Effects of one and multiple-injection fertilization on pecan growth and quality

Objectives This study investigated the effect of the injection frequency of liquid fertilizer on pecan growth and quality. We aim to provide the technical basis for the fertilization of pecan.

Methods A field experiment was conducted in Jinhua, Zhejiang Province, using 13-year-old pecan adult trees (Mahan) as test material. Fertilization treatments included no injection control, one injection, and multiple injections (5 times), drilling holes at the base of the trunk from l5 to 25 cm from the ground. Both injection treatments were applied at the same total fertilizer rate. The leaf and fruit biomass and the nutrient contents of the tree parts were determined at harvest. Further, the fruit appearance and nutritional quality indicators were investigated. The contribution of the fertilizer treatments to differences of the fruit indicators was determined by the PLS-DA method.

Results The accumulation of mineral elements was highest in the leaves, followed by the kernels, with less concentration in the xylem and phloem. Multiple injections (P<0.05) increased pecan fruit weight, diameter, and nut height by 16.99%, 7.52%, and 6.79% compared with the control, and by 13.03%, 4.50%, and 6.26% compared with one injection. Multiple injections had (P<0.05) higher unsaturated fatty acid content in kernels and the ratio of unsaturated to saturated fatty acids than one-injection. Multiple injections recorded higher Ca and Fe content in pecan leaves, Mg, Mn, Cu, and Zn content in kernels, Fe content in phloem, and N and Ca in the xylem than the control. However, fertilizer treatments did not affect (P>0.05) mineral distribution in different tree parts. The PLS-DA results showed the significant differences (P<0.05) between one and multiple injection treatments; the main substances responsible for the differences in pecan quality were palmitic acid, palmitoleic acid, and kernel Cu content, respectively.

Conclusions With the same fertilizer rate, multiple injections are more effective than one injection in promoting pecan tree growth, improving kernel quality, and accumulating mineral nutrients in various parts of the tree.