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ISSN : 2287-5824(Print)
ISSN : 2287-5832(Online)
Journal of The Korean Society of Grassland and Forage Science Vol.45 No.3 pp.223-229
DOI : https://doi.org/10.5333/KGFS.2025.45.3.223

Quality of Corn Responses of Gwangpyeongok, Dacheongok, and Shinhwangok Cultivars by Different Sowing Dates

Ilavenil Soundharrajan1, Jae Hyuk Kim2, Seung Hak Yang1, Jeong Sung Jung1, Hyo-Shim Han3, Ouk Kyu Han4, Ki Choon Choi1*
1Forage Production System Division, National Institute of Animal Science, Rural Development Administration, Cheonan 31000, Republic of Korea
2Department of Agriculture, Korea National Open University, Seoul 03087, Republic of Korea
3Department of Biotechnology, Sunchon University, Suncheon 57922, Republic of Korea
4Department of Crops and Forestry, Korean National University of Agriculture and Fisheries, Jeonju 54874, Republic of Korea

†These authors contributed equally to this work.


* Corresponding author: Ki Choon Choi, Forage Production System Division, National Institute of Animal Science, Rural Development Administration, Cheonan 31000, Republic of Korea. Tel: +82-41-580-6752, Fax: +82-41-580-6779; E-mail: choiwh@korea.kr
September 15, 2025 September 29, 2025 September 29, 2025

Abstract


This study evaluated the impact of sowing dates on the growth, yield, and nutritive quality of three corn cultivars including Gwangpyeongok, Dacheongok, and Shinhwangok. Plant height and total yield components declined with delayed sowing across all cultivars. Gwangpyeongok achieved the highest plant height (289 ± 14 cm), grain yield (9,108 ± 82 kg/ha), and total yield (18,973 ± 2,560 kg/ha) at the April 29 sowing. Dacheongok recorded the highest stover yield (17,227 ± 137 kg/ha) and total yield (22,236 ± 1,053 kg/ha) on May 13. Shinhwangok reached its maximum total yield (19,158 ± 604 kg/ha) at May 13 but showed the sharpest declines by May 16. Nutritional quality also deteriorated with later sowing. In stover, crude protein (CP) declined to 3.58% in Shinhwangok at May 16, accompanied by a rise in neutral detergent fiber (NDF) to 69.9%. In contrast, Dacheongok maintained stable CP levels (5.27–5.60%) and the lowest fiber fractions. Gwangpyeongok exhibited the highest stover CP at April 29 sowing, along with the lowest NDF and acid detergent fiber (ADF) contents. Grain CP was highest in Gwangpyeongok (8.1 ± 0.4%) and Shinhwangok (9.6 ± 0.9%) at April 29, while Dacheongok showed its maximum grain CP (8.0 ± 0.3%) at the same sowing date, coupled with relatively low fiber content. Overall, the findings highlight that timely sowing is crucial for achieving both high yield and optimal nutritive quality in maize. For Gwangpyeongok and Dacheongok, sowing from late April to mid-May provided the best balance between yield and nutritional quality. In Shinhwangok, the highest stover, grain, and total biomass yields were obtained at the May 13 sowing.


Corn cultivars , Sowing dates , Stover and grain yield , Nutrient quality

초록

    Ⅰ. INTRODUCTION

    Corn and soybean are the most important feed crops accounting for 60% of total feed stock production. In Korea, corn production is remaining unchanged at 91000 tons in 2023/2024. While, total consumption is expected to increase steadily at 11.3 MMT. In 2022/2023 consumption of corn reached 11.1 MMT, as higher feed demand more than offset declines in food, seed and industrial use. Despite the stable consumption, domestic corn production continues to cover lesss than 1% of total demand (Yoona and Neil, 2023). According to the Rural Development Administration (RDA), the self-sufficiency rate for high-quality forage remains inadequate, driven by growth in farm numbers and a limited forage production base. Consequently, Korea remains heavily dependent on forage imports (MAFRA, 2018). In order to ensure flexibility between domestic production and imports, a key strategy must be required.

    In Korea, corn breeding began in the 19th century with the development of synthetic varieties. Since the 1970s, hybrid varieties such as waxy corn for snacks (Lee et al., 2018), Topaz' for seeds (Son et al., 2017) and Dacheongok for silage production (Son et al., 2018) have been developed and distributed to farmers. Since then, corn varieties have been developed steadily to meet consumer and producer needs. To strengthen resilience, it is essential to adopt strategies that balance domestic production with import reliance. In particular, optimizing sowing periods is a more practical approach to improving corn yield and nutritive quality (Domokos et al., 2024). Therefore, the present study aims to evaluate the effects of different sowing dates on the growth, yield performance, and nutritive quality of three corn cultivars including Gwangpyeongok, Dacheongok, and Shinhwangok in order to identify the optimal sowing period for maximizing growth and productivity at the Cheonan station.

