N Sahoo

Diurnal changes in chlorophyll fluorescence and light utilization in Colocasia esculenta leaves grown in marshy waterlogged area

Diurnal cycle of chlorophyll fluorescence parameters was done in Colocasia esculenta L. (swamp taro) grown in marshy land under sun or under shade. The sun leaves maintained higher electron transport rate (ETR) and steady state to initial fluorescence ratio (Fs/F0) than shade leaves. In spite of lower ETR, higher photochemical quenching (PQ), and effective quantum yield of photosystem 2 (ΦPS2) was evident in shade plants compared to plants exposed to higher irradiance. ETR increased linearly with increase in irradiance more under low irradiance (r2 = 0.84) compared to higher irradiance (r2 = 0.62). The maximum quantum yield of PS 2 (Fv/Fm) did not differ much in sun and shade leaves with the exception of midday when excess of light energy absorbed by plants under sun was thermally dissipated. Hence swamp taro plants adopted different strategies to utilize radiation under different irradiances. At higher irradiance, there was faster decline in proportion of open PS 2 centers (PQ) and excess light energy was dissipated through non-photochemical quenching (NPQ). Under shade, absorbed energy was effectively utilized resulting in higher ΦPS2.

Effect of organic and inorganic sources of nitrogen on productivity of rice in rice-fish farming system

A field experiment was conducted at the research farm of the Water Technology Centre for Eastern Region (Indian Council of Agricultural Research), Bhubaneswar, India, to study the effect of organic and inorganic sources of nitrogen fertilizer on nutrient use efficiency and productivity of rice and rice-fish farming systems. With the increase in inorganic sources of nitrogen, the rice crop responded positively in terms of grain yield and other yield attributes. The highest grain yield, straw yield, panicles and filled grains panicle−1 of rice were recorded when nitrogen was supplied in 100% through inorganic form. Similarly, the agronomic efficiency and apparent recovery were found to be at a maximum when nitrogen was supplied in 100% inorganic form. The productivity of rice was however found to be higher when fish was integrated into the system.

Deep-water rice production as influenced by time and depth of flooding on the east coast of India

The saucer-shaped landform, high rainfall due to the south-west monsoon (June–September) and poor drainage conditions make certain parts of the east coast of India susceptible to waterlogging during the rainy season. There is no alternative other than to grow rice in the coastal lowlands, where surface water accumulation of 0.5–2.0 m occurs during the rainy season. In this study, the physical environments of a representative deep-water ecology were characterized and the performance of improved deep-water rice (DWR) varieties (Hangseswari, Saraswati, Ambika, Sabita) was compared with that of local varieties (Bankei, Dhalakartik) at three water depths (shallow flooded [0.6–0.8 m], medium flooded [0.8–1.2 m] and deep flooded [>1.2 m]). The rainfall–flooding depth relationship was also studied and the probability of successful crop production in relation to the time and depth of waterlogging was investigated, based on historical (34 years) flood data from the region. Among the varieties studied, ‘Hangseswari’ was found to have superior physiological traits for growth, development and production of grain yield and hence may be considered for inclusion in further DWR breeding programs. With the introduction of improved DWR varieties, productivity during the rainy season was enhanced and farmers received good yield (2.05–2.95 t ha−1) and net return (4500 Rs ha−1).

Studies on performance of rice as influenced by drainage in Eastern India

Field experiments were conducted in WTCER research farm, Mendhasal and in the farmers field at Bishwanathpur, Orissa, India, during two crop years to assess the performance of rice as influenced by drainage at different growth stages. In the first experiment, scented rice variety CR-689-113 was tested with drainage at different growth stages in the main plot and nitrogen levels in the sub plots. In the second experiment, rice variety Swarna was investigated and drainage at different growth stages was provided under the best nitrogen level. The results revealed that drainage at the tillering stage recorded significantly higher grain yield than drainage at all other crop stages. The grain yield of rice was found to be increased by 19–22% when drainage was provided at the tillering stage for an 8–10 day period relative to that of no drainage treatment. However, drainage at the panicle initiation stage recorded the lowest grain yield. Nitrogen at 60 kg ha−1 resulted in higher grain yield. Crop growth rate and nitrogen use efficiency were found to be higher when drainage was given at the tillering stage.