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Agronomic Traits and Forage Production in a Mixed-Planting with Corn for Forage Soybean Cultivars, Chookdu 1 and Chookdu 2
Plant Breed. Biotech. 2019;7:123-131
Published online June 1, 2019
© 2019 Korean Society of Breeding Science.

Jin-Dong Seo, Hyun Jo, Minsu Kim, Jong Tae Song, Jeong-Dong Lee*

School of Applied Biosciences, Kyungpook National University, Daegu 41566, Korea
Corresponding author: *Jeong-Dong Lee, jdlee@knu.ac.kr, Tel: +82-53-950-5709, Fax: +82-53-958-6880
These authors contributed equally.
Received April 10, 2019; Revised April 27, 2019; Accepted April 27, 2019.
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract

Soybean [Glycine max (L.) Merr.] cultivar ‘Chookdu 1’ (registration number: No. 7159) and ‘Chookdu 2’ (registration number: No. 6758) were developed as forage soybean cultivars at Kyungpook National University, Republic of Korea. They were grown in tests over three years and compared with a commercial seed cultivar for seed yield and forage productivity planted in the same row in mixed plantings with corn. Chookdu 1 and Chookdu 2 are tall, indeterminate growth habit selections from a cross between wild soybean (Glycine soja Sieb. & Zucc.), ‘PI 483463’, and cultivated soybean, ‘Hutcheson’ (PI 518664). The plant height of Chookdu 1 and Chookdu 2 were 80.9 cm and 81.4 cm, respectively, compared to 54.7 cm for the ‘Pungsannamul’ commercial seed check. The three-year seed yield of Chookdu 1 and Chookdu 2 was 2.0 and 2.2 t/ha, respectively, and not significantly different from Pungsannamul at 2.4 t/ha. Of the two cultivars Chookdu 2 averaged the most total forage fresh weight (65.0 t/ha). The three year mean forage yield of mixed-planting of corn and Chookdu 2 and Chookdu 1 was 10.4% and 3.8% greater, respectively, than corn monoculture. Results show Chookdu 1 and Chookdu 2 are suitable soybean cultivars for mixed planting in the same row with corn to improve forage yield. They should be useful as parents to use in breeding to develop forage-type soybeans of high quality and yield for use in livestock feed.

Keywords : Soybean, Mixed-planting, Forage soybean, Forage yield and quality
INTRODUCTION

Soybean [Glycine max (L.) Merr.] is an important source of animal protein due to its high protein content and other valuable nutrients. Soybean was first used in North America as a forage crop rather than as a seed crop. Hacklman (1924) reported that soybean, comparing to several other crops was a superior, annual, nitrogenous seed and hayproducing plant. However, World War II impeded oil imports from East Asia, and ever since soybean has been grown for its oil and high protein meal from the residue left after oil extraction (Upfold and Olechowski 1988). Recent data indicates that seventy percent of the world’s protein meal consumption was obtained from soybean followed by rapeseed (12%), sunflower (6%) and cotton seed (5%) (SoyStats 2018, http://www.soystats.com). Soybean has become a highly important oil and protein world crop.

Because of increased corn (Zea mays L.) use in silage and reduced use of alfalfa (Medicago sativa L.), USDA-ARS began a breeding program to increase the use of soybean as a forage in crop rotations to improve forage quality. As a result of this research, forage soybean cultivars, ‘Derry’, ‘Donegal’ and ‘Tyron’ (maturity group V, VI and VII, respectively) were released (Devine and Hatley 1998; Devine et al. 1998a, 1998b). Forage soybean cultivars, Derry, Donegal and Tyron produced an average of 23%, 66% and 8%, respectively, more total dry matter per hectare than a grain-type cultivar. In addition, they reached a height of 1.5 to 2 m, to compete well for solar radiation when intercropped with taller crops like corn or sorghum.

Since soybean is a short day and photoperiod sensitive crop, soybean biomass is influenced by photoperiod. As photoperiod response increases, a soybean cultivar generally produces more vegetative biomass matter, greater internode elongation and leaf expansion (Johnson and Major 1979; Caffaro and Nakayama 1988). In addition, the biomass of soybean is influenced by growth stage at time of harvest. The greatest dry matter of soybean is at full seed stage (R6) (Fehr and Caviness 1977). However, the total protein content of soybean continues to increase until physiological maturity (R7) (Willard 1925; Good 1942; Ritchie et al. 1982). A suitable developmental stage for the optimal biomass and quality of forage soybean is at the full seed stage (R6) (Fehr et al. 1971; Heitholt et al. 2004). In general, forage soybean can be harvested a month earlier than soybean harvested for grain. For highest yield and quality, the optimum developmental stage for forage soybean in a mixed corn planting should coincide with the time of corn harvest.

