Towards efficient N cycling in intensive maize: role of cover crops and application methods of digestate liquid fraction

Digestate, a by-product of biogas production, is widely recognized as promising renewable nitrogen (N) source with high potential to replace synthetic fertilizers. Yet, inefficient digestate use can lead pollutant N losses ammonia (NH3) volatilization, nitrous oxide (N2O) emissions and nitrate (NO3-) leaching. Cover crops may reduce some these recycle the back into soil after incorporation, but effect on balance depends cover crop species. In one-year field study, we tested two application methods (i.e., surface broadcasting, BDC; shallow injection, INJ) liquid fraction separated co-digested cattle slurry (DLF), combined different winter options (CCs, i.e., rye, white mustard or bare fallow), starter fertilizer for maize. Later, side-dressing urea was required fulfil maize N-requirements. We treatment effects yield, N-uptake, N-use efficiency parameters, N-losses in form N2O NO3- development biomass production strongly affected by their contrasting frost tolerance, spring-regrowth while killed. After crops, injection DLF increased significantly compared BDC (emission factor 2.69 vs. 1.66%). Nitrous accounted small part (11-13%) overall yield-scaled (0.46 - 0.97 kg Mg grain-1). The adoption CCs reduced fall leaching, being 51% 64% lower rye than under soil. addition, leaching during spring summer termination promoting immobilization, thus leading -57% annual mustard. method modified N-loss pathways, not cumulative losses. Overall, insights contribute inform an evidence-based design cropping systems which nutrients are recycled more efficiently.