• Authors:
    • Belina, K. M.
    • Steenwerth, K.
  • Source: Applied Soil Ecology
  • Volume: 40
  • Issue: 2
  • Year: 2008
  • Summary: Impacts of soil tillage and cover crops on soil carbon (C) dynamics and microbiological function were investigated in a vineyard grown in California's mediterranean climate. We (1) compared soil organic matter (SOM), C dynamics and microbiological activity of two cover crops [Trios 102 (Triticale x Triosecale) ('Trios'), Merced Rye (Secale cereale) ('Rye')] with cultivation ('Cultivation') and (2) evaluated seasonal effects of soil temperature, water content, and precipitation on soil C dynamics (0-15 cm depth). From treatments established in November 2001, soils were sampled every 2-3 weeks from November 2005 to November 2006. Gravimetric water content (GWC) reflected winter and spring rainfall. Soil temperature did not differ among treatments, reflecting typical seasonal patterns. Few differences in C dynamics between cover crops existed, but microbial biomass C (MBC), dissolved organic C (DOC), and carbon dioxide (CO2) efflux in 'Trios' and 'Rye' were consistently 1.5-4-fold greater than 'Cultivation'. Cover crops were more effective at adding soil C than 'Cultivation'. Seasonal patterns in DOC, and CO2 efflux reflected changes in soil water content, but MBC displayed no temporal response. Decreases in DOC and potential microbial respiration (RESPmic) (i.e., microbially available C) also corresponded to or were preceded by increases in CO2 efflux, suggesting that DOC provided C for microbial respiration. Despite similar MBC, DOC, RESPmic, annual CO2 efflux and aboveground C content between the two cover crops, greater aboveground net primary productivity and SOM in 'Trios' indicated that 'Trios' provided more soil C than 'Rye'.
  • Authors:
    • Plowden, Y.
    • Benham, E. C.
    • Franks, E. C.
    • Salon, P. R.
    • Dell, C. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 63
  • Issue: 3
  • Year: 2008
  • Summary: No-till (NT) crop production is expected to sequester soil C, but little data is available for dairy forage systems. Our objective was to quantify impacts of NT and rye (Secale cereale L.) cover crops on soil C and N pools and associated soil properties on Pennsylvania dairies. Samples were collected from seven fields following corn harvest. The NT fields had approximately 50% more C and N in particulate and mineral-associated pools in the upper 5 cm (2 in) compared to conventional tillage, but C and N accumulations below 5 cm were similar. This suggests a C sequestration rate of ~0.5 Mg ha-1 y-1 (~0.2 tn ac-1 yr-1) in the 8 to 13 years NT has been used. Soil aggregate stability and cation exchange capacity were proportional to C pool sizes. Rye cover crops had no clear impact. Findings show that expected increases in C sequestration and soil quality with NT can be achieved in dairy forage systems.
  • Authors:
    • Leistritz, F. L.
    • Bangsund, D. A.
  • Source: Management of Environmental Quality: An International Journal
  • Volume: 19
  • Issue: 1
  • Year: 2008
  • Summary: Purpose - The purpose of this paper is to identify and describe key economic and policy-related issues with regard to terrestrial C sequestration and provide an overview of the economics of C sequestration on agricultural soils in the USA. Design/methodology/approach - Recent economic literature on carbon sequestration was reviewed to gather insights on the role of agriculture in greenhouse gas emissions mitigation. Results from the most salient studies were presented in an attempt to highlight the general consensus on producer-level responses to C sequestration incentives and the likely mechanisms used to facilitate C sequestration activities on agricultural soils. Findings - The likely economic potential of agriculture to store soil C appears to be considerably less than the technical potential. Terrestrial C sequestration is a readily implementable option for mitigating greenhouse gas emissions and can provide mitigation comparable in cost to current abatement options in other industries. Despite considerable research to date, many aspects of terrestrial C sequestration in the USA are not well understood. Originality/value - The paper provides a useful synopsis of the terms and issues associated with C sequestration, and serves as an informative reference on the economics of C sequestration that will be useful as the USA debates future greenhouse gas emissions mitigation policies.
  • Authors:
    • Ngouajio, M.
    • Wang, G.
  • Source: Hortscience
  • Volume: 43
  • Issue: 6
  • Year: 2008
  • Summary: The effects of two cover crops [cereal rye ( Secale cereale L.) and oat ( Avena sativa L.)], four tillage systems [no tillage (NT), strip tillage (ST), conventional tillage with cover crops incorporated (CTC), and conventional tillage without cover crop (CTN)], and three pre-emergence herbicide rates (full rate, half rate, and no herbicide) on pickling cucumber ( Cucumis sativus L.) growth and production, weed populations, and the incidence of pythium fruit rot were studied. Weed infestations, cucumber establishment, and cucumber leaf chlorophyll content were similar between the rye and oat treatments. However, the oat treatment had higher cucumber fruit number and weight and a lower percentage of cucumber fruit infected with Pythium spp. compared with the rye treatment. The NT and CTC systems reduced cucumber stand and leaf chlorophyll content, but had equivalent cucumber fruit number and weight compared with CTN. The NT and ST had lower weed biomass and weed density than CTN and CTC. The NT also reduced the percentage of cucumber fruit affected with pythium compared with CTN and CTC. Reducing the pre-emergence herbicide rate by half did not affect weed control or cucumber fruit yield compared with the full rate. However, weeds escaping herbicide application were larger in the half-rate treatment. The experiments indicate that with the integration of cover crops and conservation tillage, it is possible to maintain cucumber yield while reducing both herbicide inputs (by 50%) and the incidence of fruit rot caused by Pythium spp. (by 32% to 60%).
