- Authors:
- Source: Climatic Change
- Volume: 60
- Issue: 1/2
- Year: 2003
- Summary: This book presents a collection of articles (n=8) concerning key topics, which examine the impacts of climate change and variability on agriculture in the southeastern USA. The main topics include an investigation of the effect of variations in the spatial scale of climatic change scenarios on an agricultural integrated assessment, methods of simulating adaptations to climate change, and the relationship between large scale climate variability and local climate and vegetation. This book will be very useful for researchers and policy makers involved in climate change impacts.
- Authors:
- Source: Web Of Knowledge
- Volume: 60
- Issue: 1/2
- Year: 2003
- Summary: This special issue contains an editorial and 8 papers on the interaction of agriculture with climatic variability and change in the Southeastern States of USA. Topics covered range from climate modelling to remote sensing to economics.
- Authors:
- Source: Agriculture, Ecosystems & Environment
- Volume: 91
- Issue: 1-3
- Year: 2002
- Summary: The atmospheric CO2 concentration is increasing, due primarily to fossil-fuel combustion and deforestation. Sequestering atmospheric C in agricultural soils is being advocated as a possibility to partially offset fossil-fuel emissions. Sequestering C in agriculture requires a change in management practices, i.e. efficient use of pesticides, irrigation, and farm machinery. The C emissions associated with a change in practices have not traditionally been incorporated comprehensively into C sequestration analyses. A full C cycle analysis has been completed for agricultural inputs, resulting in estimates of net C flux for three crop types across three tillage intensities. The full C cycle analysis includes estimates of energy use and C emissions for primary fuels, electricity, fertilizers, lime, pesticides, irrigation, seed production, and farm machinery. Total C emissions values were used in conjunction with C sequestration estimates to model net C flux to the atmosphere over time. Based on US average crop inputs, no-till emitted less CO2 from agricultural operations than did conventional tillage, with 137 and 168 kg C ha(-1) per year, respectively. Changing from conventional tillage to no-till is therefore estimated to both enhance C sequestration and decrease CO2 emissions. While the enhanced C sequestration will continue for a finite time, the reduction in net CO2 flux to the atmosphere, caused by the reduced fossil-fuel use, can continue indefinitely, as long as the alternative practice is continued. Estimates of net C flux, which are based on US average inputs, will vary across crop type and different climate regimes. The C coefficients calculated for agricultural inputs can be used to estimate C emissions and net C flux on a site-specific basis. Published by Elsevier Science B.V.
- Authors:
- Source: Soil Science Society of America Journal
- Volume: 66
- Issue: 6
- Year: 2002
- Summary: Changes agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 +/- 14 g C m(-2) yr(-1), excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 +/- 12 g C m(-2) yr(-1), excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine mar L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.
- Authors:
- Source: Biomass and Bioenergy
- Volume: 22
- Issue: 5
- Year: 2002
- Summary: The focus of this study was to develop a methodology to estimate "hectare-weighted", county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995-1997 in 37 states (north-south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.
- Authors:
- Westfall, D. G.
- Peterson, G. A.
- Ortega, R. A.
- Source: Agronomy Journal
- Volume: 94
- Issue: 4
- Year: 2002
- Summary: Crop residue is a valuable resource in Great Plains dryland agroecosystems because it aids in water conservation and soil erosion control. The objectives of our research were to (i) determine the effect of cropping intensity, climate gradient, and soil depth on levels and changes in soil C, soil N, and residue parameters after 8 yr of no-till management in dryland cropping systems and (ii) relate soil and residue parameters to soil C and N levels. Surface soil properties and residue parameters were compared in two cropping systems, wheat (Triticum aestivum L.)-fallow (WF) and wheat-corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]-proso millet (Panicum miliaceum L.)-fallow (WCMF). The effects were examined on the summit position of a catenary sequence of soils across three environments representing an evapotranspiration (ET) gradient. Soils at the low- and medium-ET sites are classified as Argiustols, and the soil at the high-ET site is an Ustochrept. There was 3.0 Mg ha-1 of residue in the surface 10 cm of soil compared with 2.7 Mg ha-1 of residue on the soil surface averaged over ET gradient and cropping systems. About 90% of the residue in the soil was found within the 2.5-cm soil depth. The highest soil organic C (SOC) and soil organic N (SON) were observed in the surface 0- to 2.5-cm depth. There was a trend (P [<=] 0.16) for the more intense WCMF cropping system to have higher SOC and SON contents than the traditional WF system (C = 6.6 g kg-1 for WF compared with 7.5 g kg-1 for WCMF and N = 0.70 g kg-1 for WF compared with 0.74 g kg-1 for WCMF). From 1985 to 1993, gains in SOC (967 kg ha-1) and SON (74 kg ha-1) occurred in the surface 0- to 2.5- and 2.5- to 5-cm depths while losses were observed in the 5- to 10-cm depth (SOC = -694 kg ha-1; SON = -44 kg ha-1). Climate strongly modified these effects but did not reflect a clear ET gradient effect. The results suggest that higher levels of surface SOC and SON can be attained by increasing cropping intensity under no-till management.
- Authors:
- Lukina, E. V.
