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Effect of Cutting Heights on Productivity and Quality of King Napier Grass (Pennisetum purpureum cv. King Grass) under Irrigation



Sumran Wijitphan, Pornchai Lorwilai and Chutipong Arkaseang
 
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ABSTRACT

An experiment to study the effect of cutting heights on yield and nutritive values of King napier grass (Pennisetum purpureum cv. King grass) was conducted on sandy loam, Korat soil series (Oxic Paleustults) under irrigation during June 2006 to November 2007 at Khon Kaen Animal Nutrition Development Research Center, Thailand. Four treatments of cutting height at 0 (T1), 5 (T2), 10 (T3) and 15 (T4) cm above ground level in randomized complete block design with 4 replications were employed. The results showed that the Total Dry Matter Yield (TDMY) and Average Dry Matter Yield (ADMY) (65,707.5, 67,070.0, 69,697.5 and 71,403.1 kg/ha/year ; 5,973.4, 6,096.4, 6,336.2 and 6,491.2 kg/ha/cut, respectively) were significantly higher (p<0.05) in T4 than T1. There were no significant differences in CP and DMD among treatments, ranging from 12.1-12.9 and 75.5-76.6%, respectively but the percentage of ADF, NDF and ash were highly significantly different (41.7-43.5, 64.6-66.2 and 13.1-14.7%), respectively. Based on this research, it can be concluded that cutting height can affect the forage DM yield and nutritive values of King Napier grass. Cutting 35 day interval at 15 cm height above ground level could be the optimal level for harvesting King Napier grass in Northeast of Thailand.

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Sumran Wijitphan, Pornchai Lorwilai and Chutipong Arkaseang, 2009. Effect of Cutting Heights on Productivity and Quality of King Napier Grass (Pennisetum purpureum cv. King Grass) under Irrigation. Pakistan Journal of Nutrition, 8: 1244-1250.

DOI: 10.3923/pjn.2009.1244.1250

URL: https://scialert.net/abstract/?doi=pjn.2009.1244.1250

INTRODUCTION

Napier grass (Pennisetum purpureum Schum.) is a perennial forage crop with high growth rate, high productivity and good nutritive value and mostly used for cut and carry system over the tropical and sub-tropical area of the world (Cook et al., 2005; Duke, 1983; Wadi et al., 2004; Santos et al., 2001b). The various cutting studies with elephant grass revealed that both the choice of cutting interval and height of cutting are crucial to their performance and found that the main factor affecting growth, yield and persistence of swards is the defoliation intensity (Werner et al., 1966; Santana et al., 1989; Santos et al., 2001b and Wadi et al., 2004). The severity of defoliation causes physiological and morphological changes at plant level, especially during the regrowth period (Briske, 1986).

The regrowth after defoliation is one of the most important physiological processes and it determines the sward structure (Matthew et al., 1995). However, herbage yield was affected by the cutting height and depend on growth character of plant or plant type and climatic condition, also. Cutting near the ground level increase total and seasonal forage production over a short period as compared to more elevated cutting heights, but plants are adversely affected as the same way as to frequent harvesting (Crowder and Chheda, 1982). Because they lost the growing point and reduced storage carbohydrate in the subterranean stem of stubble tillers (Humphreys, 1974; Ollerenshaw and Hodgson, 1977; Whiteman, 1980; Ezenwa and Aken’Ova, 1996 and Trujillo et al., 1996). However, there are many research works on the cutting height of Napier grass showed the uncertainty results. Thinnakorn et al. (1995) found no difference in the production of the Napier grass cut 30-35 day interval at 5, 10 and 15 cm; whereas, Caro-costor and Vincente-Chandler (1961) worked in Puerto Rico found that cutting the elephant grass at lower level obtained higher dry matter yield than cut at higher level; Gonçalves and Coast (1991) obtained variation in the annual production of herbage dry matter of about 19.69-25.29 t /ha on average, when varying the height of cut at 5-30 cm above the ground level. In addition to, there are adversely interaction between cutting frequency and height. High DMY may be achieved by cutting more often with higher of cutting height, whereas lower of cutting height with longer cutting intervals may get high DMY as well. Because low level cutting may loose more photosynthetic part and need to use longer time for regrowth than the higher level of cutting (Walton, 1984).

According to Wadi et al. (2004) found that Napier grass cut at a 30 cm height was superior to that of the grass cut at 0 cm height, when cut at 90 days interval, but the annual Herbage Dry Matter Yield (HDMY) was higher in the grasses at a 90 day interval and 0 cm height than at a 60 day interval and 30 cm height. With regard to grass quality, Nakamanee et al. (1996) reported that cutting at 0, 7.5 and 15 cm were not significant effect on CP content and %ADF, but significantly different in %NDF of Napier grass. Although Werner et al. (1966) have obtained very high protein levels (19.97 and 18.17%, with cutting close to the ground and 15-20 cm, respectively). However, several other studies showed that the crude protein content of the elephant grass commonly ranges from 3.4-12.9%, according to climatic condition and age of cutting (Silveira et al., 1974; Gonçales, 1985; Aveiro et al., 1991; Gonçalves and Coast, 1991; Santos, 1994). This study was conducted to investigate the effect of cutting heights on productivity and quality of King Napier grass (Pennisetum purpureum cv. King grass) under irrigation.

