Previous research sponsored by the Kansas Soybean Commission demonstrated that a high-glucosinolate mustard with biofumigant properties reduces M. phaseolina population levels in soil and in soybean plants. The research in this new proposal builds on those results by developing management practices that incorporate use of mustard as a cover crop in soybean production systems including double-cropped soybeans. The mustard cover crop will be tested for its impact on soil health, fungal disease presence, and soybean growth and yield.
a. Best management practices for implementing mustard seed cover crop.
Mustard seed will be planted in the spring. Different methods of managing the mustard seed residue will be tested to determine the best method of controlling soil fungi. Prior to planting soybeans, the field will receive a herbicide burndown. Four different methods (and one control) will be used to determine how to manage the soybean residue for optimal fungal control, including:
• control (no mustard cover crop)
• no incorporation: plant into standing mustard
• no incorporation: cover crop rolled
• no incorporation: cover crop mowed
• incorporation: cover crop disked (tillage)
Soil samples will be collected prior to planting soybeans for determination of disease presence. Soybeans will be planted and grown to maturity. Soil and soybean plant samples will be collected at the R7-R8 growth stage and measured for amount of fungus infection.
b. Management practices for implementing mustard cover crop in double-cropped soybean production.
Winter wheat with and without mustard seed will be planted in the fall. After grain harvest in the spring, soil samples will be taken to measure the amount of charcoal rot fungus. Double-cropped soybeans will be planted and grown to maturity. Soil and soybean plant samples will be collected at the R7-R8 growth stage and measured for charcoal rot fungus.
Measurements:
Soybean will be planted in research plots at the Southeast Ag Research Center experiment fields outside of Columbus, KS, and in research plots at Ashland Bottoms, south of Manhattan, KS.
Production measurements will include in-season assessment of plant development and growth stage. Soil analysis will be performed to determine presence of disease-causing fungi before planting soybeans and again after harvest. Total soil microbial activity will be determined in collaboration with Dr. Ruiz Diaz through the research proposed in his project.
Charcoal rot disease severity will be determined in the soil by counting the number of colony forming units (CFUs) using standard procedures. Charcoal rot disease severity will be measured in plants by randomly selecting ten plants per plot at the R7-R8 growth stage for root and stem severity rating. The plants will be scored by splitting the stem and taproot of each plant, and rating the degree of gray discoloration and microsclerotia in the vascular and cortical tissues on a scale of 1-5. M. phaseolina root population levels will be estimated by grinding the split roots after the severity evaluation. The ground plant tissue and soil samples will be plated on microbiological medium and incubated. CFUs of M. phaseolina will be counted and transformed to CFUs per gram of root tissue or gram of soil.
Sections of each plot will be hand-harvested at maturity to determine yield components of soybean (plants/acre; pods/plant; seed/pod; number of seed/acre; average seed weight and total seed weight/acre). Total plot yield will be taken with a plot combine and seed samples will be analyzed for seed size. Economic analysis will be performed by developing partial budgets for each treatment from harvested yield and total input expenses