Crimson Clover N Supply to Corn on Different Soil Drainage Classes.

Legume cover crops have been shown to contribute substantial amounts of N in many southeastern U.S. cropping systems.  Much of these data, however, are not representative of current intensive grain crop rotations where it is difficult to establish a legume at the optimal seeding date following soybean harvest.  The performance of Crimson clover (Trifolium incarnatum L.) in poorly drained soils is also not well characterized.  The objective of this study is to evaluate the productivity of different Crimson clover planting strategies, and the supply of N to a subsequent corn crop.  Experiments were conducted for 2 years on well-drained Coastal Plain soils: Myatt (Typic Endoaquults) and Wickham (Typic Hapludults), and on very poorly-drained Tidewater soils: Cape Fear (Typic Umbraquults).  Crimson clover was planted after soybean of different maturity groups (3, 4, and 5); with different seeding strategies (overseeded at last cultivation or prior to leaf drop, drilled after harvest); and at different seed rates (34, 67, and 101 kg/ha).  Corn was produced following incorporation of these cover crops and with inorganic N fertilizer (0, 56, 112, 168, and 224 kg N/ha).  Clover aboveground dry matter and N content, and corn leaf chlorophyll and grain yield were measured.  Clover productivity was much greater on the well drained soils, and aerial overseeding avoided poor stands associated with delaying planting until November following MG 5 soybean on the well-drained soils.   Due to moisture stress, corn response to inorganic N fertilizer was only significant on the very poorly-drained soils.  Legume N supply to corn was minimal on the very poorly-drained soils (<25 kg N/ha), and could not be evaluated due to moisture stress on the well-drained soils.