19842015
  • Authors:
    • Franzluebbers, A. J.
  • Source: Soil & Tillage Research
  • Volume: 83
  • Issue: 1
  • Year: 2005
  • Summary: Agriculture in the southeastern USA can be highly productive (i.e., high photosynthetic fixation of atmospheric CO2) due to warm-moist climatic conditions. However, its impacts on greenhouse gas emissions and mitigation potential have not been thoroughly characterized. This paper is a review and synthesis of literature pertaining to soil organic C (SOC) sequestration and greenhouse gas emissions from agricultural activities in the southeastern USA. Conservation tillage is an effective strategy to regain some of the SOC lost following decades, and in some areas centuries, of intensive soil tillage and erosion. With conventional tillage (CT) as a baseline, SOC sequestration with no tillage (NT) was 0.42 ± 0.46 Mg ha-1 year-1 (10 ± 5 years). Combining cover cropping with NT enhanced SOC sequestration (0.53 ± 0.45 Mg ha-1 year-1) compared with NT and no cover cropping (0.28 ± 0.44 Mg ha-1 year-1). By increasing cropping system complexity, SOC could be increased by 0.22 Mg ha-1 year-1, irrespective of tillage management. Taking into account an average C cost of producing and transporting N fertilizer, SOC sequestration could be optimized at 0.24 Mg ha-1 year-1 with application of 107 kg N ha-1 year-1 on N-responsive crops, irrespective of tillage management. In longer-term studies (5-21 years), poultry litter application led to SOC sequestration of 0.72 ± 0.67 Mg ha-1 year-1 (17 ± 15% of C applied). Land that was previously cropped and converted to forages sequestered SOC at a rate of 1.03 ± 0.90 Mg ha-1 year-1 (15 ± 17 years). Limited data suggest animal grazing increases SOC sequestration on upland pastures. By expanding research on SOC sequestration into more diverse pasture and manure application systems and gathering much needed data on methane and nitrous oxide fluxes under almost any agricultural operation in the region, a more complete analysis of greenhouse gas emissions and potential mitigation from agricultural management systems would be possible. This information will be necessary for developing appropriate technological and political solutions to increase agricultural sustainability and combat environmental degradation in the southeastern USA.
  • Authors:
    • Drenovsky, R. E.
    • Whisson, D. A.
    • Scow, K. M
    • Ingels, C. A.
  • Source: American Journal of Enology and Viticulture
  • Volume: 56
  • Issue: 1
  • Year: 2005
  • Summary: Several cover crop mixes were planted in a winegrape vineyard in Sacramento County to test their effects on vine growth, production, juice composition, soil microbial ecology, and gopher activity over a three-year period (1998 to 2000). The trial was conducted in a Vitis vinifera L. cv. Merlot vineyard on a silt loam soil. Vines were planted in 1993 on 5BB rootstock, spaced 2.1 x 3.4 m. The mixes used were: California native perennial grass (no-till), annual clover (no-till), green manure (disked), cereals (disked), and disked control. Cover crops were planted on either side of entire rows, with a disked alley separating treatment replicates. A 1.2-m herbicide strip was maintained under the vines. Drip irrigation and fertigation were applied uniformly across all treatments, but additional nitrogen fertilizer was applied to the grass mixes. Weed biomass increased in the clover mix but decreased in the native grass mix. Grapevine petiole nitrogen content was highest in the bell bean mix and very low in the native grass mix. There were very few differences in leaf water potential or pruning weights of the vines, and in yields or juice Brix, pH, or titratable acidity in any year. Cover-cropped soils had greater microbial biomass than disked or berm soils, and the no-till mixes had greater microbial biomass than the disked mixes. Gophers were very numerous in 1999 only, with nearly all activity exclusively in the clover mix.
  • Authors:
    • Strickland, T. C.
    • Bednarz, C. W.
    • Truman, C. C.
    • Potter, T. L.
    • Bosch, D. D.
