Yield and quality of fertilized deferred forage of Digitaria eriantha and Eragrostis curvula

A cutting experiment was carried out in Bahía Blanca (Argentina) during 1998 and 1999 using a randomized block design in a 23factorial experiment: (1) the species Digitaria eriantha and Eragrostis curvula, (2) 0 and 60 kg Nha−1fertilizer treatment and (3) deferred harvesting on 1 June and 15 July. The existing forage was cut in mid-February, the N was distributed and the deferred treatment was initiated. Dry matter yield (DM), dead (DF) and green (GF) fractions, crude protein (CP) content, nitrogen utilization efficiency (NUE), nitrogen recovery (NR) andin vitro DM digestibility (IVDMD) for each year were determined. A treatment by year interaction in DM yields (p<0•05) was found. The deferment date was not found to have any effect (p>0•05). The DM yields were substantially increased by fertilization (p<0•05). Mean DM for the control and the fertilized treatments were 942 and 2430 kg ha−1for D. eriantha and 846 and 1958 kg ha−1for E. curvula, respectively. Similarly, CP for D. eriantha was 5•2 and 6•0%, and 4•2 and 5•2% for E. curvula, respectively. The IVDMD had a small response to the fertilization (p<0•05): the average for D. eriantha was 51% and for E. curvula 39%. The quality of the forage was not influenced by the percentage relationship between DF and GF (p>0•05). The NUE (kg DM kg N−1) and the NR (%) were 24•8 and 25•4 for D. eriantha and 18•6 and 17•6 for E. curvula, respectively. Fertilization must be implemented depending on the costs and the expected increase in income due to the increase in forage production. Marked leaf lodging of D. eriantha may restrict the grazing ability of the animals.