The Korean Journal of Crop Science. December 2020. 477-484
https://doi.org/10.7740/kjcs.2020.65.4.477

ABSTRACT


MAIN

  • INTRODUCTION

  • MATERIALS AND METHODS

  •   Study field characteristics

  •   Fertilizer application and crop cultivation

  •   Soil and statistical analyses

  • RESULTS AND DISCUSSION

  •   Soil nutrient content

  •   Growth of first cropping

  •   Growth of second cropping

INTRODUCTION

Most of Korea’s edible corn is made up of waxy corn and was grown in about 15,000 ha in 2019 (MIFAFF, 2019). Generally, the cultivation of waxy corn is conducted in the form of sowing in April and harvesting in mid-July and late July, so the harvest is concentrated in the summer, causing frequent price falls due to large quantity (Kim et al., 2014).

Many studies have been conducted on the timing of sowing to prevent such harvesting concentration. Park et al. (1987) showed that waxy corn exhibited a tendency to decrease in yield due to faster transition from vegetative growth to reproductive growth when the seeding period was late. In addition, the yield of waxy corn was reduced in terms of sowing on May 27th compared to April 15th when it was grown in Hongcheon, Gangwon-do (Yoon et al., 1999) although the critical sowing period may be delayed due to recent temperature increases. Global warming is a risk factor for deepening weather disasters, including pests; on the other hand, it is also a window of opportunity due to the increased period of crop cultivation. Because the period of growth of vegetable waxy corn is relatively short, it is possible to establish the double cropping system, which is expected to increase the utilization rate of land and to improve income.

However, the lower yield and marketability of vegetable waxy corn have been pointed out as problems due to the lack of technology for the cultivation of a double cropping system (Jung et al., 2012). The present method of cultivation in the double cropping system of the newly developed and distributed waxy corn has diversified its harvest time compared with the past method. Recent studies have shown that the timing of vegetable waxy corn supply has been extended from the early part of July to the early and middle part of October by mens of advancing the sowing time of the first cropping and delaying the sowing time of the second cropping (Jung et al., 2012; Kim et al., 2000).

In addition, the use of slow-releasing fertilizer once when growing double cropping waxy corn can reduce labor and environmental pollution due to low nitrogen loss.

In previous studies, the use of slow-releasing fertilizers increased the plants’ dry weight by increasing the use of nitrogen over more effective fertilizers (Choi et al., 2002).

In the study of the crop application of slow-releasing fertilizer, Yoo et al. (1998) and Chi et al. (2013) reported that the rate of nitrogen utilization was the highest at 50 days after the nitrogen treatment and that nitrogen was slowly released based on the latex-coated fertilizer.

Therefore, this study was conducted to investigate the effects of the slow-releasing fertilizer and seeding date on waxy corn propagated through double cropping without tillage. It also compared the ear yields according to the sowing date with “Mibaek 2” as a test variety in order to investigate the effect of the slow-releasing fertilizers.

MATERIALS AND METHODS

Study field characteristics

This experiment was conducted from 2018 to 2019 at the Chungcheongbuk-do Agricultural Research and Extension Services, and the test waxy corn hybrid was called “Mibaek 2”, a crop mostly cultivated as an early maturing type in the central region of Korea. “Mibaek 2” was sown for first cropping on March 25th, April 5th, and April 15th and for second cropping on July 5th, July 15th, and July 25th six times overall, at 10-day intervals. The slow-releasing fertilizer employed in this study was Latex Coating Urea (LCU), which was used as a full-scale fertilizer once before vinyl mulching.

