Jatish Chandra Biswas

Rice straw as a source of potassium for wetland rice cultivation

Abstract Rice crops uptake large amounts of potassium (K), which is mainly supplied from inorganic fertilizer. Alternate K sources are essential to preserve natural reserves and to recycle unused K containing stubbles. We have evaluated the performance of rice straw (RS) in farmers’ field following integrated plant nutrient system (IPNS) for supplementing K requirement of rice and compared with agro-ecological zone (AEZ)-based chemical fertilizer and farmers’ practice in Tista Meander Floodplain soils of Bangladesh during 2013–2015. Application of RS @ 4.5 t ha−1 + IPNS-based fertilizer replaced full dose of chemical K fertilizer without significant reduction in grain yield of Boro rice. The K uptake with RS incorporation was similar to AEZ-based chemical fertilizer use. Considering soil health and environmental issue, RS + IPNS-based fertilizer management was the best option for growing wetland rice.

Global warming as affected by incorporation of variably aged biomass of hairy vetch for rice cultivation

Hairy vetch (Vicia villosa Roth) is cultivated during the cold fallow season in paddy soils of temperate countries such as South Korea and Japan, mostly as animal feed and green manure. Information on the effect of ageing of hairy vetch incorporation in relation to greenhouse gas (GHG) emissions and global warming potential (GWP) is not available. Therefore, hairy vetch biomass of ages 183, 190, 197, and 204 days was incorporated in paddy soil to estimate GWP during rice cultivation. The emission rates of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) gases were monitored once a week by using the closed-chamber method. The net ecosystem carbon budget was used to estimate pure CO2 emission fluxes. Biomass production of hairy vetch was 6.5 Mg ha–1 at 204 days, which was similar to other treatments. The GWP was lower with the 204-day-old vetch biomass incorporation than with other treatments. High content of cellulose and lignin in 204-day-old hairy vetch might have affected decomposition rate and subsequently reduced GHGs emissions during rice cultivation. Our results suggest that hairy vetch can be allowed to grow for 204 days before incorporation at 3 Mg ha–1 without sacrificing rice yield, while maximising biomass production and minimising GWP during rice cultivation.

Co-Composting Urban Waste, Plant Residues, and Rock Phosphate: Biochemical Characterization and Evaluation of Compost Maturity

ABSTRACT Co-composting of urban wastes (UWs) and plant residues with rock phosphate (RP) produces quality compost and reduces the use of chemical phosphorus fertilizer. Biochemical process of three compost piles (P): P1- 50% UW + 30% rice straw (RS) + 10% sawdust (SD) + 8% RP + 2% sugarcane trash (ST), P2- 50% UW + 23% RS + 10% SD + 15% mustard oil cake + 2% ST, and P3- 95% UW + 5% RP was studied. Decomposition rate followed first-order kinetics and maximum (77%) was in P3. The highest bacterial population was found in P2 having higher cumulative CO2 evolution (53.76 mg CO2 g−1 volume solid). Prevalence of phosphate-solubilizing bacteria was 2.0 to 6.3 Log10 Cfu g−1 dry weight and concentrated in RP-amended piles. Humic acid of compost was classified as rotteprudukte. Final pH (7.5 to 8.0) and germination index (>90) proved that the compost was mature. P3 compost (1 t ha−1, fresh weight) had potential to supply 25 kg phosphorus.

Effect of Elevated Air Temperature and Carbon Dioxide Levels on Dry Season Irrigated Rice Productivity in Bangladesh

Agricultural productivity is affected by air temperature and CO2 concentration. The relationships among grain yields of dry season irrigated rice (Boro) varieties (BRRI dhan28, BRRI dhan29 and BRRI dhan58) with increased temperatures and CO2 concentrations were investigated for futuristic crop management in six regions of Bangladesh using CERES-Rice model (DSSATv4.6). Maximum and minimum temperature increase rates considered were 0°C, +1°C, +2°C, +3°C and +4°C and CO2 concentrations were ambient (380), 421, 538, 670 and 936 ppm. At ambient temperature and CO2 concentration, attainable grain yields varied from 6506 to 8076 kg·ha-1 depending on rice varieties. In general, grain yield reduction would be the highest (13% - 23%) if temperature rises by 4°C and growth duration reduction would be 23 - 33 days. Grain yield reductions with 1°C, 2°C and 3°C rise in temperature are likely to be compensated by increased CO2 levels of 421, 538 and 670 ppm, respectively. In future, the highest reduction in grain yield and growth duration would be in cooler region and the least in warmer saline region of the country. Appropriate adaptive techniques like shifting in planting dates, water and nitrogen fertilizer management would be needed to overcome climate change impacts on rice production.

Long-Term Effects of Sulfur and Zinc Fertilization on Rice Productivity and Nutrient Efficiency in Double Rice Cropping Paddy in Bangladesh

Sulfur (S) and zinc (Zn) deficiencies are frequently reported in Bangladesh rice paddy. However, its effects on rice productivity and soil fertility need to be reevaluated as sulfur oxides (SOx) and heavy metals are increasingly emitted to the environment in the recent years. To examine the long-term effects of S and Zn fertilization on rice yield and nutrient efficiency, the standard fertilization plot of nitrogen, phosphorus, potassium, sulphur, and zinc (NPKSZn) was installed in a typical double rice cropping paddy at the Bangladesh Rice Research Institute (BRRI) farm in 1985. The recommended treatment (NPKSZn) and the comparison treatments (NPKZn and NPKS) were selected for calculating S and Zn efficiencies. The same levels of chemical fertilizers in NPKSZn treatment were applied with the rates of N-P-K-S-Zn as 80–25–35–20–5 kg ha−1 and 120–25–35–20–5 kg ha−1 in the wet and dry seasons, respectively. The changes in rice productivity, as well as S and Zn fertilization efficiencies, were monitored for 23 years. Sulfur fertilization significantly increased the mean grain and straw yields by around 13% in the wet season and only 4–5% in the dry season. The mean S fertilization efficiencies were 9.3% and 5.3% in the wet and dry seasons, respectively. Sulfur fertilization efficiency was relatively high until 1997 (the 13th year after the installation). Thereafter, however, S fertilization did not increase rice productivity or efficiency, regardless of the season. Also, Zn fertilization did not result in a significant increase in rice productivity, and its fertilization efficiency was similar level with a mean of 1.2%, irrespective of the season. This study revealed that S and Zn fertilization may no longer be required to increase rice productivity in Bangladesh paddy soil due to fast industrialization and urbanization.