• Authors:
    • Santen, E. van
    • Price, A.
    • Shaw, J. N.
    • Sullivan, D. G.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 6
  • Year: 2007
  • Summary: Conservation tillage is a commonly adopted best management practice for reducing runoff and erosion, and increasing infiltration. Yet current methodologies in place to monitor conservation tillage adoption are largely inappropriate for regional or national assessments. A major goal of this study was to evaluate the spectral response properties of four alternative winter cover crops using remotely derived crop residue cover indices. Experimental plots were located in east-central Alabama on a coarse-loamy siliceous, subactive, thermic Plinthic Paleudult. The experiment was a randomized complete block design having four replications of each of the following treatments: one fallow conventional tillage treatment and four no-tillage treatments with black oat ( Avena strigosa Schreb.), crimson clover ( Trifolium incarnatum L.), turnip ( Brassica rapa L. subsp.rapa), or rye ( Secale cereale L.) cover crops. Remotely sensed data were acquired three times using a 14 d sampling interval beginning near planting and using a handheld multispectral radiometer (485-1650 nm) in 2005 and 2006. Three crop residue cover indices using combinations of middle-infrared and visible spectra were compared and evaluated. Rye, clover, and black oat were spectrally similar, having an overall spectral response ranging from 8 to 45% (440-1650 nm). Increasing soil water content between remotely sensed data acquisitions was evidenced by as much as a 24% decline in middle-infrared reflectance. Despite this variability, a normalized difference ratio of middle-infrared (1650 nm) and blue (445 nm) spectra (Crop Residue Cover Index) provided the most consistent differentiation between tillage systems, varying within 8% of benchmark conditions (low soil water and low canopy cover). Considering the impact that conservation tillage may have on soil and water resources, rapid, watershed scale assessments of conservation tillage adoption may facilitate natural resource inventories, carbon sequestration estimates, and improved agricultural water management regimes.
  • Authors:
    • Hons, F.
    • Dou, F.
    • Wright, A.
  • Source: Soil Science
  • Volume: 172
  • Issue: 2
  • Year: 2007
  • Summary: Crop species and conservation tillage may enhance carbon (C) and nitrogen (N) sequestration potential in subsurface soils. The objectives of this study were to determine the effects of crop species and tillage on soil organic C (SOC) and total N distribution in six soil depth intervals from 0 to 105 cm after 20 years of treatment imposition. Tillage had the most influence on soil C and N at 0 to 5 cm, and impacts extended to the 15- to 30-cm depth for wheat and sorghum. Overall, SOC and total N for wheat were 18 and 15% higher than sorghum and soybean. Dissolved organic C (DOC) depth distribution was similar to SOC and total N. The proportion of SOC as DOC ranged from 1.3 to 3.3% and increased with soil depth. The highest soil C and N levels occurred for wheat under no tillage. The depth of soil impacted by crop species was shallower for conventional tillage than no tillage, and the depth distribution exhibited a logarithmic pattern. Soil organic C, total N, and DOC decreased 404, 507, and 205%, respectively from 0-5 to 80-105 cm. The maximum depth interval below which no further decreases in SOC and total N occurred was 30 to 55 cm for soybean, 55 to 80 cm for wheat, and 80 to 105 cm for sorghum, demonstrating the importance of subsurface soils for C sequestration. Crop management impacts below the depth of tillage demonstrate the importance of crop rooting and belowground biomass, or translocation of dissolved organic matter, to subsoil C sequestration.
  • Authors:
    • Lares, M. T.
    • Liebig, M. A.
    • Tanaka, D. L.
    • Merrill, S. D.
    • Krupinsky, J. M.
    • Hanson, J. D.
