Above and below-ground responses to contrasting soil phosphorus distribution by mungbean (Vigna radiata L.) cultivars with diverse phenology

Abstract

Abstract Background and Aim Deep placement of fertiliser has been providing strong productivity responses in rainfed cropping systems on Vertisols soils in north-eastern Australia. However, genotypic differences in root system architecture (RSA) can play an important role in response to various P rates and placement strategies. In this study we tested for genetic variation in RSA and its impact on the ability to exploit deep P bands among four contrasting, early to late maturing mungbean varieties. Methods Differences in soil P status and distribution were established by varying rates of applied P and the volume of soil P enrichment in shallow (top 5cm) and deeper (20-25cm) profile layers in root observation chambers. Intact RSA was measured in the top 30cm and bottom 30cm sections of the soil profile. Results Shallower placement of P fertiliser resulted in a wider root growth angle compared with other P treatments, whereas deeper placements resulted in greater mean root diameter and total root volume. Deep banding and deeper P-enriched sub layer treatments tended to advance the flowering and increased the mungbean pod yield for the more responsive early maturing var. Berken, without influencing the total root surface area, P uptake or shoot P concentration. This cultivar showed the lowest shoot P concentrations, least P uptake and greatest internal phosphorus use efficiency. Conclusion The varietal differences in RSA and root functioning played a major role in response to P placement strategies, where the strongest P response was observed with the deep P band fertiliser treatment for crop performance.