Effects of phosphorus fertilizer on growth, yield and quality of coconut at early reproductive stage under saline intrusion condition in Mekong Delta

Coconut palm (Cocos nucifera L.) is one of the most important oil crops in the tropics. The tree is able to grow well under saline intrusion condition. However, in the case of high level of salinity for a long period, the coconut tree is severely affected, resulting in poor growth and yield. Therefore, providing balance and sufficient nutrients would help plants tolerate better to unsuitable environment including salinity. Among plant macronutrients, phosphorus is considered to help coconut tree have more roots and leaves, stimulating flowers formation and fruit setting which lead to improve yields. The aim of this work was to determine effects of the amount of phosphorus fertilizer and the frequency of application on growth, yield and quality of coconut tree at early reproductive stage under saline intrusion condition. Two two-factor experiments were conducted in Binh Dai district, Ben Tre province and Tan Phu Dong district, Tien Giang province where the highest salinity in the dry season reached 13.8‰ and 6.3‰, respectively. The treatments of experiments were arranged in split-plot design (SPD) with three replications. The main plot factor was the frequency of phosphorus fertilizer application (2 and 4 times per year) and the sub-plot factor was the amount of phosphorus fertilizer (30, 45, 60 and 75 kg P2O5/ha/year). The results showed that coconut trees grew best with the treatment of four applications of 60 kg P2O5/ha/year, corresponding to 0.3 kg P2O5/tree/year. The trees in this treatment had more leaves, fruit setting, nut number per tree and higher yield than other treatments under saline intrusion condition.