Fertilizer application and crop cultivation

The level of distribution was different depending on the soil testing-based recommendation (STBR), which was N-P2O5-K2O = 16-3-3 kg/10a. The fertilizer level of the control was N- P2O5-K2O = 30-3-6 kg/10a, with nitrogen separated twice in the first cropping and second cropping. 50% addition to soil testing- based, recommended fertilization (150% STBR) increased the fertilizer level by 1.5 times, while 100% addition to soil testing- based, recommended fertilization (200% STBR) increased the fertilizer level by 2 times. With the aim of producing 6,600 plants per 10a, the sowing was set to 60 cm in width and 25 cm in length, while planting density was maintained uniformly by thinning out and with only one head left in the growing season. The placement of the test tools was tested through a three- repeated split-plot arrangement method, with the seeding dates as a main plot and fertilizer levels as a sub plot. Plant height was investigated in accordance with the Agricultural Science and Technology Research and Analysis Standards of the Rural Development Administration about a week before the harvest. The characteristics of ears were averaged about 26 days after silking by way of harvesting the waxy corn ears, removing the leaves, and investigating 10 pieces of ear weight, ear length, seed set ear length, and ear diameter.

Soil and statistical analyses

Soil samples were taken by a hand spiral auger at growing season. Collected soil samples were air-dried at room temperature for chemical quantification. Soil pH and EC were determined from the 1:5 of soil/water suspension using a pH/conductivity meter (Horiba, F-54). Available phosphorus was analyzed by Lancaster method employing continuous flow spectrometer (Bran + Luebbe Analytics, Autoanalyzer 3). The 1N-NH4OAC (adjusted pH 7.0) was utilized to extract exchangeable cations (K, Ca, Na and Mg) and quantified by inductively coupled plasma spectroscopy (PerkinElmer, Optima 3300DV). Experimental data were statistically analyzed through the analysis of variance (ANOVA) with the Raleigh program (SAS Inc. ver. 9.2, USA).

RESULTS AND DISCUSSION

Soil nutrient content

Prior to the test, the pH of the soil was slightly acidic at 6.5, and the organic content was 23g/kg, showing the distribution of the average organic content in the central region (Table 1). After the test, the soil showed an increase in pH value and soil salinity compared to the period prior to the test.

Table 1.

Physical and chemical properties of soil after first cropping at 115 days after fertilization.

Sowing date Fertilization method pH (1:5) OM (g/kg) P2O5 (mg/kg) K Ca Mg CEC Na EC (dS/m)
----(cmol[+]/kg)----
Pre-test 6.5 23 229 0.32 8.4 2.0 11.9 0.1 0.26
March 25th Control 6.6 21 217 0.29 7.2 1.6 12.1 0.1 0.54
STBR 6.8 22 215 0.38 6.5 2.0 11.9 0.1 0.93
150% STBR 6.9 22 228 0.38 6.6 2.0 12.5 0.1 1.36
200% STBR 7.1 24 246 0.41 7.0 2.2 12.4 0.1 1.53
Mean 6.9 22 227 0.37 6.8 2.0 12.2 0.1 1.09
April 5th Control 6.5 20 225 0.43 6.4 1.9 11.1 0.1 0.78
STBR 6.9 22 231 0.47 6.3 1.8 12.2 0.1 1.21
150% STBR 6.8 22 243 0.50 6.6 2.0 12.2 0.1 1.23
200% STBR 7.0 24 253 0.55 6.7 2.0 12.5 0.1 1.26
Mean 6.8 22 238 0.49 6.5 1.9 12.0 0.1 1.12
April 15th Control 6.6 17 209 0.43 6.4 1.8 11.9 0.1 1.13
STBR 6.6 17 220 0.48 6.5 1.8 11.6 0.1 1.16
150% STBR 6.6 18 224 0.48 6.6 1.7 11.3 0.1 1.27
200% STBR 6.6 18 241 0.51 6.8 1.7 13.4 0.1 1.35
Mean 6.6 18 224 0.48 6.6 1.8 12.1 0.1 1.23

Control : 2 split application of urea (N:P2O5:K2O=30:3:6)

STBR : 1 application of soil testing-based recommendation rates (N:P2O5:K2O=16:3:3)

150% STBR : 1 application of 50% add to soil testing-based recommendation rates (N:P2O5:K2O=24:4.5:4.5)

200% STBR : 1 application of 100% add to soil testing-based recommendation rates (N:P2O5:K2O=32:6:6

Growth of first cropping

There were no differences in the tasseling dates and silking dates according to the fertilizer levels but the days from planting to emergence was shortened as the sowing period was delayed (Table 2). Thus, the sowing on April 15th shortened the days to silking by 7 days compared to the sowing on April 5th and by 12 days compared to sowing on March 25th.

