Ⅰ. INTRODUCTION

 Researches are being carried out in various ways in many countries around the world including Korea to use animal manure as resources and fertilizers. More researches are called upon as the use of animal manure is emphasized as an alternative that can lead to sustainable and organic livestock production through reduced chemical fertilizer and cyclic farming (Lim et al., 2006). In recent years especially, in the rapidly changing livestock products use, consumers are more interested in eco-friendly and organic livestock products, and government also is focusing the direction of future livestock development on the high quality eco-friendly livestock products (Lee and Jeon, 2004). Therefore, the production of organic forage crops will play the greatest role in the production of future eco-friendly and organic livestock products, thus the use of cattle feces and urine is expected to increase. For these reasons,  lot of studies are being carried out domestically on the cultivation of forage crops using animal manure (Lee et al., 1995; Ryoo and Jacob, 1997; Shin et al., 1998a; Seo et al., 2000; Lim et al., 2003; Yook and Choi, 2005; Na et al., 2006), and on the effects of the animal manure on soil environment (Shin et al., 1998b; Lee and Jeon, 2004; Lim et al., 2007; Kim et al., 2008; Yang et al., 2008). Their studies, however, mostly focussed on the growth of forage crops and on the soil by the application of animal manure; and most researches were conducted on upland soil. However, this research was carried out to investigate the influence of the mixed application of chemical fertilizer and liquid swine manure on the productivity, amino acids, minerals, and free sugars in cultivation of silage corn on paddy soils; and to provide the results as basic data for mixing chemical fertilizer and liquid swine manure to cultivate forage crops on paddy soils in the future.

Ⅱ. MATERIALS AND METHODS

This field experiment was performed at a paddy field in the north western of Gyeongbuk. Especially, the experiment paddy field was on low-lying land, with 50 cm depth drainage ditch along the circumference of the field experiment to prevent flooding in rainy season. The field experiment was designed in a randomized block design of 3 repetitions with CF 100% treatment (C), CF 70% + LSM 30% treatment (T1), CF 50% + LSM 50% treatment (T2), CF 30% + LSM 70% treatment (T3), and LSM 100% treatment (T4) (see Table 1). 

Table 1. Experimental design

The conditions of the field experiment were a paddy field with higher organic matter and nitrogen content and lower phosphate content than the general upland soil as shown in Table 2. The cultivated variety used the P31N27. May 1, sowing and harvest time was August 28. Nitrogen, phosphorus and potassium components of using LSM were 0.42, 0.23, 0.38%, respectively (Table 3). The application rates of CF were calculated in total nitrogen (200 kg/ha), phosphorus (150 kg/ha) and potassium contents (200 kg/ha) (see Table 4). The method of CF application was applied nitrogen and potassium with 60% as basis of fertilizer, and 40% as added fertilizer; and entire phosphorus as the basis of fertilizer. Application rates of LSM were calculated in total nitrogen contents. 