  • Authors:
    • Leser, J. F.
    • Wheeler, T. A.
    • Keeling, J. W.
    • Mullinix, B.
  • Source: JOURNAL OF NEMATOLOGY
  • Volume: 40
  • Issue: 2
  • Year: 2008
  • Summary: Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log 10 (J2+1)/500 cm 3 soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log 10(J2+1)/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm 3 soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18°C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10°C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.
  • Authors:
    • Durigan, J.
    • Correia, N.
  • Source: Bioscience Journal
  • Volume: 24
  • Issue: 4
  • Year: 2008
  • Summary: To evaluate the effect of cover crops [sorghum ( Sorghum bicolor 'Sara'), coverage sorghum ( S. bicolor * S. sudanensis 'Cober Exp'), forage millet ( Pennisetum americanum 'BN2'), common millet ( Pennisetum americanum), finger millet ( Eleusine coracana) and St. Lucia Grass ( Brachiaria brizantha)] and treatment with spontaneous vegetation, in soil fertility after two years under no-tillage systems, experiment was conducted at the farm 'Tres Marcos', Uberlandia, MG - Brazil. The soil was collected in February 2005, after the harvest of the soybean grains (cv. M-SOY 6101), in depths of 0-5 cm, 5-10 cm and 10-20 cm. The coverage resulted in soil chemical properties alteration, with different responses at the sampling depths studied. In first 5 cm of soil, was observed higher pH, organic matter, exchangeable Ca and Mg, base saturation, bases content and effective cation exchange capacity than in deeper samples. The soil kept with spontaneous vegetation showed the highest pH, Ca and Mg levels, base saturation and effective cation exchange capacity, while the soil under cover crop showed higher P and organic matter levels.
  • Authors:
    • Roel, A.
    • Terra, J.
    • Pravia, M.
  • Source: Proceedings of the 9th International Conference on Precision Agriculture, Denver, Colorado, USA, 20-23 July, 2008
  • Year: 2008
  • Summary: Soil management practices impacts on sorghum ( Sorghum bicolor) productivity have rarely been evaluated at field-scale. Field-scale soil management practices effects on sorghum grain yield were evaluated in three no-till crop-pasture rotation systems during two years in Uruguay (Oxyaquic Argiudoll). Treatments were established in a randomized complete block design in strips traversing the landscape in a sorghum-soyabean ( Glycine max) sequence integrated in three rotation systems: (1) continuous cropping (CC) with a winter cover crop of Lolium multiflorum; (2) short rotation (SR): two years pasture of T. pratense and L. multiflorum and two years of CC and; (3) long rotation (LR) four years pasture of Dactylis glomerata, Trifolium repens and Lotus corniculatus and two years of CC. Strips treatments included a factorial arrangement of two levels of cover crop residues (generated by winter grazing) with and without paraplough subsoiling. Strips were harvested with a combine equipped with a yield monitor. Data were analysed with mixed models accounting for spatial correlation. Yield was affected by year and rotation system but was not affected by management practices; either residue or subsoiling. Although its lower soil quality, CC had greater yield than SR and LR in 2006 (8.61 vs. 8.1 and 7.75 tonnes ha -1, respectively); however, no differences existed in 2007 (4.58 tonnes ha -1). Yield variations between field topographic zones were only found in 2007 SR (35%). Weak evidence of spatial correlation was found for soil properties at the site. No correlations were found between soil chemical properties and yield. Accounting for spatial correlation of 2006-2007 yields improved the statistical analysis. Animal treading and grazing did not appear to affect yield. For undegraded soils in temperate climates, cropping systems including no-tillage and perennial pastures preserved soil C, but did not guaranteed the same levels of grain productivity than more intensive cropping systems.
  • Authors:
    • Kremer, R. J.
    • Sudduth, K. A.
    • Kitchen, N. R.
    • Jung, W. K.
