The impact of farming without nitrogen fertiliser for ten years on pasture yield and composition, milksolids production and profitability; a research farmlet comparison

Abstract

Two experimental farmlets were established in the 2001/02 season and run continuously to 2010/11, comparing the impact of two nitrogen (N) fertiliser systems on milksolids (MS) production, profitability and the yield and composition of ryegrass-white clover pastures. Treatments were: 1) No-N. No N fertiliser applied, stocking rate 2.56 cow equivalents/ha (including replacements); 2) Control. Average of 181 kg N/ha/year applied as urea, stocking rate 3.06 cows/ ha (replacements grazed off farm). Annual pasture production was, on average, 2.9 t DM/ha greater on the Control farmlet compared with the No-N farmlet (P<0.001). Annual MS/ha was 193 kg/ha greater (P<0.01) on the Control farmlet. Despite a reduction of 1.07 kg MS for every kg N not applied, profitability was very similar for both farmlets in 6 of the 9 years. Compared with No-N, the profitability of the Control farmlet improved as milk price increased above $5.10/ kg MS. While the farmlets confirmed that profitable milk production systems can be achieved without N fertiliser applications on well-established Waikato dairy pastures, N fertiliser is useful for increasing profitability and milk production, particularly when the ratio between milk price and the cost of fertiliser is favourable. Keywords: Nitrogen fertiliser, pasture yield, milksolids, operating profit.