Nitrogen fertilization and row spacing effects on Digitaria eriantha

Abstract

Crude protein (CP, %), yield of protein dry matter (YPDM, kg ha-1), nitrogen use efficiency (NUE, kg dry matter kg-1 N) and nitrogen recovery (NR, %) were evaluated in Digitaria eriantha after exposing this species to various field-treatments during 1998-1999 and 1999-2000 in Bahía Blanca (38 degrees 48′S, 62 degrees 13′W), Argentina. Treatments included (1) 3 N fertilization rates (0, 50 or 100 kg ha-1), (2) 2 row spacings (30 or 50 cm), and (3) 2 methods of fertilizer application (either split at the beginning of spring and summer or applied at once in early spring). Plants were cut leaving 5 cm stubble whenever they reached 26-28 cm. Studied parameters were determined on forage harvested in spring, summer or total annual. Crude protein increased (P < 0.05) as N fertilization increased in both seasons. Total annual CP averaged 9.7, 12.0 and 14.0%, respectively for the 0, 50 and 100 kg ha-1 fertilization rates, respectively. Crude protein was greater (P < 0.05) on forage which received split rather than bulk N fertilization, and mean values were 13.2 and 11.7%, respectively. Forage sown at different row spacings had a similar (P > 0.05) CP concentration. In general, YPDM responded positively (P < 0.05) to N fertilization and to a split application of N fertilizer. Although differences were not always significant, there was an inverse relationship between N fertilization rate and NUE and NR. Nitrogen use efficiency was 34.5 and 24.8 kg dry matter kg-1 N (P < 0.05), and NR was 98 and 79% (P < 0.05) when N fertilization rates were 50 and 100 kg ha-1, respectively. There was a positive (P < 0.05) relationship between rainfall and NUE or NR. Nitrogen fertilization in D. eriantha should be split with a N fertilization rate close to 50 kg ha-1, and using 30 rather than 50 cm row spacing.