Rice plant growth and nutrient leaching under different patterns of split chemical fertilization on sandy soil using a pot

摘要

Savannakhet Province has 25% of the total lowland rice cultivation area of Lao People's Democratic Republic (Laos). However, most of the fields are rainfed, with highly permeable sandy soil, which has low water and nutrient availability. In such sandy rainfed fields, high leaching loss of nutrients from applied fertilizer is expected, and rice yield is also decreased. Therefore, an efficient fertilization scheme is required to improve rice yield in this area. We conducted a pot experiment to evaluate rice plant growth and nutrient leaching under different split chemical fertilizer application patterns. Sandy soil collected in a village in Savannakhet Province was placed in test pots. Four treatments, viz., standard fertilization (control: C, three splits), subdivided fertilization (SF, six splits), intensive fertilization (IF, once at the time of transplanting), and no fertilizer (NF) were tested. Irrigation was done every 3days during the initial 3months and every 10days in the final month with reference to the rainfall pattern recorded in the rainy season of 2016. Although the maximum number of tillers in C and IF was higher than that of SF, they ultimately decreased to a smaller number than that of SF. The yield of SF was higher than that of the other three treatments. NF showed the lowest growth and yield. The six-split fertilization might supplement nitrogen (N) at the late growing stage. IF showed the largest N leaching loss among treatments. Because of low phosphorus (P) leaching loss, split P fertilization was ineffective. K leaching was completed by 39days after transplanting, suggesting that all of the K applied by fertilizer and irrigation was consumed by rice plants or lost through leaching before panicle initiation. The proposed split fertilization is advantageous in that it supplies N for panicle initiation and maturing stages in sandy paddy fields, but the timing and amount of P application must be considered.