Evaluation of nitrate fertilisers as nitrogen sources for spring pasture

Abstract

Since 1994 Ravensdown have carried out a series of pastoral trials in South Canterbury, aimed at looking at the relative effectiveness of different forms of nitrogen in the spring. These trials showed that in general those N products containing some nitrate-N (i.e., calcium ammonium nitrate - CAN, and ammonium sulphate nitrate - ASN) could be more effective than urea and ammonium sulphate when soil temperatures were low. However, responses were inconsistent because of spring climatic conditions. In 1994 and 1996 CAN produced the most dry matter but in 1995, responses to the form of N were less clear. Responses to nitrate-N were generally best when spring soil temperatures were 3-5°C at the time of application. The magnitude of N responses varied with the rate applied, and the type of pasture to which N was applied. Responses generally lasted the equivalent of two to three grazings. Keywords: ammonium-N, ammonium sulphate, ammonium sulphate nitrate, calcium ammonium nitrate, nitrate fertilisers, nitrate-N, urea