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Cover Crop and Tillage Impact on Soil Quality, Greenhouse Gas Emission, Pests, and Economics of Fields Transitioning to Organic Farming


Our overall goal for this long-term project is to demonstrate the viability of reduced- and no-till organic vegetable production systems. This multi-state, trans-disciplinary project will address critical stakeholder needs while addressing knowledge gaps regarding the effects of minimal- and low-tillage systems in transitioning vegetable cropping systems on greenhouse gas emissions, soil physical, chemical, and biological properties, crop profitability and pest dynamics. <P>The specific objectives are to: 1. Improve the management of soils in transitional and organic farming systems to maximize the benefits from soil organic matter-related properties and their influence on soil quality, soil health, and insect pest suppression. 2. Determine if different tillage systems in combination with a cover crop can hasten the decline of the weed seedbank, slow or retard early-season weed growth, and cause a shift in the weed community. 3. Determine if conservation tillage systems following a winter cover crop system can reduce greenhouse gas emissions relative to conventional organic vegetable production. 4. Evaluate cost effectiveness and profitability of conservation tillage practices. 5. Collaborate with farmer participants in on-farm demonstrations, disseminate project results, and provide training directly to organic farmers, and county extension personnel and other agricultural professionals who advise organic farmers. <P>We expect the organic community to become more knowledgeable with regards to tillage, soil health and quality, greenhouse gas emissions and multiple pest suppression. We expect growers to adopt a creditable organic transitional program that is based on trustworthy information. We anticipate more stakeholders will transition from using conventional tillage to conservational tillage practices. We anticipate the production cost of organic farming to significantly lessen as a result of our efforts and those of our farmer cooperators. Finally, we expect our project and associated adoption of our recommendations will lower production cost and in time increase the economic stability of the organic vegetable industry in both temperate and tropical areas.

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Non-Technical Summary: <BR>Frequent soil disturbances resulting from production activities such as tillage or cultivation for land preparation or weed management can be detrimental to soil quality by negatively impacting physical, chemical, and biological soil properties. Cover cropping, in combination with reduced tillage, can reverse these negative effects and concurrently reduce insect and weed pests, production costs, and CO2 emissions, while providing additional ecosystem services such as increasing nutrient-cycling organisms and soil biodiversity. Given the potential ecological and economic benefits, it seems reasonable that these practices would be a normal part of organic farming. However, these practices remain elusive to organic vegetable farmers, perhaps due to the limit number of trans-disciplinary project targeting this area of research and clientele. We aim to improve soil management practices and profits in transitional organic vegetable systems, through the dissemination of trustworthy information on the use of conservation tillage practices and cover cropping in tandem on greenhouse gas emissions, soil quality and health, crop profitability and pest dynamics. Our specific goals include to: 1) examine the direct and indirect effects of cover cropping and reduced tillage on soil quality and soil health; 2) study how different tillage systems affect weed community dynamics; 3) determine how these practices affect net greenhouse gas emissions; 4) evaluate the cost effectiveness and profitability of reduced tillage practices; and 5) provide organic vegetable producers a comprehensive best management practice plan. These goals parallel ORG priorities of documenting and understanding the effects of organic practices on soil quality and greenhouse gas emissions. <P> Approach: <BR> A randomized complete block design experiment will be established at the University of Maryland Research and Education Farm in Upper Marlboro and duplicated at a grower participant's farm on Oahu, HI to identify transitional systems that maximize soil quality and minimize greenhouse gas emissions and pest incidence for growers transitioning to organic vegetable production. The experiments will evaluate the following four transition systems that vary in crop residue management and level of tillage: 1.No-till vegetables into cover crop mulch (NT) 2.Strip-till vegetables into cover crop mulch (ST) 3.Conventional till vegetables grown on bare-ground (BG) - cover crop mowed and disked 4.Conventional till vegetables grown on black plastic mulch (BP) - cover mowed and disked prior to laying down black plastic These transition treatments represent a continuum from low disturbance, high residue (NT and ST) to high disturbance, low residue (BG and BP). The vegetable rotation for the transition system will be eggplant?bell pepper (Capsicum annuumL.)?eggplant in Maryalnd (MD) and cucumber (Cucumis sativus L.)- lettuce (Lactuca sativa)-cucumber in Hawaii (HI). The cover crops planted annually in late summer/early fall will be a forage radish-crimson clover mix in MD and a rapeseed-sunn hemp mix in HI. The no-till practice will not be conducted in Hawaii due to a generally high soil clay content that makes no-till practice difficult for Hawaiian farmers to adopt. While the lifecycles of forage radish and crimson clover in MD are such that mowing is not required to prepare for the cash crop planting in the spring, a flail mower will be used to create surface mulch for cover crops grown in Hawaii since they will not winter kill or senesce prior to the vegetable crop planting date. The research will be performed on land that is transitioning to organic certification and will be managed using organic practices, relying on cover crop residue and crop competition to suppress weeds in NT and ST and combinations of cover crop residue and mechanical weed control (rotary hoe and cultivation) in BG and ST. Additional weed control will be implemented as necessary in crop rows, using judicious rogueing and hand tools, and time spent weeding will be recorded on a per-plot basis. Fertility will be provided by applying commercial organic fertilizers according to the nutrient management requirements of each crop. Insect pests on crops will be controlled with applications of organic insecticides only if necessary according to their thresholds. In each experiment, treatments will be established in a randomized complete block design. Soil profiles will be characterized by auger descriptions and grid penetrometer measurements, so that blocks can be laid out to maximize within-block soil homogeneity. Treatment plots will be 15 m by 15 m and separated by a minimum 7 m of bare soil. Intra and inter-row spacing for eggplant, cucumber, lettuce, and pepper will be similar to standard row spacing used by growers in the Mid-Atlantic region and Hawaii.

Kolb, Lauren
University of Maryland - College Park
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