Effects of Sowing Periods on Growth and Development, Yield and Quality of Maize in Cold Area

Liu Bo-wen, Yan Ping, Zhou Yong-ji, Xu Jia-qi, Wang Yu-fan, Xue Hong-wei, and Sun Yan-kun* College of Resources and Environment, Northeast Agricultural University, Harbin 5000, China

2 Heilongjiang Province Institute of Meteorological Science, Harbin 150030, China

3 Heilongjiang Meteorological Data Center, Harbin 150030, China

Abstract: In order to determine the most suitable sowing periods for maize in the cold area of Harbin City, the field test method was adopted. From 2018 to 2019, the main maize variety Xianyu 696 which was planted in Harbin City, Heilongjiang Province, was used as the test material for the six-sowing-period treatment experiments. The sowing period settings were as the followings: April 20 (T1), April 24 (T2), April 27 (T3), May 4 (T4), May 11 (T5) and May 18 (T6). In the experiment, the effects of different sowing periods on the growth and development, yields and quality of maize were studied. The results showed that the maize through T1 treatment had the longest growth period, the lowest height and the highest ear height, and the highest grain protein content. The maize through T6 treatment had the highest height and ear height, as well as the highest starch and oil content. And the grain crude fat, soluble protein, soluble sugar and the moisture content increased and then decreased with the delay of the sowing period. The maize through T4 treatment had the highest content of soluble protein. However, other quality indicators and the number of rows, the length of the bald tip, the number of grains per spike and the weight of 100 grains first increased and then decreased with the delay of the sowing period. The dry matter accumulation through T4 treatment was significantly higher than the ones through five treatments, and the 100-kernel weight and other ear-grain traits were the highest, the maizes through T4 treatment increased the yield by 21.54% compared with that through T1 treatment. Thus, the most suitable sowing period for the maize in the cold area of Harbin City was from May 4 to May 11. It provided technical supports for guiding maize planting in the cold area of Harbin City.

Key words: cold region, maize sowing date, maize yields, grain quality

Introduction

Maize is the grain crop with the largest sown area and the highest total yields in China, and it plays an important role in ensuring national food security (Caoet al., 2010). Heilongjiang Province is the largest province in maize production (Cuiet al., 2015). The total maize output accounts for about 40% of the province's grain output and 15.1% of China's total maize output (Caiet al., 2007). The yields and quality of maize are greatly affected by the ecological environment and cultivation measures (Liuet al., 2014). In recent years, global extreme weather phenomena have occurred frequently, resulting in large fluctuations in surface temperature, solar radiation, inter-annual temperature and average rainfall (Plattneret al., 2013). With the continuous changes of climate, the yields and quality of maize in northeast China have changed. Therefore, it is particularly urgent to explore cultivation techniques to slow down the impacts of climate changes on the growth and development of maize and its yields and quality.

Sowing date is a key cultivation measure to regulate crop growth and development in production (Gaoet al., 2020), a suitable sowing date can coordinate various meteorological factors to optimize yields traits and quality parameters (Cuiet al., 2020). Studies have shown that delaying the sowing date of maize can directly lead to the shortening of the growth period of maize (Liuet al., 2009), and reduce the duration of maize filling, which leads to a serious decline in maize quality and yields (Liuet al., 2009); studies have also shown that early sowing results in a reduction in yield, due to unsuitable growth conditions (Cuiet al., 2015), at the same time, due to different genetic characteristics of various maize varieties, the most suitable sowing dates for their production areas are also different (Huet al., 2012).

Therefore, in order to in-depth study the effects of different sowing dates on the yields and quality of maize in Harbin City cold area, the main maize variety Xianyu 696 in Harbin City was used as the experimental material. Field experiments were carried out in 2018 and 2019 at the experimental base of the Harbin City Science and Technology Park of the Heilongjiang Academy of Agricultural Sciences (Harbin Democracy Township) with different sowing dates. To explore the growth and development characteristics of maize in Harbin City cold area, the accumulation of grain dry matter, and the changing laws of maize yields and quality, so as to determine the best sowing date of maize in Harbin City cold area, in order to provide guidance for timely and high-yield cultivation of maize in Harbin City cold area.

