• Authors:
    • Mosier, A. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 63
  • Issue: 2
  • Year: 2002
  • Summary: Human-induced input of fixed nitrogen (N) into the earth biosphere, primarily through combustion of fossil fuels, crop biological N-fixation and N-fertilizer use, has provided many human benefits. These benefits have not come, however, without significant cost. According to data compiled by the Food and Agriculture Organization of the United Nations, synthetic N fertilizer input into global agricultural systems increased from by approximately 430% (~19 to ~82 Tg N) from 1965 to 1998. During this period, global grain production, human population and global fossil fuel consumption increased about 250%, 190% and 240%, respectively. Although fuel consumption increased faster than population growth globally, land used to produce grain decreased from 0.2 to 0.12 ha/person over this 30-yr period. Grain production, however, increased 16%/person. Agricultural production increase has come through the use of new crop varieties which respond to increased N-fertilization, pesticide use, irrigation and mechanization. Even though agricultural production has increased dramatically, fertilizer N use efficiency remains relatively low. Globally fertilizer N use efficiency was approximately 50% in 1996. Since fertilizer N is not used efficiently in most parts of the world, N use in excess of crop potential utilization leads to losses to the environment through volatilization and leaching. These N losses result in N fertilization of pristine terrestrial and aquatic systems through NHx and NOydeposition and contribute to global greenhouse gases through N2O production and local elevated ozone concentrations due to NOx emission. Inefficient use of N and energy is exacerbated by the global inequity of use distribution. Some areas don't have enough while others use too much. Additionally, dietary patterns of food consumption which tend to be more inefficient, i.e. cereal-based diets compared to animal-based diets, are changing in global terms. The resulting increasing inefficiencies in N utilization in food production and in energy use lead to large-scale input of N into down wind and down stream terrestrial and aquatic systems. Increasing N-use-efficiency remains a clear goal by which to maintain food production while decreasing excessive N use and unwanted distribution in the environment.
  • Authors:
    • Grove, J. H.
    • Dí­az-Zorita, M.
  • Source: Soil & Tillage Research
  • Volume: 66
  • Issue: 2
  • Year: 2002
  • Summary: Surface accumulation of soil organic carbon (SOC) under conservation tillage has significant effects on stratification of other nutrients, on crop productivity and in ameliorating the greenhouse effect via atmospheric CO, sequestration. A measure of SOC stratification relative to deeper soil layers has been proposed as a soil quality index. Our objective was to determine the effects of the duration of tillage practices upon the SOC and extractable P distribution with depth in Maury silt loams (Typic Paleudalfs) at similar levels of corn (Zea mays L.) productivity without P fertilization. Soil samples (0-20.0 cm in 2.5 cm increments) were collected under moldboard tillage (MT), chisel tillage (CT) and no-tillage (NT) and in surrounding tall fescue (Festuca arundinacea L.) sods selected from three tillage experiments (1-2-, 8- and 29-year durations) in Kentucky. SOC stratification was greater under conservation tillage (CT and NT) and sods than under MT. SOC and soil-test-extractable P stratification were positively related. Increasing the duration under NT caused the thickness of C stratification to increase. In NT soils, C stratification ratio (CSR) approached CSR in the nearby long-term sods with time. Conservation tillage rapidly promoted the occurrence of CSR greater than 2 while MT always resulted in values lower than 2. The rapid initial change in CSR suggests characterization of thin soil layers (i.e. 2.5 cm depth increments) is desirable under conservation tillage. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Riedell, W. E.
    • Pikul, J. L.
    • Archer, D. W.
  • Source: Soil & Tillage Research
  • Volume: 67
  • Issue: 1
  • Year: 2002
  • Summary: Ridge tillage (RT) has been proposed as an economically viable conservation tillage alternative for row crop production; however the long-term economic viability of RT in the northern Corn Belt of the USA is largely unknown. Economic returns, risk and input use were compared for RT and conventional tillage (CT) in a corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation with high, medium and low nitrogen treatments. The analysis was based on 10 years of experimental data from Brookings, SD on a Barnes clay loam (US soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll; FAO classification: Chernozem). Economic returns were significantly higher at the highest nitrogen treatment levels. Highest average net returns to land and management were $ 78 per hectare for RT at the high nitrogen treatment level (RT-H) followed by $ 59 per hectare for CT at the high nitrogen treatment level (CT-H). Risk, measured as the standard deviation of net returns, was the lowest for CT at the medium nitrogen treatment level (CT-M) followed by RT-H and CT-H. However, net returns were substantially lower under CT-M at $ 32 per hectare. Average yields and average operating costs were not significantly different for RT-H and CT-H. Reduced equipment operating costs for CT-H were offset by increased herbicide costs for RT-H. Equipment ownership costs were significantly lower for RT-H than CT-H. There were no significant differences in fertilizer use for RT and CT. Pesticide use was significantly higher for RT-H than CT-H. Fuel use was 18-22% lower and labor use was 24-27% lower for RT-H than CT-H. Despite continued low adoption rates for RT in the northern Corn Belt, our analysis shows that RT is an economically viable alternative to CT.
  • Authors:
    • Lajeunesse, J.
    • Pageau, D.
    • Legere, A.
    • Simard, M.
    • Warwick, S.
  • Source: Weed Technology
  • Volume: 16
  • Issue: 2
  • Year: 2002
  • Summary: The presence of volunteer rape ( B. napus [ B. napus var. oleifera]) is becoming a significant agroecological concern, given the large-scale use of herbicide-tolerant varieties in some areas. Our goal was to estimate the frequency and persistence of volunteer rape in Quebec cropping systems by surveying fields that included a single rape crop since 1995 in Quebec, Canada. A survey was conducted in 131 fields in the main rape-growing areas of Quebec: in the Saguenay-Lac Saint-Jean region and the Quebec City-La Pocatiere area, Canada, during June-August 2000. Volunteer rape plants were counted in 0.25-m 2 quadrats every 10 m along a W pattern, and every 15 m along the margins of 88 fields. Volunteer rape plants were found in 90% of the fields surveyed and in a wide range of crops, including cereal, maize, and soyabean. Average densities of 4.9 and 3.9 plants/m 2 were found a year after rape production in fields and field margins, respectively. Volunteer rape densities decreased significantly over time. However, volunteer plants were still present at low densities 4 and 5 years after production. Dense stands of volunteer rape were found before postemergence herbicide application in no-till fields (9.84.1 plants/m 2), suggesting that, contrary to what was suggested in the literature, seeds could become dormant in no-till as well as in tilled systems. A small proportion of the volunteer rape plants observed in no-till fields near Quebec City and Ottawa included plants that had overwintered, either originating from autumn-germinated seedlings, harvested adult plants that had grown new leaves before the onset of winter, or spring regrowth from the base of unharvested adult plants from experimental plots. The presence and persistence of low densities of volunteer rape may not have been a cause of concern until now. However, producers should be made more aware of the potential short-term and long-term problems associated with potential gene flow between different herbicide-tolerant rape (HT rape) varieties and also between HT rape and related weed species.
  • 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:
    • 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:
    • Brookes, G.
  • Source: Web Of Knowledge
  • Issue: Ed. 1
  • Year: 2002
  • Summary: The material contained in this book aims to bring together information about the profitability of growing different arable crops in a number of European countries. It draws on many national sources of information and brings these together in an updated form to reflect the latest harvest of 2001.
  • 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:
    • 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.