Effects of Fertilizer Types and Harvesting Date on Performance and Nutritional Qualities of Brchiariahydridmulato II (Brachiaria ruziziensis) Grass in the Highlands of Ethiopia
Salew Baye
1
(Bureu of Agriculture)
Bimrew Asmare
2
(Bahir Dar)
Shigdaf Mekuriaw
3
(Andassa Livestock Research Center, Ethiopia.)
کلید واژه: harvesting date, Dry matter yield, Fertilizer type, Nutritional Qualities,
چکیده مقاله :
The experiment was conducted to assess the effects of fertilizer types, and harvesting date on plant growth characteristics, dry matter (DM) yield and nutritional qualities of Mulato II grass. Data on plant growth characteristics, DM yield, and nutritional qualities of the grass were measured. The findings elucidated that fertilizer had a significant effect on the plant growth characteristics and DM yield but not on nutritional quality, except for crude protein (CP) content. All morphological characteristics except leaf to stem ratio (LSR) have shown better performance with the application of manure than other fertilizer types in the current study. Regarding the harvesting date, the highest morphological performance of all parameters except leaf length was recorded at 105 days. The interaction effect of two factors only significantly affects PH, LSR and root number. For the nutritive value parameters CP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were better at manure than chemical fertilizer and control. The CP, LSR, and ash content were markedly decreased (P <0.05) as the harvesting age was increased, and manure application. Hybrid Mulato II grass at about 105 days at manure fertilizer application would help to achieve greater DM yield using irrigation and rainfall production systems.
چکیده انگلیسی :
Effect of fertilizer types and harvesting date on performance and nutritional qualities of Brchiaria hybrid Mulato II grass (Brachiaria ruziziensis) in the highlands of Ethiopia
Abstract: The experiment was conducted with the objective of assessing the effects of fertilizer types, and harvesting date on plant growth characteristics, dry matter (DM) yield and nutritional qualities of Brachiaria hybrid Mulato II grass. The study employed a factorial combination of two factors in a randomized complete block design (RCBD) with three replications. The spacing between blocks and plots was 1m and 0.5m respectively while between plants and rows was 0.3m and 0.5m, respectively. Data on plant growth characteristics, DM yield, and nutritional qualities of the grass were measured. For forage DM yield and chemical composition analysis a 2 kg sample was taken from each plot. All Samples were harvested at 45 day, 75 and 105 days of age and by three agronomic seasons, weighed, dried and then ground to pass l mm sieve for forage nutritive value analysis. The collected data were statistically analyzed using SAS software version 9.0. The findings elucidated that fertilizer had a significant effect on the plant growth characteristics and DM yield but not on nutritional quality, except for crude protein (CP) content. All morphological characteristics except leaf to stem ratio (LSR) have shown better performance with the application of manure than other fertilizer types in the current study. Regarding the harvesting date, the highest morphological performance of all parameters except leaf length was recorded at 105 days. The interaction effect of two factors only significantly affects PH, LSR and root number. For the nutritive value parameters CP, neutral detergent fiber (NDF), and acid detergent fiber (ADF) were better at manure than chemical fertilizer application and control. An increasing harvesting date and manure application resulted in a better (p<0.05) morphological characteristic, dry matter yield (DMY), and fiber fractions. The CP, LSR, and ash content were markedly decreased (P <0.05) as the harvesting age was increased, and manure application. Hybrid Mulato II grass at about 105 days at manure fertilizer application would help to achieve greater DM yield than cutting from chemical fertilizer application and without fertilizer, using irrigation and rainfall production systems, at the latter harvesting stage.
Keywords: Dry matter yield, Fertilizer type, Harvesting date, Nutritional Qualities.
Introduction
Ethiopia has huge livestock population with 65 million cattle, 40 million sheep, 51 million goats, 8 million camels and 49 million chickens (CSA, 2020). that contributes to the livelihoods of an estimated 80% of the rural population of the nation. The sector contributes 15–17% of national gross domestic product (GDP), 35–47.7% of agricultural GDP and 37–87% of the household income (Gebremariam et al., 2013). Nevertheless, the contribution of livestock is not as expected (Shapiro et al. 2015; CSA 2018) which might be linked to many constraints including lack of quality and in quantity feed (Mengistu et al., 2017). The major livestock feed resources in Ethiopia are grazed pasture and crop residues, which are poor in nutritive values (Mengistu et al., 2017; CSA, 2018), unable to provide the nutrients required to maximize animal productivity. This calls for the introduction and evaluation of adaptable and high-yielding forage crops that produced large amounts of fodder with limited land and resources. Among the candidate forages Brachiaria grass, which could be suitable for the existing production system and adaptable to climate change. It is known that forage management practices such as fertilizer application, and harvesting stage determine DM yield and forage quality (Miheret et al. 2018; Ziki et al. 2019). The works of Adnew et al. (2018) suggested that the grass could be one of potential fodders for livestock as well as land rehabilitation program. The extent to which these factors affect the productivity and nutritive value of Brachiaria grass in the country has not been thoroughly investigated. Hence, the objective of this study was to assess the effects of fertilizer type, harvesting days and their interaction on grass characteristics, biomass yield, and chemical composition of BMII grass.