It was thought that this was due to the delay in sowing period, which led to the arrival of the silking date of waxy corn in the range of 1,400-1,420°C, and that these results were consistent with the findings of Kim et al. (2014) who reported that silking dates from the seeding dates of the “Ilmichal” varieties were about 70 to 78 days.

Table 2.

Tasseling and silking date of “Mibaek 2” according to sowing date and fertilizer rates in the first cropping.

Sowing
date
Fertilization
method
Rate (kg 10a-1) Tasseling
Date
Silking
Date
Days to
silking
N P2O5 K2O
March 25th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
6.08
6.08
6.08
6.08
6.11
6.11
6.11
6.11
77
77
77
77
Mean 6.08 6.11 77
April 5th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
6.13
6.13
6.13
6.13
6.16
6.16
6.16
6.16
72
72
72
72
Mean 6.13 6.16 72
April 15th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
6.16
6.16
6.16
6.16
6.19
6.19
6.19
6.19
65
65
65
65
Mean 6.16 6.19 65

Refer to Table 1.

Culm height and ear length had no statistical significance, but the kernel set length was the highest at 123 cm in the sowing date on April 5th (Table 3). In addition, the seed set ear length was 17.8 cm long in the sowing date on April 5th and April 15th, indicating that the later the sowing period is, the more marketable it becomes.

Table 3.

Culm and ear length of “Mibaek 2” according to sowing date and fertilizer rates in the first cropping.

Sowing
date
Fertilization
method
Rate (kg 10a-1)
Culm
length
(cm)
Kernel set
length
(cm)
Ear
length
(cm)
Seed set
ear length
(cm)
N P2O5 K2O
March 25th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
200
209
216
217
95
100
101
106
21.1
20.6
20.5
20.5
18.2
16.5
16.8
16.8
Mean 211 101 20.7 17.1
April 5th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
227
233
234
237
120
122
125
125
20.5
20.4
20.6
20.8
18.0
17.8
17.4
18.1
Mean 233 123 20.6 17.8
April 15th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
232
233
236
240
118
118
119
120
20.3
20.9
20.3
20.8
17.1
18.1
17.8
18.2
Mean 235 119 20.6 17.8
F value
Two-way ANOVA Planting date (A) 1.02 23.67** 0.32 7.52*
Fertilizer (B) 0.73 1 0.94 0.60
A x B 0.99 0.35 2.33 1.78

Refer to Table 1.

ns, *, **, *** ; Nonsignificant of significant at p=0.05, 0.01 or 0.001 by ANOVA.

Nielsen (2007) showed that the grain line number of corn had a strong genetic effect, while the ear length and the seed set ear length had a great influence on the cultivation environment.

This test also showed that the kernel set length and seed set ear length varied depending on the sowing time.

Culm height, kernel set length, ear length, and seed set ear length tended to elongate in 100% addition to soil testing-based recommended fertilization, but there was no statistical significance. Park et al. (2015) reported that as nitrogen content increased, chlorophyll content increased until the late stages of corn production, resulting in high light utilization, whereas;Lim et al. (2014) showed that there was no significant difference in culm height, kernel set length, and ear length in the treatment zones of 18 kg and 36 kg of nitrogen per 10a.

However, despite the increased volume of the fertilizer, the fact that it did not show much difference in growth was attributed to the ingredients of the slow-release fertilizer being slowly eluted and having no significant impact on the first cropping production.

The weight of marketable ear was the heaviest in the sowing date on April 5th, although ear weight and number of marketable ears per 10a showed no statistical significance (Table 4).

Table 4.

Ear and marketable ear characteristics of “Mibaek 2” accor ding to sowing date and fertilizer rates in the first cropping.