    Ⅱ. MATERIALS AND METHODS

    1. Experimental field

    Cheonan, the most populous city in Chungcheongnam-do Province, experiences average daily temperatures above 24 °C from May 26 to September 21. The hottest month is August, with an average temperature of 29.9 °C, while the coldest month is February, averaging –5.8 °C. The cold season lasts from December 1 to February 28, with daily high temperatures remaining below 7.2 °C. Precipitation in Cheonan varies significantly throughout the year, with the wettest period occurring from June 18 to September 12, when the probability of a day with rainfall exceeds 31%.

    2. Corn cultivations

    An experiment was conducted in Cheonan, South Korea, to determine the effect of sowing dates on corn growth and yield. The corn was sown on April 29, May 7, May 13, and May 16, 2024. Crops sown on April 29 and May 7 were harvested on August 16, 2024, while corn sown on May 13 and May 16 were harvested on August 19 and 20, 2024.The experimental plots measured 12 m2 (3 × 4 m). Corn seeds were planted at a density of two seeds per rigid row with spacing of 75 cm x 20 cm). After the seventh or eighth leaf stage, the superior plant in each row was retained, and the remaining plants were removed. Basal fertilization was applied at rates of 100 kg/ha nitrogen (N), 150 kg/ha Phosphorus (P), and 150 kg/ha Potassium (K). An additional 100 kg/ha of Nitrogen was top-dressed when the corn reached 50 cm in height (four- to six-leaf stage) (Ilavenil et al., 2024).

    3. Data analysis

    Corn growth characteristics were evaluated at the yellowripening stage using the research analysis criteria for agriculture and science and technology (RDA, 2012) including stem height, stem diameter, stover yield, and total dry matter yield. The content of acid detergent fiber (ADF) and neutral detergent fiber (NDF) in forage and grain was determined (Van Soest et al., 1991). The crude protein of samples was determined (AOAC in 1990).

    4. Statistical analysis

    Data were analyzed using SPSS version 16.0. Statistical procedures included one-way ANOVA, t-tests, multivariate analysis, and descriptive statistics. Post hoc comparisons were conducted using Duncan’s multiple range test. Differences among sowing dates or cultivars were considered statistically significant at p<0.05.

    Ⅲ. RESULTS

    1. Growth and yield of different corn cultivars at different sowing periods.

    The effect of sowing periods on growth and productivity showed distinct patterns across all cultivars (Fig. 1a and b). In Gwangpyeongok, plant height declined with delayed sowing date, reducing from 289 to 236 cm by the May 16 sown. Stover yield was lowest at the early sowing dates on April 29 (9,865 ± 1891 kg/ha) and on May, 7 (9,167 ± 267 kg/ha). Stover yield reached maximum at May 13 (11,000 ± 2,466 kg/ha) and reduced to 10,296 ± 1,676 kg/ha at sowing date May 16. Grain yield was highest with early sowing (9,108 kg/ha on April 29) and decreased steadily with later dates, suggesting that early planting provided better conditions for reproductive development. Total yield (Stover and grain) was highest on April 29 (18,973 ± 2,560 kg/ha) and lowest on May 16 (16,463 ± 1,656kg/ha). In Dacheongok cultivar reached its maximum height at May 7 sowing (270 ± 21cm), whereas highest stover yield was recorded at May 13 (17,227 ± 137 kg/ha) compared to other sowing dates. Grain yield was highest with earliest sowing (7,731 ± 803 kg/ha), but later sowing date markedly reduced at May 7 and May 13. Corn sown at May 13 had highest total yield compared to other sown dates. For Shinhwangok plant height decreased with delayed sowing similar to Gwangpyeongok. Stover Grain and total yield was peaked on May 13 with 10,205 ± 1,089 kg/ha, 8,953 ± 1,204 kg/ha, 19,158 ± 604 kg/ha, respectively, whereas lowest stover, grain and total yield was recorded at sown date May 16. There were no significant differences in diameter of all corn cultivars and sown dates. Comparing cultivars with average yields across all sowing dates, Dacheongok had the highest total yield, followed by Gwangpyeongok and Shinhwangok (Table 1).

