Delayed inoculation and starter nitrogen for enhancing early growth and nitrogen status ofLespedeza cuneata

Abstract

Two growth chamber experiments were conducted to determine the response ofLespedeza cuneata (Dumont) G. Don. (sericea lespedeza) to delayed inoculation and low levels of nitrogen fertilization. Nitrogen was supplied either as NH 4 + or as NO 3 − in solution. At 0.5 and 5.0 ppm nitrogen early growth and N2(C2H2) fixation was inhibited by NH 4 + and promoted by NO 3 − . Inoculation at seeding did not negatively affect growth prior to the onset of N2(C2H2) fixation. Delayed inoculation until the trifoliate stage thus did not increase growth or N2 fixation during the first 40 days of growth. After 40 days, specific nitrogenase activity was highest for plants inoculated at the first trifoliate stage of growth. In contrast, growth and total shoot nitrogen accumulation were higher in plants inoculated at planting. The experimental results suggest that delaying inoculation is not a useful technique for improving early growth ofL. cuneata for surface mine reclamation.