Corn and sorghum [Sorghum bicolor (L.) Moench] are widely used as forage crops. However, there is less than optimum forage protein for animals when corn or sorghum is fed alone. Legume crops such as alfalfa and soybean ensiled with corn or sorghum increased protein intake (Rotz et al. 1999; Blount et al. 2013). Thus, intercropping of cereal and legume crops for forage is widespread among farmers in the world. Intercrop systems can improve the quality and yield stability of a forage crop compared to a monocrop system (Willey 1979; Horwith 1985; Fukai and Trenbath 1993).

Intercropping is the simultaneous growing of two or more crops in a field. The crops of an intercropped system do not have to be planted and/or harvested at the same time. However, the crops in the same field should be grown simultaneously for most of their growth periods. Generally, one crop of an intercropping system is economically more important than the other. Depending on planting patterns, there are numerous types of intercropping system such as mixed intercropping (crops planted without any pattern), row intercropping (crops planted together in single rows) and strip intercropping system (crops planted in alternate multiple rows).

Soybeans are not only a high protein forage crop for livestock, but also have the ability to fix nitrogen to improve soil fertility. Thus, soybean is beneficial to corn when intercropped with soybeans (Sheaffer and Seguin 2003; Sinclair and Vadez 2012). Several studies concluded that intercropping soybean and corn had higher forage production and protein content than corn as a monocrop (Ahmed and Rao 1982; Putnam et al. 1985; Toniolo et al. 1987; Marchiol et al. 1992; Seo et al. 2019). The dry matter yield of intercropped corn and soybean was 89% greater than monocropped soybean and 4% more than mono-cropped corn (Marchiol et al. 1992). Herbert et al. (1984) concluded that all but one intercrop of corn and soybean in various planting patterns produced more dry matter yield and total protein per hectare than monocropped corn. In addition, other studies concluded that a mixed planting of corn and soybean on the same row produced more and better forage quality than monocropped corn (Song et al. 2017; Seo et al. 2019). In one study, there was a 11–51% increase in crude protein content when soybean was intercropped with corn (Putnam et al. 1985). Crude protein content in soybean forage declined from R1 to R3, remained constant between R3 and R5, and increased from R5 to R7 (Hintz et al. 1994). Generally, the crude protein content in soybean hay ranges from 12 to 14% for stems, 19 to 20% for leaves, and 12 to 27% for pods depending on the soybean reproductive stage (Miller et al. 1973).

To date, little has been reported for soybean cultivars bred for forage evaluated in a mixed planting of corn and soybean planted in the same row. In this study, we evaluated forage-type cultivars Chookdu 1 and Chookdu 2 for 1) seed yield and 2) forage yield intercropped with corn planted on the same rows. We evaluated the agronomic traits, fresh weight, forage yield and seed yield of forage cultivars Chookdu 1 and Chookdu 2 over three years.

MATERIALS AND METHODS

Parental lines and pedigree information of forage soybean cultivars

Wild soybean PI 483463 and cultivated soybean Hutcheson (PI 518664, Maturity Group V) (Buss et al. 1988) were hybridized to develop the forage soybean cultivars, Chookdu 1 and Chookdu 2. PI 483463 is a maturity group III obtained from the USDA soybean Germplasm Collection. Hutcheson was developed by the Virginia Agricultural Experiment Station (Buss et al. 1988). The hybridization of PI 483463 and Hutcheson was performed in a greenhouse in 2006. F1 seed were planted in field during 2006 summer. Single Seed Descent method was used to advance generation till F4 in green house and field. Ten plants of two lines, W4 (Chookdu 1) and W11 (Chookdu 2) were selected from an F5:7 progeny row in 2010. Seeds of each of the 10 selected plants of W4 and W11 were grown in plant rows and bulk harvested in 2011 and seed used for subsequent yield trials and forage production tests.

