Effect of Balanced Fertilization on Citrus

This project was initiated in 2006 to identify the nutrients that are currently limiting citrus growth and to develop fertilizer best management practices for high yield and quality citrus production. In 2006, N, P, K, magnesium (Mg), manganese (Mn), and zinc (Zn) were identified as nutrients that were deficient. The effect of the enhanced fertilization with Mg, Zn, and Mn was examined, but no significant effects of Zn and Mn application on orange yield or quality were evident. In 2007, the experimental design was modified to study the effects of 45, 83, and 120 kg Mg/ha (i.e., Mg1, Mg2, and Mg3) and 45 kg borax (B)/ha on citrus yield and quality.

The first year of this new treatment regime has found significant yield responses to both Mg and B. The yield increase over the NPK treatment was 6.0 t/ha (9.6%), 11.6 t/ha (18.4%), and 24.8 t/ha for Mg1, Mg2 and Mg3, respectively. Compared to the NPKMg1 treatment, added B increased yield by 7.0 t/ha (11.2%). All the treatments supplying Mg and B significantly improved soluble solids, soluble sugar, and vitamin C compared to the NPK or the farmer practice. This study will continue next year to further verify the results since citrus trials usually need at least 3 years to obtain reliable data. Guangdong-BFDP-06