Foundation and evaluation of a diagnosis and recommendation integrated system for star apple (Chrysophyllum cainito L.)

Abstract

Diagnosis and recommendation integrated system (DRIS) is a greatly accurate and reliable mean of evaluating the exact nutrition status of crops via foliar analysis. DRIS has been applied to many types of crops, but DRIS has not been established for and applied to star apple, which is an important fruit in many countries. Therefore, this study aims to (i) detect soil obstacles in star apple cultivation, (ii) create a DRIS for star apple, and (iii) apply the created DRIS norms to evaluate the macro-nutrition status of star apple. In total, 90 leaf samples were obtained from 90 different star apple farms, where 90 soil samples were also collected. The soil analysis results revealed that concentrations of available nitrogen and soluble phosphorus were low and medium, indicating a high risk of reduction in star apple yield. The average yield of star apple was 200.0 kg plant−1. The high-yielding group had higher concentrations of N, K, and Mg in the leaf than the low-yielding group; however, the concentrations of Fe and Mn in the leaf were opposite, and the concentrations of P, Ca, Cu, and Zn were equivalent in the two groups. The DRIS norms have been established for star apple with 28 nutrient ratio pairs and consisted of means, coefficients of variation, variances (S2), and variance ratios (S2 l/S2 h), whose values were 0.136–182.6, 21.0–69.5%, 0.0024–10400.9, and 1.89–34.3, respectively. The results of applying the DRIS norms revealed that the nutrient status of star apple was deficient of N, K, and Mg.