Evaluation for seed yield and agronomic traits

Forage soybean, Chookdu 1 and Chookdu 2, and a check cultivar, Pungsannamul were grown in a preliminary yield test with three replications in Gunwi (36°07’N, 128°38’E), South Korea in 2013. In the preliminary yield tests in 2013 (Supplemental Table 1), Chookdu 1 and Chookdu 2 soybeans were identified as having high seed yield as well as having other desired agronomic characteristics compared to the check cultivar. Advanced yield performance was tested at Gunwi, South Korea over three years (2014, 2015 and 2016).

The experimental design was a randomized complete block (RCB) with three replications. Yield plots consisted of four rows with 4 m long spaced 70 cm apart. Seeds were planted by hand in hills within the rows spaced 15 cm apart and thinned to a final stand of two seedlings per hill. Planting dates were June 27th in 2014, June 16th in 2015, and June 9th in 2016. The two center rows of each four-row plot were harvested for seed yield at full maturity (R8). Ten randomly selected plants per plot at maturity were used to measure plant height (length in cm from the base of the stem at ground level to the tip of the top pod), number of branches per plant, number of nodes per plant, weight of 100 seeds, and number of pods per plant. Agronomic performance such as growth habit, flower color, pubescence color, seed coat color, and hilum color were also recorded.

Forage yield trials planted with corn

Soybean and corn (cultivar Kwangpyeongok, Moon et al. 2001) were planted by hand in hills within the same row each at 10 cm intervals. Seeds were planted in plot rows 4 m long with a spacing of 70 cm spacing between rows. The final stand in hills was one corn plant and three soybean plants. Fertilization and time of forage harvest were based on the recommendations for forage corn production (Seo et al. 2019).

The experimental design was an RCB with three replications. The middle two rows were collected for measuring fresh weight of the mixed planting of corn and soybean. The fresh weigh was used as a parameter for forage yield. The mixed-planting of corn and soybean were harvested separately at the recommended stage for forage corn which is approximately 120 days after corn germination. The forage yield test for the mixed-planting of corn was conducted in Gunwi, South Korea over three years (2014, 2015 and 2017). Forage yield was measured for three treatments which included mixed plantings of corn with each forage cultivar, Chookdu 1 and Chookdu 2, and the monocropped corn. The planting dates were May 2nd in 2014, May 15th in 2015, and April 27th in 2017.

Data analysis

Mean difference among the cultivars were analyzed by Fisher’s Least Significant Difference (LSD) test at P = 0.05. All statistical analyses in this study were conducted using SAS 9.2.

RESULTS

Chookdu 1, Chookdu 2 and a control soybean cultivar, Pungsannamul were evaluated for the agronomic characteristics including growth habit, 100-seed weight, and colors of flower, pubescence, seed coat, cotyledon, and hilum, shown in Table 1. Chookdu 1 and Chookdu 2 have indeterminate growth habit with purple flowers and tawny pubescence. Harvested seeds of Chookdu 1 are round with yellow seed coats color and brown hilum (Fig. 1C), whereas Chookdu 2 are black seeded with black hila (Fig. 2C). Both Chookdu 1 and Chookdu 2 have yellow cotyledons.

The variation of yield related traits and grain yield of Chookdu 1, Chookdu 2 and Pungsannamul are shown in Table 2. In 2014, the mean plant height, and number of nodes of Chookdu 1 and Chookdu 2 were statistically higher than those of Pungsannamul. However, 100-seed weight of Chookdu 1 and Chookdu 2 were statistically lower than that of Pungsannamul. The number of branches of Chookdu 1 was significantly greater than that of Chookdu 2 and Pungsannamul. There were no significant differences for number of pods and grain yield in 2014. The grain yield of Chookdu 1, Chookdu 2, and Pungsannamul were 2.2, 2.6, and 2.5 t/ha, respectively.

In 2015, Chookdu 2 had the tallest plants (72.7 cm), which was statistically taller than Pungsannamul (52.5 cm). Number of nodes and branches were significantly different among cultivars with Chookdu 1 averaging the most nodes per plant. Although the number of pods of Chookdu 1 was greater than Chookdu 2 and Pungsannamul, differences were not significant among the three soybean genotypes. The 100-seed weight was 6.9, and 4.8 g for Chookdu 1 and Chookdu 2, respectively in 2015. Seed size (12.0 g) for Pungsannamul was significantly larger than those of Chookdu 1 and Chookdu 2. The grain yield of Chookdu 2 (2.4 t/ha) and Pungsannamul (2.8 t/ha) were not significantly different, but Chookdu 1 (1.9 t/ha) was statistically lower in seed yield than the other two cultivars. In 2016, there were significant differences among cultivars for the plant height, number of nodes, branches and pods, but differences whereas not significant for 100-seed weight and grain yield.

