Evaluation of a polyolefin coated urea (Meister) as a fertilizer for irrigated cotton

The effectiveness of two polyolefin coated products, 'Meister 70' and 'Meister 270', as slow-release sources of nitrogen (N) for irrigated cotton, and uncoated calcium carbide as a source of acetylene to inhibit nitrification of urea-N and reduce losses by denitrification were studied. The crop was grown on a grey clay in the Namoi Valley of north western New South Wales. The fertilisers were applied at 50 and 150 kg N/ha, combined factorialy with two application times, either pre- or post-sowing. Meister 270 did not release N fast enough to supply the plant's requirements, and is not recommended as a source of N for cotton. Meister 70 was worthy of further study as a pre-sowing source of N because it maintained a higher concentration of ammonium in the soil for longer than urea, resulted in lower soil nitrate concentrations at all times, and increased the apparent recovery efficiency of fertilizer N. The uncoated calcium carbide was not as effective as the wax-coated material tested in previous studies.