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ISSN : 1225-8504(Print)
ISSN : 2287-8165(Online)
Journal of the Korean Society of International Agriculture Vol.34 No.1 pp.9-17
DOI : https://doi.org/10.12719/KSIA.2022.34.1.9

Selection of Optimal Forage Crops to Rotate with Kenaf on the Reclaimed Land in Jeollabukdo-Province, Korea

In-Sok Lee, Chan-Ho Kang, Ju Kim, Dae-Ho Cho
Jeollabuk-do Agricultural Research & Extension Services, Iksan City 54591, Korea
Corresponding author (Phone) +82-63-290-6038 (E-mail) bioplant325@korea.kr
August 23, 2021 January 7, 2022 January 10, 2022

Abstract


This study was performed to select the optimum combinations of a cropping system by using kenaf and four forage crops on the reclaimed land, Saemangum, in Korea. First, kenaf was cultivated for 168 days from May to mid October, and then, four forage crops, such as barley, Italian ryegrass (IRG), rye, and triticale, were cultivated from late October to May next year. The agronomic performances and physiochemical analyses of kenaf and four forage crops were investigated. The kenaf yield on the reclaimed land was 2.4 t/10a compared to the upland field’s yield of 3.25 t/10a. The germination percentage of IRG was the highest in the solution of 0.3% NaCl in comparison with the other forage crops. The agronomic performances of forage crops were estimated twice during the vegetative period. A significant difference in dry weight was observed in barley at 30 days of sowing. On second investigation at 160 days of sowing, the highest plant height was found in rye and the dry weight of IRG was the lowest. At harvest time, rye showed a significant difference in the plant height of 159.8 cm and fresh weight was the highest in IRG. At this time, there was a big difference in the dry weight of rye and IRG compared to barley and triticale. With respect to the K+/Na+ ratio, rye showed the highest increase in the K+/Na+ ratio over the other crops when cultivated on the reclaimed land. With respect to the effect of the kenaf extract on the four winter crops, the extract from kenaf reduced the germination of IRG by 81.7%. With respect to the silage quality estimation, there was no increase in barley in terms of total digestible nutrient (TDN). Taken together, IRG would be useful for the silage and rye would be useful for green manure on the reclaimed land after cultivating kenaf.



초록


    INTRODUCTION

    Kenaf (Hibiscus cannabinus L.) belongs to family Malvaceae is an annual C3 plant and a common warm season fiber plant native to India and Africa (Yazan et al., 2011). The chromosome number of kenaf is in the multiple number of 18 with 2n=36 to 2n=180 (Coetzee, 2004) Although kenaf is a tropical plant, its cultivars are now well adapted to a wide geographical and climatic range (Danalatos et al., 2010). Kenaf plants have been widely used for the production of paper, biocomposites, fiber boards and bioplastics and in the textile industry. It is an important cordage crop in many developing countries such as USA and Japan used for fiber production and forage. Due to its growth height and fibre content, kenaf represents a multipurpose crop producing biomass for energy and natural fibre for industrial uses (Dauda et al., 2013). This plant was introduced into South Asia around 1900 and in Korea in the 60’s, however, limited use in the country. In recent years, its value in Korea has been increasing for forage, biomass production and fuel (Noori et al., 2016;Tomple & Jo, 2021).

    There is a reclaimed land of 135,100ha in Korea. Of these, most of land (about 95,000 ha) have been using for production of rice over the past few years (Lee et al., 2012). Internal development for the rest of reclaimed land is being carried out. It is known that only sufficient water supply can make rice grow well in reclaimed land. The lack of water can lead to a severe decrease in rice yield from time to time. Recently, a consumption of rice per person steadily decreased in Korea. So, the rice surplus has been a major problem at the national level for years. It is essential that the reclaimed land to yield rice should be grown into other crops. A reclaimed land has poor soil environment for crop growth since it is high in salt concentration. A plant with excellent potential as alternatives to more traditional crops such as rice under salty conditions is kenaf due to increased salt tolerance (Mass, 1993).

