Intercropping is an intensive agricultural cropping system widely practiced for enhanced yield and nutrient acquisition advantages. A two-year maize–soybean intercropping (MSI) field study was performed in 2018 and 2019 to assess the effects of potassium (K) fertilizer application on biomass accumulation and distribution of essential nutrients in the various plant parts (root, green biomass and seed) of maize–soybean intercropping (MSI). Three different treatments of K fertilizer applications (T0: no potassium application; T1: maize 40, soybeans 30 and T2: maize 80, soybeans 60 kg ha−1) were designed with 2 rows of maize by wide, narrow row planting in row arrangements of 160 cm + 40 cm. Soybeans were grown in 2 wide rows at a width of 40 cm and a row spacing of 60 cm between the rows of maize and soybeans, while the sole maize (SM) and sole soybean (SS) were grown with 70-cm and 50-cm row spacing, respectively. The results of the two-year study confirmed that, as compared to T0, T2 significantly increased nitrogen, phosphate and potassium (NPK) accumulation in all maize parts by 27%, 16% and 20% grain, 23%, 22% and 14% green biomass and 30%, 17% and 15% root, respectively. In soybean treatments, T2 significantly increased NPK accumulation by 23%, 22% and 24% grain, 16%, 15% and 12% green biomass and 18%, 19% and 20% root, respectively. The increased accumulation of nutrients under T2 raised the overall biomass and its distribution to root, green biomass and grain in maize and soybeans by 11% and 18% and 16% and 19%, 20% and 12%, respectively, compared to T0. On average, after two years of experiments, the T2 intercropped maize and the soybeans showed 103% and 64% of the sole yield and attained the maximum LER of 1.66 and 1.68, respectively. Our results reveal that managing optimum K level application (80:60 kg ha−1) can accelerate biomass accumulation and distribution of other essential nutrients in the plant parts of intercropped maize and soybeans. Therefore, it is immensely important to concern potassium application levels in developing a sustainable maize–soybean intercropping systems for achieving higher productivity and land equivalent ratio (LER).

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Highlights - Potassium nutrient management in maize-soybean strip intercropping can increase the resource use efficiency. - Compared to the T0 (no potassium), T2 (80 kg ha–1 on maize) application increases the light interception and leaf area index of maize by 17% and 38% respectively. - Regression analysis reveals a positive relationship between physiological parameters measured at R2 and at R6 growth stages in maize under maize-soybean strip intercropping. - High K2O (80 kg ha–1) inputs enhanced the partitioning of biomass production in maize. - Overall, the optimum K2O application increased the maize yield by 16% under maize-soybean strip intercropping system relative to control.   Globally, maize is an essential food and fodder crop. Fertilisers, as soil amendments, particularly K2O, could increase maize yields. A Two-year field research was designed in 2018- 2019 to examine the influence of three-potassium fertiliser applications on maize-soybean strip intercropping and sole-maize yield components. A Randomized complete block design with three replications was used, and one of three K2O doses (T0, 0; T1, 40:30; T2, 80:60 kg ha–1) was given in each plot. The effects K2O treatments on photosynthetic characteristics, photosynthetic active radiation, leaf area index, total biomass accumulation, and seed yield were investigated at V6, R2, R4, and R6. Compared to T0, maize-soybean strip intercropping system and sole-maize results showed T2 maize enhanced the light interception by 14, 26, 15, and 17% at V6, R2, R4, and R6 respectively. Maize increased the partitioning of biomass to cob and seed by 8 and 10% at R6, respectively in T2, relative to T0 treatment. T2 showed a higher green leaf area than T0; K2O applications led to an enhancement in leaf area index at R6 by 38%, under T2, and subsequently increased the photosynthetic rate at R4 and R6 by 8% and 6% respectively, in both years of the study. These results suggest that we may increase the accumulation of biomass and the yield of the maize seed under maize-soybean strip intercropping system and sole-maize by optimum K application in maize plants.