Forage Radish Cover Crops Increase Soil Test Phosphorus Surrounding Radish Taproot Holes

Cover crops can influence nutrient cycling in the agroecosystem. Forage radish (FR) ( Raphanus sativus L. var. longipinnatus ) is unique in terms of P cycling because of its high tissue P concentration, rapid growth in the fall, and rapid decomposition in winter and spring. In addition, FR produces a taproot that decays during the winter and leaves distinct holes in the surface soil. This study measured P uptake by FR and cereal rye (CR) ( Secale cereale L.) cover crops; the Mehlich 3 P concentration (M3P) in bulk soil following FR, CR, and no cover crop (NC); and M3P in soil within 3 cm of FR taproot holes. Cover crop treatments of FR, CR, and NC were established at two sites each fall for three subsequent years in a cover crop–corn ( Zea mays L.) silage rotation. Cover crop shoot P uptake ranged from 5.9 to 25 kg P ha −1 for FR measured in the fall and from 3.0 to 26 kg P ha −1 for CR measured in the spring. The greatest cover crop effect on bulk soil M3P was observed at the 0‐ to 2.5‐cm depth after 3 yr of cover crops, with M3P values of 101, 82, and 79 mg P kg −1 after FR, CR, and NC, respectively. Soil within 3 cm of FR taproot holes had greater M3P than FR and NC bulk soil. Further studies should be conducted to determine if FR could increase P removal rates in excessively high P soils or increase P availability in low P soils.