  • Source: Agronomy Journal
  • Volume: 99
  • Issue: 4
  • Year: 2007
  • Summary: Field research was conducted to determine the influence of crop and crop sequencing on crop residue coverage of soil with 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat (Triticum aestivum L.)]. Crop residue production was obtained. Crop residue coverage of the soil surface was measured with a transect technique at the time of seeding spring wheat. Crop residue coverage varied and was more clearly associated with the second-year crop than with the first-year crop of a 2-yr crop sequence. Crop sequences composed of spring wheat, proso millet, and grain sorghum had higher crop residue coverage compared with sequences composed of the other crops. When these three crops and three crops that provide lower crop residue coverage of soil the subsequent year (lentil, chickpea, and sunflower) were analyzed as a subset to compare various sequences of crops providing a range of residue coverage, for example, lower (first yr)/lower (second yr), the surface residue coverage ranged from 65% for the lower/lower combination to 93% for the higher/higher combination in 2004 and from 56 to 94% in 2005, respectively. A producer operating on more fragile soil and concerned about reducing soil erosion hazards would be advised to grow crops that provide higher residue coverage in the year before crops that provide lower residue coverage.
  • Authors:
    • Warland, J.
    • von Bertoldi, P.
    • Parkin, G.
    • Jayasundara, S.
    • Barbeau, J.
    • Lee, I.
    • McLaughlin, N. L.
    • Furon, A.
    • Wagner-Riddle, C.
  • Source: Global Change Biology
  • Volume: 13
  • Issue: 8
  • Year: 2007
  • Summary: No-tillage (NT), a practice that has been shown to increase carbon sequestration in soils, has resulted in contradictory effects on nitrous oxide (N2O) emissions. Moreover, it is not clear how mitigation practices for N2O emission reduction, such as applying nitrogen (N) fertilizer according to soil N reserves and matching the time of application to crop uptake, interact with NT practices. N2O fluxes from two management systems [conventional (CP), and best management practices: NT + reduced fertilizer (BMP)] applied to a corn (Zea mays L.), soybean (Glycine max L.), winter-wheat (Triticum aestivum L.) rotation in Ontario, Canada, were measured from January 2000 to April 2005, using a micrometeorological method. The superimposition of interannual variability of weather and management resulted in mean monthly N2O fluxes ranging from - 1.9 to 61.3 g N ha(-1) day(-1). Mean annual N2O emissions over the 5-year period decreased significantly by 0.79 from 2.19 kg N ha(-1) for CP to 1.41 kg N ha(-1) for BMP. Growing season (May-October) N2O emissions were reduced on average by 0.16 kg N ha(-1) (20% of total reduction), and this decrease only occurred in the corn year of the rotation. Nongrowing season (November-April) emissions, comprised between 30% and 90% of the annual emissions, mostly due to increased N2O fluxes during soil thawing. These emissions were well correlated (r(2) = 0.90) to the accumulated degree-hours below 0 degrees C at 5 cm depth, a measure of duration and intensity of soil freezing. Soil management in BMP (NT) significantly reduced N2O emissions during thaw (80% of total reduction) by reducing soil freezing due to the insulating effects of the larger snow cover plus corn and wheat residue during winter. In conclusion, significant reductions in net greenhouse gas emissions can be obtained when NT is combined with a strategy that matches N application rate and timing to crop needs.
  • Authors:
    • Jin, H.
    • Hongwen, L.
    • Xiaoyan, W.
    • McHugh, A. D.
    • Wenying, L.
    • Huanwen, G.