Across the three-year mean, plant height (Table 2) of Chookdu 1 and Chookdu 2 (80.9 cm and 81.4 cm, respectively) were significantly taller than Pungsannamul (54.7 cm). The three-year averages for number of nodes of Chookdu 1 and Chookdu 2 were 20.0 and 18.6, respectively, and statistically greater than Pungsannamul (15.5). The three-year mean for number of branches of Chookdu 1 (7.5) and Chookdu 2 (5.9) were significantly higher than that of check cultivar, Pungsannamul (4.6). The number of nodes and branches of Chookdu 1 were greater than Pungsannamul in all three years. The 100-seed weight over the three years was 7.3, 8.2 and 11.2 g for Chookdu 1, Chookdu 2 and Pungsannamul, respectively and significantly different among cultivars. Although the mean seed yield over three years for Chookdu 1 and Chookdu 2 were lower than Pungsannamul, yield differences were generally not significant.

Forage yield for mixed planting of corn with Chookdu 1 and Chookdu 2, and monoculture corn control cultivar, Kwangpyeongok was measured in 2014, 2015 and 2017 (Table 3). In 2014, there were no significant differences for forage yield from mixed cropping with Chookdu 1 and Chookdu 2, and the corn monoculture. The total forage yield for mixed planting (corn + soybean) with Chookdu 1 and Chookdu 2 was 66.0 and 73.4 t/ha, respectively, and higher compared than corn monoculture with Kwangpyeongok (56.3 t/ha). Forage yield indexes for mixed planting with Chookdu 1 and Chookdu 2 were 117.2% and 130.4% of corn monocrop, respectively. There were no statistical differences for forage yield among cropping systems in 2015, and the forage yield indexes of mixed cropping with Chookdu 1 and Chookdu 2 were lower compared to Kwangpyeongok. In 2017, there were no differences for forage yield of monocropped corn and the intercropped corn with the two forage soybeans. The forage yield of corn was 59.8, 54.9, and 55.5 t/ha from the mixed planting with Chookdu 1, Chookdu 2 and corn monoculture, respectively. In 2017, the total forage yield for the mixed culture (corn + soybean) with Chookdu 1 and Chookdu 2 was 61.9 and 60.1 t/ha, which were significantly higher yield than the corn monoculture (55.5 t/ha). The yield index in 2017 of mixed culture with Chookdu 1 and Chookdu 2 was 111.6 and 108.4% of monocropped corn, respectively.

Averaged over the three years, there was no significant difference for the forage yield from mixed culture in this study compared with corn monoculture. However, total forage yield averaged 3–10% more forage when from mixed corn with Chookdu 1 and Chookdu 2 compared to monocropped corn.

DISCUSSION

The most popular annual summer forage crops in Korea are corn and sorghum x sudangrass hybrids, however, forage quality is not optimum because of low protein content. In addition, these forage crops deplete soil nutrients and require nitrogen and application of other nutrients to produce adequate forage yield. This can threaten maintenance of sustainable agriculture. Legumes are important crops in sustainable agriculture systems to provide nitrogen, soil stability and nutrient recycling. Thus, intercropping other crops with legumes has been used to improve sustainable crop production. In addition, intercropping systems improves forage yield stability as well as forage quality (Willey 1979; Horwith 1985; Fukai and Trenbath 1993; Asekova et al. 2014). However, dry matter yield from most intercrop planting patterns of corn and soybean were lower than that of corn monoculture (Herbert et al. 1984). Thus, it would be advantageous to develop soybean cultivars, especially for forage production and better adaptation to intercrop corn and soybean for forage.

