Can additives or controlled release coating improve the nitrogen use efficiency of urea fertiliser?

Abstract

A plot trial was undertaken to determine whether tactical use of nitrogen (N) fertiliser, applied with or without coating or additive, improved herbage yield and N use efficiency. A randomised complete block design was used to compare no fertiliser (CON), frequent low rates of urea (FL), infrequent moderate rates of urea (IM), IM with controlled release (IM+CR), IM with Progibb (IM+PG), IM with AgriSea (IM+AS), or IM with N-Boost (IM+NB) on irrigated, grazed perennial ryegrass and white clover dairy pastures in Canterbury. The total annual N applied in all fertilised treatments was 190 kg N/ha. The use of fertiliser increased annual herbage yield (16.9 vs 14.5±0.44 t DM/ha/y; P<0.05). Combining urea with a coating or additive altered the distribution of pasture growth but did not affect net annual production or herbage quality. Due to the lack of response and greater application costs with liquid versus granule products, these results highlight the need to consider expected responses to different fertiliser regimes when adopting practices to achieve economic benefits and N efficiency.