Slurry management in the milk farms of Entre Douro e Minho

Abstract

The primary milk production zone (PMPZ) of the region of Entre Douro e Minho (EDM), Portugal is under strong environmental pressure caused by intensive dairy cattle farms (DCF) in high-density population areas. Arable land (AL) of these DCF is around 10 ha, of which 97% is irrigated land. The number of milking cows (Livestock unit, LU) is greater than 5 LU/ha and its variability does not depend upon the AL/DCF. The slurry is mainly applied to the soil surface (95 m³/ha) before sowing maize in the spring, and Italian ryegrass in autumn, at rates of 266 kg/ha per year. Slurry tanks have a mean capacity of almost 40 m³/ha or 7.6 m³/LU, enough for a 5 month storage period, for the overall 10 districts of the PMPZ. To minimize environmental impacts and increase the use efficiency of slurry a series of good farming practices and strategies are discussed.