Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/29/2012
Publication Date: 5/16/2012
Publication URL: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8586498
Citation: Kremer, R.J., Hezel, L.F. 2012. Soil quality improvement under an ecologically based farming system in northwest Missouri. Renewable Agriculture and Food Systems. Volume 28(3):245-254. Interpretive Summary: Intensive tillage associated with conventional crop production contributes to soil erosion and degradation of soil quality. Such impacts are especially relevant for past crop production on sloping landscapes such as the loess hills bordering the Mississippi and Missouri Rivers. Improved management practices including no-tillage and establishment of grass waterways in fields have proven effective in reducing soil erosion and retaining plant nutrients. Additionally, alternative agricultural management continues to be of interest in further improving the soil environment by restoring soil organic matter and relying on microbial nutrient cycling for plant growth with minimal or no use of synthetic chemicals. Ecologically based farming, a subset of alternative agriculture, focuses on the biology and ecology of the farming system to provide as many services as possible to crops, livestock, and the environment through diversification of production and integration of crops and livestock with natural or restored plant communities within a landscape. Although not previously studied intensively, the management practices used in this type of farming system may benefit several soil properties that contribute to overall soil quality. An ecologically based farming system, which is currently under transition to certified organic production and located on fertile, wind-deposited (loess) soils of a hilly landscape near the Missouri River, was assessed for selected soil quality properties. The site was previously used to grow corn, soybeans and hay before various production systems including pastures for managed grazing, restored native prairie, tree fruit orchard, vegetable plots, and grapes were established beginning in 1995. Soils in the production systems were annually amended with compost produced on-farm with manure and litter originating from horse stables and a egg-laying operation. The restored prairie in the farming system served not only as a soil conservation practice but also provided refuge for pollinators and other beneficial insects for the adjacent crops. Soils were collected according to landscape position and production site during 2003 through 2009 for analyses of carbon (C) and nitrogen (N), soil aggregation, and for biological processes involved in cycling of C and N in the soil environment. Soil organic C (the main component of soil organic matter necessary for multiple functions in soil) and aggregate stability, necessary for reducing erosion and enhancing water infiltration, increased in the restored prairie regardless of landscape position (summit, shoulder, or backslope). Similar increases in soil C and aggregation were noted in the production sites. Increases in microbial enzyme activities, representing soil biological processes, were gradual in the restored prairie and pastures but were rapid in the orchard, vegetable, and grape production sites during the 7-year sampling period. The latter increases in biological activity likely reflect the increased soil organic matter developed from amendments of composts, which were applied more frequently to the horticultural crops during this period. All soil quality measurements were higher than those obtained from annually cropped field and unmanaged grass reference sites near the ecological farming system. The results suggest that the ecological farming system has improved overall soil quality since conversion of this particular landscape from annual cropping and hay systems. Farmers, extension personnel, state and federal agricultural service agencies, and other scientists will find the research results applicable because they illustrate how an ecologically based farming system can improve soil properties on soils vulnerable to erosion that may have been degraded previously through conventional crop management.
Technical Abstract: Ecologically based farming conserves and improves the soil resource and protects environmental quality by using organic or natural resources without application of synthetic chemicals. Soil quality assessment indicates the ability of management systems to optimize soil productivity and to maintain its structural and biological integrity. Our objective was to evaluate the effect of organic management on biochemical characteristics of soil (soil quality indicators) as an assessment of soil quality. The study was conducted on an ecologically based farming enterprise established on gently sloping soils of Sharpsburg silt loam (fine montmorillonitic, mesic Typic Argiudolls) in Clay County, Missouri, which was previously under conventional corn and soybean production. Transition to organic farming began in 1995, which included a primary management strategy to restore soil organic matter consisting of establishment of native prairie plants and application of composted vegetative residues and litter from horse and laying hen operations. Soils were collected at 0-10 cm depths from sites under organic horticultural production (orchard, vegetable, pasture) and from adjacent conventional fields during 2003 – 2008 and assessed for various soil quality parameters. Soil organic carbon and water-stable soil aggregates were considerably increased by up to 60 percent and 72 percent, respectively, in organic production sites compared with continuously tilled sites by the fifth year of assessment. Organically-managed horticultural and pasture fields and restored prairie sites significantly increased (P<0.05) soil enzyme activities in comparison to unmanaged grass and continuously tilled fields. For example, dehydrogenase and glucosaminidase activities increased by 60 and 73 percent, respectively, under organic vegetables compared with the continuously tilled site. Soil enzyme activities were significantly correlated with soil organic carbon content (r values up to 0.80, P<0.001). Increasing soil enzyme activity and organic carbon and nitrogen contents observed during the six-year assessment contributed to improved nutrient cycling for plant nutrition and for overall soil fertility. Results of the soil quality assessments suggest that ecologically based management successfully restored biological activity of silt loam soils previously under intensive conventional agriculture. The system practiced at the study sites illustrates how resources internal to the farm (i.e., composts) can be used to manage soil productivity.