It is known to everyone that organic fertilizer must be applied a month before planting to decompose and efficiently utilized by the growing plants. Organic fertilizer like goat manure may improve the agronomic characteristics and yield components of sweetpotato. Hence, this study was conducted to evaluate the effects, determine the appropriate and assess the profitability of sweetpotato as influenced by the timing of goat manure application. The treatments as follows; T1 = No fertilizer application (control), T2 = 45-45-45 kg ha-1 N, P2O5, K2O applied 1 week after planting, T3 = 10 t ha-1 goat manure applied 4 weeks before planting, T4 = 10 t ha-1 goat manure applied 2 weeks before planting; and T5 = 10 t ha-1 goat manure applied at planting. An experimental area of 341 m2 was prepared and the experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Sweetpotato plants applied with 10 t ha-1 goat manure applied at planting (T5) had the longest main vine with more number of lateral vines comparable to inorganic fertilizer application at the rate of 45-45-45 kg ha-1 N, P2O5, K2O (T2) as compared to other treatment plants. Plants applied with organic fertilizers regardless of timing of application was comparable in fresh herbage yields. With regards to yield components, plants applied with 10 t ha-1 goat manure regardless of timing in the application obtained number of marketable roots, weight of marketable roots (t ha-1) and total root yield (t ha-1) comparable to the unfertilized plants. The highest values on these parameters were obtained from those applied with inorganic fertilizer at 45-45-45 kg ha-1 N, P2O5, K2O (T2). Highest harvest index was obtained by 10 t ha-1 goat manure applied at planting (T5) but comparable to 10 t ha-1 goat manure applied 2 weeks before planting (T4). Plants with 10 t ha-1 goat manure applied at planting (T5) seemed to enhance the root yield of sweetpotato resulting in the higher gross margin of PhP12,016.75 ha-1. This was low compared to plants applied with 45-45-45 kg ha-1 N, P2O5, K2O of inorganic fertilizers.
Organic production, assessment, timing, fertilizer, yield and income