Amino acids: a short-term nitrogen source for establishing irrigated pastures

Although rainfed pasture is the main source of feed for dairy, meat and wool-producing livestock, irrigation is transforming regions by providing moisture, thereby extending growing seasons. Consequently, irrigated pastures require increased fertiliser application notably nitrogen (N) to sustain growth. During establishment grasses actively seek N via roots. However, applications of synthetic N fertiliser may not be fully utilised by immature roots resulting in nitrate leaching. Under irrigation, nutrient leaching poses a risk to the environment. Alternative N from amino acids (AA) transferred by clover roots sown with grasses may reduce additional N inputs until plants are established. To investigate root interactions perennial ryegrass (Lolium perenne; PRG) cv. Reward, was sown in pots with either stoloniferous red clover (Trifolium pratense; SRC) cv. Rubitas, white clover (Trifolium repens; WC) cv. Bounty or Talish clover (Trifolium tumens; TT) cv. Permatas creating a 30:70 or 70:30 grass clover composition or monocultures of 30:0 and 70:0 grass. Dry matter (DM) yields of PRG were not significantly (P > 0.05) different when clover was present at 30% and 70% compared with PRG alone. When comparing PRG 30:70 sown with either SRC, WC and TT and PRG sown alone at 30:00, the total AA (mg/g DW) of extracted PGR from roots was significantly (P<0.05) higher. Treatments analysed by species show the same significant result for PRG 30:70. Results suggest sowing PRG with clover at 30:70 may provide short-term N supply at establishment.