Table 2. Chemical properties of the soil before experiment

Table 3. Chemical characteristics of used liquid swine manure in the experiment

Table 4. Application levels of N, P and K by each treatments

The LSM was also applied as much as 60% as the basis of fertilizer, and 40% as add fertilizer. Adding fertilizer was applied in silage corn 8 leaves stage. At the time of seeding, the planting distance was 75 cm × 20 cm; each treatment area was 3 m × 5 m = 15 m²; and two grains seeding was done, and leaving only one plant was pulled at 4~5 leaf stage. For the investigation items and methods, the growth characteristics were observed after sampling 10 plants for each repetition after cutting the central 2 rows of 4 rows. Sugar degree was measured by a PR-101 saccharimeter for extracted the juice at 20cm from cutting point. Stem hardness was measured by KM spring gradiometer from the part 10 cm away from the cut. Fresh yield was weighed after cutting of the two central rows. The samples were dried for 5 days at 55^˚C  to use as analysis samples. TDN yield was obtained by the formula presented by Pioneer Hi-Bred: TDN dry matter yield = (dry matter yield of stem and leaf ×0.582) + (dry matter yield of ear × 0.85) (Holland et al., 1990). Nutritive values were analyzed using the AOAC method (1970); ADF and NDF were analyzed by Goering and Van Soest method (1970). The mineral composition was analyzed from of the pre-treated samples using ICP (Inductively Coupled Plasma, Iris Intrepid, Thermo Elemental Co., UK). The analysis of composition amino acid was done in the following sequence: 1 g of the pulverized sample was precisely taken and put in to a test tube; 10 mL of 6N-HCl was added, pressure reduced and sealed; hydrolysis at 110^˚C in a dry oven for 24 hours; pre-treated and filtered by 0.45 μm membrane filter; and the filtered sample was analyzed by amino acid automatic analyzer (Biochrom 30, Biochrom Ltd, Cambridge, England). Free sugar was analyzed in the following order: exactly 5 g of sample was taken per Wilson method (1981); 100 mL of 80% ethanol solution was added; sugar composition was extracted repetitively for 2 hours at 80^˚C from the heating mantle in the reflux cooling extraction unit; filtered by Whatman No. 5 and pre-treated; and was analyzed with HPLC analyzer (Waters 2414, Waters Co,USA) respectively. Mean values and standard deviations of the experimental results were obtained using SAS (Statistics analytical System, USA) Program (2002); Duncan’s multiple comparison test was used to identify differences among the treatments, which is considered significant when p<0.05. 

Ⅲ. RESULT ANA DISCUSSION

1. Growth characteristics and dry matter yield

The growth characteristics and dry matter yield are shown in Table 5. Ear length, ear circle, stem diameter, and stem hardness of the silage corn were high in T1, T2, T3, and T4 treatment compared to the C treatment, but significant differences were not observed. Sugar degree (in stem portion) showed significant improvement in the treatments (T1, T2, T3, and T4) with mixed application of chemical fertilizer (CF) and liquid swine manure (LSM) compared to C treatment with CF only (p<005); but there were no significant differences between the treatments (T1, T2, T3, and T4) with mixed application of CF and LSM. Dry matter yield and TDN yield were shown higher in the order of T3> T2> T4> T1> C treatments (p<0.05), especially higher in T2, T3 and T4  treatments where more amount of LSM was applied compared to C and T1 treatments. These results have the same trend as the studies by Lim et al. (2003), Choi and Yook (2000), and Lim et al. (2006). On the effect of application of LSM compared to CF, Jin et al. (1996) claimed that the animal manure application increased maize production by the chemical improvement of soil, Pain et al. (1986) and Long and Gracey (1990) reported that the application of low concentration LSM in high temperature drought period increased the production of forage crops, because it reduced moisture stress owing to the supply of a large amount of water in addition to the fertilizer effect. 

Table 5. Effects of liquid swine manure application ratio on agronomic characteristics and yield of silage corn hybrid in the paddy field cultivation

2. Chemical compositions

The chemical compositions are shown in Table 6. Crude protein content showed the highest content of 8.5% in T1 treatment, while the lowest 7.4% in T2 and T3 treatments (p <0.05). This study showed similar to the result to Park et al. (2006) in rye cultivation, and Na et al. (2006) and Lim et al. (2003) in maize cultivation, all of whom reported reduced content of the crude protein with the application of LSM the treatments with the CF only. The crude fat tended to significantly decreased in accordance with the increase of the LSM compared to the CF (p<0.05). Crude ash was shown significantly higher content in T4 treatment compared to the other treatments, but C, T1, T2 and T3 treatments did not show significant differences between them. NDF, ADF and crude fiber contents did not show significant differences between treatments, but they were slightly increased according to increasing of the application of the LSM. Shin et al. (1999b) also reported the increase in the contents of NDF and ADF according to the increase of liquid  anure application. But, Lim et al. (2003) reported the slight decrease, however not a big difference in ADF and NDF due to the application of liquid swine slurry. 