    The climate warming has caused a decrease of international grain production. Also the forage grains, for example corn, are used for bioenergy production. As a result, the international grain price has been increasing steadily (Kim et al., 2015). Korea relies on imports for 75 % of forage grains (Kim et al., 2015). In this case, if the price of the imported forage grains is increased, Korea’s animal husbandry will be threatened. So, the production amount of high quality roughage within domestic should be increased to reduce grain feed import. Therefore, forage crop production for pasture or silage can be important for the utilization of the many acres of reclaimed land in Korea. Many crops have been used to generate coarse forage in Korea. Of these, the winter crops such as barely, Italian ryegrass, rye, and triticale take up a large portion (Han et al., 2015;Kim et al., 2015;Lee et al., 2013;Park et al., 2015). To successfully cultivate barley, Italian ryegrass, rye, and triticale at the reclaimed land, a high salt tolerance of these crops is essential. Fortunately, the kenaf and previous four winter crops can tolerant moderately saline soil conditions (Mass, 1993). There is a report on the development of a cropping system using kenaf under irrigation (Bañuelos et al., 2002). However, few researches are available in the literature on the cropping system for growing kenaf as a spring crop and gramineae species as a winter crop under reclaimed land.

    Accordingly, the main objective of this study is to select optimum cropping system using kenaf and winter crops for reclaimed land in Korea. So, this paper describes five crops in morphological, physiochemical and forage traits.

    MATERRIALS AND METHODS

    Seed material and experimental location

    Seeds of kenaf var. ‘Hongma 300’, barley var. ‘Youngyang’, Italian ryegrass var. ‘Passerelplus’ one of the varieties cultivated in Jeonbuk livestock farmers, rye var. ‘Elbon’, and triticale var. ‘Shinyoung’ were used as a material. Kenaf was grown as a spring crop, whereas the remaining four crops were grown as a winter crop. The experiment was conducted at reclaimed land, Saemangeum, located in Gimje City from 2017 to 2018. A salt concentration of this place was increased up to 0.3% at a dry condition, decreased up to 0.1% at a humid condition being caused by raining.

    Field preparation and management

    To compare a yield at upland and reclaimed land, kenaf was planted on 1st May, 2017. The beds were 10 m long and 1.5 m wide. The field was cleaned of plant refuse and treated with 15-10-10 NPK granular fertilizer/10a. Seeds were sown at a spacing of 20 × 20 cm. A granular Alachlor (C14H20ClNO2) herbicide (5 kg/10a) was applied within 3 days after sowing to prevent weeds emergence. Plants were established with sprinkler irrigation of 25 mm of water at an interval of ten for a month. The plots were designed by completely randomized block with three replicates.

    To cultivate barley, Italian ryegrass, rye, and triticale at reclaimed land, those seeds were sown on 19th October, 2017. The beds were 30 m long and 10 m wide. The field was cleaned of plant refuse and treated with 15-15-15 NPK granular fertilizer/10a. Three crops (barley, rye, and triticale) were sown by the 15 kg/10a, Italian ryegrass by the 5 kg/10a. The plots were designed by completely randomized block with three replicates.

    Characteristics evaluation

    Biomass yield of kenaf at upland and reclaimed land was measured in 168 days, from 1st May to 15th October, after sowing using a one digit and expressed in ton/10a. In the conduct of germination test, seeds of four gramineae crops were surface sterilized for 1 min using with 50% sodium hypochlorite solution. The seeds were then rinsed with water and allowed to air dry for 10 min. The prepared seeds were placed on the solution of NaCl concentrations (0, 0.3%) for 7 days at 25°C in the day and 20°C in the night. Germination was scored every day for 7 days. Three replicates with 20 seeds each were placed in Twist pack asad 400 (Twist pack 3, ACE Industry, Pocheon, Korea) container with two filter paper soaked with 7 ml test solutions. As to agro-morphological evaluation during vegetative period at reclaimed land, plant height and dry weight (g/ plant) were investigated in 30 days after sowing, also previous two properties and tiller number were recorded in 160 days after sowing. Three replicates with 10 plants each were analyzed. The heading date was determined at a time of 50% heading of each crop. With regard to agronomic properties analysis during the harvest time, because the optimal silage production time is different for each crop, the characteristics evaluation was carried out on different dates based on the harvest time of each crop. Four traits (plant height, tiller number, fresh weight, and dry weight) in the harvest time were identified. These traits of barley and triticale were analyzed at yellow ripe stage which is the optimal harvest time to make silage (Choi et al., 2008;Song et al., 2017). And these traits of Italian ryegrass and rye were scored at flowering period and milk-ripe stage suitable for silage production, respectively (Song et al., 2012;Kim et al., 2015). Three replicates with 10 plants each were done for plant height and tiller number. To measure the fresh and dry weight, above-ground part of crops was sampled with a 2 m length × 2 m width as three replicates, recorded by using a two digit and expressed in ton/ 10a.