    • Kuhn, N. J.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Soil compaction caused by random traffic or repetitive tillage has been shown to reduce water use efficiency, and thus crop yield due to reduced porosity, decreased water infiltration and availability of nutrients. Conservation tillage coupled with subsoiling in northern China is widely believed to reduce soil compaction, which was created after many years of no-till. However, limited research has been conducted on the most effective time interval for subsoiling, under conservation tillage. Data from conservation tillage demonstration sites operating for 10 years in northern China were used to conduct a comparative study of subsoiling interval under conservation tillage. Three modes of traditional tillage, subsoiling with soil cover and no-till with soil cover were compared using 10 years of soil bulk density, water content, yield and water use efficiency data. Cost benefit analysis was conducted on subsoiling time interval under conservation tillage. Yield and power consumption were assessed by based on the use of a single pass combine subsoiler and planter. Annual subsoiling was effective in reducing bulk density by only 4.9% compared with no-till treatments on the silty loam soils of the Loess plateau, but provided no extra benefit in terms of soil water loss, yield increase or water utilization. With the exception of bulk density, no-till and subsoiling with cover were vastly superior in increasing water use (+10.5%) efficiency and yield (+12.9%) compared to traditional tillage methods. Four years of no-till followed by one subsoiling reduced mechanical inputs by 62%, providing an economic benefit of 49% for maize and 209% for wheat production compared to traditional tillage. Annual subsoiling reduced inputs by 25% with an increased economic benefit of 23% for maize and 135% for wheat production. Yield and power consumption was improved by 5% and 20%, respectively, by combining subsoiling with the planting operation in one pass compared with multipass operations of subsoiling and planting. A key conclusion from this is that annual subsoiling in dryland areas of northern China is uneconomical and unwarranted. Four years of no-till operations followed by 1 year subsoiling provided some relief from accumulated soil compaction. However, minimum soil disturbance and maximum soil cover are key elements of no-till for saving water and improving yields. Improved yields and reduced farm power consumption could provide a significant base on which to promote combined planter and subsoiling operations throughout northern China. Further research is required to develop a better understanding of the linkages between conservation tillage, soil quality and yield, aimed at designing most appropriate conservation tillage schemes.
  • Authors:
    • North Carolina Department of Revenue
  • Year: 2007
  • Authors:
    • Lachnicht-Weyers, S. L.
    • Tillman, P. G.
    • Whitehead, P. G.
    • Singh, B. P.
    • Schomberg, H. H.
    • Sainju, U. M.
  • Source: Soil & Tillage Research
  • Volume: 96
  • Year: 2007
  • Summary: Cover crops may influence soil carbon (C) sequestration and microbial biomass and activities by providing additional residue C to soil. We examined the influence of legume [crimson clover (Trifolium incarnatum L.)], nonlegume [rye (Secale cereale L.)], blend [a mixture of legumes containing balansa clover (Trifolium michelianum Savi), hairy vetch (Vicia villosa Roth), and crimson clover], and rye + blendfmixture cover crops on soil C fractions at the 0-150 mm depth from 2001 to 2003. Active fractions of soil C included potential C mineralization (PCM) and microbial biomass C (MBC) and slow fraction as soil organic C (SOC). Experiments were conducted in Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) under dryland cotton (Gossypium hirsutum L.) in central Georgia and in Tifton loamy sand (fine-loamy, siliceous, thermic, Plinthic Kandiudults) under irrigated cotton in southern Georgia, USA. Both dryland and irrigated cotton were planted in strip tillage system where planting rows were tilled, thereby leaving the areas between rows untilled. Total aboveground cover crop and cotton C in dryland and irrigated conditions were 0.72-2.90 Mg C ha-1 greater in rye + blend than in other cover crops in 2001 but was 1.15-2.24 Mg C ha-1 greater in rye than in blend and rye + blend in 2002. In dryland cotton, PCM at 50-150 mm was greater in June 2001 and 2002 than in January 2003 but MBC at 0-150 mm was greater in January 2003 than in June 2001. In irrigated cotton, SOC at 0-150 mm was greater with rye + blend than with crimson clover and at 0-50 mm was greater in March than in December 2002. The PCM at 0-50 and 0-150 mm was greater with blend and crimson clover than with rye in April 2001 and was greater with crimson clover than with rye and rye + blend in March 2002. The MBC at 0-50 mm was greater with rye than with blend and crimson clover in April 2001 and was greater with rye, blend, and rye + blend than with crimson clover in March 2002. As a result, PCM decreased by 21-24 g CO2-C ha-1 d-1 but MBC increased by 90-224 g CO2-C ha-1 d-1 from June 2001 to January 2003 in dryland cotton. In irrigated cotton, SOC decreased by 0.1-1.1 kg C ha-1 d-1, and PCM decreased by 10 g CO2-C ha-1 d-1 with rye to 79 g CO2-C ha-1 d-1 with blend, but MBC increased by 13 g CO2-C ha-1 d-1 with blend to 120 g CO2-C ha-1 d-1 with crimson clover from April 2001 to December 2002. Soil active C fractions varied between seasons due to differences in temperature, water content, and substrate availability in dryland cotton, regardless of cover crops. In irrigated cotton, increase in crop C input with legume + nonlegume treatment increased soil C storage and microbial biomass but lower C/N ratio of legume cover crops increased C mineralization and microbial activities in the spring.
