• Authors:
    • Williams, S.
    • Schuler, J.
    • Killian, K.
    • Kautza, T.
    • Elliott, T.
    • Easter, M.
    • Cipra, J.
    • Bluhm, G.
    • Paustian, K.
    • Brenner, J.
  • Year: 2001
  • Summary: Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric carbon- dioxide by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. Practices that increase the amount of CO2 taken up by plants (through photosynthesis), which then enter the soil as plant residues, tend to increase soil C stocks. Likewise, management practices that reduce the rate of decay or turnover of organic matter in soils will also tend to increase carbon stocks.
  • Authors:
    • Dabney,S. M.
    • Delgado,J. A.
    • Reeves,D. W.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 32
  • Issue: 7-8
  • Year: 2001
  • Summary: This article reviews literature about the impacts of cover crops in cropping systems that affect soil and water quality and presents limited new information to help fill knowledge gaps. Cover crops grow during periods when the soil might otherwise be fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microrganisms, while simultaneously increasing evapotranspiration from the soil. Cover crops reduce sediment production from cropland by intercepting the kinetic energy of rainfall and by reducing the amount and velocity of runoff. Cover crops increase soil quality by improving biological, chemical and physical properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribute nitrogen (N) to subsequent crops. Other cover crops, especially grasses and brassicas, are better at scavenging residual N before it can leach. Because growth of these scavenging cover crops is usually N limited, growing grass/legume mixtures often increases total carbon inputs without sacrificing N scavenging efficiency. Cover crops are best adapted to warm areas with abundant precipitation. Water use by cover crops can adversely impact yields of subsequent dryland crops in semiarid areas. Similarly, cooler soil temperatures under cover crop residues can retard early growth of subsequent crops grown near the cold end of their range of adaptation. Development of systems that reduce the costs of cover crop establishment and overcome subsequent crop establishment problems will increase cover crop utilization and improve soil and water quality.
  • Authors:
    • Morse, R. D.
    • Miyao, E. M.
    • Temple, S. R.
    • Lanini, W. T.
    • Mitchell, J. P.
    • Herrero, E. V.
    • Campiglia, E.
  • Source: California Agriculture
  • Volume: 55
  • Issue: 1
  • Year: 2001
  • Summary: The efficacy of no-till systems in conserving soil moisture and improving water infiltration under furrow irrigation was evaluated during 1997 and 1998 in California, USA. Two grass/legume mixtures, i.e. triticale/lana woolypod vetch (* Triticosecale/ Vicia dasycarpa [ V. villosa]) and rye/lana woolypod vetch ( Secale cereale/ V. dasycarpa), were used as cover cop mulches in no-till treatments, and compared with a winter fallow treatment with pre-plant herbicide (fallow +h) and a fallow control treatment with no herbicide (fallow -h). Tomato cv. Halley 3155 plants were transplanted in April 1997 and 1998, sprinkle irrigated during the first 6 weeks after transplanting, and furrow irrigated thereafter until 3 weeks before harvest. During 1997, soil water content between 0 and 78 inches did not differ among treatments, while soil water content during the 1997/98 winter was higher under the fallow +h than the cover crop treatments until cover crop termination. Soil water content of cover crop treatments in shallower soil layers (18 and 42 inches) was significantly lower than fallow treatments at the end of the winter. During the 1998 tomato crop season, soil water content between 0 and 90 inches was greater under the triticale and rye mulches than the fallow +h, beginning the 3rd week after furrow irrigations were started. Soil moisture in the shallower layers was also affected by cover crop mulches. In the 42-inch depth increment, there was significantly higher water content under the cover crops than under the fallow +h from about 1 month after the first furrow irrigation until 2 weeks before the last irrigation. Changes in soil water content during furrow irrigation under the fallow +h treatment appeared to be more pronounced than under the triticale or rye surface mulches. Soil compaction in the fallow +h treatment was higher than under the cover crop mulches for most of the 0.6-inch intervals, especially below 1 foot, but differences were significantly higher only for the 3, 3.6, 4.2, 17, 18, and 24-inch depth, but lower from the surface to 2.4 inches. Soil carbon was significantly higher (by 14 and 18%) under triticale and rye, respectively, compared with the fallow +h treatment. The number of earthworms was also higher in no-till (2.1 earthworms per square foot) than in the fallow treatments (0.6 earthworms). Tomato canopy growth did not reach 100% cover in either 1997 or 1998, while tomato plant growth, assessed by measuring the photosynthetically active radiation intercepted by the canopy, did not differ in the triticale, rye, and fallow +h system in either 1997 or 1998. Results showed that the no-till mulch system enhanced water infiltration and soil water conservation.
