Effects of nitrogen and potassium on wear mechanisms in perennial ryegrass: II. anatomical, morphological, and physiological characteristics
Wear tolerance is important in sports turf, but the effects of nitrogen (N) and potassium (K) on wear mechanisms in perennial ryegrass (Lolium perenne L.) are unknown. The objective of this study was to evaluate wear mechanisms in response to N and K in this species. Field studies were conducted in 2006 and 2007 using five N levels (49, 147, 245, 343, and 441 kg ha–1 yr–1) in combination with three rate levels of K (49, 245, and 441 kg ha–1 yr–1). Wear was applied in both years using wear simulators. Ten plant characteristics were measured in field plots. Nitrogen had significant effect on wear tolerance and plant characteristics. Shoot growth accounted for as much as 94% of the variation in wear tolerance (r = –0.97, P 0.001). Tissue moisture measured as relative water content and shoot water content covaried with shoot growth. Wear injury, shoot growth rate and tissue moisture increased with increasing N, especially when fertilized in excess of 245 kg N ha–1 yr–1. Tissue moisture explained as much as 66% (r = –0.81, P 0.001) of the variation in wear tolerance. Cell wall components, leaf strength, and shoot density were secondary in explaining wear tolerance. Verdure was not important. Tissue K and soil-available K were not correlated with wear tolerance. These results suggest fertilizing at no more than 245 kg N ha–1 y–1 to maintain optimum wear tolerance, shoot growth rate and tissue moisture.