    Comparison of K+/Na+ ratio

    The top of crops was taken to analyze K+ and Na+ ion in 160 days after sowing at the upland and reclaimed land as three replicates. The specimens was dried in oven at 60°C for 48 hours. The dry samples were grounded into fine powder and weighted by the 1 gram. Sodium and potassium were measured by flame photometry according to (Williams et al., 1960). The ionic fractions; K+/Na+ were computed.

    Kenaf extract impact on germination of winter crops

    The dried kenaf materials of 100 g and distilled water were added to 2000 ml flasks and placed on an Orbit Shakers at 100 rpm for 12 h at room temperature (22 °C). The samples were vacuum filtered through Whatman # 42 filter paper twice. The pH for all dilutions was adjusted to 7.0 using 1M KOH and 1M HCL. Seeds of kenaf var. ‘Hongma 300’, barley var.’ Youngyang’, Italian ryegrass var. ‘Passerelplus’, rye var. ‘Elbon’, and triticale var. ‘Shinyoung’ were surface sterilized for 1 min using with 50% sodium hypochlorite solution. The seeds were then rinsed with water and allowed to air dry for 10 min. Twenty seeds of each plant species were placed in separate Petri plates which contained 9 cm Whatman No. 2 filter papers. To each Petri plate was added 10 ml of each distilled water and kenaf plant extract. The petri plates were covered and placed in an illuminated incubator at 25°C in the day and 20°C in the night. Seven days later seed germination was measured. Seeds were considered germinated when the seed radicle was at least the length of the width of seed of the specific plant species being measured. This germination experiment was conducted twice and with 4 replicates.

    Comparison of pH, protein and organic acid of silages

    The fresh matter was cut into 2-3 cm length. The entire lot from each species was thoroughly mixed and a representative sample obtained. Ten packings (samples) of 500 g each were ensiled with the two treatments of the Control without any additive and T with the additive of 0.0002% (w/w) of Lactobacillus plantarum (1.5×1010cfu/g, CMRT, Cheongmibio, Anseong, Korea). The samples were opened in 60 days, then used as a material of analysis. A representative sample from each packing was mixed, and frozen at -15°C for chemical analysis. Silage extracts was prepared immediately by macerating a 10 g silage samples with a 100 ml of distilled water. These was collected through double cheesecloth and used to determine pH value and concentrations of volatile fatty acids. Silage pH was immediately determined from the prepared silage extracts using a pH meter (SevenExcellence pH, Mettler- Toledo AG, Schwerzenbach, Switzerland). The concentrations of volatile fatty acids (i.e., acetate, butyrate, lactate) in the silage extracts were determined by HPLC equipment (Jasco co, Tokyo Japan) using an ion exchange column (Shimadzu SCR-102 (H), 12 mm ID×30 cm, Shimadzu Co., Japan). To analyze crude protein (CP), the dry sample of 1 g was weighted with 3 replicates. And then its content was determined as described previously (Yahaya et al., 2002).

    Acid detergent fiber (ADF) and neutral detergent fiber (NDF) were measured by the method of Goering and Van Soest (1970). Total digestible nutrient (TDN) and relative feed value (RFV) were calculated by the formulae described by Holland et al., (1990). TDN was calculated from the ADF value (TDN% = 88.9 − 0.79 × ADF%), and RFV was estimated through digestible dry matter (DDM) and dry matter intake (DMI) as RFV = (DMI% × DDM%) / 1.29.

