• Authors:
    • Norsworthy, J. K.
    • Oliver, L. R.
  • Source: Weed Technology
  • Volume: 16
  • Issue: 1
  • Year: 2002
  • Summary: A field experiment was conducted in 1998 and 1999 at Keiser, AR, to evaluate glyphosate timing and soybean population in reducing hemp sesbania and pitted morningglory interference with dryland and irrigated glyphosate-resistant soybean under a narrow row, no-till production system. Soybean densities following emergence were 247,000, 475,000, and 729,000 plants/ha. Glyphosate was applied at 0.56 kg ai/ha at the V2; V4; V2 and V4; and V2, V4, and R2 stages of soybean. In dry portions of the growing season, glyphosate increased moisture availability for dryland soybean because of control of hemp sesbania and pitted morningglory. As soybean population increased from 247,000 to 729,000 plants/ha, pitted morningglory and hemp sesbania control increased from 60 to 91%, respectively, for the V2 glyphosate application. Control of both species at 14 wk after emergence was at least 90% following the V4 alone treatment and sequential applications, with no differences in control among soybean populations. Untreated, irrigated hemp sesbania produced up to 32 million seeds/ha in 1999. Irrigation did not influence pitted morningglory seed production either year, and untreated pitted morningglory produced a maximum of 1 million seeds/ha in 1998 at 247,000 soybean plants/ha. Three sequential applications of glyphosate reduced pitted morningglory seed production to 9,000 seeds/ha and eliminated hemp sesbania seed production. Soybean yielded 1,297 kg/ha greater under irrigated than dryland conditions, whereas increasing soybean density from 247,000 to 729,000 plants/ha resulted in 416 kg/ha improvement in seed yield. At the densities of pitted morningglory and hemp sesbania present in this study, seed yield of drill-seeded soybean can be maximized following a V4 alone treatment or sequential glyphosate applications.
  • Authors:
    • Nielsen, G.
    • Mortensen, D.
    • McGinn, S.
    • Coen, G.
    • Caprio, J.
    • Waltman, S.
    • Padbury, G.
    • Sinclair, R.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 2
  • Year: 2002
  • Summary: The northern Great Plains have long been dominated by conventional tillage systems and cereal-based rotations including summer fallow. Over the last decade, however, the use of conservation tillage systems has markedly increased and, through improved moisture storage, has provided an opportunity for more diversified extended rotations including oilseed, pulse, and forage crops throughout the region. Considerable research is being carried out to assess the adaptability of these new crops and to develop appropriate management strategies. Typically, this type of agronomic research is carried out at plot-sized research sites, with the findings then being extrapolated to surrounding regions where growing conditions are thought to be reasonably similar. Because the environment itself largely dictates the success of a particular cropping system, extrapolation requires knowledge of the environmental conditions of the region and, in particular, the interaction of environmental components of soil and climate in relation to specific crop requirements. This paper describes 14 agroecoregions in the northern Great Plains and provides an initial framework for extrapolating agronomic information at broad regional scales. Because climate is the dominant crop production factor in the region, most of the agroecosystems represent broad climatic zones. Each agroecoregion is described in terms of its soil and landscape characteristics, with a particular focus being given to likely key environmental parameters related to the production of the new oilseed, pulse, and forage crops being introduced in the region.
  • Authors:
    • Dillon, C. R.
    • Oliver, L. R.
    • McNew, R. W.
    • Keisling, T. C.
    • Popp, M. P.
    • Wallace, D. M.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 1
  • Year: 2002
  • Summary: Soyabean ( Glycine max) yields from non-irrigated fields in the mid-southern USA have consistently lagged behind those from irrigated fields. Nonetheless, non-irrigated fields still attract a larger share of soyabean acreage in this region. This is likely due to various irrigation constraints, which include land leasing arrangements, water shortage, lack of management time and low levels of operating capital. The objective of this study was to identify production system components consisting of tillage, cultivar selection and planting date strategies for a soil series that are most suitable for enhancing economic returns to dryland soyabean. Data from field experiments in three locations in Arkansas, USA during 1995 and 1996 were used for the study. Leading production systems were identified on the basis of their net returns. Results of the study showed that the performance of the production systems in terms of crop yields and net returns is influenced by the location and production year. While the evidence on pure planting date effects was confounded with physical field location, cultivar yields from early soyabean plantings in April and May were generally higher than those from later plantings. Furthermore, conventional and fallow production systems had higher net returns than no-till systems, largely due to higher herbicide costs associated with no-till systems. Sensitivity analysis showed that planting date and seedbed preparations are robust to changes in herbicide, fuel and soyabean prices. Further, careful attention to cultivar selection is deemed appropriate because cost differences of cultivar seeds are minor relative to net return differences that are yield driven.