There were several efforts to develop forage soybean cultivars. Forage soybean cultivars, Derry, Donegal, and Tyron were released in the US (Devine and Hatley 1998; Devine et al. 1998a, 1998b). Cho et al. (2003) evaluated forage yield and quality for grain soybean cultivars which developed in Korea and recommended several promising soybeans for forage production. Lee et al. (2014) reported the possibility of selecting forage soybeans from a population developed from a cross of a cultivated and wild soybean (G. soja). They found that several lines showed similar forage yield with better palatability and forage quality compared to cultivated soybean developed strictly for seed production. Recently, Seo et al. (2019) evaluated indigenous soybean lines from the germplasm collection of Rural Development Administration of Korea to select soybean lines for mixed cropping of corn and soybean planted in the same row. In a corn mixed cropping with selected soybean lines, forage yield increased about 19%, the silage protein content increased 1–2%, and overall silage quality increased compared with the forage from corn monoculture. They also suggested that the agronomic traits of soybean needed for mixed cropping with corn for forage planted on the same row are as follows: soybean should 1) have the ability to grow well under the corn canopy, 2) have lodging tolerance for ease of mechanical forage harvest, 3) develop to the full pod stage at the time of harvest for increased protein content, and 4) have no adverse effects on corn growth to maintain a high forage yield.

Wild soybeans grow naturally throughout in China, Korea and Japan, and have been used as forage for many centuries (Kulkarni et al. 2018). Wild soybeans are generally high in seed protein content and low in seed oil content which is advantageous for forage production. Vining growth habit is a unique trait in wild soybean, which may important for survival in wild environments like growing under species with large canopies. In this study, we used a wild soybean as a genetic source to develop forage soybeans. Two forage cultivars were selected from a population PI 483463 (G. soja) × Hutcheson (G. max). The progenies from this cross combination showed huge phenotypic variation for growth habit. Among them a breeding line W4 (Chookdu 1) had a slightly viny growth habit when planted late (late June to earl July) for seed production (Fig. 1C, 1D). However, when it was evaluated under mixed cropping with corn, it grew well under a corn canopy and climbed around 1.5 m on corn plants (Fig. 1A, 1B) depending on growing environments. Another a breeding line W11 (Chookdu 2) had more erect growth than Chookdu 1 when grown for seed production and in a mixed planting with corn (Fig. 2A, 2B). The forage cultivars viny growth habit under the corn canopy in the mixed-planting of corn within the same row were able to compete well for solar radiation and avoid ill-effects of shading from corn plants.

Previously, Song et al. (2017) used W4 (not mentioned in their manuscript but, provided by corresponding author of this manuscript) and corn for mixed cropping across 17 locations in Korea. They concluded that total forage yield and total digestible nutrients from corn-soybean intercropping (similar to mixed cropping in this article) were significantly higher than that of corn monoculture. Seo et al. (2019) also reported that when corn was mixed planted with Chookdu 1 and Chookdu 2 on the same row, the forage yield and silage quality were improved compared to corn monoculture. There were three independent studies for forage production tests using corn-soybean mixed planting on the same row. Our results showed that mixed cropping corn with Chookdu 1 and 2 was not quite as beneficial for forage production compared with the other two studies. This is likely due to different production techniques and use of a different corn cultivar. Therefore, in order to improve forage productivity, farmers need an adapted corn variety that responds favorably for improved forage production and production techniques in a mixed cropping system with soybean.

Mechanization for planting and harvesting is a key-point for the success of mixed planting corn and soybean for better forage production. It is desirable for farmers to plant corn and soybeans for mixed culture at the same time. The mixed planting of corn and soybean on the same row by sowing corn seed and then planting soybean seeds between corn plants is time-consuming and labor intensive, and results in extra costs. Ten (10) cm intervals separated the corn and soybean in the same row in our study. It is difficult to plant at the intervals of less than 20 cm between corn and soybean without a suitable mechanical planter for mixed-planting of the two crops. Recently, a new planter was developed for mixed cultivation of corn and soybean planted simultaneously on the same row (Woo et al. 2017). Photos are shown for mixed-planting of corn and soybean using the new planter (Supplementary Fig. 1A, 1B) and harvest of the intercropped plants by a forage combine (Supplementary Fig. 1C). Mechanization as shown can readily be adopted by farmers to facilitate the mixed planting of corn and soybean on the same row to improve the forage yield and quality.

In conclusion, we developed two forage soybean cultivars, Chookdu 1 and Chookdu 2, which have some wild soybean traits to facilitate improved adaptability for intercropping with corn for forage production. Several independent studies showed that new forage cultivars intercropped with corn have more forage yield and better forage quality than corn monocropped for silage. The viny growth habit is a unique trait in wild soybean and is not a preferred trait for seed production. However, we used this trait to overcome poor growth of soybean under a corn canopy in an intercropping system to improve forage production. Although the two forage-type-cultivars have shown good performance for forage in mixed cropping with corn, more breeding efforts are needed to improve the efficiency of corn-soybean mixed cropping systems.

