M. Shahid

Combined application of rice husk biochar and fly ash improved the yield of lowland rice

The effects of rice husk biochar (BC) and coal fly ash (FA) on growth and yield of rice and soil properties were investigated in a lowland rice soil. All growth parameters and yield were positively influenced by the integrated application of BC, FA and chemical fertilisers compared with sole application of chemical fertilisers. Yield increase was 16.4% when BC+FA was applied together with 50% of the recommended dose of nitrogen (N) compared with the recommended dose of N, phosphorus and potassium (NPK). Post-harvest soil analysis suggested that BC and FA both act as a supplier, as well as a reservoir of nutrients. Accumulation of heavy metals in soil and plant parts after harvest was below the toxicity threshold for plants and humans. There was also no significant change in microbial population compared with the initial soil. Therefore, combined application of BC and FA supplemented with chemical fertilisers could be recommended to improve soil fertility and crop productivity without affecting the soil quality.

Crop and varietal diversification of rainfed rice based cropping systems for higher productivity and profitability in Eastern India

Rice-rice system and rice fallows are no longer productive in Southeast Asia. Crop and varietal diversification of the rice based cropping systems may improve the productivity and profitability of the systems. Diversification is also a viable option to mitigate the risk of climate change. In Eastern India, farmers cultivate rice during rainy season (June–September) and land leftovers fallow after rice harvest in the post-rainy season (November–May) due to lack of sufficient rainfall or irrigation amenities. However, in lowland areas, sufficient residual soil moistures are available in rice fallow in the post-rainy season (November–March), which can be utilized for raising second crops in the region. Implementation of suitable crop/varietal diversification is thus very much vital to achieve this objective. To assess the yield performance of rice varieties under timely and late sown conditions and to evaluate the performance of dry season crops following them, three different duration rice cultivars were transplanted in July and August. In dry season several non-rice crops were sown in rice fallow to constitute a cropping system. The results revealed that tiller occurrence, biomass accumulation, dry matter remobilization, crop growth rate, and ultimately yield were significantly decreased under late transplanting. On an average, around 30% yield reduction obtained under late sowing may be due to low temperature stress and high rainfall at reproductive stages of the crop. Dry season crops following short duration rice cultivars performed better in terms of grain yield. In the dry season, toria was profitable when sown earlier and if sowing was delayed greengram was suitable. Highest system productivity and profitability under timely sown rice may be due to higher dry matter remobilization from source to sink. A significant correlation was observed between biomass production and grain yield. We infer that late transplanting decrease the tiller occurrence and assimilate remobilization efficiency, which may be responsible for the reduced grain yield.

Impact of Seedling Age and Nitrogen Application on Submergence Tolerance of Sub1 and Non-Sub1 Cultivars of Rice (Oryza sativa L.)

Flooding is an environmental stress that can affect crops at any stage, seriously affecting crop establishment leading to severe yield losses. The study was undertaken to understand the response of age of seedlings and nitrogen application on submergence tolerance of rice with Sub1 and non-Sub1 cultivars. This study assesses growth after recovery and several physiological mechanisms associated with submergence tolerance in rice. Survival, growth after recovery, allometric parameters, carbohydrate content, and photosynthesis decreased due to submergence with greater extent in younger seedlings. After desubmergence, all the cultivars experienced oxidative damage at all seedling ages and antioxidant activity was higher in tolerant cultivars. Forty-day-old seedlings had significantly higher submergence tolerance and recovery scores, assessed based on survival, re-generation ability, and growth, leading to higher yields. Higher maintenance of sugar and starch (60.9% higher) in forty-day-old seedlings was another reason for higher plant survival and lower mortality. The crop fertilized with post-flood nitrogen resulted in substantially better survival, leaf and root growth, photosynthesis, and yield, and the effect was more positive in older seedlings of Sub1 cultivars. These low-input cost-effective approaches have been a good option for enhancing submergence tolerance and yield in stress-prone areas of South-East Asia.

Site-Specific Nitrogen Management in Rice Using Remote Sensing and Geostatistics

ABSTRACT Proper doses of nitrogenous fertilizer are most important for rice production system because a large part of the nitrogen may be lost if it is not applied judiciously. A study was conducted covering five blocks of Balasore and two blocks of Bhadrak districts. Soil samples were collected randomly, and field visit was conducted during peak vegetative stage of rice. Two approaches have been used in this study for estimating the site-specific nitrogen (N) requirement in the study area. In one approach, geostatisical analysis and kriging was used to develop the soil test–based N recommendation map by which a minimum of 72 kg N ha−1 and maximum of 94 kg N ha−1 were recommended. In a second approach, remote sensing was used and N recommendation map was developed using the moderate-resolution imaging spectroradiometer (MODIS) leaf area index (LAI) and normalized difference vegetation index (NDVI) satellite data, and a minimum requirement of 60 kg N ha−1 and maximum of 120 kg N ha−1 was estimated through this approach.