Materials and Methods

Test design

Field trials were carried out in the Science and Technology Park of the Heilongjiang Academy of Agricultural Sciences (126°49′ east longitude, 45°50′ north latitude) in years of 2018 and 2019. The test site is located in a cold black soil area, belonging to a mid-temperate continental monsoon climate, with an altitude from 132 m to 140 m and a flat terrain, the soil in the test plot is a typical black soil. The physical and chemical properties of the soil were as the followings: alkaline hydrolyzable nitrogen 161.40 mg ? kg-1, available phosphorus 19.42 mg ? kg-1, available potassium 678.90 mg ? kg-1, organic matter content 25.8 g ? kg-1, pH=5.97. The tested maize variety was Xianyu 696 (provided by Tieling Pioneer Seed Research Co., Ltd.), which had a growth period of 125 days and required an active accumulated temperature of ≥10℃ of about 2 750℃.

There were six sowing schedules in the experiment, the six sowing schedules in 2018 were represented by TX1-TX6, and the six sowing schedules in 2019 were represented by TY1-TY6, that was, April 20th (TX1, TY1), April. 24th (TX2, TY2), April 27th (TX3, TY3), May 4th (TX4, TY4), May 11th (TX5, TY5) and May 18th (TX6, TY6), every processing set up three repetitions, a total of 18 cells, arranged in random blocks. Five ridges were planted in each plot, with a ridge spacing of 0.65 m, a length of 15 m, a planting density of 67 500 plants ? hm-2, and the fertilization measures for each treatment were the same. The mixed fertilizers applied were 300 kg ? hm-2and 225 kg ? hm-2of diammonium phosphate and urea, respectively, and 225 kg ? hm-2of urea was top dressed in the later period, and the treatment methods for sowing in 2018 and 2019 were the same. The sampling method: referred to the method of Huet al. (2017), the side rows on both sides of the five rows of maize planted in each treatment were used as protection rows, and the middle three rows were used as sampling rows, of which two rows were used to determine yields during the mature period, and one row was used to determine plant morphology and dry matter. In each growth period, the three maize plants were taken from the plant morphology sampling rows of different treatments to determine the plant morphology and dry matter weight; after full maturity, maize ears of two rows of yields sampling rows were harvested and weighed freshly weight, used the average ear method to select 20 ears of ears to weigh the fresh weights and bring them back as sample ears. After air-drying, seed test was carried out to determine the grain traits, such as panicle row number and yields.

Test methods

Referred to the research method of Duet al. (2002) to measure various physiological indicators of the plant. Following the 3rd edition ofPlant Physiological and Biochemical Experiment Principles and Techniquescompiled by Huang and Wang (2015), the crude fat content of grains was determined by cable extraction method and soluble sugar of grains was measured by anthrone colorimetry (Dorinet al., 2017). The moisture content of grains was measured by oven drying method and soluble protein was measured by Coomassie bright blue method (Bradford, 1976), the maize kernel crude protein, oil content, crude starch and other indicators were analyzed using Perten 9200 type near red grain analysis instrument (A PerkinElmer Company, Perten).

Data processing and analysis

The table was made by Excel 2010 (Microsoft Inc., WA, Redmond, USA), the data were analyzed by SPSS 25.0 least significant difference (SPSS Inc., Chicago, IL, USA), and the pictures were made by Origin 2018 (OriginLab Inc., USA) draw.

Results

Effects of sowing date on growth period of maize in cold area

As shown in Table 1, the growth period of maize postponed by the sowing date had been significantly shortened. Every time the sowing date was delayed by 1 day, the whole growth period in 2018 would be shortened by 0.28-1.3 day; the whole growth period would be shortened by 0.67-1 day in 2019, and the whole growth period of TX6 treatment was shortened by 20 days compared with TX1 treatment; the whole growth period of TY6 treatment was shortened by 23 days compared with TY1 treatment. Among the different sowing dates, the seedling stage-joint stage was most affected by the delay of the sowing date. TX6 treatment shortened 8 days compared with TX1 treatment; TY6 treatment shortened 12 days compared with TY1 treatment. With the postponement of the sowing date, various processes of maize growth and development showed a trend of shortening, while the number of growth days in the jointing stage-big horn stage of maize had increased, which might be because this period was an important period for maize nutritional supplementation, extending the growth days would increase nutrient accumulation and ensure tasseling and ear differentiation in later stages.

