Variability in Grass Forage Clipping Experiments Comparing Fertilizer Rates and Sources1

Abstract

AbstractVariability in yields of dry forage and in uptake of nutrients was studied in 10 greenhouse pot and three field plot experiments comparing various rates and sources of N, P, K, or Zn for grasses clipped three to eight times. Standard deviation (SD) increased in general with increase in mean yields of individual clippings. SD for cumulative yields, however, decreased or remained about the same with increase in cumulative mean yield, or increased proportionately less than did yield. Coefficients of variability (CV) decreased in all experiments with increase in cumulative mean yields. These results indicate that statistical analyses of cumulative yields are usually more meaningful and result in less percentage variability than do analyses of individual clipping yields. Experimental error decreased in the order sorghum‐sudangrass hybrid [Sorghum bicolor (L.) Moench ✕ Sorghum vulgare sudanense] > bermudagrass (Cynodon dactylon L.) > ryegrass (Lolium multiflorum Lam.) in greenhouse experiments and sorghum‐sudangrass hybrid > bermudagrass > fescue (Festuca sp.) in field experiments.