The Impact of Clover On Soil Physical Properties and Organic Vegetable Yield in Indiana.

Organic vegetable production can require multiple rounds of weeding between plants, twining and staking. These activities can result in compacted soil and poor soil structure. Cover crops are one method of protecting the soil from compaction and improving the soil structure after cultivation. These experiments studied the effects of clover on soil physical properties and subsequent vegetable yield on a silt loam soil in Indiana that is transitioning to organic production. Two treatments, each consisting of a different type of ground cover, were allowed to over winter. One treatment contained a clover cover crop, and the other treatment was a bare ground control. In the spring, compost was applied to half of each plot, and the plots were tilled and bedded under black plastic. In the first year, lettuce was grown as a biological indicator of nitrogen uptake following a red clover cover crop. In the second year, sweet corn was grown as indicator crop following crimson clover. The first year, the lettuce had a lower yield in the clover plots compared to the control plots, perhaps due to plant disease in the clover plots. Weekly soil nitrate and ammonium samples showed a higher concentration of soil nitrate in the clover treatment than in the bare treatment while the ammonium concentration was relatively constant across both treatment and time. Soil aggregate stability, taken as a measurement of soil resistance to water erosion, was higher in the clover treatment than in the bare treatment both at the beginning (2.0 mm mean weight diameter, MWD vs 1.3 mm MWD) and end (1.4 mm MWD vs 1.2 mm MWD) of the growing season. These results show clover to be effective at reducing the detrimental effects of cultivation and crop maintenance on soil structure and for providing available nitrogen for the subsequent crop.