Can phosphorus fertilisers alone increase levels of soil nitrogen in New Zealand hill country pastures
2006
Bowatte, Saman | Tillman, Russell | Carran, Andrew | Gillingham, Allan
In New Zealand grazed pastures, nitrogen (N) fixation by clover is the traditional method of supplying N to the grasses that make up the bulk of the pasture sward. In order to stimulate satisfactory clover growth, phosphorus (P) fertilisers are applied at levels which are generally more than adequate for grass requirements. These legumes then provided N through biological nitrogen fixation. However, studies conducted in New Zealand hill country pastures have revealed that these pastures are still highly N responsive. These results draw attention to a key issue with respect to N fertility in hill country pasture and the question arises as to the value of large P fertiliser applications to overcome N deficiency through clover growth. Here we used modelling approach to evaluate the effectiveness of adding P fertilisers to stimulate clover growth for improving soil N status in hill country pastures and to explore why the hill pastures are N responsive. In addition an attempt was made to explore the potential of fertiliser N in hill pastures based on the current model outcomes and the measured values of pasture production under non-limiting N.
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