Nitrogen uptake and leaching loss of thirteen temperate grass species under high <scp>N</scp> loading

Abstract

Abstract The intensification of grazed pasture systems in N ew Z ealand has resulted in increased nitrate ( ) leaching and associated significant reductions in water quality, resulting from high N loading in the cow urine patch. A glasshouse soil column experiment was conducted at L incoln U niversity examining the N uptake capacities and leaching losses of sixteen commercial and ‘weed’ pasture grasses, comprising thirteen species. Three dairy cow urine N treatments ( N loading rates) were applied in M ay 2010: 0 ( N 0), 300 ( N 300) and 700 ( N 700) kg N ha −1 . Grass was harvested at 21‐d intervals, leachates collected to quantify N leaching losses and root mass measured. Shoot yield, root mass, N uptake and N leaching loss varied significantly between species ( P &lt; 0·001) and were strongly driven by N loading rate. The highest yielding species at N 700 were L olium multiflorum ‘Feast 2’ and ‘Tama’ (782 and 743 g DM m −2 ), while F estuca arundinacea ‘Flecha’ and L olium perenne ‘Alto' were lowest yielding (375 and 419 g DM m −2 ). Plant N uptake and root mass followed a similar trend, and only moderate increases in total plant N uptake were observed for most species when urine N application rate was increased from N 300 to N 700. N leaching loss was highest at N 700 for F . arundinacea ‘Flecha’ (378 kg N ha −1 ) and lowest for L . multiflorum ‘Feast 2’ and ‘Tama’ (134 and 130 kg N ha −1 ). Strong negative linear relationships were observed between N leaching loss, plant N uptake and root mass. The results indicate that species such as L . multiflorum may play a critical role in reducing pasture N leaching losses, while traditionally sown L . perenne , and also F . arundinacea, may be less suitable.