    2. Nutrient content in stover of corn cultivars at different sown dates

    Stover nutrient quality showed a clear reduction under delayed sowing dates and showed distinct variations across sowing dates and cultivars (Fig. 2). The crude protein (CP) in Gwangpyeongok was decreased steadily with sowing delay from 5.24% at April 29 to 4.17% at May 16. At the same time, both NDF and ADF content was increased in later sowings particularly at May 7 and May 16. For Dacheongok, the CP level was relatively stable across sowing dates (5.27–5.60%) and NDF and ADF content was lowest on May 13 (50.6 ± 3.9 % and 29.2 ± 2.9%, respectively). Delaying sowing date to May 16, NDF and ADF contents were again increased to 59.2 ± 1.4% and 32.4 ± 3.7%. In contrast, Shinhwangok exhibited the most pronounced deterioration in nutritive value with late planting. CP content ranged from 5.23–5.88% up to May 13, it dropped sharply to 3.58% at May 16, accompanied by the highest NDF value (69.9%). ADF also increased with later sowing, reinforcing the decline in stover feeding quality. Total digestible nutrients (TDN) in both stover and grain generally declined with delayed sowing. All cultivars recorded their highest TDN values on April 29, particularly Gwangpyeongok and Dacheongok. In contrast, grain TDN remained consistently high across all sowing dates. When averaged across the all sowing dates, Dacheongok and Shinhwangok had slightly higher CP content compared to Gwangpyeongok. Whereas Dacheongok had the lowest average NDF and ADF content compared to other cultivars (Table 2).

    3. Nutrient content in Grains of corn cultivars at different sown dates

    Grain nutrient content was varied across cultivars with sown dates exhibiting a strong influence on protein and fiber content. Grains from Gwangpyeongok CP was highest with early sowing (8.1 ± 0.4 % on April 29) and declined with later sowing dates, averaging overall was 7.6 ± 0.7%. NDF and ADF levels were lowest on May 7 (17.2 ± 1.2% and 5.75 ± 0.7%, respectively) but increased again in later sown date. Crude protein (CP) content of Dacheongok in grain showed a clear decreasing trend with later sown dates, ranging from 8.0 ± 0.3% at April 29 to 6.89 % at May 16. By contrast, NDF and ADF both increased progressively with delayed planting, peaking at May 16 (25.6 ± 1.5 % and 10.1 ± 0.8 %, respectively). In Shinhwangok, CP content was consistently higher than in the other cultivars, reaching 9.6 ± 0.9 % at April 29 and averaging overall was 7.8 ± 1.2 %. However, later sowing dates resulted in gradual declines in CP (down to 7.04 ± 0.4% at May 16), while fiber fractions remained relatively stable but still increased slightly under late planting. Comparing cultivars, Shinhwangok had the highest grain protein across sowing dates, while Dacheongok had the lowest CP and the highest fiber levels. Gwangpyeongok maintained an intermediate balance, with moderate CP and lower fiber than Dacheongok. TDN values for stover and grain differed significantly between cultivars (Table 2).

    Ⅳ. DISCUSSION

    Optimization of the right sowing date allows corn to maximize favorable environmental conditions across critical growth stages, particularly from emergence to silking and kernel fill, which support higher corn production (Wang et al., 2024;Kim et al., 2017). Delaying sowing shortens the growth period, reduces accumulated growing degree days, and often leads to fewer kernels per ear, lower kernel weight, and ultimately reduced total yield. At the same time, sowing too early may also pose risks, as low soil or air temperatures can reduce germination, slow seedling growth, or increase exposure to pests and diseases, thereby reducing total yield and nutritional quality (Domokos et al., 2024). Hence, optimizing sowing dates are essential to increase both production and nutrient content in corn. Across cultivars, delayed sowing consistently decreased plant height and grain yield, while stover yield often peaked at mid-May sowing. Similarly, Wang et al., 2024 reported that optimizing maize sowing dates significantly affects solar radiation capture, stalk lodging resistance, and yield stability. Another study by Domokos et al. (2024), which assessed early, optimal, and late sowing dates across nine cultivars, found that early sowing improved stover weight and grain percentage but reduced kernel weight and grain moisture, while late sowing enhanced grain yield and kernel weight but decreased stover weight and grain percentage. Gwangpyeongok exhibited the highest plant height and grain yield at early sowing (April 29), whereas stover yield peaked on May 13 before declining. Our findings coincide with previous reports that early sowing extends the vegetative growth period, enabling higher biomass accumulation and improved grain filling, while delayed planting shortens the growth cycle and exposes crops to temperature and photoperiod conditions (Maresma et al., 2019;Sun et al., 2025).

