Physiological and agronomic responses of lowland rice (Oryza sativa L.) to pure and mixed variety cultures and organic fertilizers

To determine the physiological and agronomic responses of rice (Oryza sativa L.) to pure and mixed variety cultures and organic fertilizers, a field study and a pot experiment were conducted at the experimental farm (Block 3, Lot C-3) of the International Rice Research Institute, and screen house of the Crop Science Cluster, Los Baños, Laguna, Philippines, respectively. In the field study, three varieties in mono and mixed cultures constituted the seven treatments in Factor A, and the fertilizer sources, namely: carabao manure, chicken dung and chemical fertilizer were the treatments in Factor B. In the pot experiment, there were 10 treatments in Factor A consisting of three varieties similarly used in the field study, the monoculture planted in two or three seedlings per hill, three combinations of two varieties at a time and the mixed planting of three varieties. Organic and chemical fertilization constituted the treatments for Factor B. In terms of agronomic and physiological parameters, rice plant appeared to be more responsive to chemical fertilizer but result of one cropping season is not conclusive. Despite effects of organic fertilizers followed chemical treatments but long term sustainability must be considered than short term benefits. Pure Angelica and its combination with Burdagol were the tallest plants. Yield components such as panicle length and 1000-grain weight were significantly highest with Pure Angelica and pure Burdagol. The total number of grains and filled grains was affected by the interaction of variety with fertilizer source, with the mixture of Burdagol + Angelica + IR64 having the highly significantly highest number of grains when fertilized with chicken dung. However, for the number of filled grains, the combination of the three and pure Burdagol with chemical fertilizer had the highest number but this was not significantly different from pure Angelica fertilized with carabao manure. Angelica is the most responsive to organic fertilization compared with other varieties and their combination. Plants int he pot experiment had agronomically and physiologically responded more to chemical fertilizer than organic fertilizers. However, use of organic fertilizers must be considered because aside from being environment friendly it is cost effective. The eating quality of mixed variety is better than pure culture with Burdagol + Angelica + IR64 as the tastiest. Burdagol is the most aromatic, Burdagol + Angelica + IR64 and Burdagol + Angelica combinations had comparable aroma probably because of the Burdagol in the mixture. Considering the overall mean of the criteria used in determining raw milled rice and preference of freshly cooked rice, IR64 had the lowest value which indicates that it was least preferred.