MATERIALS AND METHODS

Location and climate of the experimental site: Field experiment was conducted under irrigation during March 2006 to November 2007 at Khon Kaen Animal Nutrition Research and Development Center in Northeast, Thailand (16o00' N, 102o30' E; elevation 1,150 m). The soil is a sandy loam, Korat soil series (Oxic Paleustals). Temperature and precipitation data were obtained from the Thapra Agro-Meteorological Station, located about 1 km north of the experiment site.

Experimental design and treatments: Four treatments of cutting height at 0 (T1), 5 (T2), 10 (T3) and 15 (T4) cm above ground level in randomized complete block design with 4 replications were employed.

Crop cultivation and maintenance: The experimental site was plowed in late March 2006. Soil samples were taken from depths of 0-15 cm as composites of four samples from four random locations within each plot. Limestone was applied at 937.5 kg/ha based on the soil analysis, before planting 7 days. The basal fertilizer with 625 kg/ha of 15-15-15 fertilizer and 6.25 t/ha of cattle manure were provided to the experimental plots. Planting King Napier grass by stem cutting with 2 nodes a piece and placed 45o with 2 pieces a hole with plant spacing of 50 x 80 cm in 3 x 4 m plot size. Each plot was applied urea at 125 kg/ha after each cutting and applied cattle manure at 1,562.5 kg/ha every 3 months. The entire plot area was kept weed-free with hand hoeing after cutting and irrigated whenever necessary.

Data collection and harvesting: In order to standardize, all plots were cut at 70 days after planting without data collection. To minimize the effect of border row, all samples were taken from the 2 x 3 m strip perpendicular to the row direction of each plot every 35 days for DMY 11 times by cutting height followed the treatments. Twelve plants were selected randomly from the central two rows and the following growth variables were recorded for each plot; height of plants, number of tillers.

Chemical analyses: The plant samples were analyzed for Crude Protein (CP) (AOAC, 1984), ADF and NDF (Goering and Van Soest, 1970) and Dry Matter Digestibility (DMD) by nylon bag technique (Orskov, 1982).

Statistical analyses: The analysis of variance was performed and compared treatment mean by DMRT (Steel and Torrie, 1960) by using GLM Procedure of SAS statistical computer package Ver. 6.12 (SAS, 1998).

RESULTS AND DISCUSSION

Climatic conditions: The climatic data of monthly mean rainfall, maximum and minimum air temperatures throughout the growing season of this study are shown in Table 1. Total precipitation, monthly mean minimum and maximum temperature during the experimental period in 2006 and 2007 were 1,415.5; 1,151.0 mm; 16.0; 24.7oC; 30.9; 36.2oC, respectively. Climatic conditions in the Northeast Thailand were generally considered to be good for Napier grass growth and forage yielding. The climatic data of the present study are consistent with Cook et al. (2005) and JLTA (1996) who quoted that the optimum growth temperature of Napier grass is between 25-40oC and little growth below about 15oC, with stop growing at 10oC, but re-grow with onset of warm and moist condition. During this study the temperature declined to 16oC during December, 2006 to January, 2007 and in some days closed to 10oC, which are likely to be having a major affect on stop growing of the grass. After then the maximum temperature at 36.2oC and 36.1oC. in March and April, 2007, respectively. The grass may storage carbohydrate in subterranean stem and regrowth very fast due to the optimum temperature, water supply and cattle manure application at that time.

Dry matter yield: Total Dry Matter Yield (TDMY) and Average Dry Matter Yield (ADMY) (65,707.5, 67,070.0, 69,697.5 and 71,403.1 kg/ha/year; 5,973.4, 6,096.4, 6,336.2 and 6,491.2 kg/ha/cut, respectively) were significantly higher (p<0.05) in T4 than T1. TDMY and ADMY were numerically highest for the T4 treatment (Table 2). The results of this study indicate that cutting height had significant effects on TDMY and ADMY of King Napier grass. The current results are in agreement with Werner et al. (1966) who reported that the annual DMY of Napier grass increased with increased the cutting height. They worked with 4 weeks of cutting interval and cutting at 1-3, 30-40 and 70-80 cm above the ground level which gave 4.5, 11.9 and 13.1 t DM/ha, respectively and Nakamanee et al. (1996) who found cutting at 7.5 and 15 cm above the ground level gave 2 year average DMY higher than cutting at 0 cm height. For the reason could be explained by Walton (1984) who stated that cutting near the ground level cause loose almost entirely of growing point or apical meristematic tissue, the photosynthetic part and the storage carbohydrate in the subterranean stem of stubble tillers. Consequently, the tillers might be died and the new ones grew instead from the lateral bud.


