Maize-peanut intercropping system can enhance resource utilization efficiency and yield. However, the yield of peanuts in the edge and middle rows decreases after the flower-pegging stage due to the shading effect of maize. Foliar spraying of potassium dihydrogen phosphate can effectively alleviate this impact. This study aimed to elucidate the regulatory effects of foliar potassium dihydrogen phosphate application on membrane system damage, defense capacity, and yield in intercropped peanut systems, for providing a theoretical basis for high-yield cultivation management of maize-peanut intercropping system.

Using the maize variety Liangyu 99 and the peanut variety Huayu 22 as experimental materials, a maize:peanut with 2:4 intercropping system was employed. During the flower-pegging stage, foliar applications of a 0.5% potassium dihydrogen phosphate solution were administered three times at a rate of 730 kg·hm^-2 per application, to investigate the effects of foliar potassium dihydrogen phosphate application on peanut membrane system damage, osmoregulatory capacity, antioxidant enzyme activity, and yield.

In maize-peanut intercropping system, foliar application of potassium dihydrogen phosphate significantly reduced both the relative electrical conductivity and malondialdehyde content in peanuts compared with no treatment. During the pod-filling stage, relative electrical conductivity values in sole cropping plots, middle rows of intercropping plots, and edge rows of intercropping plots decreased by 15.56%, 35.29%, and 43.37%, respectively, compared with untreated controls, respectively. The trend in malondialdehyde levels mirrored that of relative electrical conductivity: sole cropping < intercropping middle rows < intercropping edge rows. Foliar application also markedly increased soluble protein, soluble sugar, and free proline content in peanuts while enhancing antioxidant enzyme activity, with edge rows demonstrating significantly superior effects to middle rows, which in turn outperformed sole cropping. Consequently, foliar application substantially improved individual peanut plants' fruit number, full fruit weight per plant, and total weight per hundred fruits compared with control conditions, with yield increases 7.24%-18.86% in sole cropping, 14.48%-20.02% in middle rows, and 16.75%-33.13% in edge rows. There were significantly greater yield improvements in intercropping system than in sole cropping.

During the flower-pegging stage, foliar applications of a 0.5% potassium dihydrogen phosphate solution could help mitigate leaf membrane system damage caused by peanut shading in maize, enhance its osmoregulatory capacity and antioxidant enzyme activity, increase both the number and weight of full fruits per plant as well as the total weight per hundred fruits, thereby improving peanut yield under the maize–peanut intercropping system.

According to the current situation such as low content of available potassium and insufficient application of potassium fertilizer of peanut production in Liaoning province, this study explored the effects of different potassium levels on peanut root system, nodule characteristics, main nutrient absorption rate and yield, so as to determine the optimal application rate of potassium fertilizer and provide the theoretical basis and reference for local peanut production.

This study was conducted in Shenyang Agricultural University from 2018 to 2019. Under the condition of normal application of nitrogen and phosphorus fertilizer needed for peanut field production, four potassium fertilizer (potassium sulfate) treatments of 0 (CK), 112.5 kg·hm^-2 (T1), 225 kg·hm^-2 (T2) and 337.5 kg·hm^-2 (T3) were used to study the effects of different potassium application rates on root morphology of plough layer, nodule characteristics, nutrient absorption and yield of peanut.

Potassium application had little effect on root dry weight of peanut, and there was no significant indigenous difference in root dry matter accumulation treatments. Compared with CK, the total root length, total root surface area and total root volume in plough layer of peanut were significantly increased under T2. Root nodules were more sensitive to potassium concentration, and the number and dry weight of nodules reached the maximum at all stages when the amount of potassium application was 112.5 kg·hm^-2. The increase of potassium application might also accelerate the formation and senescence of nodules. The application of potassium fertilizer increased the maximum accumulation rate, average accumulation rate and maximum accumulation of nitrogen, phosphorus and potassium, prolonged the active accumulation period of nitrogen and potassium. The yield components such as pods per plant and yield under T2 were higher than that under other treatments.

When the potassium application rate was 225 kg·hm^-2 ( T2 ), it was most conducive to peanut root growth and nutrient absorption, and the yield increase effect was the best. When the potassium application rate was 112.5 kg·hm^-2, the growth of nodules was the best, however, the yield increase effect was weaker than that of T2.