Sowing date Fertilization
method
Rate (kg 10a-1) Ear
diameter
(mm)
Ear
weight
(g)
Wt. of
marketable ears
(kg/10a)
No. of
marketable ears
(ea/10a)
N P2O5 K2O
March 25th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
42.2
40.3
40.2
40.3
273
269
277
297
1,704
1,848
1,790
1,854
6,250
6,250
6,458
6,875
Mean 40.8 279 1,799 6,458
April
5th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
41.4
42.0
44.0
43.9
289
285
297
297
1,990
1,898
1,921
1,979
6,875
6,458
6,667
6,667
Mean 42.8 292 1,947 6,667
April
15th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
43.8
45.1
43.6
44.2
276
294
266
287
1,725
1,550
1,615
1,838
6,250
5,625
5,833
6,250
Mean 44.2 281 1,682 5,990
F value
Two-way ANOVA Planting date (A) 14.18* 0.39 20.75** 5.56
Fertilizer (B) 0.16 1.24 3.48** 1.65
A x B 3.0* 0.93 2.00 1.55

Refer to Table 1.

ns, *, **, *** ; Nonsignificant of significant at p=0.05, 0.01 or 0.001 by ANOVA.

The number of marketable ears will be the most important factor in income, as early harvests can get high prices while corn sales are most common in 30 single-sack units.

Therefore, it was thought that the sowing time for the first cropping propagated through double cropping system in the central region of the country could be advanced by March 25th.

Early April is reported to be the economic sowing limit of the super sweet corn hybrid in southern Korea (Yang et al., 2007) while it is mid-May in central and northern Korea (Sim, et al., 2019).

Therefore, given that sowing early at an appropriate time increases the number of marketable ears compared to late sowing, the sowing time could be advanced with global warming if conditions are not to advance sowing to an extreme degree.

Moreover, due to the increase in the fertilizer levels, there was no statistical significance in the ear weight and the number of marketable ears, but the weight of marketable ear was the highest when there is in the 100% addition to soil testing-based, recommended fertilization.

Growth of second cropping

There was no difference in days in terms of tasseling and silking according to the fertilizer levels but the days from planting to emergence was shortened as the sowing period was delayed (Table 5).

Table 5.

Tasseling and silking date of “Mibaek 2” according to sowing date and fertilizer rates in the second cropping.

Sowing
date
Fertilization
method
Rate(kg 10a-1) Tasseling
Date
Silking
Date
Days to silking
N P2O5 K2O
July 5th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
8.17
8.17
8.17
8.17
8.21
8.21
8.21
8.21
52
52
52
52
Mean 8.17 8.21 52
July 15th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
8.25
8.25
8.25
8.25
8.28
8.28
8.28
8.28
44
44
44
44
Mean 8.25 8.28 44
July
25th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
9. 4
9. 4
9. 4
9. 4
9. 5
9. 5
9. 5
9. 5
42
42
42
42
Mean 9. 4 9. 5 42

Refer to Table 1.

In this test, the longer the sowing date was delayed, the faster the silking date was. This is consistent with the report of Jung et al. (2012) which stated that the sooner the seeding period was, the faster it was by 33 days for the “Ilmichal” variety.

The possible reason for this decrease in silking days may be the presence of differences in photoperiod and temperature among sowing dates.

As the sowing date was delayed, the culm height, kernel set length, ear length, and seed set ear length were shortened, with the decline being the largest in the sowing date on July 25th, the latest sowing date (Table 6).

Table 6.

Culm and ear length of “Mibaek 2” according to sowing date and fertilizer rates in the second cropping.

Sowing
date
Fertilization
method
Rate (kg 10a-1) Culm
length
(cm)
Kernel set
length
(cm)
Ear
length
(cm)
Seed set
ear length
(cm)
N P2O5 K2O
July
5th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
172
174
177
180
70
72
73
72
18.4
18.4
18.7
18.7
14.9
15.0
15.1
15.4
Mean 176 72 18.6 15.1
July
15th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
171
169
174
176
71
69
72
72
16.9
17.0
17.0
17.2
14.3
14.3
14.5
14.5
Mean 173 71 17.0 14.4
July 25th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
159
158
164
166
68
67
70
71
16.2
16.4
16.4
16.5
11.8
11.8
12.0
12.3
Mean 162 69 16.4 12.0
F value
Two-way ANOVA Planting date (A) 152.9** 21.93** 189.2** 24.58**
Fertilizer (B) 56.12 18.58 0.07 0.15
A x B 2.02 4.71** 0.32 0.15

Refer to Table 1.

ns, *, **, *** ; Nonsignificant of significant at p=0.05, 0.01 or 0.001 by ANOVA.

