Enhanced assimilation rate due to seaweed biostimulant improves growth and yield of rice bean (Vigna umbellata)
¹Cebu Technological University, Crop Science Department, College of Agriculture, - Barili Campus, Cagay, Barili 6036, Cebu, Philippines
²Cebu Technological University, Crop Biotechnology Unit, Center for Studies in Biotechnology, - Barili Campus, Cagay, Barili 6036, Cebu, Philippines
³Cebu Technological University, Department of Agricultural Economics and Development Studies, - Barili Campus, Cagay, Barili 6036, Cebu, Philippines
Rice beans are traditionally planted as intercrop to corn or as the main crop during dry season when corn production is difficult. The use of biostimulants is widely studied to ameliorate the adverse effects of biotic and abiotic stresses. Three possible fermented biostimulants: seaweed, bamboo shoot, and Japanese snail were compared to a commercial organic liquid fertilizer (10 mL L-1) based on morphological, photosynthetic, and yield responses. Fermented seaweed-treated rice bean registered the greatest average vapor pressure deficit (VPD) at 4.33 KPa on the first month and is comparable to the highest average VPD of 4.39 KPa registered by plants applied with fermented Japanese snail on the second month. This interestingly, did not result in difference of transpiration rate (μmol H2O m-2 s-1). Such could be attributed to the plants reduced stomatal aperture when applied with fermented seaweed at 406.80 μmol CO2 mol stomatal conductance and 38.59 Pa total conductance on the second month. Despite this, the average carbon dioxide assimilation rate of rice beans still increased in both the first (15.26 μmol CO2 m-2 s-1) and second (16.51 μmol CO2 m-2 s-1) month. This increased assimilation rate of fermented seaweed-treated rice beans resulted to about 12 cm increase in height at 128.53 cm (R2 = 0.894), 0.02 g pod-1 (R2 = 0.978) heavier and 0.90 seeds pod-1 (R2 = 0.978) more when compared to those applied with the commercial liquid organic fertilizer. Thus, by limiting stomatal conductance, despite the differences in VPD, transpiration rate was not affected while significantly increasing assimilation rate to improve production of rice beans, thereby taking full advantage of available seaweed by-products.