Mozammel Haque

Effect of Intermittent Drainage on Methane and Nitrous Oxide Emissions under Different Fertilization in a Temperate Paddy Soil During Rice Cultivation

Although intermittent drainage is regarded as a key factor to reduce methane (CH4) emission from paddy soil during rice cultivation, it also could increase nitrous oxide (N2O) emission. However, the effects of intermittent drainage on CH4 and N2O emissions with different global warming potential (GWP) values have not been well examined. In the present study, the effect of a 26-day intermittent drainage from the 34th day after transplanting (DAT) to the 60th DAT on two greenhouse gas (GHG) fluxes and yield properties were compared with those of a continuous flooding system under different fertilization (NPK as control, PK, and NPK+straw) during rice cultivation. The effect of intermittent drainage on changing two GHG emissions was compared using the GWP value, calculated as CO2 equivalents by multiplying 25 and 298 to the seasonal CH4 and N2O fluxes, respectively. Under the same irrigation condition, addition of nitrogen to PK significantly increased seasonal CH4 and N2O fluxes, and addition of straw to NPK increased CH4 and N2O. Irrespective with fertilization background, the intermittent drainage significantly reduced the total GWP by ca. 41–70% as affected by the big reduction of seasonal CH4 fluxes by ca. 43–53% to that of the continuous flooding even with an increase of seasonal N2O emissions by ca. 16–43%. Rice productivity was not significantly different between the two different irrigation systems under same fertilization background. As a result, total GWP per grain yield was significantly lower in all fertilization treatments with intermittent drainage compared with continuous flooding.

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.

Comparison of Carbon Sequestration Potential of Winter Cover Crop Cultivation in Rice Paddy Soil

BACKGROUND: Cultivation of winter cover crops is strongly recommended to increase land utilization efficiency, animal feeding material self-production, and to improve soil and environmental quality.

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.