    Field growth conditions during the experimental period

    There is a result of climatic conditions (Table 1). During the experimental period for kenaf, from 1st May 2017 to 15th October 2017, the average minimum temperature in the area, Saemangeum located in Gimje City, was 14.2°C and average maximum temperature was 30.2°C, with a total of 714 mm rainfall. The optimum temperature for kenaf to grow ranges from 20-27°C (Monti et al., 2009) and rainfall of 600 mm (Eruola et al., 2014). From 20 October 2017 to 18th May 2018 for cultivation of winter crop, the average minimum temperature in the area was - 9.5°C and average maximum temperature was 25.2°C, with a total of 427 mm rainfall. The frost killing temperature of winter crops is minus 26 to minus 17°C (Cho, 1986;RDA, 2010) and the rainfall was sufficient to grow winter crops. Thus, the climatic conditions of the reclaimed land in Gimje City is very suitable to raise kenaf and four winter crops.

    Statistics

    Results were analyzed for analysis of variance (ANOVA) using SAS Enterprise Guide 4.2 (Statistical Analysis System, 2009, SAS Institute Inc., Cary, NC, USA). Also, comparison of means was done at 5% level of significance using Duncan’s Multiple Range Test (DMRT).

    RESULTS AND DISCUSSION

    Comparison of dry kenaf yield at upland and reclaimed land

    There is a result on dry yield of kenaf at upland and reclaimed land (Fig. 1). Significant differences of dry yield at upland with 3,250 kg/10a was observed compared to that of reclaimed land with 2,400 kg/10a which is same to 9,750 kg/10a of fresh yield. TDN yields meaning a nutrient content of feed were 1,771 kg/10a at upland and 1,308 kg/ 10a at reclaimed land. The kenaf’s TDN yield was consistent with the report of Hwang et al., 2015. Therefore, it is concluded that the kenaf cultivation is sufficiently possible at the reclaimed land. Also, Mass (1993) announced that the kenaf can tolerant moderately saline soil conditions, which supports a suitability of kenaf cultivation at the reclaimed land.

    Comparison of germination and agro-morphological properties for four winter crops

    Fig. 2 shows the varying germination difference for 4 winter crops on the distilled water and 0.3% NaCl solution. On the distilled water, the range of germination was higher in the IRG than the others. Big difference was noted when comparing four winter crops (Fig. 2). Also, IRG’s germination on the 0.3% NaCl solution was significantly higher compared to the others. The result shows that salt did not approximately give rise to problems in germination of IRG. Similarly, another researcher observed the unharmful effect of salt with 0.29% concentration in germination of IRG (Radke et al., 2018).

    The plant height and dry weight of four crops in 30 days of sowing on the reclaimed land were presented (Fig. 3). The height of the aerial part of four crops was high in the order of barley>triticale>rye>IRG, however statistically similar. As to dry weight, there was a significant difference among the cultivars. The greatest weight was reported for the barley compared to the other cultivars, which resulted in increase of maximally 76%. These results suggest that the salt used to decrease the osmotic potential caused more toxic effects in dry weight than plant height at an early vegetative period.

    The findings of plant height, tiller number, and dry weight at a late vegetative period in 160 days after sowing were shown in Table 2. As to plant height, rye presented more a significant difference than the others. As shown in Fig. 3 and Table 2 comparison, rye’s height was more increased than that of the others with time. Tiller number was similar among crops. However, a big reduction in the dry weight (g/plant) of IRG was observed, caused by the decreased osmotic potential at the reclaimed land with a salt concentration. Another research also reported that a salt affected the agro-morphological properties (Deuner et al., 2011), which is consistent with our finding.

    For K+/Na+ ratio at upland and reclaimed land in 160 days, the K+/Na+ ratio of barley was the lowest and other plants showed a similar value at upland. The highest K+/ Na+ ratio was estimated in rye with 159.4 and the lowest in barley with 10.9 at reclaimed land. The K+/Na+ ratio of rye and triticale was increased at reclaimed land, however, barley and IRG were directly opposite to previous both crops as compared to upland. It has been shown that a high K+/ Na+ ratio is related with salt tolerance of plant under salinity (Zhu et al., 2005). Another research also reported that a salt affected the agro-morphological properties (Deuner et al., 2011), which is consistent with our finding.