    Variation among cultivars was evident in their response to sowing date. Dacheongok maintained higher yields under mid- May sowing compared to Gwangpyeongok and Shinhwangok, suggesting greater resilience to delayed planting. In contrast, Shinhwangok showed marked reductions in both stover and grain yields at later sowing dates. Such cultivar-dependent variation is consistent with genotype–environment interactions in maize, where hybrids differ in their ability to adapt to shorter growing periods and fluctuating climatic conditions (Mafouasson et al., 2018;Sun et al., 2025). Notably, Gwangpyeongok was superior in plant height and grain yield, while Dacheongok achieved better stability in total biomass production, highlighting the importance of cultivar selection for achieving higher production goals. Both stover and grain nutritive quality were affected by sowing date. Across all cultivars, delayed planting decreased CP and increased fiber fractions (NDF and ADF), due to accelerated maturation and greater lignification under warmer conditions, which lowers digestibility and feeding value (Cox et al., 1994; Maresma et al., 2019). Dacheongok had the highest CP and consistently lower NDF and ADF, suggesting greater suitability for forage production under optimal sowing. A similar pattern was observed for grain composition, with CP highest at early sowing but declining with delay, while fiber fractions increased. Shinhwangok generally maintained the highest grain CP across sowing dates, though it also deteriorated under late planting. These results are consistent with previous findings that delayed sowing shortens the grain-filling period and reduces nitrogen uptake, resulting in lower protein accumulation and higher fiber fractions (Mekonnen et al., 2023).

    Ⅴ. CONCLUSIONS

    Overall, the present study highlights the crucial role of optimizing sowing date to achieve both high and optimal quality in corn. Sowing from early to mid-May provide the higher yield and forage quality. Among the different cultivars. Gwangpyeongok showed its highest grain and total yield with the April 29. Dacheongok and Shinhwangok reached their maximum total yield with May 16. Shinhwangok proved most sensitive to late sowing. These findings underscore that combining the appropriate planting dates with careful and suitable cultivar choice is critical to maximize maize productivity and ensure high-quality stover and grain for domestic uses. Maize should be sown between late April and mid-May to secure high yields and superior forage quality. The performance of Gwangpyeongok and Dacheongok during late April and mid-May is the best, but Shinhwangok shows its highest productivity on May 13. It clearly indicating that sowing after mid-May compromises both yields and its nutrition quality.

    Ⅵ. ACKNOWLEDGEMENTS

    This work was performed with the support of the Cooperative Research Program for Agriculture Science and Technology Development (Project title: Efficient succession production of Domestic Maize and Triticale silage and feeding to Hanwoo cow and heifer for growth, reproduction and beef production; Project No. PJ017203), Rural Development Administration, Republic of Korea. This study was supported by a 2025 Postdoctoral Fellowship Program of the National Institute of Animal Science, Rural Development Administration and Republic of Korea.

    Figure

    KGFS-45-3-223_F1.jpg

    Growth and Productivity of Gwangpyeongok, Dacheongok, and Shinhwangok cultivars at different sowing dates in Cheonan station. Height (a) and diameter (b) of different corn cultivars at different sowing dates. The data are presented as the mean ± STD. abcDifferent alphabets between bar graph indicate a significant difference between sowing dates within a cultivar (p<0.05).

    KGFS-45-3-223_F2.jpg

    Stover and grains nutrient content of Gwangpyeongok, Dacheongok, and Shinhwangok cultivars at different sowing dates in Cheonan station. CP: crude protein; NDF: neutral detergent fiber; ADF: acid detergent fiber; TDN; total digestible nutrients. The data are presented as the mean ± STD. abcDifferent alphabets between bar graph indicate a significant difference between sowing dates within cultivar (p<0.05). Stover (a) and Grains (b) nutrient content of different corn cultivars at different sowing dates.

    Table

    Average of all sown dates for each cultivar growth characteristics and productivity

    The data are presented as the mean ± STD.
    abcDifferent alphabets within a column indicate a significant difference between three cultivars (An average of all sown dates for each cultivar; (p<0.05).

    An average of all sowing periods stover and grains nutrient content for each cultivar

    GPK: Gwangpyeongok; DCK: Dacheongok; SHK: Shinhwangok; CP: crude protein; NDF: acid detergent fiber; ADF: acid detergent fiber.
    abcDifferent alphabets within a column indicate a significant difference between three cultivars (An average of all sown dates for each cultivar; (p<0.05).

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