Nutrient Sufficiency Ranges in Mango Using Boundary-Line Approach and Compositional Nutrient Diagnosis Norms in El-Salhiya, Egypt

Nutrient sufficiency ranges are useful for diagnosing and correcting plant nutritional status in order to optimize yield and protect the environment. This study was conducted to determine nutrient sufficiency ranges for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in mango trees grown in El-Salhiya, Egypt, through boundary-line approach (BLA) and compositional nutrient diagnosis (CND) technique. For this purpose, foliar samples from 310 mango trees were collected during two successive years from the study area and fruit yields were recorded. The nutrient sufficiency ranges generated by BLA were 0.744-1.430% for N, 0.074-0.142% for P, 0.543-1.045% for K, 1.366-2.653% for Ca, 0.155-0.305% for Mg, 389-1148 ppm for Fe, 23.1-60.5 ppm for Mn, 28.4-56.3 ppm for Zn, and 2.37-12.10 ppm for Cu. The CND-derived nutrient sufficiency ranges were 0.917-1.215% for N, 0.066-0.106% for P, 0.585-0.943% for K, 1.003-2.077% for Ca, 0.112-0.378% for Mg, 277.5-849.2 ppm for Fe, 27.9-82.4 ppm for Mn, 29.2-44.6 ppm for Zn, and 2.42-11.37 ppm for Cu. The optimum nutrient concentrations generated from BLA were in general comparable to those obtained using CND technique. Only Ca and Fe optimum concentrations showed poor match. Seven significant nutrient interactions were strongly evidenced through principal component analysis of the computed CND indexes. The positive interaction was P-K, while the negative interactions were P-Mg, K-Mg, Ca-Zn, P-Fe, K-Fe, and Zn-Cu.