Performance of alfalfa rather than maize stimulates system phosphorus uptake and overyielding of maize/alfalfa intercropping via changes in soil water balance and root morphology and distribution in a light chernozemic soil

Abstract

To investigate whether legume-dominated cereal/legume intercropping could facilitate phosphorus acquisition and yield enhancement via changes in root morphology and distribution. A field experiment was conducted for two consecutive years in a split-plot design with main plots treated with two phosphorus levels and subplots treated with maize and alfalfa grown alone or intercropped. In maize/alfalfa intercropping, alfalfa was 3.0–5.7 times more competitive than maize. Compared to monoculture, soil water balance of intercropped maize was significantly reduced by 115%, while that of alfalfa was dramatically enhanced by 469%. Thus, intercropped maize had pronouncedly reduced root growth by 17–36%, phosphorus uptake by 24%, and yield by 12%, but the associated alfalfa had significantly increased root growth by 26%–175%, phosphorus uptake by 208%, and yield by 137%, leading to significantly improved phosphorus uptake and yield of the composite population. Among root morphological and distribution traits, crown root surface area and lateral root volume were the best predictors of maize and alfalfa phosphorus uptake, respectively. Legume-dominated maize/alfalfa intercropping can significantly improve phosphorus acquisition and yield production through modifications in soil water balance and root morphology and distribution, and the system overyielding was performed via alfalfa rather than maize.