Drip nitrogen, phosphorus, and potassium fertigation of 'Spadona' pear

A field trial was carried out for 4 years in Kibbutz Lavee, Israel, to study the nitrogen (N), phosphorus (P), and potassium (K) fertigation of the pear (pyrus communis, cv. Spadona) under drip irrigation, in order to improve yield and fruit size of a 19-year-old plantation. Fertigation treatments consisted of a basic N and K rate, applied uniformly to the entire orchard, supplemented with either K alone, K and N or K and P. Supplemented fertilizers were applied under the drippers in 5-6 doses, during April-May. Potassium and P fertigation raised soil concentration of these two nutrients significantly. Concentration was raised to a greater extent at the 0-30 cm soil layer than at the 30-60 cm layer. The pear was not affected by N or K fertigation, indicating sufficient level of these nutrients. Phosphorus raised leaf P significantly and steadily, fruit P significantly in one year and the yield in the last three years by 30% (p=0.084). Fruit size was not affected by N, P, or K nutrition. The threshold and optimal concentrations values of P in 10-week-old mid-shoot leaves for interpretation of leaf analysis of 'Spadona' pear were found to be 0.14% and 0.15%, respectively.