Influence of total soil nitrogen levels on dry matter production responses to nitrogen fertilisation of dairy pastures in New Zealand

Danilo F. Guinto1, Jeff D.Morton2 , Warwick Catto1

1 Ballance Agri-Nutrients Ltd, Private Bag 12 503, Tauranga, 3143, New Zealand, [email protected]; [email protected]

2 MortonAg, Hastings, New Zealand, Email: [email protected]

Abstract

To test whether topsoil (0-7.5 cm) total soil N levels influence pasture dry matter yield (DM) responses at various rates of N fertiliser, field experiments were conducted in spring 2013 and autumn 2014 at five locations in the North Island (Whangarei, Te Awamutu, Central Hawke’s Bay 1, Central Hawke’s Bay 2, and Taihape) and two locations in the South Island (Culverden and Te Anau) of New Zealand. At each site, N fertiliser at rates of 0, 25, 50, 75, 100 and 200 kg N/ha were applied and pasture DM production data collected. At a little more than half the measurement events, the response in pasture DM production was greater at lower total soil N than at higher total soil N levels with the other sites showing a similar pasture DM production response at both low and high soil total N levels. Thus, total soil N was partially successful in predicting DM response to N fertilisation.