Site information
The study was conducted in Fogera district, Amhara region, Ethiopia. The experimental area is located at 130118.53′N latitude and 3606443′E longitude. The elevation for the experimental site is about 2050 m.a.s.l. The area receives an average annual rainfall of 1284.2mm and has average daily temperatures of 37.5°C (FDCO, 2019).
Land preparation, Soil Sampling and Analysis
The experimental land was cleared, ploughed by oxen, and harrowed again by traditional oxen for 20 to 30 days before laying out plots and planting a fine tithe to facilitate soil aeration, dry, and remove or reduce unwanted weeds. Soil samples were collected from the experimental site, pooled over, and analyzed for soil pH, organic carbon (OC), total nitrogen (N), available phosphorus (P), and organic matter (OM) using standard laboratory procedures. The total N in the soil was determined by the Kjeldahl method (Dewis and Freitas, 1975). Available P in the soil was determined by Olsen's method using a spectrophotometer (Olsen et al., 1954). The pH of the soil was determined with a glass electrode attached to a digital pH meter (FAO, 2008). Finally, organic matter was calculated as (OC × 1.72) standard methods as described by Okalebo et al. (2002).
Research Method
The experimental design used was a factorial arrangement in a randomized complete block design (RCBD) with three replications consisting of 2 factors (fertilizer type and harvesting day) with 3 replications. The fertilizer types had three levels: chemical fertilizer, manure, and control, while the three harvesting dates had three levels: 45, 75, and 105 days. Each plot measured 1.5×3 m and the inter-row spacing was the same for all treatments (0.5m). During planting, organic and inorganic fertilizer was applied at the rate of 100 kg NPS for the establishment and 25 kg/ha urea for maintenance, and organic fertilizer was 4500kg for the establishment and 1000kg/ha for maintenance (Danano,2007). Weeds were controlled by hand weeding to avoid interference by interspecific competition.
Data on the morphological and DM yield were recorded throughout the experimental period. In each plot, seven plants were randomly selected to record a number of tillers per plant , number of leaves per plant, leaf length, root length, roots number per plant, and leaf to stem ratio (LSR). Plant height was determined by measuring the height of seven randomly selected plants from ground level to the tip of the apical meristem. Harvesting was done by hand using a sickle, leaving a stubble height of 10 cm (Tudsri et al. 2002).
Representative samples from each plot were dried and ground to pass a 1-mm Wiley mill screen and stored in airtight containers for chemical analysis. Samples were subjected to chemical analysis for the determination of organic matter following the methods of (AOAC, 2004). Forage quality measurements such as DM, CP, and Ash were analyzed (AOAC, 1990). The CP content was determined using the Kjeldahl procedure, while the fibers such as neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) were analyzed using the methods of Van Soest et al. (1991). Ash was determined by igniting at 550°C overnight for 6 hours totals DM by drying at 105°C for 24 hours. To determine crude protein yield (CPY), the DM yield was multiplied with the CP content of the feed samples.
The collected data were subjected to analysis of variance (ANOVA) using the procedure outlined by Steel and Torrie (1980) for a factorial experiment using SAS9 software (SAS, 2004). When the F test was significant, treatment means were compared by Duncan’s Multiple Range Test (DMRT) (p<0.05).
Results
Plant Morphological Characteristics and Dry Matter Yield
The effects of fertilizer types and harvesting dates on morphological characteristics of BMII grass are presented in Table1.The Fertilizer type by harvesting date had no significant effect (P>0.05) on plant height, tillers number, leaves length, inter node number in the current study. However, three were significant differences (p<0.001) for leaf stem ratio, roots number per plant and DM yield. All parameters with the exception of LSR were significantly increased as harvesting stage increases from 45 to 105 days. Plants that received manure than fertilizer (NPS), generally performed better than the control.
The effect of both fertilizer and harvesting date were significant (p<0.001) on plant height. As harvesting stage increases from 45 to 75 and 105 days, the plant height increased by 35.57, 51.86b and 69.31 cm, respectively. The highest mean of plant height of 67.50, 46.82 and 43.32 cm were observed for manure followed by chemical fertilizer and control treatments, respectively (Table1). The interaction of fertilizer and harvesting date had shown significant (p<0.001) effect on the height of the grass (Table 2).
There was significant (p<0.001) effect of both fertilizer type and harvesting date on tillers number per plant of BMII grass (Table1). As harvesting stage increases from 45 to 75 and 105 days The tillers per plant were counted as 85, 117 and 184 numbers, respectively, indicating that the tillers number increased with late harvesting date as the number of tillers developed. Similarly, the application of organic fertilizer (manure), chemical fertilizer (NPS) and control produced 160, 131 and 97 tillers per plant, respectively.
