Earthworms and Phosphate‐Solubilizing Bacteria Stimulate Nitrogen Storage and Cycling in a Manured Arid Soil

Core Ideas Earthworm and PSB improved chemical properties of manure‐amended soils. Earthworm and PSB enhanced the increase of soil organic nitrogen pools by pig manure. Earthworm and PSB accelerated soil mineralization and nitrifier‐ denitrification. Improper reuse of manure could not only lead to low nitrogen‐use efficiency but also result in environmental pollution. Therefore, we studied the effect of manure amendment with or without organisms (earthworm and bacteria) on soil nitrogen cycling, aiming to develop a more scientific way to reuse manure. In this study, six treatments, including control (CK), manure (M), manure + slurry (MS), manure + slurry + earthworm (MSE), manure + slurry + bacteria (MSB), and manure + slurry + earthworm + bacteria (MSEB) were divided into two groups to study the effect of manure and the effect of organism on the soil nitrogen pools and nitrogen cycling, respectively. The results showed that manure amendment coupled with organisms increased total nitrogen from 0.538 ± 0.06 to 1.380 ± 0.22 g kg 1 , and available nitrogen from 67.28 ± 5.22 to 113.11 ± 12.21 mg kg −1 , and improved soil organic nitrogen pool by increasing acid‐hydrolyzable nitrogen (AHN) from 404 ± 39 to 974 ± 94 mg kg −1 and non‐acid‐hydrolyzable nitrogen (NAHN) from 133 ± 26 to 406 ± 155 mg kg −1 . Based on the results of soil inorganic nitrogen and soil enzyme activities, we further found that earthworms and bacteria accelerated soil nitrogen cycling by stimulating soil mineralization (ammonification and nitrification) and nitrifier‐denitrification, providing more available nitrogen to plants. Thus, we conclude that manure coupled with organisms would be a more efficient way to reuse manure via increasing soil nitrogen storage and availability simultaneously.