  • Authors:
    • Morse, R. D.
    • Miyao, E. M.
    • Temple, S. R.
    • Lanini, W. T.
    • Mitchell, J. P.
    • Herrero, E. V.
    • Campiglia, E.
  • Source: HortTechnology
  • Volume: 11
  • Issue: 1
  • Year: 2001
  • Summary: No-tillage processing tomato production in four winter cover crop-derived mulches was evaluated in 1997 and 1998 in Five Points, California, USA. The effectiveness of two medics, 'Sava' snail medic ( Medicago scutellata), and 'Sephi' barrel medic ( Medicago truncatula), and two cereal/legume cover crop mixtures, triticale/'Lana' woolypod vetch ( Triticum x Secale/ Vicia dasycarpa [ Vicia villosa]) and rye/'Lana' woolypod vetch ( Secale cereale/ V. dasycarpa), was compared with two conventionally tilled fallow controls (with and without herbicide) (fallow+h and fallow-h) in suppressing weeds and maintaining yields with reduced fertilizer inputs. The comparison was conducted as a split plot, with three N fertilization rates (0, 100, and 200 lb/acre; 0, 112, and 224 kg/ha) as main plots and cover crops and fallow controls as subplots. Tomato seedlings were transplanted 3 weeks after the cover crops had been mowed and sprayed with herbicide. There were no significant differences in weed cover in the no-till cover crop treatments relative to the fallow controls in 1997. Early season weed suppression in rye/vetch and triticale/vetch plots was similar to herbicide-treated fallow (fallow+h) in 1998, however, later in the 1998 season weed suppression was best in the fallow+h. Tissue N was highest in the fallow treatments in both 1997 and 1998. Yields were highest in the triticale/vetch and fallow and lowest in sephi treatments in 1997, but there were no differences among treatments in 1998.
  • Authors:
    • Follett, R. F.
  • Source: Soil & Tillage Research
  • Volume: 61
  • Issue: 1/2
  • Year: 2001
  • Summary: One of the most important terrestrial pools for carbon (C) storage and exchange with atmospheric CO 2 is soil organic carbon (SOC). Following the advent of large-scale cultivation, this long-term balance was disrupted and increased amounts of SOC were exposed to oxidation and loss as atmospheric CO 2. The result was a dramatic decrease in SOC. If amounts of C entering the soil exceed that lost to the atmosphere by oxidation, SOC increases. Such an increase can result from practices that include improved: (1) tillage management and cropping systems, (2) management to increase amount of land cover, and (3) efficient use of production inputs, e.g. nutrients and water. Among the most important contributors is conservation tillage (i.e., no-till, ridge-till, and mulch-tillage) whereby higher levels of residue cover are maintained than for conventional-tillage. Gains in amount of land area under conservation tillage between 1989 and 1998 are encouraging because of their contributions to soil and water conservation and for their potential to sequester SOC. Other important contributors are crop residue and biomass management and fallow reduction. Collectively, tillage management and cropping systems in the US are estimated to have the potential to sequester 30-105 million metric tonnes of carbon (MMTC) year -1. Two important examples of management strategies whereby land cover is increased include crop rotations with winter cover crops and the conservation reserve programme (CRP). Such practices enhance SOC sequestration by increasing the amount and time during which the land is covered by growing plants. Crop rotations, winter cover crops, and the CRP combined have the potential to sequester 14-29 MMTC year -1. Biomass production is increased by efficient use of production inputs. Optimum fertility levels and water availability in soils can directly affect quantity of crop residues produced for return to the soil and for SOC sequestration. Nutrient inputs and supplemental irrigation are estimated to have the potential to sequester 11-30 MMTC year -1. In the future, it is important to acquire an improved understanding of SOC sequestration processes, the ability to make quantitative estimates of rates of SOC sequestration, and technology to enhance these rates in an energy- and input-efficient manner. Adoption of improved tillage practices and cropping systems, increased land cover, and efficient use of nutrient and water inputs are examples where such information is necessary.
