Nitrogen balance and nitrate residues in pastures grazed by dairy cows and fertilised with mineral fertiliser, pig slurry or cattle compost

A code of good practices was established by each European member state according to the
nitrate directive. In Belgium, the nitrogen (N) inputs from slurry or compost are limited to
230 kg N/ha in pastures. Larger amounts can be applied when a program of additional
measurements, including soil nitrates analysis, is followed by the farmer. This trial aims to
measure nitrogen balance and soil nitrates in pastures fertilised with mineral nitrogen fertiliser
(min N), pig slurry (S) or cattle compost (C). The pastures were grazed by dairy cows and the
fertilisation allowed similar efficient N levels.
N inputs by fertilisation were different at 169, 170 and 102 kg N/ha in C, S and min N plots
respectively. The use of pig slurry and cattle compost as compared with mineral N fertiliser
increased N balance and reduced apparent N efficiency. The nitrogen, potassium and
phosphorus nutrition indexes, the number of grazing days and the milk yields per ha were not
different. The soil nitrate contents were not increased by use of slurry or compost. The overall
low nitrate contents suggested a low nitrate leaching with the three types of fertilisation.