    In harvest time, the results of various properties were indicated in Table 3. The flowering date among four crops ranged from April 26 to May 18. Barley’s flowering was the fastest as April 26. The plant height of rye was the highest as 159.8 cm. The barley, which was the tallest at the beginning of growth (Fig. 3), was the smallest at harvest time. The tiller number from Table 3 was decreased compared with Table 2. Apparently, salt stress was sufficient to affect tiller development of four crops grown in the reclaimed land. A significant difference in fresh weight was also observed among four crops. To my surprise, the fresh weight of IRG with 10,200 kg/10a was more than twice that of the others. As for dry weight, rye and IRG was the approximately same as 1,800 kg/10a and 1,810 kg/ 10a, respectively. That yield was higher than barley with 1,370 kg/10a and triticale with 1,380 kg/10a. Comparing TDN yield between kenaf (Fig. 1) and winter forage crops (Table 3), the kenaf’s yield was 12~29% significantly higher. Adaptability is also different among varieties of forage crops in reclaimed land. Since a coarse forage for livestock like cattle have been harvested with fresh in Korea, crop suitable for reclaimed land is considered to be IRG. There is a report that cultivating IRG in area with salinity up to means values of -0.2 MPa osmotic potential, 0.29% NaCl concentration, is possible (Radke et al., 2018). A salt concentration of the reclaimed land of present study ranged from 0.1 to 0.3% based on the conditions of soil moisture. Table 4 show the results of the correlation analysis between the dry weight and its components. Dry weight is determined by the value multiplied by plant height and number tiller. It in Table 4 showed a higher correlation with plant height (r = 0. 0.752*) than number tiller (r = 0.313). In other words, it is important to ensure proper plant height during maturity period in reclaimed land. In conclusion, rye and IRG showed good productivity in harvest time. When growing forage crops in reclaimed land, the selection of highly adaptable species was recommended. Kim et al., (2020) reported the result that is consistent with ours.

    Comparison of germination on the kenaf extract solution for four winter crops

    The chemical interaction between plants, which is referred to as allelopathy, may result in the inhibition of plant growth and development. To determine the impact of kenaf plant extracts on the germination growth of four plant species, the extract was applied to the seeds and the germination result after 7 days was shown in Fig. 5. Under the distilled water, the germination rate was 100% in barley, 98.3% in IRG, 50% in rye, and in 35% in triticale. As for the kenaf extract treatment, barley, rye, and triticale followed similar negative trends in their responses to the extract, whereas, IRG had the most sensitive response, resulting in decreased germination rate by 83%. The research demonstrated that kenaf extracts was the most allelopathic to IRG germination. This result is accordance with Webber et al., (2015) where the kenaf leaf extracts resulted in the greatest decrease in IRG germination. Also, previous author revealed that kenaf extract affects the germination and post-germination development of other plants (Russo et al., 1997). We strongly suggest that more seeds sowing for a sufficient yield of IRG is needed in order to rotate with a kenaf.

    Comparison of pH, protein and organic acid for five crops silage

    To make the best silage, five crops were harvested at the optimal maturity stage of each crop.

    At silage, pH of the crops varied from 3.5 to 4.5. Kenaf possessed higher (p<0.05) pH than the other crops (Table 5). Crude protein (CP) content was from 5.6 to 9.2 % and was higher (p<0.05) in silages produced from kenaf than those produced from rye and IRG. Barley and triticale were of similar CP content (Table 5). Acetic acid concentration in ensiled IRG with 3.9% was almost four times higher (p<0·05) than those from kenaf being the lowest as 0.91% (Table 3). Rye, triticale and kenaf possessed similar acetic acid concentrations. Concentrations of butric acid in silages obtained from kenaf were lower (p<0.05) than those in the other crops, however there was a big difference among barley, rye, triticale and IRG. The concentration of lactic acid was lower (p<0.05) in silages produced from kenaf compared with the other cultivars. Contents of NDF and ADF were lower (p<0.05) in barley than in other cultivars. Therefore, its TDN were higher (p<0.05) than those found in other crops (Table 5). The result of kenaf’s TDN score was similar to the results of Nam et al., (2018) and Tomple et al., (2021). They stated that kenaf had significantly higher levels of TDN at earlier stages, showing a good preference.

    Accordingly, it needs to be harvested in September to be made use of as a silage, and to stably raise the winter forage crops because winter kill occurs by the late sowing in October. The silage RFV was high in the order of barley, triticale, IRG, rye, and kenaf, statistically similar among IRG, rye, and kenaf. Previous authors revealed that barley’s RFV is higher compared to the other forage crops, which is consistent with our result (Kim et al., 2015, Kim et al., 2020).

