• Authors:
    • Merrill, S.
    • Lares, M.
    • Tanaka, D.
    • Krupinsky, J.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 1
  • Year: 2004
  • Summary: Crop diversification and crop sequencing can influence plant disease risk in cropping systems. The objective of this research was to determine the effect of 10 previous crops on leaf spot diseases of barley ( Hordeum vulgare L.) and hard red spring wheat ( Triticum aestivum L.). Barley and spring wheat were direct-seeded (no till) in the crop residue of 10 crops {barley, canola ( Brassica napus L.), crambe ( Crambe abyssinica Hochst. ex R.E. Fr.), dry bean ( Phaseolus vulgaris L.), dry pea ( Pisum sativum L.), flax ( Linum usitatissimum L.), safflower ( Carthamus tinctorius L.), soybean [ Glycine max (L.) Merr.], sunflower ( Helianthus annuus L.), and spring wheat}. Barley was evaluated for leaf spot diseases 15 times over 2 yr. Results indicate that risk for leaf spot disease on barley would be lower following wheat, crambe, canola and dry pea compared with the barley-after-barley treatment. Although barley yields were similar across all treatments one year, differences were detected in another year with the barley-after-barley treatment having the lowest yield. Spring wheat was evaluated for leaf spot diseases 22 times over 2 yr. Differences among treatments were more detectable in earlier evaluations, indicating a greater influence of crop residue and carryover of inoculum early in the season compared with later. The risk for leaf spot disease was lower when wheat was grown after canola, barley, crambe, and flax than when grown after the other crops. Although wheat yields were similar across all treatments one year, differences were detected in another year with the wheat-after-wheat treatment having the lowest yield.
  • Authors:
    • Richardson, J.
    • Hons, F.
    • Ribera, L.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 2
  • Year: 2004
  • Summary: Tillage systems that reduce the number of cultivation steps can, according to soil scientists, save soil moisture, fuel, labour, and machinery costs, as well as reduce wind and water erosion. However, many producers in south Texas, USA, are reluctant to adopt these practices. The objective of this study was to compare the economics of conventional tillage (CT) and no-tillage (NT) systems on three commercial crops produced in south Texas: grain sorghum ( Sorghum bicolor), wheat ( Triticum aestivum), and soyabean ( Glycine max). When considering the economics of both tillage systems, three areas affecting profit were addressed: changes in cost per hectare, changes in yield per hectare, and the impact on net income risk. Empirical distributions of net income for different tillage systems under risk were estimated using a Monte Carlo simulation model of net income per hectare. Certainty equivalents were used to rank the tillage systems because they can be used to rank risky alternatives for risk-averse decision makers. The risk premium for risk-averse decision makers who prefer NT over CT ranges between $12.60 and $34.25 per hectare for all five crop rotations. Risk-neutral decision makers would prefer continuous sorghum and sorghum-wheat-soyabean rotation over all other rotations under CT and NT, respectively. However, risk-averse decision makers would prefer continuous sorghum over all other rotations either under CT or NT. The results suggest that under risk-neutral rankings, NT would be preferred over CT in three out of the five crop rotations tested. However, assuming a risk-averse decision maker, NT would be preferred over CT in all five crop rotations.
  • Authors:
    • Carmo, C.
    • Lhamby, J.
    • Ambrosi, I.
    • Santos, H.