Table 6. Effects of liquid swine manure application ratio on chemical compositions of silage corn hybrid in the paddy field cultivation (DM.%)

3. Mineral contents

The mineral contents are shown in Table 7. The mineral contents of all treatments were higher in the order of K > Mg > Ca. It is consistent with the report of Kim et al. (2012b). Ca content of C, T1, T2 and T3 treatments showed similar figures, but tended a little decreasing in T4 treatment. Among the trace minerals, Cu and Mn contents were higher in T1 treatment; Fe, Na, and Zn were higher in T2, T3, and C treatments respectively. C treatment showed the highest total mineral content of 8,104.7 mg/100 g, while T4 treatment showed the lowest of 6,114.5 mg/100 g. The total mineral content was higher in the CF treatment than the LSM treatments; and tended to decrease significantly according to the increased application of the LSM (p<0.05). This result showed the same trend as Shin (1999a), who reported that the silage corn of the chemical fertilizer treatment showed the higher contents of K, Ca, and Mg than the application of the liquid swine manure as the basis of fertilizer N (120 kg/ha). 

Table 7. Effects of liquid swine manure application ratio on mineral contents of silage corn hybrid in the paddy field cultivation (DM. mg/100g)

4. Composition amino acid contents

The composition amino acid contents are shown in Table 8. Leucine showed the most abundant, and methionine content was the lowest in essential amino acids of silage corn. The content of the total essential amino acids was the highest in T1 treatment, but lowest in T3 treatment (p<0.05). Among non-essential amino acids, glutamic acid showed the highest content, and tyrosine content was the lowest. Total non essential amino acids were the highest in T1 treatment, but the lowest in T3 treatment (p<0.05). The total amino acid content was in the range of 4,416.8~5,567.6 mg/100 g according to the CF and LSM. Kim et al.(2012b) reported that silage corn varies in the content of the amino acid of 3,653.0~5,433.1 mg/100 g, and Do et. al. (2012) reported that silage corn P32W86 has 3,831.0 to 4,480.8 mg/100g according to the harvest time. Lee (2012) reported that the amino acid content of corn varieties in 4,353.2~ 5,323.2 mg/100 g according to the ridging times. Therefore, the amino acid content is considered to vary depending on the varieties, cultivation management and climatic conditions. 

Table 8. Effects of liquid swine manure application ratio on composition amino acid contents of silage corn hybrid in the paddy field cultivation (DM. mg/100g)

This experiment was the highest content of total amino acids in T1 treatment, which showed the highest content both in essential and non-essential amino acids (p<0.05). The reason of the highest content of the total amino acid in the T1 treatment is thought to be attributable to the significantly higher content of crude protein in T1 treatment, as shown in Table 6.  Chiang et al. (1972) analyzed some species of concentrated feedstuff, and Kim et al. (2012a) studied on the amino acid content of some kinds of barley; and they both reported higher amino acid contents in those with higher crude protein contents. 

5. Free sugar contents

The free sugar contents are shown in Table 9. Free sugar analysis revealed three sugars of fructose, glucose and sucrose in the silage corn. The content was higher in the order of sucrose > glucose > fructose. The content of fructose,  glucose and sucrose was higher in the treatments (T1, T2, T3 and T4) with the mixed application of CF and LSM compared to the treatment (T1) of 100% CF (p<0.05). Especially, fructose and sucrose contents were very high in the T1 reatment (p<0.05). 

Table 9. Effects of liquid swine manure application ratio on free sugar contents of silage corn hybrid in the paddy field cultivation (DM. mg/100g)

Free sugar content in the corn for silage is very important because it affects the fermentation quality of silage ingredients (Lee and Lee,2010). In particular, the free sugar content acts as a good factor enhancing the taste in fermentation (palatability) (Son et al., 2002). In addition, Jin et al. (1996) reported an increase of lactic acid in a fully fermented cattle manure(20 ton/ha) treatment compared with a standard chemical fertilizer treatment at corn cultivation, and mentioned the feasibility of the silage quality improvement depending on the amount and method of cattle manure application. 

Ⅳ. Acknowledgement

The present research was conducted with research funds from “Rural vitality promoting business” of Sang Ju Si 

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