秸秆隔层对盐碱土水盐运移及食葵光合特性的影响

在内蒙古河套灌区通过微区试验,研究了秸秆深埋(S)、上盖秸秆下埋秸秆(简称上秸下秸,S+S)、上盖地膜下埋秸秆(简称上膜下秸,P+S)和地膜覆盖(对照,CK)4种耕作措施对0-40 cm土层水盐运移及食葵光合特性的影响.结果表明:(1)不同措施对土壤水盐调控的效果与作用时期差异较大.P+S在整个生育期内土壤盐分含量和盐溶质浓度较低,控盐效果显著；S+S仅在苗期能保墒控盐,但控盐效果比P+S差,后期出现水减盐增现象,保墒控盐效果也不佳；S在整个生育期内土壤盐分含量和盐溶质浓度最高,控盐效果最差；CK在整个生育期内土壤水分含量变化不大,而盐分含量较高,控盐效果也不明显.(2)不同措施对土壤水盐运移调控程度的差异,导致食葵光合特性也有明显变化.与CK、S、S+S相比,P+S由于其较低的盐溶质浓度环境,明显改善了其光合特性,在苗期、蕾期和花期能提高净光合速率(Pn)和蒸腾速率(Tr),增加气孔导度(Gs),降低胞间CO2浓度(Ci),从而使其作物长势和干物质积累明显高于其它措施.综合试验结果,P+S是内蒙古河套灌区盐碱地改良中优选的控抑盐耕作措施.

Effects of straw interlayer on soil water and salt movement and sunflower photosynthetic characteristics in saline-alkali soils

Insufficient drainage and over irrigation make salinity still a remaining problem in the Hetao Irrigation District of Inner Mongolia. In view of the occurrence characteristics of saline-alkali soils in this area, controlling invalid soil water evaporation and increasing water use efficiency are very important. It has been demonstrated that surface mulching with straw and film and placing a straw interlayer in soil are effective measures for soil salinity control. In this paper, we investigated the influences of integrated application of mulching and straw interlayer on the movement of soil and water and photosynthetic characteristic of sunflower on a typical saline-alkali soil. Micro-plot experiment was established with four treatments: straw interlayer only (S), straw interlayer plus surface straw mulching (S+S), straw interlayer plus surface plastic film mulching (P+S), and surface plastic film mulching (CK). Water and salt contents in the 0-40 cmm soil layer and crop photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO₂ concentration (Ci) were measured during sunflower growing season. Mulching and straw interlayer significantly modified soil water and salt processes. Compared with the other treatments, the P+S treatment showed lower salt contents and solute concentration in the 0-40 cm soil layer. The S+S treatment increased soil water content and reduced salt content at the seedling stage, but the degree of changes were less than that of the P+S treatment. At later growth stages, the S+S treatment had lower soil water content and higher salt content, suggesting that a straw interlayer plus surface straw mulching was not very effective in soil salinization control. The S treatment had the highest salt content in the whole growing season, an indication that placing a straw interlayer in the soil has limited effect on reducing soil salinity. Although the CK treatment had a higher and table water content in the 0-40 cm soil layer, its salt content remained higher in sunflower growing season. In terms of crop photosynthetic characteristics, compared to the CK, S, and S+S treatments, the P+S treatment significantly increased sunflower Pn, Tr, and Gs, and reduced Ci at seedling stage, bud stage, and flowering stage. In addition, the P+S treatment promoted crop growth, reduced the growth period, and accelerated dry matter accumulation of sunflower plants. We concluded that the P+S treatment was an optimal measure on amelioration of saline-alkali soil in the Hetao Irrigation District.