Farm practices influence the photosynthetic performance and plant efficiency of Oryza sativa L.

The photosynthetic and physiological performances of Oryza sativa L. (rice) were evaluated in organic and conventional rice–rice agroecosystems for 120 days after transplantation by measuring net photosynthesis (P _N), transpiration (E), stomatal conductance (g _s), intercellular CO₂ concentration (C _i), chlorophyll content (SPAD) and JIP fluorescence rise. The soil health was measured as soil bacterial and fungi density and activities of soil microbial enzymes (amylase, invertase, cellulase, protease, alkaline phosphatase and dehydrogenase). The conventionally managed fields showed lower microbial density and activity than of organic fields especially after 60 days of transplantation. The crop grown in the conventional fields has significantly low level of P _N and chlorophyll, but E, g _s and C _i did not differ significantly till 105 days after transplantation. The JIP rise was low in conventional fields than in organic fields during 90–120 days. The efficiency and plant performance parameters (φP ₀, Ψ ₀, φE ₀, PI_φ, PI _Ψ , PI_ABS, and PI_total) showed a rapid rate of decrease in the conventional than of organic fields. Significant positive correlation could be established between the performance and soil microbial activities, whereas the stress indicating fluorescence parameters (V _J, M ₀, φD ₀, DI₀/RC) showed significant negative correlation with the soil parameters in both the farming systems. The result showed that JIP analysis can be used as an early indicator of soil fertility and plant performance.