Response of a Traditional Sweetpotato (Ipomoea batatas [L]) Variety to Fertilisation in Leyte, Philippines
Luz Asio1, Nemesio Tamayo2, Nenita Dela Cruz3
1Visayas State University, Dept. of Agronomy, Philippines
In the Philippines, very few agronomic studies have been done on traditional sweetpotato varieties despite the fact that these are very popular by local consumers. This study evaluated the response of a traditional variety (var. Siete Flores) to NPK fertilisation. Three separate N, P and K fertilisation experiments were laid out arranged in RCBD with 3 replications. The N experiment had 7 levels: 0 (no N), 40, 80, 120, 160, 200, 240 kg ha-1 N while there were 6 levels for the P experiment: 0 (no P), 20, 40, 60, 80, 120 kg ha-1 P2O5 and 9 levels for the K experiment: 0 (no K), 30, 60, 90, 120, 160, 200, 240, 280 kg ha-1 K2O. Results revealed that application of different rates of N, P2O5 and K2O significantly increased the dry matter yield, weight of marketable and non-marketable roots, and total root yield. Regardless of fertilisation, the traditional variety had low harvest index of < 20% (0.20) indicating its low yielding characteristic. The study found that 30% of the maximum yield of the crop was supplied by the inherent soil N, 50% by the inherent soil P and 60% by the inherent soil K. It proved that inherent soil fertility considerably affects the yield of sweetpotato thus, use of blanket fertiliser recommendations as is currently practised in the Philippines, could result in either under or over fertilisation. Optimum rates of NPK application for the soil used were 118, 38 and 90 kg ha-1 of N, P2O5 and K2O. NPK fertilisation did not significantly influence the nutritional quality of sweetpotato (crude protein, total carbohydrates and crude fiber). Average crude fiber was 20% indicating that this variety can be promoted as a health food.
Keywords: Fertilisation, Philippines, sweetpotato, traditional variety, tropical rootcrops
Contact Address: Luz Asio, Visayas State University, Dept. of Agronomy, College of Agriculture and Food Science, 6521 Baybay City, Philippines, e-mail: luz.asiovsu.edu.ph