Nitrogen and winter cover crop effects on spring and summer nutrient uptake

Abstract

AbstractOverseeded winter annuals in bermudagrass [Cynodon dactylon (L.) Pers.] improve annual dry‐matter (DM) yield and capture nutrients in fields receiving manure application. This study determined the DM and nutrient uptake responses of annual ryegrass (Lolium multiflorum L.), cereal rye (Secale cereale), berseem clover (Trifolium alexandrinum L.) and bermudagrass‐winter fallow to 0, 50, 100 and 150 kg N ha−1 applied approximately 2 months before a single spring harvest, and in addition to swine‐effluent N (258 and 533 kg ha−1 in summer 2000 and 2001, respectively). Under drought conditions in 2000, DM yield at the spring harvest was highest in ryegrass, and summer DM yield of bermudagrass was greater at 100 and 150 kg N ha−1 than 50 kg N ha−1(P < 0·05). The concentration and uptake of N at the spring harvest increased linearly across N rates in both years (P < 0.05). Cover crops differed in N uptake in 2000 (P < 0.01) and values ranged from approximately 141 kg N ha−1 in berseem clover to 86 kg N ha−1 in rye. Per unit of N applied, uptake of N increased by approximately 0·409 kg ha−1 in 2000 and 0·267 kg ha−1 in 2001; uptake of P increased by 0·029 and 0·014 kg ha−1 respectively. In 2000, uptake of P was responsive to N rate and this relationship was significant (P < 0·01) in winter fallow (slope = 0·032) and ryegrass (slope = 0·057). Increased uptake of N and P at the single spring harvest was due mainly to higher concentrations in herbage and not higher DM yield.