1. bookVolume 73 (2022): Edizione 1 (March 2022)
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eISSN
2719-5430
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30 Mar 2016
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Inglese
Accesso libero

Forage growth, yield, and quality responses of two hybrids of Napier and sorghum at three cutting intervals in the southern province of Sri Lanka

Pubblicato online: 28 Sep 2022
Volume & Edizione: Volume 73 (2022) - Edizione 1 (March 2022)
Pagine: 1 - 11
Ricevuto: 21 Oct 2021
Accettato: 10 Dec 2021
Dettagli della rivista
License
Formato
Rivista
eISSN
2719-5430
Prima pubblicazione
30 Mar 2016
Frequenza di pubblicazione
4 volte all'anno
Lingue
Inglese
Introduction

The performance of dairy animals depends on the constant availability of good-quality fodder in sufficient quantities. Shortage of good-quality feeds in adequate amounts is considered as an important factor affecting the development of dairy sector in Sri Lanka (Houwers et al., 2015). Most tropical grasses such as Megathyrsus maximus grass, brachiaria grass, and Pennisetum purpureum grass mature very fast and are generally low in sugar and protein and high in fiber. Therefore, highly nutritious green fodder varieties can be used as a substitute for low-quality grasses and high-cost concentrate feeds to reduce the cost of feeding.

Hybrid Napier variety CO-3 (P. purpureum × Pennisetum americanum) is a high-yielding perennial fodder that possesses higher tillering capacity, regeneration capacity, green forage yield, leaf to stem ratio, and crude protein (CP) and dry matter (DM) content; has high palatability; shows resistance to pest and diseases; and is free from adverse factors compared to other fodder verities grown in the country. In 1997, the Tamil Nadu Agricultural University in Coimbatore developed, CO-3 and it was introduced to Sri Lanka by the livestock breeding project in 1999 (Premaratne and Premalal, 2006). CO-4 is a newly introduced hybrid Napier variety and was developed by crossing between pearl millet (Pennisetum glaucum) and Napier grass (P. purpureum Schumach) at the Tamil Nadu Agricultural University in Coimbatore (Vijayakumar et al., 2009). It is most popular due to its high yield potential, good forage quality, tolerance to grazing/damages by wild animals, insect–pest disease resistances, and high response toward manure, fertilizer, and irrigation. CO-4 can give a higher yield compared to other varieties of hybrid Napier (Kumar et al., 2015). Improved fodder varieties such as hybrid Napier CO-3, CO-4, and fodder sorghum var. sugar graze (Sorghum bicolor), which have been recently introduced, are used for making silages and on the basis of physical, nutritional, and chemical quality, sorghum is a promising fodder for silage production compared with both hybrid Napier varieties (Seresinhe et al., 2020) Fodder sorghum var. sugar graze is a top-quality hybrid fodder, which is newly designed for grazing, green chop, or hay (Tew and Cobill, 2008). In addition, fodder sorghum can be cut four to five times with one planting, considering the nutritive value, production capacity, and profitability (Pushparajah and Sinniah, 2018).

Although these varieties have been tested under different agroclimatic zones of the country, optimal management practices for the southern province conditions are not clear. Appropriate cutting management is essential for high production and quality of these species (Jorgensen et al., 2010; Tessema et al., 2010), since the species are well suited for cut and carry systems (Bayer, 1990). Numerous studies have dealt with cutting management to optimize forage yield and quality of Napier grass (Premaratne and Premalal, 2006; Bayble et al., 2007; Tessema et al., 2010; Rengsirikul et al., 2011) and fodder sorghum (Bandara et al., 2016; Pushparajah and Sinniah, 2018; Seresinhe et al., 2020).

Hence, it is important to evaluate the agronomy characteristics, yield, and nutritional quality of hybrid Napier (var. CO-3, CO-4) and fodder sorghum (var. sugar graze) under different harvesting intervals to popularize them as fodder crops among dairy farmers in the southern province of Sri Lanka. Therefore, the present study was carried out to assess and compare the growth, yield, and nutritive value of the fodder varieties mentioned above over three cutting intervals, grown under local conditions.

