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.