Multi-cutting and sheep excrement influence plant growth and soil nitrogen mineralization in sown grassland

Purpose Multi-cutting and livestock excrement application are two key agricultural practices affecting nutrient cycling in the plant-soil system of sown grasslands. However, little is known about the combination of multi-cutting and livestock excrement application on nitrogen mineralization and utilization and their mechanisms regulating plant growth. Methods The experiment was carried out in a salinized grassland at Linze Grassland Agricultural Station, Gansu Province, China. We tested the effects of plant multi-cutting (MC), sheep excrement (SE), multi-cutting and sheep excrement (MC + SE), and plant only (CK) on the soil nitrogen mineralization and plant growth of two forage plants, the spring wheat ( Triticum aestivum L., cv. Yongliang 15) and common vetch ( Vicia sativa L., cv. Lanjian 3). We measured the plant height, branch number, tiller number and crude protein content, and soil nitrification rate, ammonium rate, microbial nitrogen and microbial carbon, and abundance of soil ammonia-oxidizing bacteria and ammonia-oxidizing archaea. Results MC and MC + SE significantly increased plant height, dry matter, and branch and tiller number of both forage crops. Although crude protein content and tiller number of spring wheat in SE decreased, these in MC + SE increased. SE and MC + SE significantly promoted nitrification rate in the soil by increasing the soil microbial nitrogen and soil ammonia-oxidizing bacteria abundance of the two forage crops. Conclusions Combined application of both multi-cutting and sheep excrement could accelerate soil nitrogen mineralization and plant nitrogen uptake, which could be considered in pasture management to improve the sustainable productivity of grass-soil systems of sown grassland.