These results are due to the shorter day effect of late sowing during the growth period of the waxy corn and supported by Jung et al. (2012) who reported that growth temperature was decreased during the ripening stage of second cropping.

In particular, the large decrease in the ear length and seed set ear length in the sowing date on July 25th was thought to have a significant impact on the decline in the marketability of waxy corn.

The culm length and the kernel set length tended to increase as the fertilizer levels increased, but there was no statistical significance, so it was thought that a one-time, slow-releasing fertilizer application could result in a reduction in labor force without any difference in growth compared with the conventional distribution. The characteristics of culm length and ears differed greatly in the first cropping and the second cropping, showing 69-83% of the previous cropping in culm length, 80-90% in ear length, and 67-88% in seed set ear length.

In the second cropping, growth occurred under higher temperatures, with associated reductions in the duration of growing cycles (Jung et al., 2012; Kim et al., 2014).

Also, as the sowing date was delayed, the diameter of the ears was reduced, and the weight of marketable ears and the number of marketable ears decreased. At the sowing date of July 25th, especially, the decline was significant (Table 7).

Table 7.

Ear and marketable ear characteristics of “Mibaek 2” according to sowing date and fertilizer rates in the second cropping.

Sowing
date
Fertilization
method
Rate (kg 10a-1) Ear
diameter
(mm)
Ear
weight
(g)
Wt. of
marketable ears
(kg/10a)
No. of
marketable ears
(ea/10a)
N P2O5 K2O
July 5th Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
43.8
42.6
43.5
43.6
215
217
211
214
1,069
949
1,010
1,207
4,653
4,514
4,861
5,625
Mean 43.4 214 1,059 4,913
July
15th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
38.3
39.9
39.1
38.9
216
201
217
219
590
680
665
697
3,381
3,542
3,750
4,075
Mean 39.1 213 658 3,687
July
25th
Control
STBR
150% STBR
200% STBR
30.0
16.0
24.0
32.0
3.0
3.0
4.5
6.0
6.0
3.0
4.5
6.0
38.8
37.9
38.9
37.8
186
197
192
204
483
483
522
536
2,431
2,292
2,635
2,639
Mean 38.4 195 506 2,499
F value
Two-way ANOVA Planting date(A) 48.0** 6.80 104.6** 134.2**
Fertilizer(B) 0.26 0.60 3.54** 4.57**
A x B 1.16 0.89 1.84 0.68

Refer to Table 1.

ns, *, **, *** : Nonsignificant of significant at p=0.05, 0.01 or 0.001 by ANOVA.

Statistical analysis of the data revealed that marketable ear yield of waxy corn was significantly affected by sowing date and fertilizer. Waxy corn plated on July 5th produced more yild (1,059 kg/10a), while the July 25th sowing produced the lowest marketable ear yield (506 kg/10a).

In particular, since the income of waxy corn is determined by the number of marketable ears (Lee & Kim, 1986), it was thought that the sowing of the second cropping in the cultivation of double cropping without tillage in the central region of the country should be completed by July 15th to secure the yield . The diameter of the ear and the average ear weight were not statistically significant, depending on the difference in the levels of the fertilizers.

However, the weight of marketable ears and the number of marketable ears were high in the 100% addition to soil testing- based recommended fertilization. It was also thought that it would be appropriate to add 100% to the soil testing-based recommendation for slow-releasing fertilizer. Lim et al. (2014) reported that as the ratio of nitrogen increases, photosynthesis also increases, showing a defined correlation with the content of follicle nitrogen. In this test, the weight of marketable ears and the number of marketable ears differed significantly between each treatment due to an increase of up to 32kg of nitrogen per 10a.

Therefore, it was thought that 100% addition would not only reduce the labor force, but also increase the number of marketable ears, which would be advantageous for farming households.

However, since the effects of the fertilization are thought to vary depending on weather and soil conditions, it was thought that additional fertilizer spraying in the double cropping of waxy corn should be determined by the examination of the growth of the waxy corn.

References

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