantly altered SMB and the associated mineralizable N level, which supplies crops with mineral N. High clay content soils of central Texas can be effectively managed to increase the active and passive pools of SOM using minimal fallow with NT.
  • Authors:
    • Black, A. L.
    • Bauer, A.
  • Source: Soil Science Society of America Journal
  • Volume: 58
  • Issue: 1
  • Year: 1994
  • Summary: The positive effects of soil organic matter (OM) on soil properties that influence crop performance are well documented. But definitive and quantitative information of differential effects of soil OM contents is lacking for the northern Great Plains. The objective of this study was to quantify the contribution of a unit quantity of soil OM to productivity. Experiments were conducted on Williams loam (fine-loamy, mixed, Typic Argiboroll) for 4 yr in the same field. The variables were soil OM content of the upper 30.5 cm together with all combinations of three postplanting soil available N levels (55, 90, and 125 kg N ha-1 as NO3-N to 1.2 m) and three water levels. Water levels were uniformly maintained with a trickle system that independently metered water to each plot for each soil available N level. Pretillering spring wheat (Triticum aestivum L.) plant population decreased as soil OM content decreased in 3 of 4 yr. On an annual basis, highest total aerial dry matter and grain yields were associated with highest OM contents. The contribution of 1 Mg OM ha-1 to soil productivity, across the range of 64 to 142 Mg OM ha-1, was calculated as equivalent to 35.2 kg ha-1 for spring wheat total aerial dry matter and 15.6 kg ha-1 for grain yield. Loss of productivity associated with a depletion of soil OM in the northern Great Plains is primarily a consequence of a concomitant loss of fertility.
  • 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:
    • 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.