• Authors:
    • Cooper, R. J.
    • Carroll, J. P.
    • Cederbaum, S. B.
  • Source: Conservation Biology
  • Volume: 18
  • Issue: 5
  • Year: 2004
  • Summary: Among the major agricultural crops in the southeastern United States, cotton (Gossypium hirsutum L.) generally provides the least suitable habitat for most early successional songbirds. Newer cropping approaches, such as use of conservation tillage and stripcover cropping, offer hope for improving the ecological value of cotton fields. We examined the effects of clover stripcover cropping with conservation tillage versus conventionally grown cotton with either conventional or conservation tillage on avian and arthropod species composition and field use in east-central Georgia. Stripcover fields had higher bird densities and biomass and higher relative abundance of arthropods than both conservation tillage and conventional fields. During migration and breeding periods, total bird densities on stripcover fields were 2-6 times and 7-20 times greater than on conservation and conventional fields, respectively. Abundance and biomass for epigeal arthropods were also greatest on stripcover fields during much of the breeding season. Although the clover treatment attracted the highest avian and arthropod densities, conservation fields still provided more wildlife and agronomic benefits than conventional management. Our findings suggest that both conservation tillage and stripcropping systems will improve conditions for birds in cotton, with stripcropped fields providing superior habitat. The reduction of inputs possible with the clover system could allow farmers to lower costs associated with conventional cotton production by $282-317/ha. This reduction of input, coupled with similar or possibly increased yield over conventional systems makes stripcover cropping not only a good choice for reducing negative impacts on wildlife and surrounding ecosystems, but also an economically desirable one.
  • Authors:
    • USDA-ARS
    • Clapp, C. E.
    • Linden, D. R.
    • Allmaras, R. R.
  • Source: Soil Science Society of America Journal
  • Volume: 68
  • Issue: 4
  • Year: 2004
  • Summary: Soil organic carbon (SOC) is sensitive to management of tillage, residue (stover) harvest, and N fertilization in corn (Zea mays L.), but little is known about associated root biomass including rhizodeposition. Natural C isotope abundance ({delta}13C) and total C content, measured in paired plots of stover harvest and return were used to estimate corn-derived SOC (cdSOC) and the contribution of nonharvestable biomass (crown, roots, and rhizodeposits) to the SOC pool. Rhizodeposition was estimated for each treatment in a factorial of three tillage treatments (moldboard, MB; chisel, CH; and no-till, NT), two N fertilizer rates (200 and 0 kg N ha-1), and two corn residue managements. Treatments influenced cdSOC across a wide range (6.8-17.8 Mg C ha-1). Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha-1, and increased rhizodeposition by at least 110% compared with that with no N fertilizer. Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC. The amount of stover source carbon (SSC) responded to tillage (MB > CH > NT), but tillage affected the amount of cdSOC differently (NT > CH > MB). Total SOC was maintained only by both N fertilization and stover return during the 13-yr period. The ratio of SC in the nonharvestable biomass to SSC ranged from 1.01 to 3.49; a ratio of 0.6 conforms to a root-to-shoot ratio of 0.4 when the root biomass includes 50% rhizodeposits. Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH), even though N fertilization, stover harvest, and tillage all significantly influenced SC. Decomposition of labile rhizodeposits was a major component of the nonhumified fraction. Rhizodeposition was as much as three times greater than suggested by laboratory and other controlled studies. To understand and manage the entire C cycle, roots and rhizodeposition must be included in the analysis at the field level.
  • Authors:
    • Lindwall, W.
    • Kulshreshtha, S.
    • Desjardins, R.
    • Junkins, B.
    • Boehm, M.
  • Source: Climatic Change
  • Volume: 65
  • Issue: 3
  • Year: 2004
  • Summary: Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2-Eq yr-1 in1990 to 52 Tg CO2-Eq yr-1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2-Eq yr-1 (L), 42 TgCO2-Eq yr-1 (M) or 36 Tg CO2-Eq yr-1 (H). Among the sink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992).
  • Authors:
    • Schoenau, J.
    • Mohr, R.
    • McLaren, D.
    • Irvine, R.
    • Derksen, D.
    • Monreal, M.
    • Grant, C.
  • Source: Better Crops with Plant Food
  • Volume: 88
  • Issue: 2
  • Year: 2004
  • Summary: Field experiments were conducted at the Research Centre and the Zero-Till Farm, Manitoba, Canada, during 1999-2000, 2000-01 and 2001-01, wherein rape and spring wheat were sown using conventional tillage (CT) and no-till (NT) in the first year of study. The crops were supplemented with 0, 22 or 44 lb P 2O 5/acre, side-banded at sowing. After rape and spring wheat harvest, the stubble in the CT plots was tilled. In the second year, flax was sown into both stubbled and tilled plots, and supplemented with P fertilizer side-banded at 0 or 44 lb P 2O 5/acre. The roots were evaluated for mycorrhizal association at 5 weeks of growth and seed yield was collected at crop maturity. The P nutrition of flax was most influenced by the preceding crop in rotation, while tillage system and P fertilizer management had minor impact on flax. Comparative data on the effect of P fertilizer application to current year flax, previous crop type and P fertilizer management, and tillage system on mycorrhiza incidence and flax seed yield are tabulated.
  • Authors:
    • Spurlock, S.
    • Heatherly, L.
    • Reddy, K.
  • Source: Agronomy Journal
  • Volume: 96
  • Issue: 3
  • Year: 2004
  • Summary: Management inputs that maximize economic return from the early plantings of soyabean ( Glycine max) in the midsouthern USA have not been evaluated fully. The objective was to compare perennial weed control in and yields and economic returns from plantings of maturity group (MG) IV and V soyabean cultivars grown in the field (Mississippi, USA) under different weed management systems (WMS) following shallow (ST) and deep (DT) fall tillage. Adjacent experiments were conducted near Stoneville, Mississippi. Weed management systems were (i) glyphosate ( N-(phosphonomethyl)glycine)-resistant (GR) cultivars with preemergent (PRE) nonglyphosate herbicides followed by postemergent (POST) glyphosate; (ii) GR cultivars with POST glyphosate; (iii) non-GR cultivars with PRE plus POST nonglyphosate herbicides; and (iv) non-GR cultivars with POST nonglyphosate herbicides. Control of perennial redvine ( Brunnichia ovata) declined in the ST environment when non-GR cultivars were used, but this did not result in a yield decline. Control of perennial johnsongrass ( Sorghum halepense) at the end of the study period averaged 93% when GR cultivars were used regardless of tillage treatment, and this was associated with lower yield. Use of PRE+POST vs. POST-only weed management sometimes resulted in lower profits regardless of fall tillage treatment. The fall tillage treatment * WMS interaction was not significant for yield or net return, which indicates that use of DT for perennial weed management is not economical.
  • 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.