The experimental design was deliberately ambitious. The team established plots at agrometeorological stations representing local production conditions, each covering at least 1,000 square meters and surrounded by maize fields to minimize edge effects and microclimatic interference. Four sowing-date treatments were tested at every site: ten days earlier than the local normal date, the normal date itself, ten days later, and twenty days later. A randomized complete block design with four replications underpinned the statistical rigor, and meteorological data came from nearby observation stations, seven of eight located within eight kilometers of the trial fields. Daily temperature extremes, precipitation, sunshine hours, relative humidity, surface temperatures, and soil temperatures at three depths were all recorded, giving the researchers an unusually complete environmental record against which to interpret crop performance.

The first headline result concerns the sheer magnitude of location effects in spring maize. Using two-way analysis of variance, the team decomposed the variation in key traits into contributions from location, sowing date, and their interaction. For spring maize, geographical location explained up to 84.2 percent of the variance in traits such as hundred-grain weight and stem diameter, dwarfing the sowing-date effect. Hundred-grain weight at Yushu reached 40.33 grams, well above the 33.35 grams recorded at Harbin and 30.89 grams at Wulanwusu. Stem weight at Yushu exceeded every other site, while grain number per plant at Xifeng, at 681.69 kernels, surpassed both Harbin and Jinzhou. In other words, for spring maize, where you grow matters far more than when you sow.

Summer maize told a different story. Here, sowing date produced a significant main effect on hundred-grain weight, and its effect size actually exceeded that of location. The normal sowing date, designated T2, delivered the highest mean hundred-grain weight, suggesting that timely planting is the safest bet for summer growers seeking heavier grains. Yet the subsequent Scheffé multiple-comparison test found no significant pairwise differences among the four sowing dates, and most other agronomic traits barely responded to shifting the calendar. The practical implication is nuanced: adjusting sowing dates within the tested window offers limited leverage for summer maize beyond protecting grain weight, and the normal date remains the most favorable choice for that particular trait.

Grain quality traits proved remarkably stable across environments. Starch, protein, crude fiber, and fat contents showed no significant variation with location or sowing date in either cropping system, and the ranking was identical everywhere: starch highest, followed by protein, crude fiber, and fat. Crude fiber displayed the greatest phenotypic variability, while starch and protein were the most consistent. This stability is itself informative, echoing earlier work showing that genetic control over certain quality traits, particularly fat content, can outweigh environmental influence. But stability at the level of analysis of variance did not mean the quality traits were blind to weather. Stepwise regression, which identifies only factors with significant linear correlations, uncovered clear meteorological signatures hiding beneath the surface.

Those signatures diverged sharply between the two systems. For spring maize, hundred-grain weight and protein content were both positively correlated with average relative humidity during the post-flowering period, a relationship the authors attribute to improved plant water status supporting continued dry matter accumulation and nitrogen translocation into the kernels. Starch content and stem diameter, by contrast, declined with higher average minimum temperatures. Ear diameter rose with precipitation, and grain number per plant fell as accumulated temperature increased. For summer maize, accumulated temperature emerged as the dominant positive factor, correlating with hundred-grain weight, stem diameter, stem weight, ear diameter, and starch content. But heat carried costs: protein content was negatively correlated with the average diurnal temperature range, and starch content declined as average soil temperature at five centimeters depth rose. Crude fiber content increased with precipitation. Notably, fat content showed no significant relationship with any meteorological factor in either system, reinforcing the view that lipid biosynthesis in maize is under strong genetic control.

The grain filling process itself, modeled with a logistic curve, provided a mechanistic bridge between weather and yield. For spring maize, a longer active filling period and a faster average filling rate were associated with thicker stems, more grains per plant, heavier hundred-grain weights, and higher starch content. A later date of maximum filling rate thickened ears and increased grain number but lowered protein and crude fiber content. Summer maize showed parallel patterns, with later peak filling rates linked to thicker stems and ears, heavier stems and grains, and higher starch and crude fiber. These correlations, all statistically significant at the 0.05 level, confirm that the temporal dynamics of kernel development translate environmental conditions into the physical and biochemical properties of the harvested grain.

Perhaps the most nutritionally significant findings concern amino acids. The team measured all 17 amino acids in the grain, from glutamic acid, the most abundant, to methionine, the scarcest. Lysine, the first limiting amino acid for human nutrition, averaged 2.59 grams per kilogram in spring maize but only 1.77 grams per kilogram in summer maize. Principal component analysis of the amino acid profiles retained four components explaining 86.6 percent of total variance, and the resulting composite scores revealed that spring maize from Northeast China, at Harbin, Yushu, and Jinzhou, possessed superior amino acid quality. The amino acid score, calculated against FAO and WHO reference patterns for adults, consistently favored spring maize as well. Crucially, the drivers differed: amino acid accumulation in spring maize was primarily temperature-sensitive, whereas in summer maize it tracked precipitation, with higher post-flowering rainfall generally raising amino acid content, an observation consistent with recent transcriptomic evidence that water replenishment under heat enhances amino acid metabolism in developing kernels.

The authors are candid about the limits of their design. Because genotype is confounded with cropping system and location, the observed superiority of spring maize in yield-related traits and protein content reflects agronomic performance under the specific conditions tested rather than inherent genetic potential. The analytical strategy of treating the two systems separately was intended to mitigate, not eliminate, this confounding, allowing a clearer focus on meteorological associations within each system. Future work with factorial designs, in which the same genotypes are grown across both spring and summer sowing conditions at multiple sites, will be needed to partition genotype, environment, and their interaction definitively.

Even with those caveats, the study delivers a data-driven framework with immediate relevance for a warming world. Summer maize in the Huang-Huai-Hai plain already faces some of China’s highest risks of heat stress during grain filling, and the negative correlations between protein, starch, and temperature-related variables documented here suggest that continued warming could erode grain quality in that system. Spring maize growers, by contrast, may find that humidity and moderate minimum temperatures are the levers that matter most, and that Northeast China’s cooler filling season is a genuine asset for protein quality. As climate variability intensifies, the ability to match sowing strategies and regional expectations to the specific meteorological sensitivities of each cropping system, rather than applying one-size-fits-all prescriptions, may prove essential for safeguarding both the quantity and the nutritional quality of one of the world’s most important staple crops.

Subject of Research: Effects of meteorological factors and sowing date on yield components and grain quality of spring and summer maize in China

Article Title: Evaluation of yield components and grain quality of maize in China: Relationships with grain filling characteristics and meteorological factors

Article References: Li, R., Liu, Y., Wang, Q., & Guo, J. (2026). Evaluation of yield components and grain quality of maize in China: Relationships with grain filling characteristics and meteorological factors. Theoretical and Applied Climatology, 157(9), Article 605. https://doi.org/10.1007/s00704-026-06533-z

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06533-z

Keywords: maize, grain quality, grain filling, meteorological factors, sowing date, spring maize, summer maize, amino acids, protein content, starch, accumulated temperature, China