A Salt Stress Tolerance Effect Study in Peanut Based on Peanut//Sorghum Intercropping System

The main objectives of this study were to investigate the response of peanut to salt stress under peanut//sorghum intercropping, and hope to provide new insights on develop stress cultivation.

In this study, peanut cultivar “Huayu 25” and sorghum cultivar “Liaoza 15”, with characteristics of salt tolerance and a high yield potential, were selected as experimental materials to carry out the field planting box experiment for two consecutive years. Sole-cropped peanut (SP) and intercropped peanut (IP) experiments were then performed under normal (N) and salt stress (S) soil conditions, respectively. The experiment was comprised of four treatments: sole-cropped peanut under normal condition (N-SP), intercropped peanut under normal condition (N-IP), sole cropped peanut under salt stress condition (S-SP), and intercropped peanut under salt stress condition (S-IP). Therefore, the salt tolerance index (STI), relative interaction index (RII), Na⁺/K⁺, and rhizosphere nutrient of peanut were investigated in the present study to evaluate the response of peanut to salt stress under different planting patterns.

In the peanut//sorghum intercropping system, both RII of peanut were negative. However, the negative RII was decreased significantly and the STI was increased significantly under S-IP with salt stress, especially after continuously being planted for two years. Of these, the negative RII of S-IP decreased by 66.78% in 2019 than that of in 2018, and the negative RII under S-IP decreased by 88.76% than that under N-IP. Furthermore, the STI under S-IP increased by 27.68% than that under S-SP in both 2018 and 2019. Peanut//sorghum intercropping has been found to change the overall root distribution and architecture by favoring the development of different types of roots, and also affected rhizosphere nutrients of peanut, the rhizosphere soil nutrient content of N-IP and S-IP increased by an average of 6.19% and 3.73% than N-SP and S-SP, respectively. Under salt stress, the content of soil potassium increased significantly compared with normal soil conditions, this might be the initial defensive response utilized by plants to maintain Na⁺/K⁺ homeostasis in rhizosphere soil, which regulated Na⁺/K⁺ homeostasis in peanut by influencing the Na⁺ and K⁺ selective absorption and transportation. Compared with S-SP, the leaf Na⁺/K⁺ ratio of S-IP decreased by 20.63%, the leaf salinity hazard coefficient (LSHC) decreased by 53.95%, so the photosynthetic potential and light energy conversion efficiency were significantly improved too. Ultimately the dry matter accumulation capacity and yield potential were improved, in which the yield potential under S-IP had the most obvious increase, and the yield under S-IP increased by 17.95% in 2019 compared with 2018.

The continuous peanut intercropped with sorghum under salt stress could be an effective technique to alleviate peanut negative interactions, which significantly improved STI and alleviate salt stress of peanut by improving soil nutrient status and regulating peanut Na⁺/K⁺ homeostasis, which ultimately maintained the dry matter accumulation capacity and increased yield potential.