Development of Environment Friendly Paddy Ecosystem for Sustainable Rice Farming through Soil Amendments with Biochar and Alternate Wetting-Drying Irrigations

Climate change may badly affect the availability of water and soil nutrients to rice plant. Research experiments were conducted at the Environmental Science Departmental field, Bangladesh Agricultural University, Mymensingh during July 2017 to June 2019, to find out the suitable combination of biochar with inorganic fertilizers for minimizing seasonal yield scaled CH4 emissions, reducing global warming potentials (GWPs) and sustainable rice farming under feasible irrigation practices. There were ten experimental treatments with different combinations of inorganic NPKS fertilizers and biochar (15 - 30 t/ha) under conventional flooding (CF) and alternate wetting-drying irrigations (AWDI). This study revealed that NPKS fertilization (50% of the recommended doze) with 15 t/ha biochar amendments under AWD irrigation maximized rice yield 6750 kg/ha and 4380 kg/ha in dry boro and wet aman seasons respectively, while the lowest rice yield 1850 kg/ha and 1550 kg/ha were recorded in continuously irrigated control treatment (T1) during the dry and wet seasons respectively. Seasonal cumulative CH4 emission, yield scaled CH4 emission and GWPs were suppressed significantly with biochar amendments 15 - 30 t/ha under both conventional and AWDI irrigation systems during the wet and dry seasons of rice cultivation. Significant interactions were observed among biochar amendments and irrigation practices during the dry boro rice cultivation. Dry seasonal cumulative CH4 emissions were decreased by 14.7%, 18.9% and 24.8% with biochar amendments at 15 t/ha, 20 t/ha and 30 t/ha respectively under conventional irrigation;while cumulative CH4 emissions were reduced by 10.6%, 26% and 41.6% respectively, under AWDI system. Finally, total global warming potentials (GWPs) were decreased by 6% - 15%, 13% - 30% with biochar amendments under conventional and AWDI irrigations respectively, in wet season;while global warming potentials (GWPs) also decreased by 14% - 25%, 11% - 42% with biochar amendments under conventional and AWDI irrigations, respectively, in the dry boro season. Biochar amendments increased water productivity index to some extent, but AWD irrigations significantly increased water productivity over the conventional irrigation in both wet and dry seasons. After experimental period, it was found that soil porosity, redox status, soil organic carbon (SOC) as well as overall soil properties were improved significantly with biochar amendments and AWD irrigations. Conclusively, biochar amendments @15 - 20 t/ha with half of the recommended inorganic (NPKS) fertilizers under alternate wetting-drying irrigations revealed an environment friendly integrated package approach to reduce seasonal cumulative CH4 emissions as well as GWPs, while improving rice rhizosphere environment and rice productivity to meet the national food security.

Optimization of equitable irrigation water delivery for a large-scale rice irrigation scheme

Equitable water allocation is essential in an irrigation scheme for obtaining potential crop yields from the entire scheme,especially when water supply is inadequate.An optimization model achieved this goal by coupling an optimal water allocation model with available water supply and irrigation water demand for a river-fed rice irrigation system in Malaysia.This model consists of a paddy field water balance module and an optimization module.The outputs from the module are daily irrigation demand and surface runoff,if there is any.The optimization module consists of an objective function,which minimizes water shortage across the scheme area while maintaining equity in water allocation.This model performs optimization subject to several system constraints,and the decision variable of the model is daily releases or supply to the tertiary canals.Performance of this model remained unaffected under different water supply conditions,and the optimization model reliably examined the effects of alternate water allocation and management rules with field information.It improves efficiency and equity in water allocation with respect to crop growth stages and water shortages rather than simply cutting irrigation supply on a proportional basis to overcome water shortages.

Mulching type-induced soil moisture and temperature regimes and water use efficiency of soybean under rain-fed condition in central Japan

Soybean(Glycine max)is a high water-demand crop and grown under moderate temperature in Japan.To protect the crop from hot summer and to utilize rainfall for its cultivation,selection of appropriate mulching material(s)is crucial.For optimum production of the crop,soil moisture and temperature regimes as well as water use efficiency(WUE)of the crop were investigated under straw,grass,paper,plastic and bare soil(control)mulching under rain-fed condition at Gifu university farm in Japan.The mulching treatments,compared to the control,lowered soil temperature by 2°C at 5 cm depth and 0.5°C at 15 and 25 cm depths.The plastic and straw mulching stored the highest quantity of soil moisture at 5 and 15 cm depths;the bare soil stored the lowest quantity.At 25 cm depth,soil-moisture content was the highest under paper mulch but invariable under the other mulches.Plastic mulching reduced evaporation rate from the soil surface and,consequently,the reduced soil-water consumption(SWC)from the root zone augmented WUE of soybean.The paper mulching,by conserving soil-moisture and reducing soil temperature,provided better crop growth attributes,while the plastic mulching improved WUE of green soybean.Therefore,the plastic mulch performed best in reducing soil-water consumption and increasing WUE,while the paper mulch was good for soil-moisture conservation and temperature modification that increased soybean yield.

Climate change impact assessment on three major crops in the north-central region of Bangladesh using DSSAT

The potential consequences of climate change emanated from global warming are very alarming;the greatest concern is the potentially disastrous consequences on crop agriculture and food security in many parts of the world.Bangladesh is a country highly susceptible to climate change,but information in this regard is still inadequate.This study investigated the effects of climate change on three major crops-wheat,potato and rice-in the north-central region of Bangladesh.Two climate change scenarios,A2 and B2,of the Intergovernmental Panel on Climate Change(IPCC)were generated by employing MAGICC/SCENGEN model together with the observed climate data of the region.The growth and yield of the crops were simulated using DSSAT CERES-Wheat,SUBSTOR-Potato and CERES-Rice models under the present and projected future changing climatic conditions.For a predicted 5.32℃ increase in temperature in the year 2100,the yield of wheat,rice and potato would decrease by 47.6%,67.8%and 38.6%,respectively.The increased temperature would accelerate physiological maturity of the crops as reflected by their reduced length of growing season(LGS)by 1.20%to 18.5%.The reduced LGS would reduce seasonal evapotranspiration(ET)of the crops by shortening time-span for ET generation.Due to dominant yield reduction over ET reduction,the water use efficiency(WUE)for grain/tuber and biomass yields would decrease with the changing climate.The reduced crop yields are an indicative of a potential future risk of food security in Bangladesh.The results of this study can therefore guide to adopt coping mechanisms in the light of climate change to ensure future food security of the country.