The Form and Vertical Distribution of Soil Nitrogen as Affected by Forage Radish Cover Crop and Residual Side-Dressed N fertilizer
2018
Wang, Fang | Weil, Ray R.
Forage radish (Raphanus sativus L. var. longipinnatus) is an increasingly popular winter cover crop in the mid-Atlantic region of the United States. This crop can be used to scavenge residual soil nitrate (NO3) and ammonium (NH4), with the goal of reducing nitrogen (N) loss from agricultural fields and increasing N availability for subsequent crops. In the present work, two sites in Maryland were examined to investigate the influence of forage radish cover crop and residual N fertilizer from corn side-dressing on the forms and vertical distribution of soil N and the yield of subsequent no-till silage corn (Zea mays L.). Forage radish dry matter ranged from 1,965 to 3,360 kg ha for shoots and 1,531.5 to 3,740 kg ha for fleshy taproots. Forage radish had a marked influence on the distribution of NO3-N in the soil profile; in the spring following a radish cover crop, NO3-N was concentrated in the surface soil, with no accumulation in deep soil, even at the highest fertilization rate of 168 kg N ha. The cover crop had no significant influence on the NH4-N or total N profile. The average silage corn yield was significantly improved following cover cropping. In addition, the yield increased with the highest N fertilization rate but was not affected by low or medium N fertilization rate. In conclusion, a radish cover crop captures large quantities of residual N from the deep soil following N side-dressing and can improve the yield of subsequent silage.
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