Directly linking plant N, P and K nutrition to biomass production in cotton-based intercropping systems

Growth performance under intercropping relies heavily on the nitrogen (N), phosphorus (P) and potassium (K) levels of the plants involved. However, few studies on intercropping advantages have established a direct link between growth performance and plant nutrient uptake. Using a 3-year field study (2019–2021) with four cotton-based cropping systems (cotton monoculture and garlic/cotton, peanut/cotton, and wheat/cotton intercropping) and three root partitions (no, mesh, and plastic), we measured the biomass and nutrient concentrations of cotton organs to explain differences in nutrient uptake between monoculture and intercropping. Additionally, the contributions of these nutrients to agricultural biomass under monoculture and intercropping were distinguished. Intercropping significantly increased the biomass of cotton aboveground parts by 15.5%, with the peanut/cotton intercropping system showing the greatest improvement. Intercropping also increased aboveground N, P and K concentrations and contents. In terms of cotton partial land equivalent ratio (pLER) values based on aboveground biomass, the root partitions ranked plastic > mesh > no. The relative N, P, and K content totals of intercropped cotton were higher than the pLER for biomass, indicating that the greater biomass under intercropping was accompanied by even greater percentage increases in the pools of N, P and K relative to those under monoculture. In the three intercropping systems, enhanced nutrient uptake was driven similarly by increases in plant nutrient concentration and biomass. Compared with cotton monoculture, intercropping improved the biomass production contributions of N by 46.7%, P by 57.3%, and K by 106%. Thus, intercropping enhanced plant nutritional potential to produce more biomass, and the yield benefit was amplified when belowground competition between intercrops was partially (or fully) diminished by root partitions.