摘要：
探明河套盐渍化地区生物降解地膜覆盖下土壤水热氮盐的分布规律以及生育期的降解特征,明确生物地膜覆盖下盐渍化地区节水控盐机理,为提高作物产量、水氮利用效率提供理论依据.在内蒙古河套干旱盐渍化地区设置普通塑料地膜覆盖(PM)、生物可降解地膜覆盖(BM)及无覆盖(NM)3个处理,探索BM降解过程及覆盖后对葵花Helianthus annuus农田不同生育期土壤温度、含水率、盐分和硝态氮含量的影响效应.结果表明,(1)BM 的降解率和破损面积比率在葵花生育期呈抛物线增长趋势,在崩解期降解率和破损面积比率分别为23.15%和28.88%,是PM的32.2倍和7.6倍,显著高于PM处理.(2)覆膜显著提高土壤上层(0~40 cm)地温和含水率,随着BM破损面积比率增加,BM与PM处理地温和土壤含水率差异逐渐增大.在作物生长后期(7月下旬—9月),PM、BM和NM处理0~20 cm土层地温差异显著,分别为22.17、20.94和19.49 °C;在作物生长期,PM与BM处理土壤含水率差异不大,仅BM在崩解期(9月)0~20 cm土层存在显著差异.(3)覆膜能有效降低0~40 cm土层电导率(EC),而对40 cm以下土层的EC影响较小.PM与BM处理在葵花生长前中期差异不显著,仅在崩解期0~40 cm土层PM处理EC显著低于BM处理,PM处理分别比NM和BM处理低27.34%和11.66%(P＜0.05).(4)地膜覆盖仅对0~40 cm土层硝态氮有影响.覆膜120 d后,PM与BM处理差异逐渐变大,崩解期PM、BM和NM处理0~40 cm土层硝态氮质量分数分别为20.63、14.48、11.84 mg·kg-1(P＜0.05).(5)BM处理和PM处理葵花干物质和籽粒质量均无显著差异,且BM处理千粒质量、每株籽粒质量分别比NM处理提高了15.65%和20.85%.综上所述,在干旱盐渍化地区,BM处理和PM处理在葵花生长前期和中期,覆膜效果无显著差异,在BM崩解期差异明显.因此,覆盖降解膜是缓解农田残膜污染的有效措施.%The mechanism of water-saving and salinity control can be known explicitly by studying its distribution law of soil water, temperature, nitrogen and salinity and degradation characteristics under biofilm mulch in saline-alkali area, which will provide theory gist to improving crop yield and water and nitrogen use efficiency. In the study, three treatments including plastic film mulching (PM), biodegradable film mulching (BM) and no mulching (NM) were carried out to study the degradation characteristics of biodegradable film, and the effects of biodegradable film on distribution of soil water, temperature, nitrogen and salt in sunflower field which located in Hetao Irrigation District of Inner Mongolia. The results showed that the rate of degradation and breakage for BM treatment were almost an parabola up in the growth period, and were respectively 23.2% and 28.9% under its disintegrating period, which were 32.2 times and 7.6 times compared with PM treatment. The soil temperature and soil water content (SWC) in the upper soil layer (0~40 cm) were significantly improved for BM and PM treatment, and the difference for soil temperature and SWC between BM and PM treatment were gradually increased with the increase of breakage of biodegradable film. There were significantly different for soil temperature in 20 cm soil layer among PM, BM and NM treatments during sunflower late growth stage (from late July to September), and it was 22.2, 20.9 and 19.5 °C (P＜0.05) , respectively. There was no significant difference for SWC between PM and BM treatments (P＞0.05), and the significant difference was only found in 0~20 cm soil layer during the collapse stage of BM (September). Moreover, the soil conductivity (EC) in 40 cm soil layer was obviously reduced under the mulching condition, and no significant difference between PM and BM treatment was found. However, the EC for PM treatment was significantly lower than BM treatment in 0~40 cm soil layer during the collapse stage of BM, and the EC for PM treatment was lower at 27.3% and 11.7% (P＜0.05) than that of NM and BM treatment, respectively. The effect of mulching on nitrate nitrogen was only found in 0~40 cm soil layer, and the difference was gradually bigger after 120 d mulching. The nitrate nitrogen contend was 20.6, 14.5, 11.8 mg·kg-1(P＜0.05), respectively, for PM, BM and NM treatment during the collapse stage of BM. There was no significant difference between BM and PM treatment for sunflower dry matter and grain dry weight of sunflower, and thousand seed mass and per plant seed mass for BM treatment improved 15.7% and 20.9%, respectively, comparing with NM treatment. In summary, the difference of mulching effect was no significant between BM and PM treatment during early and middle growth period of sunflower apart from the collapse stage in arid saline area. Therefore, covering degradation film is an effective measure to alleviate farmland soil pollution.
