亚表层培肥结合覆膜提高干旱区盐碱地土壤肥力及优势菌群丰度的机理

【目的】针对西北干旱气候条件下表层土壤贫瘠多盐的特点，研究亚表层(10—30 cm)培肥结合地膜覆盖对盐碱地土壤化学性质及微生物区系的影响，为盐碱地合理耕层的构建提供参考。【方法】试验设在内蒙古五原县，以向日葵为供试作物进行田间小区和微区试验。设常规翻耕(CK)、翻耕 + 地膜覆盖(PM)、施有机肥(106.8 t/hm2)于亚表层(OM)、亚表层有机培肥 + 地膜覆盖(OMP)共4个处理。测定了春灌前、后以及向日葵收获后，不同耕作措施下土壤剖面的pH值、盐分、有机质和速效养分含量以及微生物区系。【结果】春灌前，亚表层培肥处理(OM、OMP)10—30 cm土层盐分含量比CK、PM处理分别增加了37.1%～52.9%、32.1%～47.2% (P < 0.05)，但在春灌后盐分含量无显著差异。地膜覆盖具有很强的抑制返盐效果，OMP处理效果好于PM处理。作物收获后，OMP处理0—10 cm表层返盐率相对CK、PM和OM处理分别降低了131%、77.6%和106%，PM处理相对CK和OM处理分别降低了53.5%和28.7% (P < 0.05)。与CK相比，OM、OMP处理10—30 cm土层pH值分别降低了0.36、0.60个单位(P < 0.05)，有机质、速效氮、速效磷、速效钾分别增加了100%和127%、88.7%和105%、564%和514%、453%和400% (P < 0.05)；30—40 cm土层pH值分别降低了0.45、0.44个单位(P < 0.05)，速效磷和速效钾含量显著增加了517%和604%、191%和157%，OMP处理有机质含量显著增加了33.6% (P < 0.05)。高通量测序结果表明，OM、OMP处理显著提升了芽孢杆菌属(Bacillus)、交替赤杆菌属(Altererythrobacter)、降解类固醇杆菌属(Steroidobacter)、链霉菌属(Streptomyces)与诺卡氏菌属(Nocardioides)等优势菌群丰度(P < 0.05)，但微生物多样性(Shannon指数和Simpson指数)和丰富度(ACE指数和Chao1指数)与CK、PM处理差异不显著。相关性分析结果表明，芽孢杆菌属、交替赤杆菌属、降解类固醇杆菌属、链霉菌属与诺卡氏菌属相对含量均与收获后0—40 cm有机质与速效养分含量呈极显著正相关，与pH值呈极显著负相关(P < 0.01)，但与全盐含量无显著相关性。【结论】亚表层培肥结合地表覆膜一方面可有效降低盐分表层集聚，快速增加土壤有机质和速效养分，另一方面可提高土壤优势菌群丰度，增强有机物的矿化分解，是改良西北干旱区盐碱土的有效耕作措施。

Mechanism of subsurface organic amendment combined with plastic mulching increasing soil fertility and microflora in an arid saline soil

【Objectives】The soils in arid Northwest China are unfertile and have high salinity in surface tillage layers. Applying organic fertilizers into 10–30 cm of subsurface layer and plastic mulching were attempted in order to constructing a fertile subsurface layer in saline-alkali land.【Methods】A field micro-plot experiment was conducted in Wuyuan County, Inner Mongolia, using sunflower as tested crop. Four treatments were designed, as conventional ploughing (CK), ploughing plus plastic mulching (PM), applying 106.8 t/hm2 of manure in 10–30 cm subsurface (OM), and subsurface manure application plus plastic mulching (OMP). Before and after spring irrigation and after harvest, the pH, total salt, organic matter and available nutrient contents in 0–100 cm soil profile were determined, and the microflora in moderate saline soil were investigated during sunflower growth period.【Results】Before spring irrigation, the OM and OMP treatments significantly increased the salt contents in the 10–30 cm soil layer (P < 0.05), the increase to CK was by 37.1%–52.9%, and to PM by 32.1%–47.2%. After spring irrigation, there was no significant differences among all treatments. Plastic mulching strongly inhibited salt returning, and the effect of OMP was better than of PM. After harvest, the salt return rate in 0–10 cm soil layer under OMP was reduced by 131%, 77.6% and 106%, compared with CK, PM and OM; and the salt return rate under PM was reduced by 53.5% and 28.7%, compared with CK and OM (P < 0.05), respectively. Compared with CK, the pH values under OM and OMP were decreased by 0.36 and 0.60 units in 10–30 cm soil layer, and by 0.45 and 0.44 units in 30–40 cm soil layer, respectively (P < 0.05). Compared with CK, the organic matter contents in 10–30 cm soil layer under OM and OMP were increased by 100% and 127%, and the contents of available N, P and K under OM and OMP were increased by 88.7% and 105%, 564% and 514%, 453% and 400%, respectively (P < 0.05). Compared with CK, the organic matter content in the 30–40 cm soil layer under OMP was increased by 33.6%, and the available P and K contents under OM and OMP were increased by 517% and 604%, and 191% and 157%, respectively (P < 0.05). The high-throughput results showed that all the treatments had an effect on the content of the horizontal bacterial population to a certain extent. The OM and OMP treatments significantly increased the abundance of dominant bacteria such as Bacillus, Altererythrobacter, Steroidobacter, Streptomyces and Nocardioides (P < 0.05), but the differences in diversity of soil microbial community (Shannon index and Simpson index) and abundance (ACE index and Chao1 index) among all the treatments were not significant. Correlation analysis showed that the relative contents of the above five bacteria were significantly and positively correlated with organic matter and available nutrient contents in 0–40 cm soil layer, significantly and negatively correlated with pH value (P < 0.01), not significantly correlated with the total salt content.【Conclusions】Subsurface manure application combined with plastic mulching is proved of effective in reducing the salt accumulation on soil surface, and increasing the soil organic matter and available nutrient contents rapidly, and improving the soil microbial structure and abundance of dominant bacteria at the same time, which stimulate the mineralization of organic matter consequently.