Characteristics and Validation of a Recommended Fertilization Approach for Lychee Based on Yield Response and Agronomic Efficiency

Abstract

Lychee is one of the most popular tropical fruits in South China. However, excess fertilizer application is reducing soil productivity and lychee production. Little information is available to develop a rational and feasible recommended fertilization approach for lychee. This study aimed to optimize fertilizer management for lychee production with a nutrient recommendation model that simplifies complex principles of fertilization into a user-friendly "nutrient expert (NE)" system. Analyses of extensive database for lychee revealed that the average yield responses (YRs) of lychee to nitrogen (N), phosphorus (P), and potassium (K) were 4.2 t ha -1 , 3.0 t ha -1 , and 4.3 t ha -1 , respectively. The average relative yields (RYs) of lychee for N, P, and K were 0.73, 0.80, and 0.77, respectively. The mean values of soil indigenous nutrient supply for N, P, and K were 52.4 kg ha -1 , 5.7 kg ha -1 , and 44.2 kg ha -1 , respectively. The average agronomic efficiencies (AEs) were 15.8 kg N kg -1 , 62.8 kg P kg -1 , and 18.2 kg K kg -1 , respectively. The YR and AE of N, P and K were well fitted by quadratic equations. Significant negative exponential correlations were detected between the YR and the indigenous nutrient supply. A significant negative linear correlation was detected between YR and RY in lychee production. In validation experiments, the NE approach outperformed farmers' practices in terms of yield, output-input ratio, the net return, and N use efficiency. The NE system is a feasible approach to making fertilization recommendations for small-scale lychee farmers without the need for testing.