Effects of sowing periods on height and ear position of maize plants in cold area

As shown in Fig. 1a and b, the plant height and ear height of maize showed a continuous upward trend with the delay of sowing date. Compared with TX1-TX3 treatments, the plant height of TX6 treatment was significantly increased by 0.13-0.22 m, and the ear height of TX6 treatment was also significantly higher than that of TX1-TX5 treatment. The effect of TY treatment on maize plant height and ear height was the same as TX treatment. The results showed that the appropriate postponement of the sowing date of maize promoted plant growth and significantly increased the ear height of maize.

Fig. 1 Effects of sowing periods on morphological characteristics of maize plants in cold areaDifferent lowercase letters indicate significant variations due to different treatments (P＜0.05).

Effects of sowing periods on kernel quality of maize in cold area

Fig. 2 a and b showed that the dry matter weight of maize during the whole growth period increased in a curve. The dry matter accumulation rate was relatively slow before the big bell mouth stage, and the difference between treatments was not obvious. Its rapid growth stage was in the big bell mouth stagetasseling and spinning stage, followed by the filling stage-mature stage. In the big bell mouth stage, the dry matter accumulation of T4 treatment was significantly higher than that of other treatments. Compared with other five treatments, TX4 and TY4 increased by 10.99%-22.51% and 5.16%-17.98%, respectively. Among the six treatments, T2 treatment had the lowest dry matter accumulation, TX2 was 31.64% lower than that of TX4, and TY2 was 33.81% lower than that of TY4. The results showed that as the sowing date was postponed, the dry matter accumulation of maize showed a trend of first rising and then falling, reaching the highest value under T4 treatment and the lowest under T2 treatment, indicating that the dry matter accumulation in maize was affected by the sowing date. Obviously, advance or delay of the sowing date would reduce the accumulation of dry matter. Choosing an appropriate sowing date would influence the accumulation of dry matter in the maize.

Effects of sowing periods on height and ear position of maize plants in cold area

It could be seen from Fig. 3 that there were significant differences in the protein contents (Fig. 3a), soluble protein content (Fig. 3b), crude starch content (Fig. 3c) and crude fat content (Fig. 3d) of maize kernels under different sowing dates. In general, with the delay of the sowing date, the protein contents of maize kernels showed a declining trend, the soluble protein content and crude fat content both increased first and then decreased, while the crude starch content gradually increased. The maize grain protein content of T1 treatment was the highest, which was significantly higher than those of T5 and T6 treatments.

The soluble protein content of maize kernels in T4 treatment was the highest, TX4 and TY4 were 6.55 and 6.36 ug ? g-1, respectively, which were 46.1% and 41.51% higher than those TX1 and TY1 treatments with the lowest soluble protein content. The crude starch content of maize kernels under T6 treatment was also significantly higher than that of T1-T4 treatments, while the crude starch content of maize kernels under T5 treatment was the second only to T6 treatment and was significantly higher than those of T1-T3 treatments. Compared with other five treatments, the crude fat content of maize kernels under T4 treatment increased significantly from 6.94% to 15.22%. The results showed that a proper postponement of the sowing date of maize could significantly increase the protein, soluble protein, crude starch and crude fat content of maize kernels, but too late sowing would also cause its content to decrease.

