Effect of Location , Year and Variety on Forage Yield and Quality of Winter Rye

The objective of this experiment was to determine agronomic characteristics, and forge yield and quality responses of rye variety to location and year for a double-cropping system in South Korea. Five forage rye varieties (‘Koolgrazer’, ‘Jlee select’, ‘9909’, ‘Homill22’, ‘Danko’) were evaluated for forage quality and yields during the two growing years (the First year; 2001-2002, and the Second year; 2002-2003) at two locations (the central and southern zone). The heading date of rye in the central zone (Cheonan) was 15 April, and that of the southern zone (Daegu) was 10 April. The heading dates of ‘Koolgrazer’, ‘Jlee select’ and ‘9909’ were earlier than those of the others. Although the five varieties had resistance to foliar diseases and insects, these had less lodging resistance. Dry matter (DM) content, DM and total digestible nutrients (TDN) yields had significant differences among rye varieties. DM and TDN yields of the rye varieties at the second year were higher than the first year in the central zone. In the southern zone, DM and TDN yields at the first year were lower than the second year. ‘Jlee select’ and ‘9909’ had higher DM and TDN yields than the other varieties in both location and year except the first year of the central zone (p<0.001). The crude protein (CP) contents of rye grown in Cheonan were higher than Daegu. The CP content of ‘Danko’ variety was highest among tested varieties. The acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were greater for the varieties grown in Cheonan and in the second year. The ADF and NDF contents of ‘Danko’ were lowest, while ‘Danko’ in TDN and relative feed value (RFV) was highest among rye varieties. Our study showed that there are differences in forage production and quality from location to location, year to year and variety to variety. Therefore, forage quality and forage production are an important factor for screening forage rye varieties. Early maturing varieties should be recommended as high-yielding forage in a double-cropping system because their production of forage was greatest early in the season. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 7 : 997-1002)


INTRODUCTION
Two distinct types of rye (Secale cereal L.) are grown in Korea, winter and spring rye, but approximately ninety nine percent of the rye is sown in the fall.Rye is grown primarily for grain but occasionally for hay or pasture.The importance of rye cover crop in soil erosion control and enhancement of soil productivity via organic matter maintenance or even build up has long been recognized in agriculture.
However, the most important use of rye in Korea is for green forage as well as green manure.Seven thousand tons of rye seed for both forage and green manure were imported in 2003, because of its higher forage yield as a cool season component of a double-cropping system in Korea (Kim et al., 2001a;Kim, 2004).
The forage production and quality of rye are a fraction of numerous interacting factors, namely, environment, management practices, and genetics.For example, the environment such as temperature, precipitation, location etc. strongly influence forage production and quality (Williams et al., 1995;Kim et al., 2001b).Late maturing rye variety can increase dry matter yield because it responds to the higher heat units of a long growing season.The late maturing variety, however, must be harvested by mid-May in Korea to plant corn for silage.In some years, late maturing rye used as forage has been difficult to head by mid-May because of its late maturity (Kim, 2004).
Recently winter rye varieties have been evaluated and recommended primarily on the basis of forage yield and agronomic characteristics, but the evaluation of forage rye has ignored potential variety differences in quality.Some previous studies have identified variation in quality of rye (Brundage et al., 1979;Jung and Allen, 1995;Elizalde et al., 1999;Firdous and Gilani, 2001;Go, 2001;Kim, 2004;Yu et al., 2004) and also the forage quality evaluation has been mostly done in the central zone of Korea.
Increased nutritional demands for optimal animal performance challenge rye producers to select variety and management practices for high forage yield and favorable quality characteristics.
Therefore, the objective of this experiment was to determine forage yield and quality responses of rye variety to location and year.

MATERIALS AND METHODS
The experiment was conducted at two locations, Cheonan in the central zone and Daegu in the southern zone over a 2-yr period, 2001-2002 and 2002-2003.The soil at Cheonan was silt loam, and the soil at Daegu was sandy loam.
The experimental design was a randomized complete block in a split-split arrangement with three replications.Main plots consisted of two locations (the central zone and the southern zone), subplots consisted of two years (2001-2002 and 2002-2003), and sub-subplots consisted of five rye varieties; 'Koolgrazer', 'Jlee select', '9909', 'Homil22' and 'Danko'.
Seeds were hand-planted in each experimental plot (1.5×4 m).Fertilizer was broadcasted at 150, 100 and 100 kg ha -1 of N, P and K, respectively (Table 1 A subsample (800 to 1,000 g) was randomly selected from each harvested plot to estimate DM content and provide samples for forage quality analysis.The samples were weighed and dried for 72 h by forced-air drying oven at 65°C.The dried samples were reassembled and ground through a 1 mm screen in a Wiley mill.
Crude protein (CP) was determined by the Kjeldahl method (AOAC, 1990), acid detergent fiber (ADF) and neutral detergent fiber (NDF) were measured by the methods of Goering and Van Soest (1970).
Data were analyzed with analysis of variance (ANOVA) procedures using the SAS statistical software package (1999).The mean separation among treatment means for location, season and variety was obtained by using the Least Significant Difference (LSD) test (Steel and Torrie, 1980).Effects were considered in all statistical calculations for p-values<0.05.season are presented in Table 2.The average temperature of the southern zone (Daegu) was 2.5°C above the central zone (Cheonan).However, the precipitation of the southern zone was 120 mm less than the central zone.Temperature patterns were similar between the first year (2001)(2002) and second growing year (2002)(2003) while, precipitation differed markedly between the two growing years.