The effect of both harvesting date and fertilizer was highly significant (p<0.001) on the leaves length per plant. The BMII grass harvested at 45, 75 and 105 days, produced leaf length per plant of 17.07, 20.49 and 18.21 cm, respectively, indicating that, the leaf length was increased progressively with enhanced age of harvesting. Application of manure, chemical fertilizer and control were given 22.59, 16.84 and 16.57 cm leaf length per plant, respectively, which shows that application of manure produced longest leaf length per plant.
Internode number
The effect of harvesting date was highly significant (p<0.001 and effect of fertilizer type was also significant (p<0.05) on the internode number per stem (Table 1). The BMII grass harvested at 45, 75 and 105 days produced 4.43, 6.72 and 9.59 internode number, respectively. Indicating that, the internode number was increased with enhanced age of harvesting. For fertilizer type, the manure, NPS fertilizer and control produced 7.79, 6.53 and 6.46 internode number, respectively.
The effect of fertilizer type and harvesting date were highly significant (p<0.001) on leaf to stem ratio (LSR) of BMII grass (Table 1). As harvesting stage increases from 45 to 75 and 105 days, the LSR values were decreased by 4.07, 3.66 and 2.81, respectively. In comparisons between fertilizer levels, by application of manure, NPS fertilizer and control the LSR values were 3.46, 3.04 and 4.02, respectively.
The interaction effect between harvesting date and fertilizer type was highly significant (p<0.001) on the leaf to stem ratio of the grass indicating that the responses of fertilizers to harvesting date were not similar. The leaf stem ratio of the grass was also significant by the interaction of factors fertilizer type and harvesting dates.
The LSR obtained at earlier stage compared to intermediate harvesting (75 days) and sharply decreased in 105 days harvesting. The lowest LSR was observed from late harvesting date and from chemical fertilizer (NPS) application, respectively. The overall mean of a leaf to stem ratio was 3.51.
The effect of fertilizer type and harvesting date was highly significant (p<0.001) on number of roots per plant of BMII grass (Table 1). As harvesting stage increases from 45 to 75 and 105 days, the roots number were decreased from 46.39, 137.33 and 245.08, respectively. The highest number of roots was counted from late harvesting date (105 days). Highest root number counted from intermediate harvesting date (105 days). The lowest root numbers were counted from control and from early harvesting date (45 days), respectively. For fertilizer type, application of the manure, NPS fertilizer and control produced 190.88, 131.25 and 111.11 roots number, respectively. The interaction of fertilizer type and harvesting dates was highly significant (P<0.001) which shows that the different fertilizer type and harvesting date was not similar. The interaction between fertilizer type and harvesting date was highly significant (p<0.001)(Table 2). Indicating that the responses of fertilizer type in different harvesting date were not similar.
Root length
The effect of both harvesting date and fertilizer were highly significant (p<0.001 on the root length (Table 1). The BMII grass harvested at 45, 75 and 105 days produced 18.87, 28.79 and 31.68, respectively. Indicating that, the root length was increased progressively with enhanced age of harvesting. For fertilizer type, the application of manure, NPS fertilizer and control produced 30.20, 23.50 and 25.50 cm, root length, respectively, indicating the highest value was obtained using manure fertilizer.
The effect of both harvesting date and fertilizer were highly significant (p<0.001 on DM yield (Table 1). The total DM yield of the harvesting period (45, 75 and 105 days) were 15.13, 25.24 and 17.67 ton/ha respectively. Also, by application organic fertilizer (manure), NPS and control the values of DM yield were 11.9, 7.91 and 6.51 kg/plot, respectively. The DM yield increased progressively with effect of fertilizer type called manure than chemical fertilizer with the least in the control. The yield based on harvesting dates is showed an increasing pattern from the early harvesting age up to moderate harvesting date.
Table 1. Effect of harvesting stage, fertilizer type and their interaction on plant morphological characteristic and yield of Bracheiaria hybrid Mulato II.