  • Authors:
    • Delaney, D. P.
    • Reeves, D. W.
  • Source: E. van Santen (ed.) 2002. Making Conservation Tillage Conventional: Building a Future on 25 Years of Research. Proc. of 25th Annual Southern Conserva­tion Tillage Conference for Sustainable Agriculture. Auburn, AL, 24-26 June 2002. Special Report no. 1.
  • Year: 2002
  • Summary: Intensive cropping and conservation tillage can increase soil organic C (SOC) and improve soil quality, however, economic reality often dictates cotton ( Gossypium hirsutum) monoculture. We conducted a study on a Compass loamy sand (coarse-loamy, siliceous, subactive, thermic Plinthic Paleudults) from 1998-2001 to compare an intensive conservation cropping system to standard cotton production systems used in the southeastern USA (Alabama). The system uses sunn hemp ( Crotalaria juncea) and ultra-narrow row (UNR; 8-inch drill) cotton in a rotation with wheat ( Triticum aestivum) and maize ( Zea mays). The standard systems used continuous cotton (both standard 40-inch rows and ultra-narrow row) and a maize-cotton rotation with standard row widths. A cover crop mixture of black oat ( Avena strigosa [ A. nuda])/rye ( Secale cereale) was used in all systems preceding cotton and a white lupin ( Lupinus albus)/crimson clover ( Trifolium incarnatum) mix was used before maize in the maize-cotton and intensive system. All systems were tested under conservation and conventional tillage in a split plot design of four replications; main plots were cropping systems and subplots were tillage. We used extension budgets to calculate net returns over variable costs and determined C balance of all residues returned to the soil. At the end of the experiment, soil C was determined by dry combustion (0-0.4, 0.4-2, 2-4, 4-8, and 8-12 in depths). Cropping system had a more consistent effect on cotton yield than tillage system. Four-year average lint yields were 872, 814, 711 and 663 lbs acre -1 for continuous UNR, intensive, maize-cotton, and continuous 40-in cotton systems, respectively. The UNR systems with conservation tillage had the highest net returns ($105 acre -1 year -1 (continuous) and $97 acre -1 year -1 (intensive)) while the conventional tillage continuous 40-in system had the lowest returns ($36 acre -1 year -1). Conservation tillage increased SOC concentration in the top 2 inches of soil 46% compared to conventional tillage. Cropping system affected SOC levels to the 4-in depth and the maize-cotton rotation resulted in the lowest SOC levels of all systems. Results suggest that small grain cover crops and wheat for grain in the intensive system were the dominate factor in SOC changes. For these drought-sensitive soils, UNR cotton production systems with conservation tillage and small grain cover or cash crops have the potential to rapidly increase soil organic matter; improving soil productivity and enhancing economic sustainability of cotton production in the southeastern USA.
  • Authors:
    • Reeves, D. W.
    • Burmester, C. H.
    • Motta, A. C. V.
  • Source: Making Conservation Tillage Conventional: Building a Future on 25 Years of Research. Proceedings of 25th Annual Southern Conservation Tillage Conference for Sustainable Agriculture, Auburn, AL, USA, 24-26 June, 2002 - Special Report no. 1, Alabama Agricult
  • Year: 2002
  • Summary: A replicated cotton (Gossypium hirsutum) rotation experiment has been conducted for 22 years (1980-2001) on a Decatur silt loam (fine, kaolinitic, thermic, Rhodic Paleudults) in the Tennessee Valley of northern Alabama, USA. The highly productive soil with little disease and nematode problems resulted in cotton yield increases from rotations of generally less than 10% during the first 15 years of the study. A switch to no-tillage in all rotations except continuous cotton in 1995 greatly improved cotton yield response to rotations. From 1995 to 2001 cotton yield increases to rotation have averaged between 5% and 18%. In this study, yield increases due to rotations seem linked to increases in soil organic matter and consequent improvements in soil quality. From 1979 to 1994 using conventional tillage, the only rotation that produced a greater than 10% yield increase was cotton rotated with wheat ( Triticum aestivum) and double-cropped soyabean ( Glycine max). This rotation was also the only rotation that significantly increased organic matter levels under conventional tillage. From 1995 to 2001, all rotations were no-tilled and the greater yield increases to rotations can also be associated with higher soil organic matter levels. Wheat as a grain rotation or cover crop often produced the greatest yield increases to the following cotton crop. Under conventional tillage the wheat residue provided increased organic matter residue. With no-tillage the wheat cover crop reduced surface soil compaction. No-tillage and rotations that increased residue production were linked to increased cotton yields on this soil.
