A new approach to develop nitrogen fertilizer recommendation: a case study for Washington Navel orange cultivar

Abstract

The quantitative recommendation of nutrients is one of the most important problems in plant nutrition and soil fertility. In this study, we explored a recommendation based on the correlation between N in soil saturation extract (NSSE) and that in plant organs (NPO). For this purpose, 39 Washington Navel Orange (WNO) orchards were selected in Jahrom (Iran), and from each orchard three WNO were chosen. For two consecutive years, in March and late May samples were taken from root, leaves, stem, fruit, and soil, and their nitrogen concentration determined. Orchards were divided into two categories, the first group was high-yield orchards and the second group included other orchards. A correlation matrix was run between NPO and NSSE; variables with significant correlation with NSSE were chosen and a multivariate regression was established between them. The results showed a significant positive correlation between plant organs with each other. Also, there was a significant correlation between NSSE and NPO, and the highest correlation was observed between nitrogen in young leaves and soil. A formula for estimating the amount of nitrogen fertilizer required for each orchard group was developed.