Morpho-physiological Responses of Tropical Rice to Potassium and Silicon Fertilization Under Water-Deficit Stress

A factorial experiment consisting of three factors, namely six fertilizer doses including different combinations of potassium (K) and silicon (Si) along with nitrogen (N) and phosphorus (P) and the control (NP100 [control], NP100 + K-100, NP100 + Si-100, NP100 + K-75 + Si-25, NP100 + K-50 + Si-50, NP100 + K-25 + Si-75), three soil water potential levels (0, -15, -30 kPa), and two cultivation methods (wet direct seeding, transplanting), was conducted to evaluate the response of rice in terms of growth, physiological traits, yield, and water productivity. The experiment was laid out in a completely randomized design with three replications and the data were collected on selective growth parameters, physiological traits, yield components, and grain yield of rice. Supplementing N and P with only K (NP100 + K-100) helped in alleviating the harmful effect of water-deficit stress, and resulted in 11%, 8%, 47%, 40%, 40%, and 42% higher leaf greenness, leaf relative water content, net photosynthetic rate, free proline content (wet direct-seeded plants), grain yield (wet direct-seeded plants), and water productivity, respectively, than NP100 at - 30 kPa, while transpiration rate was reduced by 22% for the same treatment combinations. Silicon supplementation either with NP100 alone or in combination with different proportions of K also promoted rice growth, physiological traits, and grain yield; however, the response of rice was largely similar among different K and Si combinations, except for NP100 + K-25 + Si-75. Inclusion of K and Si with N and P in a fertilizer management program where the share of K is at least 50% could be a promising approach to minimize the harmful impact of water-deficit stress in rice cultivated through either wet direct seeding or transplanting method.