Factors | Plant height
| NTillers no. | Leaf length
| Internode No. | Leaf/stem ratio | Root no | Root length
| DM yield
|
Harvesting stage (H) |
|
|
|
|
|
|
|
|
45 days | 35.57c | 85.58c | 17.07b | 4.43c | 4.07a | 46.39c | 18.87b | 6.81b |
75 days | 51.86b | 117.48b | 20.49a | 6.72b | 3.66a | 137.33b | 28.79a | 11.36a |
105 days | 69.31a | 184.65a | 18.21b | 9.59a | 2.81b | 245.08a | 31.68a | 7.95b |
Significant | *** | *** | *** | *** | *** | *** | *** | *** |
|
|
|
|
|
|
|
|
|
Fertilizer type (F) |
|
|
|
|
|
|
|
|
Manure | 67.50a | 160.41a | 22.59a | 7.79a | 3.46ab | 190.88a | 30.20a | 11.9a |
chemical fertilizer | 46.82b | 131.78b | 16.84b | 6.53b | 3.04b | 131.25b | 23.50b | 7.91b |
Control | 43.32b | 97.84c | 16.57b | 6.46b | 4.02a | 111.11b | 25.50b | 6.51b |
Significant | *** | *** | *** | * | ** | *** | ** | *** |
|
|
|
|
|
|
|
|
|
Mean | 52.25 | 129.24 | 18.59 | 6.91 | 3.51 | 142.94 | 26.45 | 8.71 |
standard error | 4.27 | 12.64 | 0.88 | 0.47 | 0.27 | 14.33 | 1.53 | 1.4 |
R2 | 0.96 | 0.90 | 0.93 | 0.92 | 0.92 | 0.93 | 0.88 | 0.93 |
CV% | 18.65 | 33.26 | 14.23 | 21.23 | 24.36 | 23.18 | 17.66 | 47.85 |
F×H interaction | 0.06 | 0.15 | 0.17 | 0.30 | *** | *** | 0.31 | 0.19 |
*, **, ***= significant at 0.05, 0.01and 0.001 probability levels.
Means within column followed by the same letters are not significantly different
F=Fertilizer; H=harvesting date.
Table 2. Harvesting date by fertilizer interaction on yield and morphological traits of BMII grass
Harvesting stage (H) | Fertilizer type | Plant height cm | Tillers no. | Leaf length cm | Internode No. | Leaf/stem ratio | Root no | Root length cm | DM yield kg/plot |
45 days | Manure | 47.49 | 95.64 | 20.39 | 5.12 | 5.32 | 51.90 | 21.44 | 2.79 |
| Chemical | 29.84 | 83.66 | 15.31 | 3.92 | 3.30 | 40.60 | 16.35 | 156.00 |
| Control | 29.41 | 77.49 | 15.50 | 4.23 | 2.03 | 44.95 | 20.51 | 2.39 |
| Mean | 35.58 | 85.60 | 17.07 | 4.42 | 3.55 | 45.82 | 19.43 | 53.73 |
75 days | Manure | 66.43 | 153.23 | 22.93 | 7.91 | 3.46 | 213.50 | 33.40 | 4.96 |
| Chemical | 48.72 | 112.58 | 19.25 | 6.17 | 3.43 | 97.58 | 26.26 | 3.87 |
| Control | 40.42 | 86.71 | 19.32 | 6.05 | 4.07 | 48.34 | 27.14 | 2.07 |
| Mean | 51.86 | 117.51 | 20.50 | 6.71 | 3.65 | 119.81 | 28.93 | 3.63 |
105 days | Manure | 82.54 | 215.84 | 23.46 | 9.59 | 2.25 | 277.85 | 35.38 | 3.69 |
| Chemical | 61.92 | 199.08 | 15.50 | 9.26 | 2.38 | 255.60 | 27.90 | 2.43 |
| Control | 63.43 | 138.99 | 15.31 | 9.87 | 3.82 | 201.85 | 31.77 | 1.81 |
| Mean | 69.30 | 184.64 | 18.09 | 9.57 | 2.82 | 245.10 | 31.68 | 2.64 |
| standard error | 4.27 | 12.64 | 0.88 | 0.47 | 0.27 | 14.33 | 1.53 | 1.4 |
| R2 | 0.96 | 0.90 | 0.93 | 0.92 | 0.92 | 0.93 | 0.88 | 0.93 |
| CV% | 18.65 | 33.26 | 14.23 | 21.23 | 24.36 | 23.18 | 17.66 | 47.85 |
| F×H | 0.06 | 0.15 | 0.17 | 0.30 | *** | *** | 0.31 | 0.19 |
FXH= fertilizer and harvesting interaction;*, **, ***= significant at 0.05, 0.01and 0.001 probability levels.
Means within column followed by the same letters are not significantly different
The highest DM content was obtained at early harvesting date (45days), followed by the moderate and last harvesting date, respectively(P<0.001). However, there was no significant between moderate and last harvesting date. The effect of fertilizer type had no significant (p>0.05) effect on DM content of BMII grass.
The 45 days harvesting date had the highest ash content (12.53%) than 75 and 105 days with values of 10.36 and 9.15%, respectively (Table 3). However, the result suggests that the mineral (ash) content of the grass was reduced with increased in the stage of maturity. Regarding the interaction of harvesting date and fertilizer, ash content of the grass has shown significant (P<0.001) difference (Table 4).
Crude protein content
The highest CP% was obtained at early harvesting date (45days), followed by the moderate (75 days) and late harvesting date (105 days) with values of 14.84, 12.88 and 11.61%, respectively. For fertilizer type, the application of manure, NPS fertilizer and without fertilizer (control) produced CP with values12.38, 13.80 and 13.15%, respectively. Indicating the highest CP value was obtained using NPS fertilizer (Table 3).
