Effect of Biochar and Irrigation on Soybean-Rhizobium Symbiotic Performance and Soil Enzymatic Activity in Field Rhizosphere

Abstract

Nitrogen (N) in soybean (Glycine maxL.) plants derived from biological nitrogen fixationwas shown to be a sustainable N resource to substitute for N fertilizer. However, the limitedwater supply in sandy soil is a critical factor for soybean nodulation and crop growth. This studyinvestigated the potential mechanism of the effect of biochar and irrigation on the soybean-Rhizobiumsymbiotic performance and soil biological activity in a field trial. In the absence of N fertilizer,10 t ha−1of black cherry wood-derived biochar were applied under irrigated and rainfed conditionson an experimental, sandy field site. The plant biomass, plant nutrient concentrations, nodulenumber, nodule leghemoglobin content, soil enzyme activities, and soil-available nutrients wereexamined. Our results show that biochar application caused a significant increase in the nodulenumber by 35% in the irrigated condition. Shoot biomass and soil fluorescein diacetate hydrolyticactivity were significantly increased by irrigation in comparison to the rainfed condition. The activityof soil protease reduced significantly, by 8%, with the biochar application in the irrigated condition.Further, a linear correlation analysis and redundancy analysis performed on the plant, nodule, andsoil variables suggested that the biochar application may affect soybean N uptake in the sandy field.Nodulation was enhanced with biochar addition, however, the plant N concentration and nodule Lbcontent remained unaffected.