N in granular compost accelerates crop use of soil N

Abstract

Abstract Granulation represents a promising strategy for modifying nitrogen (N) release from compost in soil. Nevertheless, there is a lack of large-scale field trials exploring its impact on crop production and soil N supply. We conducted a preliminary study by employing 15N tracing technology to investigate the effects of granular compost on soil N transformation and supply, on the yield and quality of tobacco leaves, and on the distribution of granular compost-derived N among the different soil N pools and tobacco plant organs. The results revealed that the 2 cm diameter granule fertilizer treatment (G2) significantly increased tobacco leaf yield by 15% compared to CK. However, the G4 treatment resulted in a reduction in leaf yield. Notably, the quality of tobacco leaves remained unaffected, with N content ranging from 15 to 25 g kg-1, which was within a normal range. The results also indicated that direct N supply to the crops from granular compost was limited. The G2 and G4 treatments provided 2.8% and 2.2% of the N in the fertilizer to the tobacco plants, respectively, with more than 93% of the N in the tobacco plants derived from the soil. Therefore, granular compost facilitated the absorption of soil N by tobacco plants. At the end of the growth period, the N content derived from the G4 granular fertilizer in the soil was significantly higher than that from the G2 fertilizer. This may be due to the slower nutrient release mechanism and longer release period of the G4 fertilizer compared to G2. Our results suggested that granulated compost fertilizer has the potential to enhance soil N supply. However, G2 may also have a higher potential for N loss. Further investigations under field conditions are necessary to validate the applicability of granular fertilizer and its specific mechanisms of impact.