中国西北地区膜下滴灌对棉田土壤CO2通量和浓度的影响

In northwestern China,there has been a change from traditional cultivation system (TC) with no mulching and flood irrigation to a more modern cultivation system (MC) using plastic film mulching with drip irrigation.A field study was conducted to compare soil CO 2 concentrations and soil surface CO 2 fluxes between TC and MC systems during a cotton growing season.CO 2 concentrations in the soil profile were higher in the MC system (3 107-9 212 μL L-1) than in the TC system (1 275-8 994 μL L-1) but the rate of CO 2 flux was lower in the MC system.Possible reasons for this included decreased gas diffusion and higher soil moisture due to the mulching cover in the MC system,and the consumption of soil CO2 by weathering reactions.Over the whole cotton growing season,accumulated rates of CO2 flux were 300 and 394 g C m-2 for the MC and TC systems,respectively.When agricultural practices were converted from traditional cultivation to a plastic film mulching system,soil CO 2 emissions could be reduced by approximately 100 g C m-2 year-1 in agricultural lands in arid and/or semi-arid areas of northern and northwestern China.

Carbon dioxide fluxes and concentrations in a cotton field in northwestern China:Effects of plastic mulching and drip irrigation

Extensive worldwide use of oxytetracycline (OTC), a member of the tetracyclines, has resulted in its accumulation in soils, posing a potential risk to food production and safety. A pair of OTC-sensitive (Heyou 1) and OTC-tolerant (Yannong 21) wheat (Triticum aestivum L.) cultivars was compared hydroponically at 0.01, 0.02, 0.04, and 0.08 mmol L-1 OTC in terms of wheat growth and photosynthesis. Biomass and shoot length decreased significantly with the addition of OTC, with the decreases in dry biomass and shoot length being 5.61%--13.75% and 3.33%--8.57% larger, respectively, for Heyou 1 than Yannong 21. Photosynthesis of Heyou 1 was suppressed by OTC as indicated by the significant decreases in photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) and the significant increase in intercellular CO2 concentrations (Ci), at all OTC levels. Stomatal limitation (Ls) and water use efficiencies (WUE) of Heyou 1 also increased significantly, but not at 0.08 mmol L-1 OTC. However, photosynthesis of Yannong 21 was suppressed by OTC only at high OTC levels from 0.02 to 0.08 mmol L-1 as indicated by the decreases in Pn, Gs, Tr, and Ls; at 0.01 mmol L-1 OTC, Pn, Ci, Gs, and Tr significantly increased. It was noted that WUE of Yannong 21 was not affected by OTC addition. The results from this hydroponic test suggested that OTC had a potential risk to crop growth through inhibition of photosynthesis, requiring further confirmation with soil tests.