Nitrogen Partitioning in Arrowleaf, Crimson, Rose, and Subterranean Clovers without and with Defoliation

Abstract

Cool‐season annual clovers are used in the southeastern United States as a N source but there is limited information on the N concentration and distribution in the clover plant during the growing season. The objective of the study was to document N concentration and accumulation in shoots and roots of ‘Yuchi’ arrowleaf (Trifolium vesiculosum Savi), ‘Tibbee’ crimson (T. incarnatum L.), ‘Mt. Barker’ subterranean (T. subterraneum L.), and ‘Overton R‐18’ rose (T. hirtum All.) clovers for three growing seasons when uncut, and after cutting once, or cutting twice. When uncut, shoot N concentration decreased throughout the growing season with plant maturity from about 35 to 40 g kg−1 in autumn to 10 to 15 g kg−1 at maturity in late spring. Shoot N concentration after cutting once or twice was greater than in the uncut treatment on the same sampling date. Root N concentrations were about one‐half that of the shoot N concentration and declined slowly during the growing season regardless of cutting treatment. When uncut, average maximum shoot N accumulations were 382 kg ha−1 for arrowleaf, 227 kg ha−1 for crimson, 203 kg ha−1 for subterranean, and 226 kg ha−1 for rose clovers. Cutting once or twice reduced maximum shoot N accumulations of all clovers except subterranean clover. Root N accumulations increased during the growing season when uncut, were not affected after cutting once but decreased after a second cutting. The optimum species as a N source would be crimson clover through April and arrowleaf clover in May and June.