Materials and methods
Site, design, and establishment of forages

The field experiment was conducted at the Faculty of Agriculture Research Farm, University of Ruhuna, Kamburupitiya, Sri Lanka, starting from February 2017 to May 2019 (low country wet zone, 58 m above mean sea level, latitude and longitude: 7.8731° N, 80.7718° E, mean annual rainfall: 2400 mm, mean annual temperature: 27°C–31°C). The experimental design was a factorial arrangement in a randomized complete block design having three forages (hybrid Napier var. CO-3 and var. CO-4 and fodder sorghum var. sugar graze), three cutting frequencies (4, 6, and 8 weeks), and three blocks. The plot size was 5 × 5 m. A total of 27 plots were used. Two stem cuttings of hybrid Napier grasses having two nodes were planted with 1 × 1 m spacing in one spot on the February 14, 2017. An equalizing cut was performed for hybrid Napier grasses at a standardized height of 5 cm after 3 months of planting (May 14, 2017). Sorghum seeds were planted on the date of equalizing cut. Three seeds of sorghum were planted manually in one spot with 45 × 15 cm spacing. After germination, two healthy seedlings were selected from each spot and the other seedling was thinned out. All plots were irrigated (three to four irrigation at 10–12 days interval) when it was not raining to ensure adequate soil moisture for plant growth. Weeds were uprooted manually after 1 month of establishment.

Measurement of agronomy characteristics

During the first year, three plants from each variety from the middle of each net plot (16 m2) were randomly selected to measure the growth. Plant height, number of leaves, number of tillers, leaf length, leaf width, and stem diameter were determined at weekly intervals up to eighth week of growth. The tallest tiller of each plant was used to measure the plant height, stem diameter, leaf length, and leaf width. Height of the plant was measured by using a flexible ruler from the base where it touched the soil to the vertically held leaf tip. Number of tillers and number of leaves were counted manually. Damaged and dried leaves were discarded for calculating the total number of leaves. A ruler was used to measure the length and width of a randomly selected leaf from the tallest tiller in each plant, and an averaged value was calculated. Diameter of the lowest node was measured with a vernier calliper.

Harvesting, measurement of DM yield

All three forages were harvested at three intervals at 4th, 6th, and 8th weeks up to 2 years. Plants were clipped at standardized height of 3–5 cm from the ground level. First, guard rows were discarded and net plots were harvested to record fresh weights. Representative samples were taken from the harvested herbage and chopped into 1–2 cm pieces. The chopped samples were dried at 60°C in an oven for 48 h to a constant weight. This procedure was repeated for the three harvesting frequencies throughout the year for the three varieties. Harvest dates are given in Table 1.

Harvest dates for cutting treatments in 2017 and 2018.

Tabelle 1. Erntedaten für Schnittbehandlungen in den Jahren 2017 und 2018.

Cutting interval Harvest dates Number of cuts
4 weeks 2017: June 14, July 12, Aug 9, Sep 6, Oct 4, Nov 1, Nov 29, Dec 27 13
2018: Jan 24, Feb 21, Mar 21, Apr 18, May 16
6 weeks 2017: Jun 25, July 6, Sep 17, Oct 29, Dec 10 9
2018: Jan 21, Mar 4, Apr 15, May 27
8 weeks 2017: Jul 9, Sep 3, Oct 29, Dec 24, 6
2018: Feb 4, Apr 29
Analysis of nutritive composition

Dried samples were ground to pass through a 1-mm sieve. Samples were stored in labeled glass bottles for further nutritional analysis. DM, CP (by Kjeldhal method; Kjeltec TM 8400; FOSS Analytical Company, DK Hilleroed, Denmark), and crude fiber (CF; acid and alkali method) were determined according to the Association of Official Analytical Collaboration (AOAC (2005) procedure.

Calculations

Annual dry matter yield (t/ha) = annual fresh herbage yield (t/ha) × dry matter content (%)

Annual crude protein yield (t/ha) = annual dry matter yield (t/ha) × crude protein content (%)

Rainfall data

Total monthly rainfall data were extracted from the meteorological station of the Department of Agricultural Engineering at the University of Ruhuna, Mapalana, Kamburupitiya. Annual rainfalls during 2017 and 2018 were 1935 and 1983 mm, respectively (Figure 1). It was lower than the average annual rainfall of 2400 mm. Rainfall was very low in February 2017 at the establishment of forages. However, it was increased dramatically during the growing period of forages and reached a lower peak during the period of equalizer cut in May 2017 and October 2018. A higher peak was observed during November 2017 and May 2018 (Figure 1).

Figure 1

Total rainfall during 2017 and 2018. Data extracted from the records of the meteorological station, Department of Agricultural Engineering, Mapalana, Kamburupitiya, Sri Lanka.

