Leaf chlorophyll readings as an indicator of nitrogen status and yield of spinach (<i>Spinacia oleracea</i>L.) grown in soils amended with<i>Luecaena leucocephala</i>prunings

Abstract

A field study was conducted to evaluate the nitrogen status and yield of spinach grown in soils amended with prunings of Leucaena leucocephala, (applied at a rate of 3, 5, 7 or 11 t ha−1). A ‘no fertilizer’ 0 nitrogen (N) and 150 kg N ha−1 (recommended) were the control treatments. SPAD readings were recorded for the top six leaves. Nitrogen sufficiency indices were used to indicate the N status of plants. Application of L. leucocephala prunings increased spinach yields (8.98–13.86 t DM ha−1) relative to the 0N treatment (1.35 t DM ha−1) and yields increased with increasing rate of pruning application. SPAD readings showed a linear increase with the increase in applied prunings. There was preferential distribution of N to upper leaves. The relationship between shoot N concentration and SPAD readings was linear and strongest for the top three leaves (r2 = 0.84–0.92). The results indicate the potential of chlorophyll meter readings in assessing N status of leafy vegetables grown on soils amended with different levels of legume tree prunings.