Long-term dairy manure application in a no-tillage system: crop yield and soil fertility

Dairy activity expansion has resulted in increased manure volume produced, with the main destination application in agricultural areas. Accordingly, the aims of this study were to (i) evaluate the effects of dairy liquid manure (DLM), in addition to mineral fertilisation, on crop yields over a 9-year period and (ii) identify the soil chemical attributes modified by the manure, and which most affect grain yield. The experiment was conducted from 2005 to 2015 in a no-tillage system, in Paraná state, Brazil, in soil with sandy clay loam texture. The treatments consisted of four doses of DLM (0, 60, 120, and 180 m3 ha−1 year−1) in addition to mineral fertiliser (same amount for all treatments). The DLM application increased maize and black oat yield but did not affect soybean and wheat yield. The DLM improved all evaluated soil chemical attributes and, even with application on the soil surface and no soil disturbance, the effect was observed in deeper layers. Maize grain yield was strongly correlated with soil chemical attributes, especially with pH (positive) and potential acidity (negative). The DLM application, in addition to mineral fertilisation, increased grain yield in a rotation system, especially of maize, with the effect mainly attributed to improvement in soil acidity attributes and the effect on nutrient availability. The estimated dose of DLM for maximum maize yield was 150 m3 ha−1 year−1, with 16% increment in grain yield.