  • Authors:
    • Thill, D. C.
    • Daugovish, O.
    • Shafii, B.
  • Source: Weed Science
  • Volume: 50
  • Issue: 5
  • Year: 2002
  • Summary: Wild oat, a troublesome weed in small grain cereals, infests about 11 million ha of cropland in the United States Diversifying cereal production with alternative crops, such as yellow mustard and canola, provides flexible cropping systems, decreases production risks, and may allow more effective weed suppression A greenhouse study was conducted to assess the competitive ability of yellow mustard and canola with wild oat in 1999 and 2000, using replacement series interference experiments to relate the results to plant development stages Yellow mustard, regardless of its proportion in mixture, reduced aboveground biomass of wild oat 33 to 66%, leaf and tiller number 34 to 36%, and panicle production 58% compared with wild oat in monoculture Canola did not affect wild oat biomass in mixtures Yellow mustard per plant biomass in 2000 and inflorescence production in 1999 decreased 30 and 20% with increased density of yellow mustard in mixtures Yellow mustard biomass was not affected by the addition of wild oat to the mixture, indicating the greater importance of intraspecific competition between yellow mustard relative to interspecific competition with wild oat Canola per plant biomass was affected more by interspecific competition with wild oat than by intraspecific competition A second greenhouse experiment was conducted to compare plant height and biomass accumulation by the three species over 7 wk Yellow mustard had the greatest biomass accumulation and plant elongation rate, followed by canola and wild oat The greater competitive ability of yellow mustard with wild oat, compared with canola, is likely associated with the rapid growth and canopy elevation of yellow mustard.
  • Authors:
    • Blackshaw, R. E.
    • Anderson, R. L.
    • Derksen, D. A.
    • Maxwell, B.
  • Source: Agronomy Journal
  • Volume: 94
  • Issue: 2
  • Year: 2002
  • Summary: Cropping systems in the northern Great Plains (NGP) have evolved from wheat Triticum aestivum L.)-fallow rotations to diversified cropping sequences. Diversification and continuous cropping have largely been a consequence of soil moisture saved through the adoption of conservation tillage. Consequently, weed communities have changed and, in some cases, become resistant to commonly used herbicides, thus increasing the complexity of managing weeds. The sustainability of diverse reduced tillage systems in the NGP depends on the development of economical and effective weed management systems. Utilizing the principle of varying selection pressure to keep weed communities off balance has reduced weed densities, minimized crop yield losses, and inhibited adverse community changes toward difficult-to-control species. Varied selection pressure was best achieved with a diverse cropping system where crop seeding date, perennation, and species and herbicide mode of action and use pattern were inherently varied. Novel approaches to cropping systems, including balancing rotations between cereal and broadleaf crops, reducing herbicide inputs, organic production, fall-seeded dormant canola (Brassica napus and B. rapa), and the use of cover crops and perennial forages, are discussed in light of potential systems-level benefits for weed management.
  • Authors:
    • McNew, R. W.
    • Bacon, R. K.
    • Moldenhauer, K. A. K.
    • Windham, T. E.
    • Anders, M. M.
    • Cartwright, R. D.
    • Gibbons, J. W.
