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| DOI：10.13522/j.cnki.ggps.2022700 |
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| Effects of Irrigation with Mixed Saline and Fresh Waters on CO2 Emission from Cotton Fields |
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LI Huiwen, GUAN Yao, HE Xinghong, FAN Debao, WANG Yuqiang
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1. School of Water Conservancy and Architectural Engineering, Tarim University, Alar 843300, China;
2. Nanjiang Geotechnical Engineering Research Center of Tarim University, Alar 843000, China
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| Abstract: |
| 【Objective】In northwestern China, freshwater resources are scarce while saline water is abundant. Irrigation using mixed fresh and saline waters has been adopted as an improved practice to maximize water resource use and sustain agricultural production in this region. This paper is to study the effect of mixed saline and fresh water irrigation on CO2 emissions from cotton fields. 【Method】 Saline waters with salt concentration of 2 (S1), 3 (S2), and 5 g/L (S3) were used in the experiment. Each saline water was mixed with freshwater at four ratios (saline water/freshwater): 1∶1 (P1), 1∶4 (P2), 4∶1 (P3) and 1∶0 (P4). The mixed waters were used to drip-irrigate the cottons. The emission of CO2 from soil irrigated by different mixed waters was measured daily using static headspace-gas chromatography method.【Result】Compared with freshwater irrigation, irrigation with mixed saline and fresh waters reduced average daily CO2 emissions from the soil by 12.64% to 28.57% (P<0.05), depending on the mixture ratio and concentration of the saline water. The cumulative CO2 emissions under freshwater irrigation were significantly higher than that from other irrigations. There was a significant difference (P<0.05) in cumulative CO2 emissions between the soil irrigated by saline water with salinity of 2 g/L and those irrigated by saline waters with salinity of 3 g/L and 5 g/L. No significant difference in CO2 emission was found between soils irrigated by saline waters with salinity of 3 g/L and 5 g/L. When water salinity was the same, the impact of saline-freshwater ratio on daily CO2 emissions was ranked in the order of 1∶4<1∶1<4∶1<1∶0. Correlation analysis showed that CO2 fluxes from the soils were significantly correlated to temperature, water content, pH and electrical conductivity of the soils.【Conclusion】 Mixing freshwater and saline water with salinity of 2 g/L at ratio of 1∶4 (saline water/freshwater) had the least effect on soil salt accumulation and CO2 emission. It can be used as an effective irrigation practice for cotton production in northwestern China. |
| Key words: brackish water quality; combined irrigation; irrigation proportion; daily CO2 emission from soil |
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