Evaluation of nitrate fertilisers as nitrogen sources for spring pasture

Abstract

<jats:p>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</jats:p>

Fertiliser Nitrogen and Factors Affecting Pasture Responses

“…CAN and ASN (containing nitrate-N) gave higher pasture responses than AS (containing ammonium-N) and urea. Nitrate-N gave the best response when applied at soil temperature of 3-5 o C. Craighead et al [63] further suggested that winter-active grasses (i.e. short-rotation ryegrass) could give a larger response to nitrate-N during early spring.…”

“…Soil microbes are involved in the hydrolysis and nitrification of urea-N. It would be expected that low temperature limits plant responses to urea [63].…”

“…Craighead et al [63] measured ryegrass/WC pasture responses in South Canterbury, NZ to four forms of fertilisers (calcium ammonium nitrate (CAN), ASN, AS, and urea) at 30 kg N ha -1 at three different soil temperatures. At 0-2 o C, DM yield differences among forms of fertiliser N were not significant ( Table 5).…”

“…short-rotation ryegrass) could give a larger response to nitrate-N during early spring. Adapted from Craighead et al [63].…”

Winter beef weight gain on Italian grass seed crops in South Canterbury

“…This reduces the amount of autumn nitrogen required (such as used in 1995) to boost a marginal feed supply. Nitrogen fertilisers containing nitrate nitrogen were preferred for late autumn and winter nitrogen applications, since ongoing work on the farm showed these were more reliable than urea at cool soil temperatures (below 6°C) (Craighead et al 1997).…”