Table 1: Monthly weather data during the experimental period
Source: Thapra Agro-Meteorological Station, Khon Kaen (2007)

Table 2: Effect of cutting heights on dry matter yield of King Napier grass grown under irrigation
Means within a row followed by the different letter are different (p<0.05).
NS = Non significant difference (p>0.05)** = Highly significant difference (p<0.01)

So, the initials of plant regrowth were lower than the higher level of above ground cutting. However, these findings of the current study are inconsistent with Santana et al. (1989) studied the interaction between frequency and cutting height of 3 cultivars of Napier grass and concluded that the higher productivity was combining with cut to the ground at an 8 week interval. It can explain that the low level of cutting may loose more photosynthetic part and use more time for regrowth than the high level of cutting (Walton, 1984). In addition to Thinnakorn et al. (1995) who worked at Pakchong district, Thailand, whereas the soil was quite high fertility. They found that cutting at 5, 10 and 15-cm height at 30-35 days of cutting interval were no significant effects on average 2 year of DMY which obtained 12.00, 13.08 and 12.53 t/ha/year, respectively. It is noted that DMY of work done by Thinnakorn et al. (1995) was quite low compare with the current study. This might be due to irrigation and cattle manure was not practiced.

Table 1 showed DMY distribution of King Napier grass in one year round of 4 different cutting heights with 35 days cutting interval. Figure 1 showed the relation between DMY with air temperature. The DMY of current study was 71,403.1 kg/ha which sufficient for feeding 24 milking cows throughout the year (NRC, 2001). However, the distribution of DMY of Napier grass all year round was fluctuated, either lower or higher than requirement; in the 4th cut, a lower DMY (3,183.3 kg/ha) was obtained, whereas in the 11th cut an excess DMY (8,176.5 kg/ha) was obtained for example. Therefore, during the time that DMY was excess or lower than requirement of the cows. The amount of cutting area should be considered for determined the DMY of the grass.

Moreover, Wadi et al. (2004) reported that annual Herbage Dry Matter Yield (HDMY) of King Napier grass was higher in the plants at a 90 day interval and 0 cm height than at a 60 day interval and 30 cm cutting height. Tekletsadik et al. (2004) found that lax cutting (20 cm) produced significantly higher yield than close cutting (5 cm) and cutting every 2 months (3 times) tended to give higher yield than cutting more and less frequencies of dwarf Napier grass.


Fig. 1: Relationship between dry matter yield of King Napier grass with air temperature

So, the results of this present study indicated that DMY of King Napier grass greatly related to cutting height and cutting intervals. High DMY may be achieved by cutting more often with higher of cutting height, whereas lower of cutting height with longer cutting intervals may get high DMY as well. Because low level cutting may loose more photosynthetic part and use longer time for regrowth than the high level of cutting (Walton, 1984).

Nutritive values: There were no significant differences in CP and DMD among treatments, ranging from 12.1-12.9 and 75.5-76.6%, respectively. However, percentage of ADF, NDF (41.7, 43.5, 42.2 and 42.8; 64.6, 66.2, 65.6 and 65.4 %, respectively) were highly significantly higher (p<0.01) in T2, T3 and T4 compared with T1, but there was no significant difference among T2, T3 and T4; whereas, percentage of Ash (14.7, 13.3, 13.2 and 13.1%, respectively) were highly significantly lower (p<0.01) in T2, T3 and T4 compared with T1, but there was no significant difference among T2, T3 and T4 (Table 4).

The average of CP percentage of the current study were similar to the results of Santos et al. (2001a) and Nakamanee et al. (1996), who worked with the same cultivar in Chainat province, Thailand and obtained 8.9% CP. The average CP percentage of the present study was 12.4%. This CP value is higher than CP level in roughage that affects to animal’s intake. Milford and Minson (1966) stated that the 7%CP was a critical level in the forage. If the CP content of the grass is less than 7%, it is factors limiting animal production due to low voluntary intake, lower rate of digestibility and negative nitrogen balance. The minimum level of protein in feed, to have adequate rumen fermentation, must contain 7%CP content (Minson, 1981).