  • Source: Ciencia Rural
  • Volume: 34
  • Issue: 1
  • Year: 2004
  • Summary: Soil tillage and crop rotation and succession systems were assessed in Passo Fundo, Rio Grande do Sul, Brazil, from 1994/95 to 1997/98. Four soil tillage systems, i.e. no-tillage, minimum tillage, conventional tillage using a disc plough, and conventional tillage using a mouldboard plough, and three crop rotation and succession systems, i.e. system I (wheat/soyabean), system II (wheat/soyabean and common vetch [ Vicia sativa]/sorghum or maize) and system III (wheat/soyabean, common vetch/sorghum or maize, and white oats/soyabean), were compared. An experimental design of randomized blocks with split-plots and three replications was used. The main plot was formed by the soil tillage systems, while the split-plots consisted of the crop rotation and succession systems. Two types of analysis were applied to the net return of soil tillage and crop rotation and succession systems: mean-variance and risk analysis. By the mean-variance analysis, no-tillage and minimum tillage, which presented higher net returns, were the best alternatives to be offered to the farmer. By the stochastic dominance analysis, no-tillage and crop rotation with two winters without wheat showed the highest profit and the lowest risk.
  • Authors:
    • Arshad, M.
    • Soon, Y.
  • Source: Canadian Journal of Soil Science
  • Volume: 84
  • Issue: 4
  • Year: 2004
  • Summary: A field study was conducted to determine the effects and interactions of crop sequence, tillage and residue management on labile N pools and their availability because such information is sparse. Experimental treatments were no-till (NT) vs. conventional tillage (CT), and removal vs. retention of straw, imposed on a barley ( Hordeum vulgare L.)-canola ( Brassica rapa L.)-field pea ( Pisum sativum L.) rotation. 15N-labelling was used to quantify N uptake from straw, below-ground N (BGN), and fertilizer N. Straw retention increased soil microbial biomass N (MBN) in 2 of 3 yr at the four-leaf growth stage of barley, consistent with observed decreases in extractable soil inorganic N at seeding. However, crop yield and N uptake at maturity were not different between straw treatments. No tillage increased soil MBN, crop yield and N uptake compared to CT, but had no effect on extractable soil inorganic N. The greater availability of N under NT was probably related to soil moisture conservation. Tillage effects on soil and plant N were mostly independent of straw treatment. Straw and tillage treatments did not influence the uptake of N from its various sources. However, barley following pea (legume/non-legume sequence) derived a greater proportion of its N from BGN (13 to 23% or 9 to 23 kg N ha -1) than canola following barley (non-legumes) (6 to 16% or 3 to 9 kg N ha -1). Fertilizer N constituted 8 to 11% of barley N uptake and 23 to 32% of canola N uptake. Straw N contributed only 1 to 3% of plant N uptake. This study showed the dominant influence of tillage on N availability, and of the preceding crop or cropping sequence on N uptake partitioning among available N sources.
  • Authors:
    • Rice, C. W.
    • Claassen, M. M.
    • Nelson, R. G.
    • Williams, J. R.
  • Source: Environmental Management
  • Volume: 33
  • Issue: 1
  • Year: 2004
  • Summary: An economic analysis of wheat and grain sorghum production systems that affect carbon dioxide (CO2) emissions and sequester soil carbon (C) in metric tons (MT) is conducted. Expected net returns, changes in net C sequestered, and the value of C credits necessary to equate net returns from systems that sequester more C with those that sequester less is determined with and without adjustments for CO2 emissions from production inputs. Experiment station cropping practices, yield data, and soil C data for continuously cropped and rotated wheat and grain sorghum produced with conventional tillage and no-tillage are used. No-till has lower net returns because of somewhat lower yields and higher overall costs. Both crops produced under no-till have higher annual soil C gains than under conventional tillage. However, no-till systems have somewhat higher total atmospheric emissions of C from production inputs. The C credit values estimated in this study will equate net returns of no-tillage to conventional tillage range from $8.62 to $64.65/MT/yr when C emissions from production inputs are subtracted from soil C sequestered, and $8.59 to $60.54/MT/yr when atmospheric emissions are not considered. This indicates accounting for CO2 emissions from production inputs may not be necessary in the process to issue C credits.
  • Authors:
    • Reddy, G. B.
    • Brock, B.
    • Naderman, G.
    • Raczkowski, C. W.
