Effects of phosphorus fertilizer on starch granule size distribution in corn kernels

Phosphorus is one of the main management factors affecting yield and quality in crops. Starch granule size distribution is an important characteristic that may affect the functionality of corn products. Two corn cultivars were used to investigate the starch granule size distribution in kernels. The results showed the volume percentages of < 3 μm and 3–18 μm starch granules increased with phosphorus rates from 60 to 180 kg ha⁻¹. In contrast, the volume percentages of > 18 μm granules decreased markedly with phosphorus rates from 60 to 180 kg ha⁻¹ in low and normal nitrogen conditions. It has been suggested that phosphorus is favorable for the formation of small and midsize granules. Phosphorus had little influence on the number percentages of > 18 μm and < 18 μm granules in corn kernels. The protein content was positively correlated with volume percentages of < 18 µm granules, but was negatively correlated with > 18 µm granules. The amylose content was negatively correlated with volume percentages of 3–18 µm granules, but was positively correlated with volume percentages of > 18 µm granules. The results suggested that the kernels with more small and midsize starch granules are higher in protein content and lower in amylose content. And a decrease in volume percentage of large granules reduced the amylose content in corn kernels induced by phosphorus. Correlation analysis showed that the peak and final viscosities were negatively correlated with volume percentages of 3–18 µm granules, but were positively correlated with > 18 µm granules. It indicates that the large granules have higher peak and final viscosities compared with small and midsize granules in corn kernels. Phosphorus can reduce the proportion of large starch granules and then reduce the peak and the final viscosity in corn kernels.