• Authors:
    • Wilkinson, S. R.
    • Stuedemann, J. A.
    • Franzluebbers, A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 65
  • Issue: 3
  • Year: 2001
  • Summary: Improved forage management impacts on soil organic C and S depth distribution and surface residue accumulation could be large, but detailed temporal data are not available. We evaluated the factorial combination of three levels of N fertilization [inorganic, crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and broiler litter] and four levels of harvest strategy (unharvested, low grazing pressure, high grazing pressure, and hayed monthly) on soil bulk density, soil organic C, and total S, and surface residue C and S during the first 5 yr of 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] management. Soil bulk density of the 0- to 6-cm depth responded very little to management, but across treatments it decreased 0.06 Mg m-3 yr-1 due to increasing soil organic matter with time. Soil organic C did not respond significantly to fertilization strategy during the 5 yr, but total S of the 0- to 6-cm depth was greater under broiler litter than under other fertilization strategies at the end of 3, 4, and 5 yr. Low and high grazing pressure were similar in their effect on soil organic C accumulation, averaging 140 g m-2 yr-1. Most of the net change in soil organic C occurred in the 0- to 2-cm depth. Soil under unharvested and hayed management accumulated organic C at rates less than one-half of those observed under cattle grazing. Cattle grazing shunted C more directly from forage to the soil, which contributed to greater sequestration of soil organic C than with haying or unharvested management.
  • Authors:
    • Ruiz-Suárez, L. G.
    • González-Avalos, E.
  • Source: Bioresource Technology
  • Volume: 80
  • Issue: 1
  • Year: 2001
  • Authors:
    • Powell, C.
  • Source: New South Wales Department of Agriculture
  • Year: 2001
  • Summary: Variety trials conducted in New South Wales, Australia in 2000 are reported for winter crops of barley, canola [rape], chickpeas, faba beans, field peas, lentils, lupins ( Lupinus albus and L. angustifolius), mixed cereals, oats, triticale and wheat.
  • Authors:
    • Williams, R. G.
    • Truman, C. C.
  • Source: Journal of Soil and Water Conservation Society
  • Volume: 56
  • Issue: 2
  • Year: 2001
  • Summary: Runoff and sediment yields were measured from eight field plots (40 m(2)) over a three year period to determine the effect of peanut cropping practices and canopy cover conditions on runoff and sediment loss. Plots were located on a Tifton loamy sand, and were exposed to four 30 min simulated rainfall sequences (I = 63.5 mm h(-1)) four to eight times per growing season. Runoff and sediment losses were measured from four soil cover conditions: continuous fallow, bare bedded, single row peanuts (Arachis hypogea L), and twin row peanuts (2 to 4 peanut rows per 2 m wide bed). percent cover (PC) and leaf area index (LAI) increased to a maximum then leveled off as plants matured or were harvested. PC for single and twin row peanuts was related to days since planting (DSP) (r - 0.96 for single row peanuts and r = 0.98 for twin row peanuts). LAI values for single and twin row peanuts were related to PC (r = 0.98 for single row peanuts and r = 0.94 for twin row peanuts). Single and twin row peanut plots had as much as eight times less runoff and as much as 63 times less sediment loss than continuous fallow or bare bedded plots. Twin row peanut plots had as much as three times less runoff and sediment loss than single row peanut plots. Sequence-based erodibility values calculated from continuous fallow plots (K-FC) and bare bedded plots (K-BB) ranged from 4-24 (3 yr mean = 11.3, s.d. = 5.3) and 2-36 kg ha h MJ(-1) ha(-1) mm(-1) (3 yr mean = 12.9, s.d. = 11.6), respectively. Soil loss ratios (SLR) ranged from 0.001-2.61. SLRs decrease to a low for cropstage 3 when percent canopy cover was greatest (DSP = 81-107), then increased as peanut plants mature or were harvested. Results show how management practices, such as twin row peanuts, can maximize peanut canopy development early in the growing season and minimize the time in which bare soil is vulnerable to a runoff producing rainstorm, thus reducing runoff and soil loss and conserving valuable natural resources.
  • Authors:
    • Spurlock, S. R.
    • Elmore, C. D.
    • Wesley, R. A.
