Phytotoxic effects from biuret fed as a supplement to cattle

A series of experiments conducted in 1972 at Rutherglen, north-eastern Victoria, investigated phytotoxic effects, observed in oats and annual pasture, on land where steers had previously been fed biuret, NH(CONH2)2, as a supplement. Soil samples from the necrotic areas, three months later, revealed that biuret content in the 0-10 cm layer was 150 p.p.m. w/w. It was hypothesized that this biuret had been voided in urine by the biuret-fed steers. In a subsequent experiment, yearling steers were fed crushed oats +0.23 kg head-1 day-1 of biuret for 33 days and had a urinary concentration of 1.02 per cent biuret. When this urine was applied to bare soil in the field, wheat and oat seedlings failed to emerge. Urine from steers fed crushed oats only, or crushed oats + linseed meal, was much less toxic to germinating seeds. These findings indicate that, under certain conditions, urine voided from cattle fed biuret can have marked phytotoxic effects in annual crop and pasture species, reducing establishment by up to 20 per cent.