Morphological responses in peanut pod development to intercropping and nitrogen application rates

Short species in intercropping likely suffer from yield losses due to shading, but this can be mitigated through morphological changes and nitrogen (N) fertilization. However, little is known of the role of morphological responses to N supply and intercropping in peanut pod development. A two-year field experiment compared maize/peanut intercropping with single species cultivation at five N rates. Growth of branch and peg were measured at four growth stages for sole cropped and intercropped peanuts. Intercropped peanut promoted canopy elongation, which impeded the development of peanut pegs to the pods. Mature intercropped peanut plants increased the main stem height and the first pair of lateral branch length by 6.8% and 4.4%, respectively, but it decreased the total branch number, the node number of the main stem and the leaf area index by 4.6%, 5.9% and 12.7%, respectively. From anthesis to maturity, the peg biomass of the intercropped peanut firstly increased from 0.5 g to 1.0 g and then decreased to 0.6 g, which was much lower than that of sole cropping at corresponding phase (0.9, 1.8 and 1.6). The number of peg per plant was on average 49.0 in the mono cropping and 30.8 in the intercropping. Intercropping had negative effects on numbers of full pod, immature pod and total pod, but had no impact on the percentage of the full pod. N fertilization had little impact on aboveground morphological changes but significantly increased the full and total pod number of intercrops. Increasing N fertilizer from 0 to 270 kg ha−1 increased the full pod number of intercropped peanuts from 6.3 to 9.5 pods per plant, but the number decreased to 6.9 pods per plant when N was applied at 360 kg ha−1, while the total pod number was increased with N input from 9.4 per plant at N0 to 12.1 per plant at N270 and then decreased to 11.2 per plant at N360. The effect of N input on peg biomass was only significant at the pod setting stage. In general, the positive elongation in the intercropping could not compensate the failure in peanut pod development, but N fertilization could be considered as an effective compensatory measure which could promote pod setting and filling. This study provides a strategy for proper N fertilization beneficial for peanut’s pod development in intercropping.