Fig. 2 Effects of sowing date on dry matter accumulation of maize in cold area

Fig. 3 Effects of sowing periods on protein contents, soluble protein content, crude starch content and crude fat content of maize kernel in cold area

It could be seen from Fig. 4 that with the delay of the sowing date, the soluble sugar content (Fig. 4a) and the oil content (Fig. 4b) of maize kernels showed an overall trend of first increasing and then decreasing, while the water content (Fig. 4c) showed an up and down trend of first increasing, then decreasing and then increasing. The soluble sugar content of maize kernels in the two years was the highest in T4 treatment, which was significantly increased by 38.38% and 34.71% compared with T1 treatment; the oil content of the T6 treatment was the highest, which was significantly higher than that of T1-T3 treatments, but the difference with T4 and T5 treatments was not significant. The results showed that the appropriate postponement of the sowing date had an impact on the soluble sugar content, grain oil content and grain water content of maize kernels. The appropriate sowing date was conducive to the accumulation of soluble sugar and oil content, thereby improving the quality of the kernels.

Fig. 4 Effects of sowing periods on soluble sugar content, oil content and moisture content of maize kernel in cold area

Effects of sowing periods on ear, kernel characters and yields of maize in cold area

As shown in Table 2, there were significant differences in maize ear and kernel traits at different sowing dates. From the results of maize ear and grain traits, different sowing dates had few effect on maize ear thickness, number of ear rows bald tip length and sowing dates had few effect on ear length, number of rows, grains per ear and 100-kernel weight of spring maize. The impact was more obvious. Compared with T1 treatment, the ear length of maize in T4 treatment was significantly increased by 2.5 cm, the number of maize rows in T4 treatment was significantly increased by 13.3% and 11.1% compared with T1 and T2 treatments, and the number of ears in maize was significantly increased by 6.04% compared with T1 treatment. In addition, the 100-kernel weight of spring maize under T1 and T2 treatments decreased significantly, which was 14.32% and 12.84% less than that of T4 treatment, this might be due to the adequate accumulation of dry matter due to proper late sowing, which was beneficial to increase the number of grains per ear and 100-kernel weight. The results showed that a proper postponement of the sowing date would increase the ear length, 100-kernel weight and number of rows of maize, but had few effects on other maize ear and kernel traits.

The yields of spring maize with the postponed sowing date increased first and then decreased. As shown in Fig. 5, T4 treatment achieved the highest yields, which was significantly higher than that of treatments (P＜0.05). The output of TX4 reached 12 686.95 kg ? hm-2, which was 1.5%-7.2% higher than that of five treatments. At the same time, the yield of TY4 treatment was 10 216.55 kg ? hm-2, which was significantly higher than that of four treatments except the TY5. In terms of two years, the yields performance was as the following T4＞T5＞T6＞T3＞T2＞T1. This showed that an appropriate postponement of the sowing date would help to increase maize production, but too late sowing would also affect the yields of maize.

Table 2 Effects of sowing periods on ear and kernel characters of maize in cold area

Fig. 5 Effects of different sowing periods on maize yields in cold area

By analyzing the correlation among sowing date, yields and maize ear and kernel traits, it could be seen that there was a positive correlation among sowing date, maize yields and maize ear and kernel traits (Table 3). There was also a certain relationship among yield, maize ear and kernel traits. It was positively correlated with but negatively correlated with the number of ear rows. The results showed that the sowing date was one of the main factors that affected the yields and quality of maize. Choosing an appropriate sowing date could greatly promote the increase of maize yields and quality.

Table 3 Analysis of correlation of sowing periods, yields, ear and grain characters of maize in cold area

Discussion

Effects of sowing periods on growth and physiological morphology of maize in cold area

