Abstract
To investigate the influence of gypsum application on methane (CH4) emission from paddy rice soil affected by saline irrigation water, two pot experiments with the rice cultivation were conducted. In pot experiment (I), salinity levels 30 mMNaCl (S30) and 90 mMNaCl (S90), that showed maximum and minimum CH4 production in an incubation experiment, respectively, were selected and studied without and with application of 1 Mg gypsum ha-1(G1). In pot experiment (II), CH4 emission was investigated under different rates of gypsum application: 1 (G1), 2.5 (G2.5) and 5 (G5) Mg gypsum ha-1 under a non-saline and saline condition of 25 mMNaCl (S25). In experiment (I), the smallest CH4 emission was observed in S90. Methane emission in S30 was not significantly different with the non-saline control. The addition of gypsum showed significant lower CH4 emission in saline and non-saline treatments compared with non-saline control. In experiment (II), the CH4 emissions in the saline treatments were not significantly different to the non-saline treatments except S25-G5. However, our work has shown that gypsum can lower CH4 emissions under saline and non-saline conditions. Thus, gypsum can be used as a CH4 mitigation option in non-saline as well as in saline conditions.
Highlights
The hydroponic nature of rice enables it to grow in coastal areas of humid tropical regions
Gypsum was added as Ca2+ source to maintain appropriate Na+/Ca2+ in the soil, no improvement of rice growth due to gypsum addition in saline condition might be due to the high Na+/Ca2+ ratio under addition of saline water into the limited space of pot
As continuous application of saline water suppressed the above-ground plant biomass yield, and the intermittent application of saline water with saline condition of 25 mMNaCl (S25) did not severely suppress the yield, saline water with 25 mMNaCl can be used for rice cultivation with intermittent irrigation if fresh water is unavailable
Summary
The hydroponic nature of rice enables it to grow in coastal areas of humid tropical regions. To improve the crop productivity in saline environment, there are two major approaches: selecting cultivars that are tolerant to saline environment and modifying the growing environment that is suitable for the normal growth of plant. Salinity resistance in rice has been a concern of plant breeding for a long time and the progress in breeding for salt tolerance and its related abiotic stress have been slow (Reddy et al, 2014). This is partly due to the complexity of the phenomenon and the susceptibility of rice to changes in salinity during the plant’s various developmental stages. The second approach: the addition of organic and inorganic amendments
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