Estimated nitrogen use efficiency, surplus, and partitioning in young apple trees grown in varied organic production systems

Abstract

A certified organic apple ( Malus × domestica Borkh.) orchard was established to study the interaction of ground cover management systems (GMS) and nutrient sources (NS) on nitrogen (N) use efficiency and N surplus in the Southern U.S. for three years. Trees treated with green compost (GC) and wood chips (WC), regardless of the NS, had greater N accumulation and leaf N use efficiency compared to the shredded paper or mow-and-blow treated trees. The WC-treated trees had comparably low N surplus relative to the GC trees that induced more [NO 3 −] in soil or soil solution in the rooting zone in September in year 3. GC trees had the highest [NO 3 −] mineralization in the soil during winter. GMS had greater overall effects on the tree response variables than did the NS.