Abbildung 1. Gesamtniederschlag in den Jahren 2017 und 2018 aus den Aufzeichnungen der Wetterstation, Abteilung für Agrartechnik, Mapalana, Kamburupitiya, Sri Lanka.

Data analysis

Generalized Linear Model with two-factor analysis of variance (ANOVA) was used to compare the mean differences and interaction between cultivars and three cutting intervals. Tukey's Least Significant Difference (LSD) test was used to test the differences between means. Differences between means were considered significant at p < 0.05. Statistical analysis was done with Minitab version 16.

Results
Growth characteristics

The effect of cultivar and cutting interval on plant height, leaf length and width, number of tillers, number of leaves, and stem diameter and their interaction effects are presented in Tables 2 and 3, respectively. Significant interactions between cultivar and cutting interval were found for plant height, stem diameter, leaf length, and leaf width. In accordance with the main effects, for cultivars, plant height followed the order sugar graze > CO-4 > CO-3, while stem diameter for CO-3 was greater, which was followed by CO-4 and sugar graze. Cutting interval had similar effect on plant height and stem diameter. Plant height increased progressively when the cutting interval increased. At 4 weeks, CO-4 had the lowest plant height, with no significant difference found between CO-3 and sugar graze, while no significant difference was recorded in all varieties at 6 and 8 weeks. Sugar graze had the lowest leaf length and highest leaf width at all cutting intervals, and there was no significant difference between hybrid Napier varieties. There was no significant difference in the number of tillers and leaves between CO-3 and CO-4 varieties across all cutting intervals. Stem diameter at 6 and 8 weeks cutting interval exceeded that of 4 weeks interval. At all cutting intervals, CO-4 gave the highest number of tillers and was followed by CO-3.

Effects of variety and cutting interval on plant height, leaf length, leaf width, number of tillers, number of leaves, and stem diameter of three forages at the first harvesting year. Means ± standard error followed by different letters within columns show statistically significant differences (p < 0.05).

Tabelle 2. Auswirkungen von Sorte und Schnittintervall auf Pflanzenhöhe, Blattlänge, Blattbreite, Anzahl der Ackerbauern, Anzahl der Blätter und Stammdurchmesser von drei Futtermitteln. Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05).

Treatment Plant height (cm) Leaf length (cm) Leaf width (cm) No. of tillers No. of leaves Stem diameter (mm)
Variety
CO-3 163.0 ± 19.6b 94.4 ± 6.1a 3.6 ± 0.3c 33.5 ± 0.4a 254.8 ± 13.1a 15.2 ± 1.7a
CO-4 164.7 ± 28.3ab 91.0 ± 6.4b 3.9 ± 0.3b 35.1 ± 0.6a 266.8 ± 15.8a 13.9 ± 1.0b
Sugar graze 169.0 ± 25.9a 66.6 ± 10.2c 7.2 ± 1.3a 0.0b 8.5 ± 0.7b 12.9 ± 0.9c
Harvesting interval
4 weeks 118.3 ± 4.8c 69.3 ± 11.5c 3.6 ± 0.5c 22.2± 0.4 157.8 ± 75.4b 11.6 ± 0.3b
6 weeks 177.8 ± 3.0b 88.3 ± 7.3b 5.3 ± 1.3b 23.2 ± 0.5 188.8 ± 90.0a 15.0 ± 0.9a
8 weeks 200.6 ± 5.5a 94.4 ± 7.4a 5.7 ± 1.6a 23.1 ± 1.1 183.5 ± 88.2ab 15.0 ± 0.9a

Interaction effects of variety and cutting interval on plant height, leaf length, leaf width, number of tillers, number of leaves, and stem diameter of three forages at the first harvesting year. Means ± standard error followed by different letters within columns differ statistically significant (p < 0.05). V: Variety, H: Harvesting interval.