In a fixed ecological environment, the sowing date was one of the cultivation factors that affected the growth and development of maize (Luet al., 2007). The change of sowing date would affect the environmental conditions (including light, temperature, water, air, etc.) of maize in different growth stages, and has a significant impact on the growth and development of maize, most studies had shown that the growth period of maize had been shortened after the sowing period was delayed (Donget al.,2012; Andrade and Cirilo, 1994). This was slightly different from the results of this study, this experiment found that in the cold northeast area, the whole growth period would be shortened by 0.42 to 1 day every time the sowing date was delayed by an average of 1 day during the two-year period. However, the number of growing days during the jointing-big horn period of maize had increased. This might be due to the postponed sowing period, which made the temperature of the crop in the vegetative growth stage higher, faster growth and significantly shorter growth period (Donget al.,2012), but the nutrient accumulation was still insufficient at this time to ensure later tasseling and female ear differentiation, to supplement nutrition by extending the growth days of maize jointing-flare period (Luo and Xia, 2005). In this experiment, the plant height and ear height of maize showed an increasing trend with the postponement of the sowing date, and the plant height and ear height showed obvious synergistic effects. The later the sowing date, the higher the plant height and ear height, which increased the risk of lodging; at the same time, the dry matter quality of a single plant was also low, which might have a lot to do with the short growth period and fast growth process of the late sowing treatment (Donget al.,2020). Dry matter quality was the material basis for the formation of grain yields, and increasing the amount of dry matter accumulation was beneficial to increase grain yield (Luet al., 2011). In this study, the dry matter accumulation of maize in T4 treatment was the highest, and its dry matter accumulation was significantly higher than that of other five treatments in the big horn period, and the maize yields in T4 treatment was the highest, indicating that sowing in this period could better utilize rain heat resources (Donget al., 2019).

Effects of sowing periods on kernel quality of maize in cold area

Different sowing dates also had a significant impact on maize quality (Caoet al., 2013). With the postponement of the sowing date, the protein contents of maize kernels showed a downward trend. The protein content of maize kernels under T1 treatment was significantly higher than that of T5-T6 treatments, while the crude starch content of maize kernels under T6 treatment was significantly higher than that of T1-T4 treatments. Previous studies believed that under suitable sowing date treatments, the weather conditions during maize filling period had a significant impact on maize quality. Generally, the maize filling period was mid-August, after maize pollination, the effective accumulated temperature of ≥10℃ was reached, above 2 750℃, it was conducive to the accumulation of protein content (Chenet al., 2006), which was consistent with the results of this study.

T4 treatment with higher grain protein content had lower starch content. On the contrary, T6 treatment with lower protein content had higher starch content, which indicated that the protein and starch content in maize grains were significantly negatively correlated (Hanet al., 2010), indicating the maize grain filling process. There was a mutually restrictive relationship among various nutrients in the protein, and the accumulation of protein would inhibit the formation of starch (Liet al., 2010). Therefore, postponing the sowing date would promote the accumulation of starch in maize kernels, but inhibit the accumulation of protein.

Effects of sowing periods on yields, ear and grain characters of maize in cold area

Different sowing dates had significant effects on maize ear and grain traits and yields. A large number of studies had shown that delays in sowing dates reduce maize yield (Nieet al., 2013); Liuet al. (2009) had shown that sowing dates had significant effects on yield; the study concluded that the number of grains per ear and the weight of 100 grains vary significantly with the sowing date (Luo and Xia, 2005). This study showed that the yields increased first, and then decreased with the postponement of the sowing date, the sowing date mainly affected the yields through the weight of 100 seeds. Therefore, a proper postponement of the sowing date would help increase maize yields, but too late sowing would be detrimental to the late growth of maize, thereby reducing maize yields.

Conclusions

Relevant studies had shown that climate changes had different degrees of impacts on the quality and yields of spring maize. Adjusting the sowing date was an effective mean to coordinate crop growth and matching of light and heat resources. Heilongjiang Province in the cold area was the main producing area of maize. Therefore, the physiological characteristics and quality indicators of maize were measured through six different sowing date treatments to define the most suitable sowing date range in Harbin City. In summary, Harbin City was located in the middle and high latitudes. Sowing in the early May could maximize the growth and development of maize, which was beneficial to make full use of natural resources, such as light, temperature, water and climate. Therefore, in order to obtain high-starch and high-oil maize could be planted around May 18, in order to ensure the quality and yields of maize in Harbin City, the most suitable sowing time range from May 4th to May 11th could be chosen as sowing time. At the same time, the appropriate sowing period should also consider the spring soil moisture and other issues. It was expected to provide guarantees for the growth and development of maize and high-quality and high efficiency production and improve economic benefits.