Effects of biogas slurry on crop yield, physicochemical properties and aggregation characteristics of lime concretion soil in wheat-maize rotation in the North China Plain

Purpose: Biogas slurry is a potential sustainable substitute for chemical fertilizers and a soil amendment to restore soil organic matter depletion and structural deterioration. The effects of substituting biogas slurry for chemical fertilizer on a lime concretion soil in the North China Plain were investigated.
Methods: A field experiment examined the consequences of applying different proportions (0, 25, 50, 75 and 100%) of biogas slurry, while maintaining the same total nitrogen supply, over a period of 5 years. We determined effects on crop yield (winter wheat/summer maize rotation), soil physiochemical properties and aggregation characteristics (using dry- and wet-sieving) in the last experimental year.
Results: All fertilizer treatments increased crop yield relative to a control. 50% substitution by biogas slurry gave the highest yield of wheat and maize. Increasing substitution progressively increased soil pH, water holding capacity, organic matter content, total nitrogen content, available phosphorus and potassium contents and C/N ratio; conversely, bulk density declined. Soil aggregate size distribution and stability were improved to varying degrees by biogas slurry substitution, in comparison with chemical fertilizer application alone and unamended control; optimal values for macro-aggregate mass proportion, fractal dimension and percentage of aggregate destruction were achieved with 50% substitution, coinciding with the highest crop yield.
Conclusions: Lime concretion black soil was readily amenable to improvement by biogas slurry application, while maintaining optimal crop yields. Its use should be a priority for environmentally coordinated crop production and animal husbandry in this region.