  • Source: Transactions of the ASAE
  • Volume: 48
  • Issue: 6
  • Year: 2005
  • Summary: Conservation tillage has significant potential as a water management tool for cotton production on sandy, drought-prone soils. Plant residue remaining at the soil surface from prior crops serves as a vapor barrier against water loss, reduces raindrop impact energy, slows surface runoff, and often increases infiltration. By increasing infiltration, the potential for greater plant-available water can be enhanced and irrigation requirements reduced. Five years of data were collected to quantify the hydrologic differences between strip till and conventional till production systems. Surface runoff and lateral subsurface flow were measured on six 0.2 ha plots in South Georgia in order to quantify the water-related effects of conservation tillage. Significant differences in surface and subsurface water losses were observed between the conventional and strip tilled plots. Surface runoff from the conventionally tilled plots exceeded that from the strip tilled plots, while subsurface losses were reversed. Surface runoff losses from the conventionally tilled plots exceeded those from the strip tilled plots by 81% (129 mm/year). Shallow lateral subsurface losses from the strip tilled plots exceeded those from the conventionally tilled plots by 73% (69 mm/year). Overall, a net annual gain of 60 mm of water was observed for the strip tilled plots.
  • Authors:
    • Parton, W. J.
    • Del Grosso, S. J.
    • Paustian, K.
    • Conant, R. T.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 71
  • Issue: 3
  • Year: 2005
  • Summary: Carbon sequestration in agricultural, forest, and grassland soils has been promoted as a means by which substantial amounts of CO2 may be removed from the atmosphere, but few studies have evaluated the associated impacts on changes in soil N or net global warming potential (GWP). The purpose of this research was to (1) review the literature to examine how changes in grassland management that affect soil C also impact soil N, (2) assess the impact of different types of grassland management on changes in soil N and rates of change, and (3) evaluate changes in N2O fluxes from differently managed grassland ecosystems to assess net impacts on GWP. Soil C and N stocks either both increased or both decreased for most studies. Soil C and N sequestration were tightly linked, resulting in little change in C:N ratios with changes in management. Within grazing treatments N2O made a minor contribution to GWP (0.1-4%), but increases in N2O fluxes offset significant portions of C sequestration gains due to fertilization (10-125%) and conversion (average = 27%). Results from this work demonstrate that even when improved management practices result in considerable rates of C and N sequestration, changes in N2O fluxes can offset a substantial portion of gains by C sequestration. Even for cases in which C sequestration rates are not entirely offset by increases in N2O fluxes, small increases in N2O fluxes can substantially reduce C sequestration benefits. Conversely, reduction of N2O fluxes in grassland soils brought about by changes in management represents an opportunity to reduce the contribution of grasslands to net greenhouse gas forcing.
  • Authors:
    • Quine, T. A.
    • Djurhuus, J.
    • Heckrath, G.
    • Van Oost, K.
    • Govers, G.
    • Zhang, Y.
  • Source: Journal of Environmental Quality
  • Volume: 34
  • Issue: 1
  • Year: 2005
  • Summary: Tillage erosion had been identified as a major process of soil redistribution on sloping arable land. The objectives of our study were to investigate the extent of tillage erosion and its effect on soil quality and productivity under Danish conditions. Soil samples were collected to a 0.45-m depth on a regular grid from a 1.9-ha site and analyzed for Cs-137 inventories, as a measure of soil redistribution, soil texture, soil organic carbon (SOC) contents, and phosphorus (P) contents. Grain yield was determined at the same sampling points. Substantial soil redistribution had occurred during the past decades, mainly due to tillage. Average tillage erosion rates of 2.7 kg m(-2) yr(-1) occurred on the shoulderslopes, while deposition amounted to 1.2 kg m(-2) yr(-1) on foot- and toeslopes. The pattern of soil redistribution could not be explained by water erosion. Soil organic carbon and P contents in soil profiles increased from the shoulder- toward the toeslopes. Tillage translocation rates were strongly correlated with SOC contents, A-horizon depth, and P contents. Thus, tillage erosion had led to truncated soils on shoulderslopes and deep, colluvial soils on the foot- and toeslopes, substantially affecting within-field variability of soil properties. We concluded that tillage erosion has important implications for SOC dynamics on hummocky land and increases the risk for nutrient losses by overland flow and leaching. Despite the occurrence of deep soils across the study area, evidence suggested that crop productivity was affected by tillage-induced soil redistribution. However, tillage erosion effects on crop yield were confounded by topography-yield relationships.
  • Authors:
    • Klepker, D.
    • Yamada, M.
    • Hitsuda, K.