  • Source: Proceedings of the 26th Southern Conservation Tillage Conference for Sustainable Agriculture 8-9 June, 2004, Raleigh, North Carolina
  • Year: 2004
  • Summary: This study reports the results of sampling soil within a field experiment at CEFS, the Cherry Farm, Goldsboro, North Carolina. The experiment tested effects of six years of conservation tillage with cover crops, contrasted with chisel plow/disk tillage without cover crops, under three crop rotations. In April, 2003 two sets of undisturbed core samples were collected from six mapped soil areas, at depth increments of 0-2 and 2-5 inches, replicated four times. One set was used for soil bulk density; the other provided soil carbon and total nitrogen contents. The study found strong and consistent inverse correlations between soil carbon content and bulk density. Under conservation tillage the surface two inches generally sustained suitable density for root activities. However, at 2-5 inches density approached or exceeded 1.6 g cm-3. Given the textures involved, this density likely would affect root growth, especially under non-ideal, wet/cool or dry/hard conditions. This would be especially important for crop establishment within this prime rooting zone. This low carbon/high-density problem was less likely for soils containing the influences of more silt with less sand. It was greater when corn, peanut and cotton were grown compared to producing soyabean or wheat/soybean with corn. This study revealed increased carbon sequestration from the conservation tillage systems used, along with increased total N content in the surface five inches of soil. Conservation tillage as practiced helped to reduce the "greenhouse effect" and lessened N leaching losses, holding more of these elements within the topsoil.
  • Authors:
    • O'Connell, P. J.
    • Allard, J. L.
  • Source: Weed management: balancing people, planet, profit. 14th Australian Weeds Conference, Wagga Wagga, New South Wales, Australia, 6-9 September 2004: papers and proceedings 2004
  • Year: 2004
  • Summary: Australian winter broadacre crops have been planted on 19.4 million ha on average, over the five years 1999-2003. The cropped area is dominated by cereals and in particular wheat. Annual ryegrass (ARG, Lolium rigidum) is the most widespread, difficult to control and important weed of Australian winter broadacre farming systems, and is arguably the greatest threat to sustainability of these systems. It was calculated that it infests ~6 million ha. Syngenta's analyses of herbicide sales suggest that the area treated for annual ryegrass could be as high as 8 million ha. Herbicide sales have been used to estimate the area treated for ARG control. This analysis focuses on herbicides for which there is not yet widespread ARG resistance. Grain producers are heavily dependant on two groups of herbicides. Group M (glyphosate) is applied as a non-selective burn-down treatment prior to planting and is applied to as much as 25 million ha (applied up to 132% of the winter crop area). The Group D herbicides, especially trifluralin, are used for pre-emergent weed control on nearly 7 million ha, 36% of the cropped area, up from 25% in 2001. There is circumstantial evidence that Group D herbicides are mostly applied for the management of ARG, and there is a high risk of over-use. Minimum- and no-tillage are used on 76% of the cropped area, while burning as a weed control technique (hot burn) is used on just over 10% of the area. In view of the current willingness of grain growers to rely heavily upon herbicides for weed control, a greater burden is placed on ensuring herbicide rotational strategies are carefully thought through and implemented. This has resulted in extension of double-knockdown techniques with Spray.Seed to reduce the likelihood of glyphosate resistant ARG in reduced tillage environments. A similar education programme needs to be directed towards Group D herbicides and alternatives promoted. Group K herbicides, including S-metolachlor (Dual Gold), are potential alternatives. Group K herbicides are generally well-tolerated by barley, oats, legumes and canola and can be used at higher rates in these crops. Wheat is less tolerant at the rates required to manage ARG effectively. Rotating to Group K herbicides outside wheat is proposed. The grains industry could evaluate the model the Australian cotton industry has established for the very successful management of insecticide resistance. A better way to manage herbicide use and rotation needs to be found, particularly as fewer new active ingredients are expected to be developed than in the past.