  • Source: Agronomy Journal
  • Volume: 93
  • Issue: 1
  • Year: 2001
  • Summary: Deep tillage (subsoiling) of clayey soils in the fall when the profile is dry is a new concept that results in increased yields and net returns from soyabean (Glycine max) grown without irrigation. Crop rotation may also result in increased crop yields. Field studies were conducted on Tunica clay (clayey over loamy, smectitic, nonacid, thermic, Vertic Haplaquept) near Stoneville, Mississippi, USA (33degrees 26′ N lat), during 1993-97, to determine the individual and combined effects of fall deep tillage and crop rotations on crop yields and net returns. Treatments included monocrop cotton (Gossypium hirsutum cultivars DES 119 and Suregrow 125), soyabean (cultivars Pioneer 9592 and DPL 3588), and grain sorghum ( Sorghum bicolor cv. Pioneer 8333), and biennial rotations of cotton with grain sorghum and soyabean with grain sorghum grown without irrigation and in either a conventional-till (CT) or deep-till (DT) production system. Yields from all cotton and soyabean crop sequences grown in the DT respectively averaged 541 kg ha -1 and 525 kg ha -1 greater than comparable cotton (2184 kg ha -1) and soyabean (2983 kg ha -1) crop sequences grown in the CT. Net returns from monocrop cotton ($552 ha -1) and soyabean ($462 ha -1) in the DT respectively averaged $392 ha -1 and $121 ha -1 more than similar crop sequences in the CT. Rotations increased cotton and soyabean yields but not net returns because of the low value of the grain sorghum component. These data indicate that fall deep tillage should be incorporated into monocrop cotton and soyabean crop sequences to maximize and stabilize net returns from these crops on Tunica clay.
  • Authors:
    • Christoffoleti, P. J.
    • Shiratsuchi, L. S.
  • Source: The BCPC Conference: Weeds, 2001, Volume 1 and Volume 2. Proceedings of an international conference held at the Brighton Hilton Metropole Hotel, Brighton, UK, 12-15 November 2001
  • Year: 2001
  • Summary: Weed control represents a high percentage of the production costs in no-till systems in Brazil, and chemical control using herbicides is by far the most important method used. However, the weeds are not uniformly or randomly distributed but have a patchy distribution such that the broadcast application of herbicides can spray post-emergence herbicides in areas where there are no weeds. Therefore, this work had the objective of demonstrating the potential of saving of herbicides in the no-till production system of the Brazilian agriculture, based on weed seed bank and weed seedling maps. The density of several weeds was mapped using a backpack DGPS and laptop computer. Experiments were conducted in Sao Paulo [date not given] in a 17.7-ha field of no-till maize under centre pivot irrigation. Seed bank data was determined from soil cores collected from a depth of 0.05 m in the centre of a 20*20 m grid and emergence assessments in a greenhouse. On the same grid size, weed seedlings were counted in 0.25 m 2 quadrats. Resultant maps showed a high weed density in the seed bank over just 4.67 ha, which was only 26% of the field area. The seedling maps demonstrated that grasses and broadleaf weeds had different distributions with broadleaf weeds occupying 12.6% of the field and grasses 87.4%. The targeting of herbicide to weed patches using pre- and postemergent herbicides has the potential to reduce herbicide use compared to broadcast application giving both environmental and economic advantages.
  • Authors:
    • Duarte, G. A.
    • Diaz-Zorita, M.
  • Source: Siembra Directa II
  • Year: 2001
  • Summary: Notes are given on the effects of incorporation of direct grazing in systems of continuous zero tillage in western Buenos Aires, Argentina. It is concluded that incorporation of grazing with direct sowing practices in mixed production systems is feasible, with the aim of maintaining high levels of stubble cover. The removal of crop residues reduces the potential for conservation of soil water and attenuates the impact of trampling by animals.