    Taken together, rye and IRG exhibited the best productivity among forage crops in reclaimed land. And, IRG germination rate was not affected by salt treatment. With regard to the silage quality estimation, the mean of crude protein was the highest in IRG, and its TDN content was not critical issue. In practice, growing the IRG and rye in reclaimed land, where salt concentration is high and it is a limiting factor for crop production, may be significant as compared to barley and triticale as they exhibited the low productivity. Accordingly, IRG would be useful for the silage and rye for the green manure at reclaimed land after cultivating kenaf.

    적 요

    새만금간척지 면적은 40,100ha이며, 이중 농생명용지는 9,430ha로 본 토양의 활용도를 높이기 위해서는 다양한 작물 의 개발이 요구되고 있다. 본 연구는 새만금간척지에서 하계 작물인 케나프와 윤작이 가능한 동계작물(보리, IRG, 호밀 및 트리트케일)을 선발하기 위해서 실시하였다.

    • 1. 케나프를 5월부터 10월 중순까지 168일 재배하고, 그 이 후에 보리, 호밀 IRG 및 트리트케일을 파종하여 이듬해인 5 월까지 재배하였다.

    • 2. 간척지에서 케나프 수량은 2.4톤/10a로 일반 포장(3.25톤 /10a)의 75%로 재배적 가치가 있음을 확인하였다.

    • 3. 간척지에 동계작물을 파종하고 30일후에 식물체의 건조 중은 보리에서 가장 높게 조사되었다. 두번째 조사(파종 후 160일, 영양생장기)에서 건조중은 보리, 호밀 및 트리트케일이 통계적으로 차이가 없었으나 초장은 호밀이 가장 높았다.

    • 4. 수확기(생식생장기)에 호밀의 초장은 159.8cm로 가장 높 았고, 생체중은 IRG가 가장 우수하였다. 그러나 건조중은 호 밀과 IRG가 동일하였다.

    • 5. K+/Na+ ratio는 내염성 지표로 이용되는데, 간척지 포장에 서 호밀의 K+/Na+ ratio가 가장 높아 동계작물 중 내염성이 가장 우수한 것으로 판단된다.

    • 6. 케나프 줄기 추출물의 allelopathy를 확인한 결과 IRG 의 발이율이 81.7%까지 억제되어, IRG를 케나프 후작물로 이용할 경우에는 기준량보다 많은 종자를 파종해야 할 것으 로 판단된다.

    • 7. 수확기 건조량 및 사료가치를 고려할 때 IRG는 silage에 적합하고, 호밀은 간척지 토양 물리성을 개선하는 녹비작물로 적합한 것으로 판단된다.

    ACKNOWLEDGMENTS

    This work is supported by a fund of project designated as No. PJ01477901, Rural Development Administration (RDA), Republic of Korea.

    Figure

    KSIA-34-1-9_F1.gif

    Difference in the kenaf dry yield cultivated on the upland and reclaimed land. A different letter shows a significant difference (p<0.05) using the Duncan’s Multiple Range Test.

    KSIA-34-1-9_F2.gif

    Difference in germination of four crops raised on the solution of H2O and 0.3% NaCl. A different letter shows a significant difference (p<0.05) using the Duncan’s Multiple Range Test.

    KSIA-34-1-9_F3.gif

    Difference in the plant height and dry weight of four crops cultivated on the reclaimed land at 30 days of sowing, a vegetative period. A different letter shows a significant difference (p<0.05) using the Duncan’s Multiple Range Test.

    KSIA-34-1-9_F5.gif

    Difference of germination of four crops raised on the distilled water (DW) and kenaf extract (KE) solution after 7 days. The different letter shows significant difference (p<0.05) using Duncan’s Multiple Range Test.

    Table

    Climatic conditions of the field during the experimental period.

    Agronomic properties of four crops at 160 days of sowing, a vegetative period, on the reclaimed land.

    Agronomic properties of four crops in harvest time on the reclaimed land.

    Pearson’s correlation coefficient among the characteristics.

    Forage quality of silage of five crops fermented by lactic acid bacteria for 60 days.

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