BMII grass harvested at earlier age (45 days) with the application of chemical fertilizer (NPS) resulted in higher CP content. While, the lowest CP content was observed at the late harvesting age (105 days). On the other hand, the effect of fertilizer type (manure) statistically was similar with the control. The CP content of the grass was significant (P<0.001) for the interaction of interaction of harvesting date and fertilizer in the current result (Table 4).
Neutral detergent fiber content (NDF)
The effect of harvesting date was highly significant (p<0.001) on NDF (Table 3). As harvesting stage increases from 45 to 75 and 105 days, the NDF values were 51.08, 48.26 and 57.10%, respectively. The effect of fertilizer type was not significantly different (p>0.05) in terms of NDF content. BMII grass harvested at late harvesting period (105days) had higher NDF content, whereas the lowest NDF value was observed at moderate harvesting date (75days). The interaction of interaction of harvesting date and fertilizer had significant (P<0.001) effect on the NDF content of the grass in the present finding (Table 4).
Acid detergent fiber content (ADF)
The effect of harvesting date was highly significant (p<0.001) on ADF (Table 3). ADF of BMII grass harvested at late (105days) harvesting date resulted in higher ADF=22.46% concentration, while intermediate harvesting age (75 days) had given relatively lower content of ADF=25.5%. The effect of fertilizer and the interaction between harvesting date and had no significant effect on ADF content in the current experiment.
Acid detergent lignin content (ADF)
The effect of harvesting date was significant (p<0.01) on ADF (Table 2). As harvesting stage increases from 45 to 75 and 105 days, the ADL values were increased from 4.33, 4.41 and 7.75%, respectively. The highest ADL was recorded at late harvesting date (105 days) and intermediate ADL was recorded at intermediate harvesting date (75days). The effect of fertilizer and the interaction between harvesting date and had no significant effect on ADL content in the current experiment.
Table 3. Effect of harvesting date, fertilizer type and their interaction on nutritional quality and yield of BMII grass
Factor | DM % | Ash % | CP % | NDF % | ADF % | ADL % |
Harvesting stage (H) |
|
|
|
|
|
|
45 days | 90.06a | 12.53a | 14.84a | 51.08b | 27.46a | 4.33b |
75 days | 88.65b | 10.36b | 12.88b | 48.26b | 25.50b | 4.41b |
105 days | 88.80b | 9.15c | 11.61c | 57.10a | 35.78a | 7.75a |
Significant | *** | *** | *** | *** | * | ** |
|
|
|
|
|
|
|
Fertilizer type (F) |
|
|
|
|
|
|
Manure | 89.14a | 11.01a | 12.38c | 51.23a | 29.32a | 6.44a |
chemical fertilizer | 89.02a | 10.10a | 13.80a | 51.23a | 28.82a | 4.43a |
Control | 89.36a | 10.93a | 13.15b | 53.82a | 30.60a | 5.62a |
Significant | ns | ns | *** | ns | ns | ns |
|
|
|
|
|
|
|
Mean | 89.17 | 10.68 | 13.11 | 52.15 | 29.58 | 5.5 |
standard error | 0.57 | 0.74 | 1.09 | 1.67 | 1.87 | 0.5 |
R2 | 0.995 | 0.99 | 0.997 | 0.96 | 0.81 | 0.84 |
CV% | 0.42 | 7.7 | 4 | 6.05 | 25.98 | 33.8 |
F×H interaction | ns | ** | *** | * | ns | ns |
ns, *, **, ***= non-significant and significant at 0.05, 0.01and 0.001 probability levels.
Means within column followed by the same letters are not significantly different
F=fertilizer; H=harvesting date; DM=Dry Matter; CP=Crude Protein; NDF=Neutral Detergent Fiber; ADF=Acid Detergent Fiber % and ADL=Acid Detergent Lignin.
