Sulfur added to cattle slurry as a means to improve the nitrogen economy of maize during the grain filling period

Mineral additives to cattle slurry based on sulfur compounds improve the nitrogen (N) economy of grain maize during the grain filling period (GFP). This hypothesis was validated on the basis of a field experiment with maize, conducted in three consecutive seasons (2017-2019) on soil low in available sulfur and calcium. The field experiment was conducted at Lipie (51°51′34″ N, 17°5′5″ E, Poland) on soil formed from sandy loam, classified as an Albic Luvisol. The two-factor experiment included two forms of sulfur fermented with cattle slurry: elemental sulfur (S-0) and calcium sulfate dihydrate (Ca-S), applied in four doses of S: 0, 22.5, 45 and 90 kg ha-1. The N contained in cattle slurry was 133 kg ha-1. The average grain yield (GY) after applying slurry only (control S) was 9.6, 10.1 and 8.6 t DW ha-1 in 2017, 2018 and 2019, respectively. The increase in GY in response to S application was revealed in two of three years of the study, and amounted to 0.75 t DW ha-1 (+10% compared to S control) in 2017 and 1.4 t DW ha-1 (+16%) in 2019. In the latter season, GY depended on both N sources, i.e. on its remobilization from plant resources and uptake from the soil. However, the driver of GY increase in response to the applied S was post-flowering N uptake. The study showed that the application of cattle slurry enriched with sulfur is a simple agronomic solution to increase the productivity of N in maize, especially in years with drought, as in 2019. For this reason, this treatment should be considered as a preventive measure.