- Thomason, W. E.
- Freeman, K. W.
- Mullen, R. W.
- Stone, M. L.
- Johnson, G. V.
- Solie, J. B.
- Raun, W. R.
- Source: Agronomy Journal
- Volume: 94
- Issue: 4
- Year: 2002
- Summary: In 2001, N fertilizer prices nearly doubled as a result of increased natural gas prices. This was further troubling when considering that the world N use efficiency (NUE) in cereal grain production averages only 33%. Methods to improve NUE in winter wheat (Triticum aestivum L.) have not included high spatial-resolution management based on sensed plant growth properties nor on midseason prediction of grain yield. Our objective was to determine the validity of using in-season estimates of grain yield (INSEY) and a response index (RI) to modulate N at 1-m(2) spatial resolution. Four winter wheat field experiments were conducted that evaluated prescribed midseason N applications compared with uniform rates that simulated farmer practices. Our methods recognize that each 1-m(2) area in wheat fields needs to be sensed and managed independently and that the need for fertilizer N is temporally dependent. Averaged over locations, NUE was improved by >15% when N fertilization was based on optically sensed INSEY, determined for each 1-m(2) area, and a RI compared with traditional practices at uniform N rates.
- Authors:
- Schuman, G. E.
- Reeder, J. D.
- Source: Environmental Pollution
- Volume: 116
- Issue: 3
- Year: 2002
- Summary: We evaluated the effects of livestock grazing on C content of the plant-soil system (to 60 cm) of two semi-arid grasslands: a mixed-grass prairie (grazed 12 years), and a short-grass steppe (grazed 56 years). Grazing treatments included season-long grazing at heavy and light stocking rates, and non-grazed exclosures. Significantly higher soil C (0-30cm) was measured in grazed pastures compared to non-grazed exclosures, although for the short-grass steppe higher soil C was observed with the heavy grazing treatment only. Excluding grazing caused an immobilization of C in excessive aboveground plant litter, and an increase in annual forbs and grasses which lack dense fibrous rooting systems conducive to soil organic matter formation and accumulation. Our data indicate that higher soil C with grazing was in part the result of more rapid annual shoot turnover, and redistribution of C within the plant-soil system as a result of changes in plant species composition.
- Authors:
- Whitehead, W. F.
- Singh, B. P.
- Sainju, U. M.
- Source: Soil & Tillage Research
- Volume: 63
- Issue: 3-4
- Year: 2002
- Summary: Maintaining and/or conserving organic carbon (C) and nitrogen (N) concentrations in the soil using management practices can improve its fertility and productivity and help to reduce global warming by sequestration of atmospheric CO2 and N2. We examined the influence of 6 years of tillage (no-till, NT; chisel plowing, CP; and moldboard plowing, MP), cover crop (hairy vetch (Vicia villosa Roth.) vs. winter weeds), and N fertilization (0, 90, and 180 kg N ha-1) on soil organic C and N concentrations in a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Kandiudults) under tomato (Lycopersicon esculentum Mill.) and silage corn (Zea mays L.). In a second experiment, we compared the effects of 7 years of non-legume (rye (Secale cereale L.)) and legume (hairy vetch and crimson clover (Trifolium incarnatum L.)) cover crops and N fertilization (HN (90 kg N ha-1 for tomato and 80 kg N ha-1 for eggplant)) and FN (180 kg N ha-1 for tomato and 160 kg N ha-1 for eggplant)) on soil organic C and N in a Greenville fine sandy loam (fine-loamy, kaolinitic, thermic, Rhodic Kandiudults) under tomato and eggplant (Solanum melogena L.). Both experiments were conducted from 1994 to 2000 in Fort Valley, GA. Carbon concentration in cover crops ranged from 704 kg ha-1 in hairy vetch to 3704 kg ha-1 in rye in 1999 and N concentration ranged from 77 kg ha-1 in rye in 1996 to 299 kg ha-1 in crimson clover in 1997. With or without N fertilization, concentrations of soil organic C and N were greater in NT with hairy vetch than in MP with or without hairy vetch (23.5-24.9 vs. 19.9-21.4 Mg ha-1 and 1.92-2.05 vs. 1.58-1.76 Mg ha-1, respectively). Concentrations of organic C and N were also greater with rye, hairy vetch, crimson clover, and FN than with the control without a cover crop or N fertilization (17.5-18.4 vs. 16.5 Mg ha-1 and 1.33-1.43 vs. 1.31 Mg ha-1, respectively). From 1994 to 1999, concentrations of soil organic C and N decreased by 8-16% in NT and 15-25% in CP and MP. From 1994 to 2000, concentrations of organic C and N decreased by 1% with hairy vetch and crimson clover, 2-6% with HN and FN, and 6-18% with the control. With rye, organic C and N increased by 3-4%. Soil organic C and N concentrations can be conserved and/or maintained by reducing their loss through mineralization and erosion, and by sequestering atmospheric CO2 and N2 in the soil using NT with cover crops and N fertilization. These changes in soil management improved soil quality and productivity. Non-legume (rye) was better than legumes (hairy vetch and crimson clover) and N fertilization in increasing concentrations of soil organic C and N.