  • Authors:
    • Mitchell, J. P.
    • Horwath, W. R.
    • Veenstra, J. J.
  • Source: Soil Science Society of America Journal
  • Volume: 71
  • Issue: 2
  • Year: 2007
  • Summary: Conservation tillage (CT) and cover cropping (CC) are agricultural practices that may provide solutions to address water and air quality issues arising from intensive agricultural practices. This study investigated how CT and CC affect soil organic matter dynamics in a cotton(Gossypium hirsutum L.)-tomato (Lycopersicon esculentum Mill.) rotation in California's San Joaquin Valley. There were four treatments: conservation tillage, no cover crop (CTNO); conservation tillage with cover crop (CTCC); standard tillage, no cover crop (STNO); and standard tillage with cover crop (STCC). After 5 yr, the top 30 cm of soil in CTCC had an increase of 4500 kg C ha(-1), compared with an increase of 3800 kg C hat in STCC from initial soil C content in 1999. To enhance our understanding of C dynamics in CT systems, we pulse-labeled cotton with (CO2)-C-13 in the field and followed the decomposition of both the roots and the shoots through three physical fractions: light fraction (LF), which tends to turnover quickly, and two relatively stable C pools-intraaggregate LF (iLF) and mineral-associated carbon (mC). Soil under CT treatments retained more of the cotton-residue-derived C in LF and iLF than ST 3 mo after placement in the field. These differences disappeared after 1 yr, however, with no discernable differences between CT and ST regardless of CC. In California's Mediterranean climate, CT alone does not accumulate or stabilize more C than ST in tomato-cotton rotations, and the addition of cover crop biomass is more important than tillage reduction for total soil C accumulation.
  • Authors:
    • Harben, R.
    • Beyer, J.
    • Dusault, A.
    • Fry, R.
    • Shrestha, A.
    • Klonsky, K. M.
    • Mitchell, J. P.
  • Source: Australian Journal of Experimental Agriculture
  • Volume: 47
  • Issue: 12
  • Year: 2007
  • Summary: While there have been several similarities between the development of cropping systems in Australia and California ( including climate, the need for irrigation and very diverse, highly specialised crop rotations), the historical patterns of conservation tillage development in the two regions have been quite different. Current estimates indicate that conservation tillage ( CT) practices are used on less than 2% of annual crop acreage in California's Central Valley. Tillage management systems have changed relatively little since irrigation and cropping intensification began throughout this region, more than 60 years ago. The University of California ( UC) and United States Department of Agriculture ( USDA) Natural Resource Conservation Service ( NRCS) CT Workgroup is a diverse group of UC, NRCS, farmer, private sector, environmental group and other public agency people. It has provided wide- ranging services aimed at developing information on reduced tillage alternatives for California's production valleys. In a short span of 7 years, the CT Workgroup has grown to over 1000 members and has conducted over 60 demonstration evaluations of CT systems. While CT is still quite new in California, a growing number of farmers has become increasingly interested in it, for both economic and environmental reasons. They are now pursuing a wide range of activities and approaches aimed at developing sustainable CT systems. As successful CT systems continue to be demonstrated, the rate of adoption is expected to increase.
  • Authors:
    • Essah, S. Y. C.
    • Sparks, R. T.
    • Dillon, M. A.
    • Delgado, J. A.
  • Source: Journal of Soil and Water Conservation
  • Volume: 62
  • Issue: 5
  • Year: 2007
  • Summary: This literature review examines a decade of advances in cover crops including how cover crops with limited irrigation can increase yields, crop quality, and nutrient and water use efficiencies while protecting the environment.