  • Authors:
    • Raper, R. L.
    • Runion, G. B.
    • Reeves, D. W.
    • Reicosky, D. C.
    • Prior, S. A.
  • Source: Soil & Tillage Research
  • Volume: 54
  • Issue: 3-4
  • Year: 2000
  • Summary: Recent research indicates tillage operations result in a rapid physical release of CO2 and water vapor from soil. However, effects of soil disturbance on gas fluxes during planting operations have not been adequately explored. Our objective was to measure short-term gas loss resulting from the use of different planting preparation implements on long-term residue-covered soil (no-till) on a Norfolk loamy sand (Typic Kandiudults; FAO classification Luxic Ferralsols) in east-central Alabama, USA. A crimson clover (Trifolium incarnatum L.) cover crop was killed with herbicide two weeks prior to the study. Due to dry soil conditions, 15 mm of water was applied 24 h prior to study. Gas fluxes were measured with a large canopy chamber (centered over two rows) for an integrated assessment of equipment-induced soil disturbance. Increased losses of CO2 and water vapor were directly related to increases in soil disturbance. Although these short-term C losses are minor in terms of predicting longterm C turnover in agro-ecosystems, results suggest that selecting planting equipment that maintains surface residue and minimizes soil disturbance could help to conserve soil water needed for successful seedling establishment in these coarse textured soils. Published by Elsevier Science B.V.
  • Authors:
    • Subak, S.
  • Source: Global Environmental Change
  • Volume: 10
  • Issue: 3
  • Year: 2000
  • Summary: The Kyoto Protocol introduces the possibility that changes in carbon stock on agricultural and forest land and soils may be counted against countries' commitments to reduce their greenhouse gas emissions. Including activities related to land use change and forestry in the international climate change agreement may stimulate new incentives for soil-conservation practices domestically. However, a primary criteria for their inclusion relates to the level of accuracy and transparency with which carbon stock changes can be assessed. Parties will also be concerned with the wider environmental impact of different sequestration practices, and the impact of offsets on overall emissions targets. This paper examines these issues for agricultural soils, considering recent research in North America. It is argued that incentives for carbon sequestration practices may need to be implemented independently of actual stock changes because farm-level soil monitoring would be very costly. In the USA, priority should be given to establishing incentives for cover crops and to expanding conservation tillage programs. These activities provide a range of ancillary environmental benefits. In contrast, improvements in biomass yield tend to rely on higher fertilizer inputs with their related environmental costs. Carbon accumulated through any of these activities is easily lost if the practices are discontinued, and so assessment procedures are needed that would avoid overestimating sequestration. Annual accumulation in agricultural soils could be equivalent to about 10% of Annex I carbon dioxide emissions, and therefore options for limiting sink credits from soils should be considered.
  • Authors:
    • TCG
    • Teasdale,John R.
    • Rosecrance,R. C.
    • Coffman,Charles B.
    • Starr,J. L.
    • Paltineanu,I. C.
    • Lu,Y. C.
    • Watkins,B. K.
