• Nitrogen and row spacing on Digitaria eriantha production and digestibility

      Gargano, A. O.; Adúriz, M. A.; Busso, C. A.; Amela, M. I. (Society for Range Management, 2003-09-01)
      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.
    • Water, nitrogen and ploidy effects on Russian wildrye mineral concentrations

      Karn, J. F.; Frank, A. B.; Berdahl, J. D.; Poland, W. W. (Society for Range Management, 2003-09-01)
      High quality forage for spring and autumn grazing can be obtained from Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], a cool-season bunchgrass. However, little is known about mineral concentrations critical to livestock production, especially in the relatively new tetraploid plants. A knowledge of plant mineral concentrations and how they can be manipulated to more nearly meet animal requirements is necessary to optimize animal production. A study was undertaken to determine the extent that concentrations of critical minerals in leaf and stem tissue of Russian wildrye were affected by ploidy level, growing-season water (50 and 150% of average), and N fertilizer (10 and 134 kg N ha-1). Plants were sampled at vegetative, boot, anthesis, and anthesis plus 10-day stages of maturity in 1994, 1995, and 1996. Ploidy level resulted in small but significant differences in some mineral concentrations, with diploid plants usually having higher levels. An exception was P in stem tissue. This finding indicates that in breeding and selection for other traits, forage quality was not adversely affected. Growing-season water level also had minimal effects on mineral concentrations, except for P which was enhanced (P < 0.05) by greater amounts of soil water. Fertilizer N increased forage levels of Ca, K, Cu, and Zn, and decreased levels of P. Higher concentrations of K are not desirable, because they increase the possibility of a grass tetany problem. Advancing plant maturity caused a decrease in P and Zn concentrations, but Ca and Mg in leaf tissue increased as plants matured. These results suggest that concentrations of P, Ca, Mg, and Cu were marginal for high producing cattle at some stages of maturity, but we found the effects of nitrogen and growing-season water did not result in leaf and stem mineral concentration changes that would adversely affect the safety and nutritive quality of Russian wildrye.