  • Source: Research Series - Arkansas Agricultural Experiment Station 2000 No. 476
  • Issue: 495
  • Year: 2002
  • Summary: Net returns for the full-season 2000 crop treatment combinations were between $89.57/acre for the continuous rice, no-till, enhanced fertility, 'LaGrue' treatment combination and $326.71/acre for the rice following corn, conventional tillage, standard fertility, 'Wells' treatment combination. Net returns, on average, were lowest ($141.49/acre) for the continuous rice rotation and highest ($234.61/acre) for the rice following soybean rotation. Lower production costs from the no-till plots were more than offset by increased yields in the conventional till plots resulting in higher net returns for the conventional tillage plots. The enhanced fertility treatment did not result in sufficient yield gains to offset fertilizer costs, thus net returns were higher for the standard fertility treatments. Consistently higher grain yields from Wells resulted in overall higher net returns from this variety. The only short-season rice variety combination resulting in positive net returns was with the variety 'XL-6'. Overall grain yields declined from 178 bu/acre in 2000 to 158 bu/acre in 2001. The mean grain yield from the continuous rice rotation was approximately 20 bu/acre lower than rice following soybean or corn. The enhanced fertility plots yielded only 6 bu/acre more than the standard fertility treatment. Yields declined in the short-duration rice treatments with highest grain yields from the variety XL-6. Water-use measurements indicated that, on average, all rice plots used approximately 29 acre-inches of irrigation water during the season. Water savings came from a reduced need to flush no-till plots. Above-ground plant nutrient uptake values indicated that the variety Wells generally took up more nutrients when compared to LaGrue. Rotation had the biggest impact on nutrient uptake in 2000 and there was a trend of increased nutrient uptake from the enhanced fertility treatments when compared to the standard fertility treatments even though there was no increase in grain yield.
  • Authors:
    • Petersen,SO
    • Frohne,PS
    • Kennedy,AC
  • Source: Soil Science Society of America Journal
  • Volume: 66
  • Issue: 3
  • Year: 2002
  • Summary: In arable systems, seasonal fluctuations of microbiological properties can be significant. We hypothesized that adaptation to soil environmental conditions may contribute to the variation observed, and this was examined by characterization of different microbial community attributes under a range of soil conditions. Soil was sampled from no-till and chisel-tilled fields within a long-term experiment in eastern Washington during growth of spring wheat (Triticum aestivum). The range of soil environmental conditions covered was extended by amendment of crop residues. Soil samples were characterized with respect to biomass N and biomass P, substrate utilization dynamics, phospholipid fatty acid (PLFA) profiles and whole-soil fatty acid (MIDI-FA) profiles, and with respect to soil environmental variables (bulk density, soil organic C [SOC], temperature, moisture, and inorganic N and P). Bacterial and fungal lipid biomarkers were negatively correlated (P < 0.001), confirming that these subsets of fatty acids are associated with contrasting components of the microbial biomass. Biomass N was closely associated with soil conditions, notably N availability. The proportion of substrates used with no apparent lag phase decreased during summer and was negatively correlated with lipid stress indicators. Cyclopropyl fatty acids accounted for more than 60% of the variation in bacteria] PLFA. These observations suggest that adaptation to environmental stresses was partly responsible for the microbial dynamics observed. Tillage practice had little effect on the relationships between soil conditions and microbiological properties. The results showed that MIDI-FA included a significant background of nonmicrobial material and was less sensitive to soil environmental conditions than PLFA.
  • Authors:
    • Power, J. F.
    • Wiese, R.
    • Flowerday, D.
  • Source: Journal of Environmental Quality
  • Volume: 30
  • Issue: 6
  • Year: 2001
  • Summary: The U.S. Department of Agriculture funded the Management Systems Evaluation Area (MSEA) research project in 1990 to evaluate effectiveness of present fanning systems in controlling nitrate N in water resources and to develop improved technologies for farming systems. This paper summarizes published research results of a five-year effort. Most research is focused on evaluating the effectiveness of farming system components (fertilizer, tillage, water control, cropping systems, and soil and weather variability). The research results show that current soil nitrate tests reliably predict fertilizer N needed to control environmental and economic risks for crop production. A corn (Zea mays L.)-soybean [Glycine mar (L.) Merr.] rotation usually controls risk better than continuous corn, but both may result in unacceptable nitrate leaching. Reduced tillage, especially ridge-till, is better than clean tillage in reducing risk. The drainage controls nitrate in ground water, but discharge may increase nitrate in surface waters. Sprinkler irrigation systems provide better water control than furrow irrigation because quantity and spatial variability of applied water is reduced. Present farming systems have two major deficiencies: (i) entire fields are managed uniformly, ignoring inherent soil variability within a field; and (ii) N fertilizer rates and many field practices are selected assuming normal weather for the coming season. Both deficiencies can contribute to nitrate leaching in parts of most fields.