Tabelle 3. Interaktionseffekte von Sorte und Schnittintervall auf Pflanzenhöhe, Blattlänge, Blattbreite, Anzahl der Bestocker, Anzahl der Blätter und Stängeldurchmesser von drei Futtermitteln im ersten Erntejahr. Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Harvesting interval p-Value
4 weeks 6 weeks 8 weeks
Plant height CO-3 125.0 ± 6.1e 173.4 ± 4.2d 190.6 ± 0.5bc V 0.038
CO-4 109.0 ± 7.2f 183.6 ± 3.8cd 201.6 ± 2.1ab H 0.000
Sugar graze 120.9 ± 3.2e 176.5 ± 9.3cd 209.6 ± 4.3a V × H 0.000

Leaf length CO-3 82.7 ± 1.6c 96.8 ± 1.5ab 103.6 ± 3.7a V 0.000
CO-4 78.7 ± 1.0cd 94.5 ± 1.5b 99.9 ± 1.2ab H 0.000
Sugar graze 46.4 ± 1.5e 73.7 ± 0.4d 79.7 ± 1.5cd V × H 0.000

Leaf width CO-3 3.0 ± 1.8e 3.8 ± 0.0d 4.0 ± 0.1d V 0.000
CO-4 3.2 ± 0.2e 4.1 ± 0.0d 4.3 ± 0.0cd H 0.000
Sugar graze 4.6 ± 0.6c 8.0 ± 0.4b 8.9 ± 0.0a V × H 0.000

No. of tillers CO-3 32.8 ± 6.1a 34.2 ± 7.1a 33.4 ± 7.4a V 0.000
CO-4 33.8 ± 7.9a 35.5 ± 7.1a 36.0 ± 6.6a H 0.672
Sugar graze 0.0b 0.0b 0.0b V × H 0.969

No. of leaves CO-3 229.4 ± 55.3b 272.9 ± 56.6ab 262.2 ±50.7ab V 0.000
CO-4 237.0 ± 42.7ab 284.4 ± 57.2a 284.4 ± 57.2a H 0.002
Sugar graze 7.1 ± 0.8c 9.0 ± 0.5c 9.3 ± 0.5c V × H 0.240

Stem diameter CO-3 11.7 ± 0.5d 16.5 ± 0.9a 17.2 ± 0.9a V 0.000
CO-4 12.0 ± 0.7cd 15.0 ± 1.2ab 14.8 ± 1.1ab H 0.000
Sugar graze 11.0 ± 0.3d 13.5 ± 1.2bc 14.1 ± 1.3bc V × H 0.009
Annual DM (ADM) yield and nutritive composition

The effects of cultivar and cutting interval on ADM and nutritive composition are presented in Tables 4 and 5, respectively. Among the main effects, cultivar had a significant effect on ADM production (CO-3 > CO-4 > sugar graze) and cutting interval had a significant effect too (8 weeks > 6 weeks > 4 weeks) during both years. Cultivar had a significant effect on herbage CP concentration, with sugar graze exceeding (p < 0.05) CO-4 and CO-3. Herbage CP concentration declined dramatically with increase in cutting interval from 20.4% at 4 weeks to 13.9% at 8 weeks during the first harvesting year and from 20.7% at 4 weeks to 13.6% at 8 weeks during the second harvesting year. Annual CP yields of three cultivars followed the same pattern as ADM yield during both years. Cultivar had a significant effect on CF concentration, wherein sugar graze had the lowest effect compared with CO-3 or CO-4.

Effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the first harvesting year (2017–2018). Means ± standard error followed by different letters within columns differ statistically significant (p < 0.05).

Tabelle 4. Auswirkungen der Sorte und des Schnittintervalls auf die jährliche Trockenmasseausbeute, den Trockenmassegehalt, das Rohprotein, die jährliche Rohproteinausbeute und den Rohfasergehalt von drei Futtermitteln (2017–2018) Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05).

Treatment Dry matter (%) Annual dry matter yield (t/ha) Crude protein (%) Annual crude protein yield (t/ha) Crude fiber (%)
Variety
CO-3 14.25 ± 0.91b 29.30 ± 8.08a 15.89 ± 2.16b 4.31 ± 0.79a 28.88 ± 0.84b
CO-4 15.15 ± 1.39ab 26.02 ± 7.21b 15.96 ± 2.09b 3.87 ± 0.71a 29.45 ± 1.19a
Sugar graze 15.73 ± 2.09a 24.68 ± 11.61b 18.22 ± 1.73a 4.10 ± 0.13a 25.87 ± 2.02c
Harvesting interval
4 weeks 12.66 ± 0.30c 10.04 ± 3.40c 20.35 ± 0.22a 2.02.82 ± 0.68c 25.62 ± 1.79c
6 weeks 14.78 ± 0.61b 29.32 ± 2.22b 15.86 ± 1.54b 4.62.26 ± 0.41b 28.36 ± 0.82b
8 weeks 17.69 ± 0.96a 40.63 ± 1.42a 13.86 ± 0.54c 5.64.47 ± 0.39a 30.22 ± 0.80a

Effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the second harvesting year (2018–2019). Means ± standard error followed by different letters within columns shows statistically significant differences (p < 0.05).