  • Source: Agronomy Journal
  • Volume: 97
  • Issue: 1
  • Year: 2005
  • Summary: Sulfur deficiency symptoms are more often observed in crops at early stages of growth since S can be easily leached from the surface soil. The objectives of this study were to evaluate some of the popular rotation crops grown in Brazil for tolerance to low external S levels and to determine the critical tissue concentration for S deficiency during early stages of growth. Germinated seedlings of soybean [ Glycine max (L.) Merr.], rice ( Oryza sativa L.), maize ( Zea mays L.), field bean ( Phaseolus vulgaris L.), wheat ( Triticum aestivum L.), cotton ( Gossypium spp.), sorghum ( Sorghum bicolor L.), and sunflower ( Helianthus annuus L.) were transferred to water culture with 0.0 to 32.0 mg S L -1 and were grown for 29 d. The minimum S concentration required in nutrient solutions was 2.0 mg L -1 for sunflower; 1.0 mg L -1 for cotton, sorghum, wheat, and soybean; and 0.5 mg L -1 or less for field bean, rice, and maize. All crops achieved optimum growth at 2.0 mg S L -1. Critical shoot S concentration at early stages of growth was 0.8 g kg -1 in maize and soybean; 1.1 to 1.3 g kg -1 in cotton, sorghum, and rice; and 1.4 to 1.6 g kg -1 in wheat, sunflower, and field bean. Our results demonstrate that the tolerance to low external S (
  • Authors:
    • Cooke, F. T.,Jr.
    • Robinson, J. R. C.
    • Martin, S. W.
    • Parvin, D.
  • Source: Crop Management
  • Issue: April
  • Year: 2005
  • Summary: This study compared conventional, reduced tillage and no-till systems for cotton, maize, soyabean and sorghum in the Mississippi Delta. Most of the necessary parameters (e.g. yields, costs, equipment, field operations) were obtained from published budgets. The conventional systems typically involved subsoiling, discing, field cultivation, hipping and in-season cultivation. The reduced tillage systems substituted herbicides for heavy pre-plant soil preparation and in-season cultivation, while no-till systems substituted herbicides for all tillage operations. A whole-farm, mixed integer programming model was developed to determine the most profitable crop/tillage combinations at different acreage sizes, assess the actual economies of size (in dollars per acre) in row crop farming, determine the number of acres required to maximize economic viability, determine the best acreage size to minimize or optimize full-time labour, and evaluate profitability trade-offs, including farm programme eligibility, under different tillage systems.
  • Authors:
    • Peterson, G. A.
    • Westfall, D. G.
    • Ortega, R. A.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 36
  • Issue: 19/20
  • Year: 2005
  • Summary: In the West Central Great Plains of the United States, no-till management has allowed for increased cropping intensity under dryland conditions. This, in turn, has affected the carbon (C) and nitrogen (N) mineralization dynamics of these systems. In this region, moisture stress increases from north to south due to an increase in evapotranspiration (ET), resulting in a climatic gradient that affects cropping system management. The objectives of this study were to determine the interaction of cropping system intensification and climatic gradient (ET) on C and N mineralization and to determine if the presence or absence of crop residue on the soil surface affects C and net N mineralization. Two cropping systems, winter wheat-fallow (WF) ( Triticum aestivium L.) and winter wheat-corn (sorghum)-millet-fallow (WCMF) [ Zea mays (L.), Sorghum bicolor (L.) Moench, Panicum milaceum (L.)] were studied at three locations across this aforementioned ET gradient. The treatments had been in place for 8 yrs prior to sampling in the study. These results showed that the more intense cropping system (WCMF) had a higher laboratory C mineralization rate at two of the three locations, which the study concluded resulted from larger residue biomass additions and larger quantities of surface residue and soil residue at these locations (Soil residue is defined as recognizable crop residue in the soil that is retained on a 0.6 mm screen). However, no differences in N mineralization occurred. This is most likely due to more N immobilization under WCMF as compared to WF. Presence or absence of crop residue on the surface of undisturbed soil cores during incubation affected potential C and net N mineralization more than either cropping system or location. Soil cores with the surface residue intact mineralized as much as 270% more C than the same soils where the surface crop residue had been removed. In laboratory studies evaluating the relative differences in cropping systems effects on C and N mineralization, the retention of crop residue on the soil surface may more accurately access the cropping system effects.
