The impact of organic and mineral fertilizers on soil quality parameters and the productivity of irrigated maize crops in semiarid regions

Pig slurry (PS) is widely used as a fertilizer for the production of maize in Spain. Field testing was carried out over a ten-year period to compare the performance of maize fertilized with PS (45 m3 ha-1, equivalent to 315 kg nitrogen (N) ha-1 year−1) (PS45) and mineral fertilizer (300 kg N ha-1) (N300) along with a N-free control (N0). Grain yield, biomass at physiological maturity, plant N uptake and soil nitrates (NO3−–N) were measured as agronomic properties. Soil physical, chemical and biological parameters (as acid-phosphatase activity, earthworm abundance, CO2 Flux, Shannon H′ diversity index (H’), number of utilized substrates (NUS), microbial biomass carbon (MBC), resistance to penetration (RP) and organic matter (OM) among others) were measured at harvest in the last two years of the experiment. The mineral fertilizer promoted the highest grain yield and N uptake by the plants, but also resulted in the highest residual NO3−–N levels in the soil. Interestingly, most of the indicators revealed no statistically significant differences between the treatments in either test years, although a general trend was observed (N0 < N300 < PS45). The repeated application of PS had a beneficial impact on the soil quality over time but did not improve grain yields.

► Applications of 45 m3 ha−1 of pig slurry in sprinkler-irrigated maize in Ebro Valley did not improve the grain yield. ► Continues applications of pig slurry improve soil quality. ► Earthworm abundance is an inexpensive and early indicator of soil quality.