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It is crucial to synergistically improve the yield and quality of sweet maize by implementing precise and strategic planting methods. However, a comprehensive understanding of how increasing plant density affects the sweet maize fresh ear yield, grain-filling rate, and grain carbohydrate concentration is not fully understood. Thus, a field experiment was performed using a split-plot design in Southeast China in 2021 and 2022, involving four sweet maize varieties (MT6855 and WT2015 were compact-type varieties, XMT10 and YZ7 were flat-type varieties) and three plant densities (D1: 4.5 plants m−2; D2: 6.0 plants m−2; and D3: 7.5 plants m−2). The results showed that an increasing plant density markedly increased the fresh ear yield of sweet maize varieties (MT6855 and WT2015) over the two years. However, it did not influence the fresh ear yield of XMT10 and YZ7. Across all four varieties in 2021 and 2022, the increasing plant density decreased the sweet maize filled ear length, while it did not affect the grain soluble solid concentration and grain residue ratio. The sweet maize grain weight, the maximum grain-filling rate, and the mean grain-filling rate decreased significantly with the increase in planting density across all four varieties. However, plant density did not significantly affect the grain soluble sugar, sucrose, fructose, and starch concentrations across different varieties at most stages during the grain filling. The current study also found that the sweet maize fresh ear yield was dramatically positively correlated with ears ha−1, grains per ear, grain-filling rate, and grain starch concentration but negatively correlated with the bare plant rate. Notably, a parabolic relationship existed between the fresh ear yield and 100-grain weight. These findings suggest that optimizing the plant density, particularly with compact-type varieties, can improve the sweet maize fresh ear yield without decreasing its quality. [ABSTRACT FROM AUTHOR]

To clarify the effects of phosphorus fertilizer on nutritional characteristics of sweet corn kernels, the temporal (different filling stages) and spatial (upper, middle, and lower cob; kernel skin dregs, endosperm and embryo) variations of phytic acid (PA), phosphorus (P) and zinc (Zn) contents and Zn bioavailability of sweet corn kernels and their responses to exogenous phosphorus fertilizer were investigated using filed phosphorus fertilizer experiment (P fertilizer location experiment for sweet corn genotypes and P fertilizer level experiment). The results were as follows: P fertilizer mainly inhibited Zn bioavailability by suppressing Zn concentration in sweet corn kernels, and increased PA concentrations concurrently. P fertilizer input showed significant effects on the accumulation of PA, P, and Zn (mg plant-1) after 16-24 days of silking, while inhibitory effects were detected on Zn bioavailability at different kernel filling stages. There was no significant difference in the kernel of PA (g kg-1) and zinc bioavailability among different cob positions under medium P treatment. However, the high P level significantly improved the accumulation of PA in the middle and lower cob, while the inhibitory effect was found on the kernel of Zn concentration and Zn bioavailability at all cob positions. Among different parts of the kernel (skin dregs, endosperm, and embryo), the concentrations of PA, P, and Zn were the highest values in the embryo and their accumulation were the highest value in the endosperm, while Zn bioavailability was also the highest in the embryo. High P treatment significantly increased PA and P concentrations and decreased Zn concentration and its bioavailability at different kernel positions. Hence, optimized phosphorus fertilizer application could promote kernel Zn accumulation, while excessive P fertilizer input significantly increased PA accumulation at different filling stages, as well as in the endosperm and embryo, and eventually had a significant inhibitory effect on kernel Zn bioavailability in sweet corn at different cob and kernel positions. This study provides a theoretical reference for the biofortification of Zn in sweet corn seeds. [ABSTRACT FROM AUTHOR]