Table 4. Interaction of harvesting date and fertilizer on quality traits of BMII grass
Harvesting stage (H) | Fertilizer type | DM % | Ash % | CP % | NDF % | ADF % | ADL % |
45 days | Manure | 90.13 | 12.11 | 14.39 | 50.88 | 31.53 | 4.99 |
| Chemical | 89.94 | 11.90 | 15.31 | 51.27 | 25.22 | 3.84 |
| Control | 90.13 | 13.57 | 14.81 | 51.09 | 25.64 | 4.15 |
| Mean | 90.07 | 12.53 | 14.84 | 51.08 | 27.46 | 4.33 |
75 days | Manure | 88.67 | 11.58 | 12.57 | 46.19 | 24.63 | 3.81 |
| Chemical | 88.59 | 9.50 | 13.62 | 48.94 | 24.88 | 3.83 |
| Control | 88.69 | 9.99 | 12.47 | 49.65 | 26.98 | 5.59 |
| Mean | 88.65 | 10.36 | 12.89 | 48.26 | 25.50 | 4.41 |
105 days | Manure | 88.63 | 9.35 | 10.17 | 56.63 | 31.80 | 10.52 |
| Chemical | 88.53 | 8.89 | 12.48 | 53.93 | 36.37 | 5.62 |
| Control | 89.25 | 9.22 | 12.18 | 60.72 | 39.18 | 7.11 |
| Mean | 88.80 | 9.15 | 11.61 | 57.09 | 35.78 | 7.75 |
| standard error | 0.57 | 0.74 | 1.09 | 1.67 | 1.87 | 0.5 |
| R2 | 0.995 | 0.99 | 0.997 | 0.96 | 0.81 | 0.84 |
| CV% | 0.42 | 7.7 | 4 | 6.05 | 25.98 | 33.8 |
| F×H interaction | Ns | ** | *** | * | ns | ns |
Discussion
Plant Morphological Characteristics and DM Yield
Increment in plant height in the current finding at later harvesting date is in agreement with the findings of Zemene et al.(2020), in which the mean plant height was low in early stage of growth. The mean plant height of BMII grass from the current result is significantly lower than earlier reports (53.76cm) Adnew et al. (2018) and (180cm) Zemene et al. (2020) for the same species. The difference of this result from earlier reports might be due to cultivar differences, management of the plant, harvesting date difference, soil type and climatic condition of the area where the experiment was done. The plant height obtained in the present finding was higher than the results of Susan et al. (2015) who reported that plant height for Brachiaria hybrid Mulato II grass was 28.2cm after 12 weeks. However, the present finding is less than the finding of Mustaring et al. (2014) at the same species. The reason for this variation may be due to different management system and agronomic season.
The observed number of tillers in the current study was in line with the study conducted by Kizima et al. (2014) who reported that application of optimal level of nitrogen fertilization significantly affects the appearance of new tillers and increases the dynamics of tiller population of Cenchrus ciliaris in Morogoro municipal, Tanzania. The effect of manure had shown higher value than that of NPS and control treatment in the present finding is greater than the finding of Mustaring et al. (2014) for the same grass in Indonesia. The reason for this variation might be due to different management system, soil type, agronomic season, and fertilizer type use and agroecological variations.
According to Silva et al. (2013), among the B. brizantha cultivars, leaf length values did not differ, with average values of 20.96, 21.55 and 26.92 cm/tiller for the cvs. Marandu, Piatã and Xaraés, respectively. However, this information demonstrated that those cultivars were given higher value as compared to the current result. This variation might be due to the difference in their species, soil fertility, and maturity stage and climate of the area where the study was conducted. The current result support by Mihret et al. (2018) who revealed that chemical fertilizer and manure were significantly different on leaf length of Desho grass. In the report, length of leaf was greater than earlier report. This could be associated with environmental condition, genetic makeup of forages.
The leaf to stem ratio (LSR) declined sharply as the harvesting date increases. The reason for decreasing LSR with increasing harvesting date might be attributed to the accumulation of more cell wall components in plant tissues as a result of stem development with advancing maturity. But, it is an important factor affecting diet selection, quality and intake of forage of animals (Smart et al. 2004). Therefore, this result is in agreement with different studies. Although Geleti and Tolera (2013) reported that, the LSR of panicum coloratum was significantly affected by the age of re-growth. The significant of value of LSR at the interaction of harvesting date and fertilizer might be related to the fact that leaves decrease though fertilizer has positive effect on growth habits of plant. This difference might come from the genetic variation of grasses, environmental condition, altitudes, soil type, and level of fertilizer, rainfall, temperature and management practices.
The number roots per plant increases linearly with maturity of the plant. This might be due to fact that environmental condition, soil type and management system.
The DM yield increased due to the rapid increase in the tissues of the plant, development of additional tillers and leaf formation, leaf elongation and stem development with increasing plant age. But the current result showed that at harvesting day 75 had greater DM yield than 105 days; due to chemical fertilizer reduce when harvesting day was long (Awoke et al.2020). Although DM yield increased as fertilizer applied which means organic fertilizer (manure) more increase than chemical fertilizer. This result is in agreement with the report of Asmare et al. (2017) who observed that, the total DM yield of the longest harvesting period (150d) was the highest as shown in table 1. Whereas, the lower DM yield was produced from the shortest harvesting period (90d).
Chemical Composition
Application of fertilizer had no significant (p>0.001) effect on DM content of BMII grass in the current study which agreed with Desho grass as reported by Mihret et al. (2018) on type of fertilizer had no significant effect on DM content at 120 days of harvesting date. The overall mean of DM content in the current result was lower than Brachiaria mutica grass as reported by Zemene et al. (2020) was 94.46%. This difference might be due to difference in soil condition, genetics, fertilizer, interaction effect and drying methods of samples of authors where both studies were conducted.