Supplementary Information
ACKNOWLEDGEMENTS

This research was supported by the Bioindustry Technology Development Program (314024-3), Ministry of Agriculture, Food and Rural Affairs, Republic of Korea.

Figures
Fig. 1. Field performance and seed for Chookdu 1. (a) Machine harvesting corn and soybean simultaneously, (b) Mixed planting of corn and soybean before harvest, (c) Seed of Chookdu 1, (d) Matured Chookdu 1 plants at field maturity.
Fig. 2. Field performance and seed for Chookdu 2. (a, b) Mixed planting of corn and soyben to grow simutaneosouly, (c) Seed of Chookdu 2, (d) Matured Chookdu 2 plants at field maturity.
Tables

Quantitative traits of Forage soybean cultivars ‘Chookdu 1’ and ‘Chookdu 2’ compared with the Pungsannamul check.

Cultivar Growth habit Flower color Pubescence color Seed coat color Cotyledon color Hilum color
Chookdu 1 Indeterminate Purple Tawny Yellow Yellow Brown
Chookdu 2 Indeterminate Purple Tawny Black Yellow Black
Pungsannamul Determinate Purple Grey Yellow Yellow Yellow

Agronomic traits and seed yield of ‘Chookdu 1’, ‘Chookdu 2’ and Pungsannamul as check over three years.

Year Genotype Plant height
(cm)
No. of
Nodes
No. of
branches
No. of
pods
100-seeds
weight (g)
Yield
(t/ha)
2014 Chookdu 1 96.0 19.9 8.0 120.3 7.5 2.2
Chookdu 2 96.8 19.8 5.4 98.8 7.6 2.6
Pungsannamul 62.6 15.1 4.8 75.8 11.9 2.5
LSDz) (P = 0.05) 18.9 3.2 1.0 44.9 1.0 1.0
2015 Chookdu 1 70.7 19.5 8.4 125.7 6.9 1.9
Chookdu 2 72.7 17.3 6.3 107.4 4.8 2.4
Pungsannamul 52.5 15.6 5.4 102.9 12.0 2.8
LSDz) (P = 0.05) 18.6 2.5 2.2 48.5 0.9 0.5
2016 Chookdu 1 75.9 20.6 6.1 84.9 7.0 1.8
Chookdu 2 74.7 18.7 6.0 91.0 8.7 1.5
Pungsannamul 49.1 15.9 3.6 56.8 10.7 2.1
LSDz) (P = 0.05) 12.3 3.2 1.1 19.4 4.9 1.6
Mean Chookdu 1 80.9 20.0 7.5 110.3 7.3 2.0
Chookdu 2 81.4 18.6 5.9 99.1 8.2 2.2
Pungsannamul 54.7 15.5 4.6 78.5 11.2 2.4
LSDz) (P = 0.05) 12.1 1.5 1.0 23.2 2.0 0.6
LSD is the least square difference and is calculated at 5% level of significance.

Mean of forage yield test for the mixed-planting of corn and soybean over three years.

Year Genotype Fresh weight (t/ha)

Corn Soybean Corn + Soybean Index (Corn + soybean/Corn)
2014 Chookdu 1 65.1 0.9 66.0 117.2
Chookdu 2 71.5 1.9 73.4 130.4
Kwangpyeongok 56.3 - 56.3 100.0
LSDz) (P = 0.05) 26.7 1.0 27.4 -
2015 Chookdu 1 49.2 5.8 55.0 82.7
Chookdu 2 56.5 4.9 61.4 92.3
Kwangpyeongok 66.5 - 66.5 100.0
LSDz) (P = 0.05) 12.8 2.8 11.8 -
2017 Chookdu 1 59.8 2.1 61.9 111.6
Chookdu 2 54.9 5.2 60.1 108.4
Kwangpyeongok 55.5 - 55.5 100.0
LSDz) (P = 0.05) 5.0 3.6 5.6 -
Mean Chookdu 1 58.0 2.9 61.0 103.8
Chookdu 2 61.0 4.0 65.0 110.4
Kwangpyeongok 59.4 - 59.4 100.0
LSDz) (P = 0.05) 9.9 2.3 9.1 -
LSD is the least square difference and is calculated at 5% level of significance.

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