  • Authors:
    • Price, A.
    • Saini, M.
    • van Santen, E.
  • Source: 2005 Southern Conservation Tillage Systems Conference, Oral Proceedings, Clemson University
  • Year: 2005
  • Summary: An integral component of a conservation-tillage system in corn (Zea mays L.) and cotton (Gossypium hirsutum L.) is the use of a winter cover crop. A field experiment was initiated in 2002 to evaluate winter weed dynamics following various winter cover crops in both continuous cotton and a corn and cotton rotation. Winter cover crops included black oats (Avena strigosa Schreb.); two crimson clover entries (Trifolium incarnatum L.); two cultivars of forage rape (Brassica napus L. var. napus), spring and winter; oil radish (Raphanus sativus var. oleiformis Pers.); three cultivars of turnip ( Brassica rapa L. subsp. rapa); white lupin ( Lupinus albus L.); and a mixture of black oat and lupin. Two-year conservation-tillage rotational sequences included conventionally tilled continuous corn and cotton winter fallow systems as controls. The 10 conservation-tillage, winter cover-crop systems investigated were three continuous cotton systems that alternated a winter legume (lupin or clover), six cotton-corn systems, where lupin preceded cotton and radish, rape, or turnip preceded corn, and a cotton-corn system that had a lupin-black oat mixture as a winter cover crop every year. Use of lupin or 'AU Robin' clover resulted in weed biomass reduction of up to 80% and 54%, respectively, in weed biomass compared to the fallow system. The highest yielding corn-cotton conservation tillage rotation with a winter cover yielded 200 lbs/acre more that the continuous cotton winter fallow system. Continuous conventional corn with winter fallow yielded 30 bu/acre less than the highest yielding 2-yr, conservation tillage winter crop system.
  • Authors:
    • Whitehead, W. F.
    • Sainju, U. M.
    • Singh, B. P.
  • Source: Plant and Soil
  • Volume: 273
  • Issue: 1-2
  • Year: 2005
  • Summary: Soil and crop management practices may influence biomass growth and yields of cotton (Gossypium hirsutum L.) and sorghum (Sorghum bicolor L.) and sequester significant amount of atmospheric CO, in plant biomass and underlying soil, thereby helping to mitigate the undesirable effects of global warming. This study examined the effects of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)],. four cover crops [legume (hairy vetch) (Vicia villosa Roth), nonlegume (rye) (Secale cereale L), hairy vetch/rye mixture, and winter weeds or no cover crop], and three N fertilization rates (0, 60-65, and 120-130 kg N ha(-1)) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain. their stalks (stems + leaves) and roots, and underlying soil from 2000 to 2002 In central Georgia, USA. A field experiment was conducted on a Dothan sandy loam (fine-loamy, kaolinitic, thermic. Plinthic Kandiudults). In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha(-1) but in stalks, it was greater in ST with 60 and 120 kg N ha(-1) than in CT with 0 kg N ha(-1). In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha(-1) than in NT with or without N rate. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha(-1) and in sorghum ranged from 3.4 to 7.2 Mg ha(-1). Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. In NT, soil organic C at 0-10 cm depth was greater in vetch with 0 kg N ha(-1) or in vetch/rye with 120-130 kg N ha(-1) than in weeds with 0 and 60 kg N ha(-1) but at 10-30 cm, it was greater in rye with 120-130 kg N ha(-1) than in weeds with or without rate. In ST, soil organic C at 0-10 cm was greater in rye with 120-130 kg N ha(-1) than in rye, vetch, vetch/rye and weeds with 0 and 60 kg N ha(-1). Soil organic C at 0-10 and 10-30 cm was also greater in NT and ST than in CT. Since 5 to 24% of C accumulation in lint and grain were harvested, C sequestered in cotton and sorghum stalks and roots can be significant in the terrestrial ecosystem and can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Conservation tillage, such as ST, with hairy vetch/rye mixture cover crops and 6065 kg N ha(-1) can sustain C accumulation in cotton lint and sorghum grain and increase C storage soil compared with conventional tillage, such as CT, with no cover crop and N fertilization, thereby maintaining crop yields, improving soil quality, and reducing erosion.