Influence of level of self-sufficiency on the nutrient budgets of an organic dairy farm (OF0180)

Summary

This is the final report of Defra project OF0180
In 1998, the organic dairy herd at Ty Gwyn, Trawsgoed was split into two herds to examine the physical and financial implications of adopting different feeding strategies and levels of feed self-sufficiency (DEFRA Project OF0146). A self-sufficient system (SS) in which cows were fed a high forage diet supplemented with home-grown cereals was compared with a system in which concentrate feeds were purchased from outside the farm (PC). The present study determined nutrient budgets for the two systems and used models to estimate the various forms of N loss. These studies were supported by field studies to provide additional information about areas of uncertainty identified in previous budget calculations.
Specific objectives were:
1. To determine whole-farm budgets and internal flows of N, P and K for the SS and PC organic dairy systems at Ty Gwyn.
2. To measure the effect of slurry applications on N fixation in grass/clover fields at Ty Gwyn and effects on the uptake of P, K and Mg.
3. To measure possible changes in the P and K content of soils in the SS and PC systems at Ty Gwyn and evaluate recommended laboratory tests as indicators of P and K deficiencies in these soils.
The attached main report starts with a detailed Executive Summary.