Nitrogen and row spacing on Digitaria eriantha production and digestibility

Abstract

Research on the effects of the rate and method of fertilizer application or row spacing on dry matter yield and digestibility of perennial forage crops either is scarce or has produced contradictory results. The objective of this study was to determine the effects of various rates of N fertilization, method of fertilizer application and row spacing on dry matter yields and in vitro dry matter digestibility (IVDMD) in the cultivated, perennial forage grass Digitaria eriantha Steud. subsp. eriantha cv. Irene. Field studies were conducted on a petrocalcic Ustipsament, sandy loam soil. The total annual N fertilizer (0, 50 or 100 kg ha-1) was applied once (in early spring) or split (half in early spring, half in early summer) on rows 0.3 or 0.5 m apart. Plants were clipped, leaving 50 mm of stubble, whenever they reached 260-280 mm height during the 1998-1999 and 1999-2000 growing seasons. All fertilized treatments produced higher (P < 0.05) dry matter yields than unfertilized controls. Averaged across both seasons, annual dry matter yields were 3.5, 5.2, and 6.0 Mg ha-1 for 0, 50, and 100 kg ha-1 N treatments, respectively. Dry matter yields during summer were greater (P < 0.05) under split than single application. Row spacing did not affect dry matter yield. Although small, increases in IVDMD due to fertilization were significant (P > 0.05). Mean IVDMD was 602, 633, and 656 g kg-1 for N fertilization rates of 0, 50, and 100 kg ha-1. It is suggested that N application should be between 50 and 100 kg ha-1 for D. eriantha, and that this application should be split rather than applied at one time in early spring.