Regulation effects of carbonized apple branches on absorption, distribution, and utilization of 15N single-labeled ammonium nitrate (15NH4NO3 or NH415NO3) in Malus hupehensis

Abstract

To improve the utilization of nitrogen fertilizer and orchard waste, the apple branches were separated and pyrolyzed into carbonized wood and carbonized bark, and then applied to root-zone soil of potted Malus hupehensis. The physiological characteristics of leaves and roots were detected, and the absorption, utilization, and distribution of ¹⁵NH₄NO₃ and NH₄¹⁵NO₃ in plants were analyzed using the ¹⁵N isotope tracer technique. The results indicated that the net photosynthetic rate and water use efficiency of leaves, the root growth, and the activity of nitrate reductase and glutamine synthetase were greatest increased by 1.0% (w:w) carbonized bark and carbonized wood, and the effect of carbonized bark was more effective. The carbonized bark more effectively increased nitrogen derived from fertilizer (Ndff) value in all organs, the distribution of ¹⁵N in roots, and utilization of the ¹⁵NH₄NO₃ and NH₄¹⁵NO₃ of Malus hupehensis compared with carbonized wood at the same application ratio, and 1.0% ratio performed better than other ratios in these terms. The Malus hupehensis treated with carbonized bark had the highest utilization ratio of ¹⁵NH₄NO₃ (10.54%) when the application ratio was 1.0%, and the corresponding parameter of NH₄¹⁵NO₃ was 12.98%. The soil immobilization capacity of ¹⁵N was improved, and carbonized bark resulted in the greatest decrease in the loss ratios of ¹⁵NH₄NO₃ and NH₄¹⁵NO₃ under 1.0% ratio, which decreased by 27.33% and 30.08%, respectively. For reducing nitrogen loss and improving nitrogen utilization, carbonized bark was more effective than carbonized wood, mainly because bark contained more cellulose and less lignin than wood.

Keywords: (15)N; Ammonium nitrogen; Carbonized bark; Carbonized wood; Nitrate nitrogen; Nitrogen utilization.