Mean temperature and precipitation during the growing
Cumulative precipitation in the first year was about 70 mm less than the 30-year mean, and the dry conditions existed in November and February when only 1.5 to 6.3 mm of precipitation were recorded.Consequently, rye was stressed by water supply before and after winter.Conversely, the second growing year was exceptionally wet.Cumulative precipitation in the central zone was 93 mm above the 30year mean.
All rye varieties showed cold hardiness of 9 rating.The heading date was observed before and after 10th of April for 'Koolgrazer', 'Jlee select' and '9909', 15th of April for 'Homil22', and 20th of April for 'Danko'.The heading date of rye in the central zone was 15th of April, and that of the southern zone was 10th of April.The heading date was earlier 1 to 2 days in the first growing season than the second season.In general, the heading date of variety was delayed as maturity progressed, showing conclusively that heading date affected yield and quality of forage rye.Because the heading date strongly influenced quality of rye (Kim et al., 1998;Kim, 2004), our results further confirmed that the heading date of variety selection can influence forage quality.
All the varieties had resistance of foliar diseases and insects, but the lodging resistance was poor.Especially, early maturing varieties had less lodging resistance (Table 3).
Significant main effects (location, year, and variety) and their interactions were observed for most measured parameters (Table 4).Differences in dry matter (DM) content were significant among location, growing year and variety (p<0.001;Tables 4 and 5).Early maturing rye was highest in DM content.
Dry matter (DM) yield had significant differences among rye varieties.The DM yields of the early maturing varieties ('Jlee select' and '9909') were higher than other varieties except the first season of the central zone.Total digestible nutrients (TDN) yield also had significant differences among rye varieties.'Jlee select' and '9909' had higher in DM and TDN yields than the other varieties.
The DM and TDN yields of the rye varieties in the second year were higher than the first year in the central zone.This result was due to water stress rather than temperature.The second growing year (2002)(2003) in the central zone had high rainfall and above normal.In contrast, in the southern zone, the DM and TDN yields in the first were slightly higher than the second year (Table 5).
The crude protein (CP) content of the rye varieties in the central zone was higher than that of the southern zone.The CP content of 'Danko' was highest among the rye varieties (Table 6).
The content of acid detergent fiber (ADF) and neutral detergent fiber (NDF) significant differed with location, growing year, and variety (Tables 4 and 6).The contents of ADF and NDF were decreased as heading date was delayed.Consequently, the ADF and NDF contents of 'Danko' for late maturing rye were lowest among the rye varieties.This reflected in the calculated values for TDN and relative feed value (RFV) (Table 6).We concluded that any prospective differences in chemical composition of the rye varieties and the relationships to forage quality of the varieties, probably would be best determined from ADF and NDF contents.This conclusion is consistent with the finding of Kwon and Kim (1994) and Kim (2004), who studied yields and chemical composition of rye varieties.The ADF and NDF contents were greater for Cheonan than Daegu.Then the ADF and NDF contents in the first year were lower than those of the second in both locations.
Treatment differences in TDN and RFV values (Table 6) were observed from different location, growing year and variety (p<0.001).As maturity was delayed, TDN and RFV increased.'Danko' in TDN was the highest among the rye varieties.Because TDN and RFV values were calculated from ADF and NDF, the observed differences were reflective of previously described ADF and NDF differences.This suggests that quality improvement via late heading date is important in screening forage varieties (Kwon and Kim, 1994;Kim, 2004).
In this study, large differences among the five rye varieties were shown according to different location and growing year.The differences found were primarily in fiber composition (ADF and NDF) and heading date, which probably resulted in the differences in the digestible nutrient that would be available to the ruminant animal.While conventional thought is that a superior forage rye must have  superior forage production, data from this study suggest that the rye varieties with equal forage production do indeed have differences in forage quality.On the basis of the findings in our study, the selection of variety may even be more important than high production so that the effects of low fiber composition could improve animal productivity.Utilization of forage rye in the field, therefore, should consider both quality and forage production.Although late maturing varieties are higher in forage quality, in a doublecropping system in which forage growth is restricted by short growing period, early maturing varieties should be recommended because their high production and early heading date.

Table 1 .
Field characteristics and culture practices at two locations, Cheonan and Daegu, in Korea Fertilizer (kg ha -1 )

Table 2 .
Mean air temperature and precipitation at two locations, Cheonan and Daegu from 2001 to 2003

Table 4 .
Significance of main effects and their interactions in analysis of variance for forage yield and quality of winter rye

Table 5 .
Dry matter (DM) content, DM and total digestible nutrients (TDN) yields of five rye varieties at Cheonan and