Abstract
Space availability and the maintenance of adequate phosphorus (P) supply in the root zone are essential for achieving high yield and P-use efficiency in maize production by manipulating the root morphology and arbuscular mycorrhizal (AM) fungi colonization. A major trade-off exists between root growth and AM colonization that is influenced by soil P supply intensity and space availability. However, how soil P manipulates the root morphological characteristics and AM colonization to compensate for the limitation of root-growth space induced by high-planting density is not clear. Therefore, pot experiments were conducted to investigate interactions between the root growth and AM fungi by optimizing soil P supply to compensate for limited root growth space induced by high-planting density. Similar shoot biomass and P uptake values were obtained in P200 (200 mg P kg−1 soil) under D = 40 (i.e., diameter of the pot is 40 cm) and P400 under D = 30, and similar values were obtained for root length, tap root length, root angle, lateral root density, and AM colonization. However, the improvement in P supply in the root zone, shoot biomass, and P uptake in P400 under D = 20 were lower than in P200 under D = 30, and there were no significant differences in the root parameters between P200 and P400 under D = 20; similarly, the root growth and AM colonization exhibited similar trends. These results suggest that optimizing P supply in the root zone to regulate the interaction between root morphological traits and AM colonization can compensate for limited root-growth space. Although P supply in the root zone increased after the root-growth space was compressed, it could not meet the P demand of maize; thus, to achieve the most efficient use of P under intensive high-density maize production, it is necessary to optimally coordinate root growth space and P supply in the root zone.
Highlights
The sustainable use of phosphorus (P) is a major challenge in agricultural production, especially in high-density planting systems (Testa et al, 2016)
Shoot biomass increased as the soil P supply increased, and the highest shoot biomass was obtained in the P400 treatment groups, followed by in the P200 and P0 treatments
The effect of space availability on shoot biomass was more prominent when more P was added to the soil (P200 and P400 treatments); the limited space availability could restrict the growth of shoot biomass
Summary
The sustainable use of phosphorus (P) is a major challenge in agricultural production, especially in high-density planting systems (Testa et al, 2016). Smallholders often employ the insurance approach, that is, large amounts of mineral P fertilizer are applied in excess to increase the P availability to crop plants, resulting in low P-use efficiency (PUE) (Dhillon et al, 2017; Zhang et al, 2019), with considerable adverse environmental impacts, such as non-point source pollution of surface waters (Ni et al, 2015). Both the P supply and root growth space availability should be considered when attempting to increase the PUE under intensive high-density planting maize systems
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