[Comprehensive Effects of the Application of Water and Fertilizer Amount on CO2 Emission from Soils of Summer-maize Field].

Abstract

Field experiments were conducted to determine the effects of water and fertilizer amount on soil CO2 emissions by using the method of static chamber/gas chromatography in summer maize farmland ecosystem. Three factors (three irrigation levels including 90 mm, 76.5 mm and 63 mm, four nitrogen fertilizer levels including 300 kg·hm-2, 255 kg·hm-2, 210 kg·hm-2 and 0 kg·hm-2, and four phosphate fertilizer levels including 90 kg·hm-2, 76.5 kg·hm-2, 63 kg·hm-2 and 0 kg·hm-2) were designed in the experiment. The results showed that soil CO2 emission under different water and fertilizer conditions showed obvious seasonal fluctuation, the main and secondary peak appeared at jointing to tasseling stage and tasseling to grouting stage. The soil CO2 emissions were relevant to the supply levels of fertilizer and irrigation. In the high fertilizer F1 (N 300 kg·hm-2, P2O5 90 kg·hm-2) and low fertilizer F0.7 (N 210 kg·hm-2, P2O5 63 kg·hm-2) conditions, average soil CO2 emissions flux during the whole growth period of high water W1 (90 mm) was significantly higher than that of low water W0.7 (63 mm); the difference of soil CO2 emissions between medium water level W0.85 (76.5 mm) and low water level was not significant under medium and low nutrient condition F0.85 (N 255 kg·hm-2, P2O5 76.5 kg·hm-2). Soil CO2 emissions intensity of high fertilizer F1 was significantly larger (by 14.82%) than that of low fertilizer F0.7 under high water supply W1 (P<0.05), and that of F0.85 was significantly bigger (by 8.03%) than that of F0.7 in the medium water supply(P<0.05), while the difference between treatments at low water level was not significant(P>0.05). Compared with nonfertilized treatment, soil CO2 cumulative emissions of the whole growth period with application of nitrogen fertilizer (210 kg·hm-2), phosphate fertilizer (63 kg·hm-2) and nitrogen mixed with phosphate fertilizer (210 kg·hm-2, 63 kg·hm-2) were significantly increased by 23.70%, 19.00% and 12.30%, respectively. And interaction effects between nitrogen and phosphorus fertilizer were extremely significant (P<0.01). Variance analysis of the interaction of water and fertilizer showed that the average soil CO2 fluxes of the whole growth period were not statistically significant but cumulative emissions of soil CO2 were significant (P<0.05) when the difference of supply level was 15%. In addition, soil CO2 flux and cumulative emission in the whole growth period were significant when supply differed by 30%. Obviously, soil CO2 emissions were promoted significantly by application of irrigation amount, nitrogen fertilizer, phosphorus rate and water and fertilizer interaction, while it was inhibited by nitrogen mixed with phosphorus. It was effective to regulate soil CO2 emission by water and fertilizer controlling measures.