Marlito M. Bande1,4, Jan Grenz2, Victor B. Asio3 and Joachim Sauerborn4
Abaca, being a shallow rooted plant and a gross feeder, is able to exploit a limited zone soil. Hence, a careful evaluation of its nutrient uptake is needed, particularly under reduced light condition, irrigation, and NPK fertilization. These field trials were performed to investigate the effect of different shade conditions, irrigation, and fertilizer application on NPK plant uptake and fiber yield of abaca. Light infiltration was reduced by 30%, 40%, and 50% of full sunlight using polypropylene shade nets. Irrigation was applied at a rate of 5 liters plant-1 application day-1. Placement application of N, P2O5, K2O using complete fertilizer was done at 14 grams plant-1 quarter-1 for the first six months and was increased to 40 grams plant-1 quarter-1 for the next six months after planting. Results showed that shade (p≤ 0.01) and irrigation- fertilization (p≤0.05) significantly influenced NPK plant uptake, root and leaf uptake rates of abaca from seedling stage until flagleaf stage. The amount of NPK absorbed was proportional to the amount of growth made as influenced by shade and irrigation-fertilization at different stages of plant growth. The abaca grown in 0% shade was negatively affected by high radiation causing photoinhibition and photooxidative damage of the crop at seedling and early vegetative stages that significantly affected NPK uptake rates and fiber yield. The combination of irrigation and fertilization could further enhance fiber yield to as much as 41% but this was not enough to offset the effects of shade on the growth performance and NPK plant uptake of abaca which significantly (p<0.01) increased fiber yield to as much as 165%.
Keywords: nutrient uptake rates, photoinhibition, photooxidative damage, fiber crop, shade, irrigation-fertilization