An ecological study of the dung patch on dairy pastures : thesis presented in partial fulfilment of the requirements for the Degree of Master of Agricultural Science at Massey University

Abstract

The fertility cycle is an inherent feature of pasture production. The animal grazes the pasture, retains the digestible energy and small amounts of the plant nutrients it requires and returns the remainder to the sward as excreta. The pasture may then use the nutrients in the excreta for further growth. In countries such as New Zealand where the animals graze the pasture all the year round the fertility cycle remains intact. The animals excreta is deposited as discrete dung and urine patches on virtually the same pasture from which it was derived, where it is immediately subjected to an environment responsible for its decay and incorporation into the soil. This fertility cycle is broken, however, in countries where the animal is fed indoors for part of the year. Under this system of management, the excreta becomes mixed with the bedding material of the stalls in which the animals are housed. The mixture, commonly termed "farmyard manure", is eventually redistributed back onto the pasture or mixed with the soil as a manure for crops. Also while in the stalls, the animals are fed meal and conserved fodder which may not necessarily have been grown on land to which the "farmyard manure" is returned. Consequently, although many experiments have been conducted overseas with "farmyard manure", the results have very little relevance to the situation as it exists in New Zealand.