Growth Physiology and Crop Yields of Direct-seeded Rice under Diverse Input Systems in the Dry Zone of Sri Lanka

The dynamics of organic and inorganic nutrient sources in diverse input systems can affect physiological processes of rice. Understanding these nutrient dynamics and their relation to final yields are important to devise optimum nutrient management strategies. This experiment was conducted to evaluate the relationships between nutrient availability from different sources, and growth physiology and crop yield of rice during 2019 Yala and 2019/20 Maha seasons. The Department of Agriculture (DOA) recommended inorganic fertilizer application (conventional system), 50% of DOA recommended inorganic fertilizer with organic manure mixture (integrated system), and 100% organic manure mixture application (organic system) were used as three treatments. Organic manure mixture was added to equalize the nitrogen supply through DOA rate. The systems were arranged in a randomized complete block design with six replicates and Bg 300 rice variety was used. The conventional and integrated systems were similar, while the organic system was weak in canopy light interception, photosynthetic rate, and leaf chlorophyll content at panicle initiation and heading stages. The treatment effect was significant (P<0.05) in 2019 Yala (dry season) but not in 2019/20 Maha (wet season). The correlations between leaf nitrogen concentration and yield were observed with respect to input systems. Most physiological parameters showed no robust correlation to biomass and crop yield. Crop yields were higher in the conventional and integrated systems compared to the organic system. However, the differences are expected to be narrowed down with the development of long-term nutrient status in the organic system as this study was conducted during the first year of the transition.