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 2
  • Year: 2004
  • Summary: With renewed interest in legumes as green manures, it is important to understand their effect on in-season N uptake of following non-legume row crops. This study assessed the effect of legumes as green manures on in-season N uptake by subsequent grain sorghum [Sorghum bicolor (L.) Moench] grown in conservation tillage systems in the eastern Great Plains. Treatments were (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. The experiment was conducted on two adjacent sites (Parson silt loam: fine, mixed thermic Mollic Albaqualf) similar in organic matter but Site 1 higher in pH, P, and K than Site 2. In-season N uptake was often statistically greater in reduced-tillage than no-tillage systems. At both sites, red clover as a previous crop resulted in about 25% greater N uptake by sorghum vs. sorghum grown continuously with no previous legume crop. Nitrogen uptake by sorghum at the boot and soft dough growth stages responded linearly to increasing N rate, but the slope was 135 kg ha(-1) during the first year for both legumes at each site, but values for red clover remained greater than those for hairy vetch in subsequent years, especially at the higher fertility site. Grain yield tended to be maximized when N uptake at the soft dough stage exceeded 100 kg ha(-1) at Site 2 but continued to increase as N uptake increased at the higher-fertility Site 1. Utilizing legumes as green manures can increase in-season N uptake by following grain sorghum crops compared with continuous sorghum in these prairie soils.
  • Authors:
    • Sharma, R. D.
    • Corrêa, J. C.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 39
  • Issue: 1
  • Year: 2004
  • Summary: An experiment was carried out on a heavy red yellow latosol to evaluate crop rotation on herbaceous cotton ( Gossypium hirsutum) yields in no-till system under rainfed Savannah conditions. The treatments were: soyabean-millet ( Pennisetum glaucum)-soyabean-millet-cotton; soyabean-amaranth ( Amaranthus hypochondriacus)-soyabean-forage radish-soyabean-cotton; soyabean-grain sorghum ( Sorghum vulgare [ S. bicolor])-soyabean-grain sorghum-cotton; soyabean-black rye ( Avena strigosa [ A. nuda])-soyabean-black rye-cotton and soyabean-soyabean-cotton. The highest cotton seed yield and best weed control were recorded in the sequence soyabean-millet-soyabean-millet-cotton.
  • Authors:
    • Sanders, D. C.
    • Paullier, J.
    • Maeso, D.
    • Arboleda, J.
    • Gilsanz, J. C.
    • Hoyt, G. D.
    • Behayout, E.
    • Lavandera, C.
  • Source: Proc. XXVI IHC – Sustainability of Horticultural Systems Eds. L. Bertschinger and J.D. Anderson Acta Horticulturae 638, ISHS 2004
  • Issue: 638
  • Year: 2004
  • Summary: Seven rotational systems were evaluated for vegetable crops in USA and Uruguay. Rotational systems that include both winter and summer cover crops and vegetable crops were used. Treatments comprised: continuous cropping system, T1; multiple vegetable system, T2; green manure system, T3; chicken manure system, T4; fallow system, T5; strip tillage system, T6; and no-tillage system, T7. The crops used were sweet potato, squash, oat or triticale winter cover crop, sorghum or Sudan grass summer cover crop, sweetcorn, garlic, carrot with chicken manure and fallow. Different insects, diseases and weed infestations were recorded in the systems. The study began in spring 1999 in Uruguay and spring 2000 in North Carolina, USA. This paper reports only results from Uruguay. The yields obtained were good compared to the national average in most cases. The average yield is 7 t/ha for sweet potato and 3.5 t/ha for garlic. T6 had the highest soil macrofauna (70 worms/m 2 compared to 4.2 in T1). Soil biomass was sampled for four times: 13 April, 26 May, 17 August and 08 November 2000. T7 system had greater soil biomass during the period of observation than T1 or T4 systems. T6 and T7 treatments had the lowest nitrate levels in the soil among all treatments. T4 was enough for garlic growth. T6, T7 and T4 systems had less sclerotia (from Sclerotium rolfsii [ Corticium rolfsii]) than T1 and T2 systems.