The declining mineral content is due to the fact that, as grasses mature, the mineral content declines due to a natural dilution process and translocation of minerals to the roots (Minson, 1990). Concentration of minerals in forage varies due to factors like plant developmental stage, morphological fractions, climatic conditions and soil characteristics (McDowell and Valle, 2000).Beside to this, ash concentration declined significantly as harvesting date increased and progressive increases in plant spacing resulted in significant increases in ash concentration of Desho grass (Tilahun et al., 2017). The reason might be associated with species difference; soil type and fertility and management system of the plant. Although Ahmad et al. (2011) reported ash content increased application of inorganic, organic and mixed both type of fertilizer than without fertilizer forage of oat (Avena sativa L.). Mineral (ash) nutrients in the feed play major roles in the body function of the overall animal production and productivity activity including skeletal development and maintenance, energy, milk production and body function (Rasby et al., 2011).
The decline in CP content with advancing stage of maturity is due accretion of higher proportion of fiber corresponding to plant growth. Although, this could be attributed mainly to dilution of the CP contents of the forage crops by the rapid accumulation of cell wall carbohydrates at the later stages of growth (Van Soest, 1994). The decreasing CP contents of grasses with increasing plant harvesting may be because of reduced leaf to stem ratio (Chaparro et al. 1997). The CP content is one of the most important criteria to determine the nutritional nutritive value of livestock feeds; this due to a level of CP increases, the dry matter intake by livestock and rumen microbial growth would also increase (Chanthakhoun et al., 2012). In the present finding, late harvesting contained low levels of CP (11.61%) at harvest, which is higher the level above which feed intake is restricted. But, despite the decline in CP content with increasing stage of maturity, the intermediate and earlier harvesting concentration (12.88 and 14.84%) exceeded the minimum CP level (7.5%) required for rumen function (Jusoh et al., 2014). This indicates the possibility of improving the feeding of animals in tropical regions by early, intermediate and late harvesting of Brachiaria hybrid Mulato II grass, thus enhancing the quality of nutrients supplied to animals. As fertilizer applied, the CP content was higher at experimental cultivar chemical fertilizer types. CP increased from inorganic fertilizer (chemical fertilizer) in the current study. This might be because of continued application fertilizer, allowed to continuous sprouting of the grasses of new leaves, which was a bit fresh even during the harvest of forage biomass (Hassan, et al., 2015). This difference might due to forage genetics, harvesting date, environmental conditions and fertilizer type, and cultivar.
Additionally, harvesting date and effect of fertilizer type significant effect on CP content BMII grass in the current study is in line with Mustaring et al. (2014), CP content of Brachiaria grass was affected by type and species of grass. The lowest CP was from Brachiaria Mutica grass (8.64) followed by Brachiaria brizantha (11.77) while, the highest was from Mutica grass (11.93) at similar harvesting date 60 days in dry lands of Central Sulawesi Indonesia. The current result of CP content was higher than as reported by the same author within the same species Brachiaria cultivar of the current study. The highest CP content was recorded from Brachiaria decumbens (16.7) and the lowest was from Brachiaria hybrid Multo (13.8) at 90 days of harvesting date. The current result from a cultivar was lower CP content than as reported by the same author. Susan et al. (2015) reported also the type of species and cultivars had a significant effect on the CP content of Brachiaria grasses.
On the other hand, Adnew et al. (2018) reported that the CP content was different among the type of Brachiaria brizantha ecotypes. The highest CP content was recorded from var Eth.13726 (12.36) followed by var Eth.1377 (11.17) and the lowest were from var Eth.13809 at 90 days of harvesting date. The current result of CP content from hybrid Mulato II was higher than as reported by the same author but different harvesting ages. This difference might become from the genetic variation of grasses, environmental conditions etc. Zemene et al. (2020) reported that harvesting date significantly affects the CP content of Brachiaria mutica. The CP content was increasing trend (6.16 to 9.46 to 13.52%) as harvesting date decreased form (120 to 90 to 60 days), respectively. The current result is higher than the same species of Brachiaria hybrid Mulato II as reported by the same author at the different harvesting date and with the fertilizer of the current study. The results obtained in this finding were in agreement with those reported by Fraser et al. (2001) who attributed that, the decline in CP concentration to higher cell wall contents were observed in more mature grasses. The CP concentration of leaves declined dramatically with increase in cutting interval from 28.2% at 40 days to 8.8% at 80 days, respectively. The CP content serves as an important indicator of fodder quality (Jusoh et al., 2014).
This is due to the fact that, as the plant becomes mature the cellulose, hemicelluloses, lignin and silica which are found in the insoluble portion of the forage become increased. Beside this, in the present finding, there is high production of more seed at plant maturity is another indication for high fiber accumulation. This might be due to the translocation of protein from leaf and stem to seed, thereafter high fiber is remaining on the plant. Aganga et al. (2005) has also reported clearly that, when the maturity of grass is increased, the quality and digestibility decreased which in turn could be related to increment in the quantity of fiber fractions. In fact, progress in the vegetative cycle triggers increase in lignin rate and in cell wall thickness in the plant´s tissues, mainly due to a decrease in the leaf: stem ratio.