  • Source: American Journal of Alternative Agriculture
  • Volume: 15
  • Issue: 2
  • Year: 2000
  • Summary: Sustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillage-intensive operation. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recomended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillages system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, (4) manure systemd including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporatin manure and rotary hoe plus cultication for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year. both systems average 7.8 Mg ha-1 compared to 5.7 Mg ha-1 in both the croen vetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crown vetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding system, partly because of competitions from uncontrolled weeds. Several measures of the efficience of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external N input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system perfomed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.
  • Authors:
    • Mielniczuk, J.
    • Martin-Neto, L.
    • Bayer, C.
    • Ceretta, C. A.
  • Source: Soil & Tillage Research
  • Volume: 53
  • Issue: 2
  • Year: 2000
  • Summary: In weathered tropical and subtropical soils organic matter is crucial for soil productivity and its quantity depends heavily on soil management systems. This study evaluated the effect of no-till cropping systems on organic matter content and quality in a sandy clay loam Acrisol soil (Paleudult in US taxonomy) from Southern Brazil. Ten cropping systems with varying additions of C and N were conducted for 12 years (from 1983 to 1994), The addition of crop residues increased total organic carbon (TOC) and total nitrogen (TN) in the soil at 0-17.5 cm depth, and this increase was directly related with C and N added or recycled by the systems. The crop residues added to the soil were associated with reduced semiquinone free radical concentration, detected by electron spin resonance (ESR), in the organo-mineral aggregates <53 mu m and humic acid (HA) samples, in the soil at 0-2.5 cm depth. This showed that stable organic matter originating from crop residues was less humidified than the original soil organic matter. Results obtained from organo-mineral aggregates showed a higher amplitude (highest and lowest values were 5.47 and 2.09 x 10(17) spins g(-1) of TOC, respectively) of semiquinone free radical concentration than HA samples (highest and lowest values were 2.68 and 1.77 x 10(17) spins g(-1) of HA, respectively). These data showed that alterations due to tillage in soil organic matter characteristics, e.g,, humification degree can be better identified through a combination of soil physical fractionation and spectroscopic analysis. Semiquinone content in the HA samples, detected by ESR, related significantly to aromaticity, as measured by nuclear magnetic resonance (NMR) of C-13. Management systems including no-till and cropping systems with high C and N additions to the soil improved its quality in Southern Brazil. (C) 2000 Elsevier Science B,V. All rights reserved.
  • Authors:
    • Nacci, S.
    • Ramos, M. C.
    • Pla, I.
  • Source: Soil Science
  • Volume: 165
  • Issue: 5
  • Year: 2000
  • Summary: In the vineyards of the Anoia-Alt Penedes region of NE Spain, erosion problems arising from a combination of soil and climate characteristics and their relief have been accelerated in the last few decades as a consequence of new cropping/planting patterns and soil management practices involving continuous tillage, which leaves the soil bare most of the time. In the rain-fed vineyards of the area, rainfall water conservation in situ has also become a problem that influences the production of high quality wine. The determination of the actual and potential erosion processes required for rational selection, design, and application of soil and water conservation practices requires identification and quantification of the hydrological properties and processes that induce runoff and soil erosion. Laboratory studies in 10 representative surface soils of the region, using simulated rainfall, proved that erosion losses were highly related to the surface sealing susceptibility of the soils, which reduced minimum rainfall water intake rates to 1 to 7 mm h(-1) or less after only 10 minutes of rainfall. This susceptibility was highly correlated with the high silt and low organic matter content of the soils. In most of the soils, surface protection by a cover was found to increase the minimum rainfall water intake rate 50 to 200 times. A simple laboratory test, based on the measurement of saturated hydraulic conductivity and the time to reach its minimum value, measured efficiently the sealing susceptibility of the studied soils and the relative effect of a protective cover. The minimum value of saturated hydraulic conductivity was highly correlated to runoff and soil erosion losses in soil boxes under simulated rainfall.