The average fraction of ADF and NDF in this experiment were 41.9 and 72.3% and similar to Queiro Filho et al. (1998), who cut the Roxo elephant grass at the ground level with 40 day interval, received 41.6 and 71.8%, respectively. In addition to, Nakamanee et al. (1996) showed cutting King Napier grass at 0-15 cm height and 40 days cutting interval received the average of ADF and NDF were 44.9 and 69.0%. However, the fractions of NDF and ADF, which normally increase with age of the plant. Santos et al. (2001a) who found that cutting the Roxo elephant grass at 0, 15, 30, 45 cm height and 60 days interval obtained the averages of ADF and NDF were 42.75 and 76.41%, when the cutting interval extended to 90 days, the average of ADF and NDF decreased to 41.02% and 71.13%, respectively.

Although, the result showed that cutting height had different effect on ADF and NDF components. The forage quantity of this study were higher than animal requirement which recommended by NRC (2001), the forage crops should have ADF and NDF not less than 17% and 33 %, respectively. The different amount of ADF and NDF in forage crops depend on varieties and age of plant (Preston and Leng, 1987). The percentage of ash decreased with increasing level of cutting height. The current results are in agreement with Thinnakorn et al. (1995) who found that range of the ash content of King Napier grass were 14.3-15.4%, when cut at 5-15 cm height and 30-35 days of cutting interval.

Number of tillers and tiller weight: The effect of cutting heights on Number of Tillers (NT) and Mean Tiller Weight (MTW) of King Napier grass are presented in

Table 3: Effect of cutting heights on nutritive values of King Napier grass grown under irrigation (% On DM basis)
Means within a row followed by the different letter are different (p<0.05)
NS = Non significant difference (p>0.05)** = Highly significant difference (p<0.01)

Table 4:

Effect of cutting heights on Number of Tillers (NT) and Mean Tiller Weight (MTW) of King Napier grass grown under irrigation

Means within a row followed by the different letter are different (p<0.05)
NS = Non significant difference (p>0.05)** = Highly significant difference (p<0.01)

Table 4. There were no significant differences in NT and MTW (138, 131, 138 and 133 tillers/m2; 5.26, 5.41, 5.33 and 5.44 g/tiller) among treatments. The current results are in agreement with Miyaki (1990) who found that NT and MTW were not significantly affected by cutting height. This behavior can be explained using the size-density compensation index, the least size of tillers is compensated by high tiller population density (Hernández et al., 1999).

In winter (during January to February, 2007) from the observation plant density in experimental plots found that the growth of grass was slow with the number of tillers increased but the size or weight of tillers was decreased. The leave size of grass was also small without new stems produced. This probably due to the grass may storage Total Non-structural Carbohydrate (TNC) in the stem during winter. Thus, a high TNC concentration may be beneficial to increase the tiller buds under a low temperature condition. TNC is considered as the source of energy for winter survival and regrowth after cutting (Kobayashi and Nishimura, 1978; Wadi et al., 2004). In addition, Jacques (1994) suggested that the largest number of vegetative tillers means greater numbers of leaves and consequently, greater numbers of buds for the development of axillary tillers.

However, it is known that some grasses have morphological and physiological and adaptations that allow bear repeated defoliation (Matches, 1992), hence the regrowth is dependent on the activation of the basal buds and the plant's ability to mobilize reserved carbohydrates from various parts (Caldwell et al., 1991).

Effect of cutting heights on pasture management: It is noted that management to fix the cutting height all year round is very hard to practice because after cutting the stubbles getting older which could lead to dying of grass. Hence, Tekletsadik et al. (2004) have suggested farmers refraining frequent cutting of their pasture in the dry season if they desire to produce maximum yield and get maximum benefit in the subsequent wet season. Tudsri et al. (2002) found that delaying the closing date of the pasture into the dry season produced a negative effect on regrowth in the following season, especially when a low cutting height had been imposed. Thus, a better understanding of cutting management during the drought period (November to April) is essential to improve dry season production and also reduce the effect of drought on subsequent pasture production. NRC (2001) recommends that milking cow weighting 450 kg giving 15 kg/day, should be fed at 2.8% DM of body weight and require 1,624 g CP/day. Thus, one cow fed 12.6 kg DM/day. If the ratio of roughage: concentrate is 60: 40. So, roughage for 1 cow is 7.56 kg/day or 2,760 kg/year. Hence, 1 ha of the King Napier grass pasture in 1 year can produces 71,403.1 kg and can feed 24 heads of milking cow throughout the year.

Conclusion: Based on this research, it can be concluded that the cutting height can affect the forage DM yield and nutritive values of King Napier grass. Cutting 35-day interval at 15 cm height above ground level could be the optimal level for harvesting King Napier grass in Northeast of Thailand. However, the experiments in second and third year crops still need to be clearly defined in order to provide practical recommendations to farmers especially those in the Northeast of Thailand.

ACKNOWLEDGEMENT

The authors wish to express sincere thanks to Khon Kaen Animal Nutrition Research and Development Center, T. Thra Pra A. Muang Khon Kaen and faculty of Agriculture, Khon Kaen University for providing financial support of research and research facilities.

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