  • Source: Soil Science and Plant Nutrition
  • Volume: 54
  • Issue: 6
  • Year: 2008
  • Summary: Crop management has the potential to either enhance or degrade soil quality, which in turn impacts on crop production and the environment. Few studies have investigated how crop management affects soil quality over different landscape positions. The objective of the present study was to investigate how 12 years of annual cropping system (ACS) and conservation reserve program (CRP) practices impacted soil quality indicators at summit, backslope and footslope landscape positions of a claypan soil in north-central Missouri. Claypan soils are particularly poorly drained because of a restrictive high-clay subsoil layer and are vulnerable to high water erosion. Three replicates of four management systems were established in 1991 in a randomized complete block design, with landscape position as a split-block treatment. The management systems were investigated: (1) annual cropping system 1 (ACS1) was a mulch tillage (typically >= 30% of soil covered with residue after tillage operations) corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation system, (2) annual cropping system 2 (ACS2) was a no-till corn-soybean rotation system, (3) annual cropping system 3 (ACS3) was a no-till corn-soybean-wheat (Triticum aestivum L.) rotation system, with a cover crop following wheat, (4) CRP was a continuous cool-season grass and legume system. In 2002, soil cores (at depths of 0-7.5, 7.5-15 and 15-30 cm) were collected by landscape position and analyzed for physical, chemical and biological soil quality properties. No interactions were observed between landscape and crop management. Relative to management effects, soil organic carbon (SOC) significantly increased with 12 years of CRP management, but not with the other management systems. At the 0-7.5-cm soil depth in the CRP system, SOC increased over this period by 33% and soil total nitrogen storage increased by 34%. Soil aggregate stability was approximately 40% higher in the no-till management systems (ACS2 and ACS3) than in the tilled system (ACS1). Soil aggregation under CRP management was more than double that of the three grain-cropping systems. Soil bulk density at the shallow sampling depth was greater in ACS3 than in ACS1 and ACS2. In contrast to studies on other soil types, these results indicate only minor changes to claypan soil quality after 12 years of no-till management. The landscape had minor effects on the soil properties. Of note, SOC was significantly lower in the 7.5-15-cm soil depth at the footslope compared with the other landscape positions. We attribute this to wetter and more humid conditions at this position and extended periods of high microbial activity and SOC mineralization. We conclude that claypan soils degraded by historical cropping practices will benefit most from the adoption of CRP or CRP-like management.
  • Authors:
    • Reddy, K. N.
    • Zablotowicz, R. M.
    • Locke, M. A.
  • Source: Pest Management Science
  • Volume: 64
  • Issue: 4
  • Year: 2008
  • Summary: BACKGROUND: Conservation practices often associated with glyphosate-resistant crops, e.g. limited tillage and crop cover, improve soil conditions, but only limited research has evaluated their effects on soil in combination with glyphosate-resistant crops. It is assumed that conservation practices have similar benefits to soil whether or not glyphosate-resistant crops are used. This paper reviews the impact on soil of conservation practices and glyphosate-resistant crops, and presents data from a Mississippi field trial comparing glyphosate-resistant and non-glyphosate-resistant maize (Zea mays L.) and cotton (Gossypium hirsutum L.) under limited tillage management. RESULTS: Results from the reduced-tillage study indicate differences in soil biological and chemical properties owing to glyphosate-resistant crops. Under continuous glyphosate-resistant maize, soils maintained greater soil organic carbon and nitrogen as compared with continuous non-glyphosate-resistant maize, but no differences were measured in continuous cotton or in cotton rotated with maize. Soil microbial community structure based on total fatty acid methyl ester analysis indicated a significant effect of glyphosate-resistant crop following 5 years of continuous glyphosate-resistant crop as compared with the non-glyphosate-resistant crop system. Results from this study, as well as the literature review, indicate differences attributable to the interaction of conservation practices and glyphosate-resistant crop, but many are transient and benign for the soil ecosystem. CONCLUSIONS: Glyphosate use may result in minor effects on soil biological/chemical properties. However, enhanced organic carbon and plant residues in surface soils under conservation practices may buffer potential effects of glyphosate. Long-term field research established under various cropping systems and ecological regions is needed for critical assessment of glyphosate-resistant crop and conservation practice interactions. Published in 2008 by John Wiley & Sons, Ltd.
  • Authors:
    • Balkcom, K. S.
    • Delaney, D. P.
    • Mitchell, C. C.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 5
  • Year: 2008
  • Summary: After more than 110 yr, the Old Rotation experiment on the campus of Auburn University in Alabama continues to document the long-term effects of crop rotation and winter legume cover crops on sustainable cotton (Gossypium hirsutum L.) production in the southeastern United States. Long-term yields indicate that winter legumes are as effective as fertilizer N in producing maximum cotton yields and increasing soil organic carbon (SOC). Higher SOC resulted in higher crop yields. However, rotating cotton with corn (Zea mays L.) in a 2-yr rotation or with corn, winter wheat (Triticum aestivum L.), and soybean [Glycine max. (L.) Merr.] in a 3-yr rotation produced little long-term cotton yield advantage beyond that associated with SOC. Cotton yields without winter legumes nor fertilizer N are only slightly higher than they were 110 yr ago. Nonirrigated corn grain yields in rotation with cotton are typically low for central Alabama and appear limited by N. Yields of all crops on the Old Rotation increased with increasing rates of P and K through the 1950s. Since adoption of in-row subsoiling, high-residue, conservation tillage, and genetically modified cultivars; in 1997, all crops have produced their highest, nonirrigated, recorded yields since the experiment began: 1910 kg cotton lint ha(-1) in 2006, 14.8 Mg corn grain ha(-1) in 1999, 6.34 Mg wheat ha-1 in 2001, and 4.50 Mg soybean ha(-1) in 2004.