  • Authors:
    • Ayuk, E. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 61
  • Issue: 1-2
  • Year: 2001
  • Summary: In recent years and in some situations the status of soil organic matter (SOM) has deteriorated considerably due to long periods of continuous cultivation and limited external inputs in the form of mineral fertilizers. Deterioration of SOM varies by agro-ecological zones, by soil types and by cropping patterns. It is more intense in East Africa, followed by coastal West Africa and Southern Africa and least intensive in the Sahel and Central Africa. It is also more serious in areas under low-input agriculture irrespective of the prevailing cropping system. The major consequence of the decrease in SOM in the tropics is lower agricultural productivity with a direct negative effect on food security. While biophysical dynamics of SOM have been extensively covered in the literature, social considerations have not received similar attention. This paper examines the social, economic and policy factors associated with the management of tropical soil organic matter. Empirical data from a range of environments in Africa show that SOM improvement options yield a positive return to land as well as labour. However, there are a number of constraints. Social constraints are related to the large quantities of organic matter that are required (case of farmyard manure), the competitive uses for the material (case of crop residues), land and labour requirements, and gender-related issues. From a policy stand point, unsecured tenure rights together with price distortions and other market failures may be important constraints. Challenges for sustainable management of SOM are identified. These include management conflicts, land tenure arrangements, the divergence in goals between individuals and society, land and labour requirements, inadequate support systems for land users, profitability issues, the role of subsidies, and the absence of national action plans. A number of opportunities are identified that could enhance the improvement or maintenance of SOM. These include: exploring the need and potential role of community-based SOM management practices; development of an integrated plant nutrient management strategy involving both organic and inorganic inputs; and development of concrete national action plans. It is argued that because externalities of SOM improvement or maintenance extend beyond the farmer's fields, SOM investment may require cost sharing between individuals and the society. Policies on subsidies need to be reconsidered. Research priorities are identified that require closer collaboration between scientists from a variety of disciplines.
  • Authors:
    • Khosla, R.
    • Alley, M. M.
    • Davis, P. H.
  • Source: Agronomy Journal
  • Volume: 92
  • Issue: 2
  • Year: 2000
  • Summary: Grain sorghum [Sorghum bicolor (L.) Moench] is grown in rotation with wheat (Triticum aestivum L.) and soybean [Glycine mar (L.) Merr.] in the mid-Atlantic Sufficient data on N fertilization of sorghum are not available for this region. Our objective was to evaluate the influence of multi-rate N fertilization on dryland sorghum. Treatments consisted of factorial combinations of four starter-band N rates (11, 34, 56, and 78 kg N ha(-1)) and four sidedress N rates (0, 45, 90, and 134 kg N ha(-1)). A broadcast treatment of 67 kg N ha(-1) at planting was also included. Starter-band was applied 5 cm to the side and below the seed. Sidedress was applied 35 days after emergence at the eight-leaf growth stage. Grain yield ranged from 1.7 to 11.9 Mg ha(-1) over eight site-years and was responsive and nonresponsive to N applications on four sites each. Nonresponsiveness was either due to high levels (>85 kg N ha(-1)) of residual soil mineral N, or severe water stress conditions. Our results indicate that production of sorghum on soils testing high in mineral N (50 kg N ha(-1) in the surface 0.3 m) at planting should not receive any starter-band N in conjunction with sidedress N application of 130 kg N ha(-1) for optimum economic return to N fertilization. For soils testing low in mineral N, 40 kg N ha(-1) starter-band in conjunction with 130 kg N ha(-1) sidedress N should optimize the sorghum yields in most situations.
  • Authors:
    • Nyakatawa,E. Z.
    • Reddy,K. C.
  • Source: Agronomy Journal
  • Volume: 92
  • Issue: 5
  • Year: 2000
  • Summary: Inadequate and less vigorous crop stand is a constraint to adoption of conservation tillage in cotton (Gossypium hirsutum L.) production. We evaluated the effects of tillage (conventional till, mulch-till, no-till), cropping system (cotton-winter fallow, cotton-winter rye, Secale cereale L.), and N source and rate (ammonium nitrate and poultry litter; 0, 100, and 200 kg N ha(-1)) on rotten seedling emergence on a Decatur silt loam soil (Typic Paleudults) in northern Alabama, from 1996 to 1998. Cotton seedling counts under no-till were 40 to 150% greater than those under conventional till at 1 and 2 d during seedling emergence. Cotton-winter rye cropping system had 14 to 50% greater seedling counts than cotton-winter fallow cropping during the first 4 d of emergence in 1998. Poultry litter source of N gave 17 to 50% greater cotton seedling counts than ammonium nitrate during the first 4 d of emergence in 1998, In all these cases, the differences progressively narrowed down by the 4th day of seedling emergence. Cotton seedling counts were significantly correlated to cotton growth parameters and lint yield, especially in the drier year (1998). These results were attributed to soil moisture conservation during seedling emergence. Our results show that conservation tillage improved cotton germination, emergence, dry matter, and lint yield. Therefore, no-till with winter rye cover cropping and poultry litter can be used for achieving early cotton seedling emergence and growth in the U.S. cotton belt where dryland cotton production systems are on the increase and safe disposal of poultry litter is becoming an environmental problem.