The effect of rate and time of application of nitrogen in cow slurry on grass cut for silage

Farmers are increasingly concerned to maximise the fertiliser potential of slurry applied to pasture. The availability of the nitrogen in cow slurry for grass growth has been investigated by a number of workers and values from 14% to 84% have been reported for the season after application. Results are presented for 7 field experiments undertaken in southern England on four different farms in the harvest years 1977–1979. Spring and summer slurry applications were 25–30% as effective as ammonium nitrate in promoting dry matter yield of ryegrass swards and winter applications somewhat less at around 15%. When combined with applications of ammonium nitrate the average response was similar but there were appreciable differences in responses between sites. The apparent recovery of slurry nitrogen in herbage was 13% averaged over all treatments.