土壤熏蒸剂对土壤硝化、反硝化作用的影响

采用化学分析和变性梯度凝胶电泳(DGGE)技术,以大田威百亩、棉隆、溴甲烷、硫酰氟熏蒸100 d土壤为研究对象,探究土壤熏蒸对土壤硝化活性、反硝化活性及amoA基因型硝化型细菌、nirS基因型反硝化细菌群落结构影响。研究表明,威百亩、棉隆、硫酰氟熏蒸剂处理下,土壤硝化活性与对照无显著差异;而溴甲烷处理的硝化活性比对照降低13.19%,差异显著(P0.05);熏蒸剂之间土壤硝化活性无显著差异。4种熏蒸剂之间以及与对照之间土壤反硝化活性无显著差异。4种熏蒸剂中溴甲烷处理土样amoA型硝化细菌多样性指数、均匀度显著低于对照土样和其他3种熏蒸剂处理土样;而丰富度指数无显著差异。威百亩、棉隆和硫酰氟熏蒸土样之间及与对照之间amoA型硝化细菌3种生态指数无明显差异。4种熏蒸剂处理土壤nirS型反硝化细菌多样性指数、均匀度与对照无显著差异(P0.05);熏蒸剂之间存在显著差异(P0.05)。研究表明,溴甲烷对土壤硝化活性的抑制是通过抑制amoA型硝化细菌的多样性而实现,其他3种熏蒸剂对土壤硝化活性无显著影响。4种熏蒸剂对土壤反硝化活性无显著影响。

Effects of soil fumigants on soil nitrification and denitrification

To investigate the effect of irrigation and fertilization on photosynthetic physiology of super rice, a pot experiment was conducted using super rice "Zhongzheyou 1" as experimental crop. The study analyzed the photosynthetic physiology parameters net photosynthetic rate, Pn; intercellular CO2 concentration, Ci; photosynthetic light response curve and photosynthetic pigment contents of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoid (Car), total chlorophyll content (TCC)] of rice under three irrigation methods controlled irrigation (CIR), intermittent irrigation (IIR) and flood irrigation (FIR)] and three fertilization levels non-fertilization (F₀), low fertilization (F_L) and high fertilization (F_H)]. It also conducted correlation analysis for Pn and chlorophyll contents. The results showed that compared with FIR, CIR and IIR treatments (saving-water irrigation methods) significantly increased Pn. It, however, failed to significantly enhanceCi at the jointing, heading and milking stages. Both CIR and IIR increased light saturation point (LSP) by 9.2%~36.8% at the jointing and heading stages and apparent quantum yield by 6.7%~31.5% respectively at the three growth stages, while they decreased light compensation point by 3.2%~12.8% at the jointing, heading and milking stages. Compared with FIR, CIR respectively increased the contents of Chl a, Chl b, Car and TCC by 19.1%~76.3%, 44.5%~98.5%, 31.5%~117.4% and 45.4%~145.0% at the jointing, heading and milking stages. IIR treatment respectively enhanced the contents of Car and TCC by 4.2%~45.8% and 31.5%~117.4% at the three growth stages. Under the three irrigation treatments, photosynthetic indices and photosynthetic pigment contents were higher under fertilization than non-fertilization treatments. High fertilization also resulted in higher photosynthetic indices and photosynthetic pigment content than low fertilization. Correlation analysis showed significant correlation between Pn and photosynthetic pigments contents, which correlations were influenced by growth stages. CIR and IIR improved photosynthetic capacity under strong light, and adaptability to weak light; and significantly increased light utilization rate. Compared with FIR, CIR and IIR increased photosynthetic pigment content but delayed photosynthetic pigment degradation. It was concluded that CIR and IIR treatments enhanced photosynthetic capacity, improved the photosynthetic light response curve and increased photosynthetic pigment contents. In terms of fertilization rate, high fertilization increased photosynthetic capacity of "Zhongzheyou 1" under saving-water irrigation treatments.