Nitrogen responses on pastures in the southern South Island of New Zealand

Abstract

increasing farm production is the low pasture production in early spring and late autumn. In order to accurately predict the effect of nitrogen (N) fertiliser on production at these times, four smallplot mowing trials looking at pasture responses to N fertiliser were established on two dairy farms and one sheep farm in Southland and one sheep farm in Central Otago in August 1998. Monthly applications of 50 kg N/ha as urea were applied from August to May. Pasture production was measured monthly using a pasture probe in Southland and by cutting and drying the herbage in Central Otago. Results show that the August- September applications of N gave pasture responses of 1.5-9 kg DM/kg N in 1998 and 6-23 kg DM/kg N in 1999. The October-November N applications gave responses of 4-20 kg DM/kg N in 1998 and 4-15 kg DM/kg N in 1999. The February-March applications of N produced responses of 6-14 kg DM/kg N in 1999 and 3.2-20 kg DM/kg N in 2000. The response to August-applied N was similar in the second month after application to the first month. For the March application, most of the response occurred in the first 30 days following application, although small responses were measured up to 90 days after application at some sites. N applied in May had a small carryover effect on spring (September) pasture production, but the August application resulted in the greatest overall production increase in September. This study showed that a single application of N in August or March can result in large pasture production increases under mowing with clippings removed, without depressing clover growth. Keywords: autumn, nitrogen fertiliser, nitrogen response, pasture production, spring