The NDF obtained in the present finding was lower (57.10%) at the late harvesting (105day) than the results of Zemene et al. (2020) and Beyadglign (2019), who reported for Brachiaria Mutica, BMII grass was (70.98, 65.75%) at 120 and 90 days of harvesting, respectively. The differences in NDF attributed to nature of the grass, soil, the harvesting day variation and climatic conditions. The current result is also lower than the findings of Adnew et al., (2018) that report, the NDF content, of Brachiaria brizantha ecotypes was highest (74.08%) from late harvesting (120d after planting) while it was comparatively lower for earlier harvesting periods (61.60% at 60 d and 67.08% at 90 days). Thought, the NDF recorded by the author is higher as compared to the current finding (48.26% at 75day and 57.10% at 105 day). This variation might be due to the reason that BMII has high leaf material than Brachiaria brizantha ecotypes. According to Mustaring et al. (2014) who noted that, the NDF content of B. brizantha, B. mulato and B.mutica as 65.66, 63.66 and 71.96% at 8 weeks after planting, respectively. As reported by the same author, the NDF content of B. mulato (63.66%) is higher as compared to the present result (48.26%) at relatively similar age. This difference might be due to climatic condition and available soil nutrient in study area.
The current finding is similar to Nemera et al. (2017). The application of organic and inorganic fertilizer did not significantly affect the NDF content of natural pasture at (p>0.05). This might be interconnected with stage of harvest rather than treatments as plants at matured stage plants become lignified and have highest neutral detergent fiber as indicated in (Zewdu et al., 2010). In contrast the current finding to Nemera et al. (2017) who reported that the effect of organic and inorganic fertilizer application on improvement of degraded grazing land of the grass by using fertilizer and manure to decrease NDF content for different grass species. This is means, chemical fertilizer and manure improves the plant growth and raise new leaves and shoots, which minimize the NDF content of the grass. NDF concentration is the component most consistently associated with forage intake (Van Soest, 1994). According to Van Saun (2006), forage grass with less than 50% NDF described as high nutritive value whereas NDF greater than 60% considered as low nutritive value. The current result of NDF content form experimental cultivar classified as high nutritive value forage according to the same author classification.
In the current study it has been observed that ADF content is increased as maturity of the plant. This is due to the fact that the structural cell wall components increase as plant gets matured because photosynthesis components are converted to structural components at the expense of soluble carbohydrates (Ammar et al., 2010). The ADF is the percentage of highly indigestible and slowly digestible material in a feed or forage by ruminant animals. Higher forage ADF results in reduced dry matter digestibility as a consequence of increased lignifications of cellulose in the latter stage of the plants (Depeters, 1993). In the current study, ADF content is increased as maturity of the plant increases. An increase in ADF content in the current result with the advance in harvesting days of grass was reinforced by the results of Adnew et al., (2018) who shows, Brachiaria brizantha ecotypes harvested at 120 days after planting had a higher ADF (52.88) than for samples harvested at 60 days and 90 days after planting (40.65and 47.52%, respectively) which is greater than the result of the present finding (35.78% at 105days). The current finding corresponds to the finding of Mustaring et al. (2014) who demonstrated that, the ADF content of B. brizantha, B. mulato and B. mutica (38.21, 38.79 and 46.09%) are increasing with plant maturity. But, among the Brachiaria cultivar B. mutica score higher ADF which is again higher as compared to the current result (35.51%). The variation might be due to the agro-ecology and season of the experiment where the research was conducted.
The result indicated that, ADL was increased linearly with increased plant maturity. This is due to the reason that, with the age increase the level of lignin in plant also increase which show a rapid lignification to occur in late development stage and the presence of insoluble fiber, particularly lignin, lowers the overall digestibility of the feed by limiting nutrient availability (Van Soest, 1994). Therefore, forages with lower ADL concentrations are more desirable in livestock feeding (Ansah et al., 2010). The effect of chemical fertilizer and manure were not significant difference of ADL concentration of BMII grass. This result is, similarly to Olanite et al (2010) report that different nitrogen rate was not significantly affect ADL concentration of Columbus grass in southwest Nigeria. The current result is lower than (Mustaring et al., 2014) who reported ADL content of (8.18%) for BMII grass. The reason might be associated with environmental condition, soil type and management system of the grass.
Conclusion
The results of this study showed that most of the morphological characteristics of the grass were less affected by the interaction among fertilizer type and harvesting days. Therefore, based on this information, beneficiary making their decisions based on the relative importance of forage yield and quality in their operations. BMII grass should be cultivated using manure to maximize biomass yield if accessible by smallholder farmers, otherwise it is possible to use chemical fertilizer could be an alternative to produce good quality forage. Hence, BMII grass harvested from at 105 days of harvesting would be more beneficial to get high quantity yields and as an option to solve the shortage of feed.
Data Availability Statement
The data that support this study will be shared upon reasonable request to the corresponding author.
Conflicts of interest
All authors declare there is no conflict of interest in the publication of this paper.
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