Tabelle 5. Auswirkungen von Sorte und Schnittintervall auf die jährliche Trockenmasseausbeute, den Trockenmassegehalt, das Rohprotein, die jährliche Rohproteinausbeute und den Rohfasergehalt von drei Futtermitteln während des zweiten Erntejahres (2018–2019). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0.05).

Treatment Dry matter (%) Annual dry matter yield (t/ha) Crude protein (%) Annual crude protein yield (t/ha) Crude fiber (%)
Variety
CO-3 13.29 ±1.03b 29.58 ± 8.20a 15.98 ± 2.20b 4.14 ± 0.81a 28.32 ± 0.82b
CO-4 14.41 ± 1.10ab 26.31 ± 7.49b 15.53 ± 2.37b 3.70 ± 0.79a 29.03 ± 1.29a
Sugar graze 15.69 ± 1.73a 25.96 ± 11.20b 18.49 ± 2.02a 4.22 ± 0.17a 25.89 ± 1.70c
Harvesting interval
4 weeks 12.49 ± 0.41c 10.78 ± 2.56c 20.72 ± 0.82a 1.89 ± 0.56c 25.36 ± 1.39c
6 weeks 14.03 ± 0.65b 29.67 ± 2.30b 15.65 ± 1.80b 4.56 ± 0.51b 28.19 ± 0.69b
8 weeks 16.87 ± 1.07a 39.39 ± 1.58a 13.63 ± 0.56c 5.61 ± 0.41a 29.69 ± 0.86a

Interaction effects of variety and cutting interval on ADM and nutrient composition of first and second harvesting years are presented in Tables 6 and 7, respectively. ADM production during both years was higher at longer cutting intervals (8 weeks) for all varieties (Figure 2). Repeated cutting at short intervals (4 and 6 weeks) resulted in low herbage yields, compared with longer (8 weeks), uninterrupted periods of growth. Although DM productions of both Napier varieties were superior at shorter cutting intervals, sugar graze out yielded both varieties at 8 weeks during both years. The pattern of the ADM yield was not much different during both production years for the three varieties (Figure 2). All three varieties showed the highest value for CP percentage at 4 weeks cutting interval during both years. In both years, sugar graze had higher CP than hybrid Napier varieties at all cutting intervals. Even though there was no significant difference in CP contents of CO-3 and CO-4 at the first year, it was higher (p < 0.05) in CO-3 at 6 and 8 weeks of cutting intervals in the second year. CP yield followed the same trend and increased when the cutting interval increased. CP yield of sugar graze was superior at 8 weeks during both years. Sugar graze recorded the lowest CF at all cutting intervals and there were no significant differences between the hybrid Napier varieties at 4 and 6 weeks during both years.

Figure 2

Effect of variety and cutting interval on ADM yield, CP content, and ACP yield of three varieties during the first (2017–2018) and the second (2018–2019) harvesting years, respectively. abcdefg Interactions means with different superscripts in bars are significantly different at (p > 0.05). ACP: annual crude protein, ADM: annual dry matter, CP: crude protein.

Abbildung 2. Auswirkung von Sorte und Schnittintervall auf den jährlichen Ertrag an Trockenmasse (ADM), den Gehalt an Rohprotein (CP) und den jährlichen Ertrag an Rohprotein (ACP) von drei Sorten während des 1. (2017–2018) bzw. 2. (2018–2019) Erntejahres. Interakton mittel mit unterschiedlichen hochstellungen in takten unterscheiden sich signifikant bei (p > 0.05).

Interaction effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the first harvesting year (2017–2018). Means ± standard error followed by different letters within columns shows statistically significant differences (p < 0.05). V: Variety, H: Harvesting interval.

Tabelle 6. Interaktionseffekte von Sorte und Schnittintervall auf den jährlichen Trockenmasseertrag, den Trockenmassegehalt, das Rohprotein, den jährlichen Rohproteinertrag und den Rohfasergehalt im ersten Erntejahr (2017–2018). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Cutting interval p-Value
4 weeks 6 weeks 8 weeks
Dry matter (%) CO-3 11.67 ± 0.41cd 13.01 ± 0.04cd 15.21 ± 0.92abc V 0.000
CO-4 12.86 ± 0.36cd 13.84 ± 0.71bcd 16.53 ± 2.03ab H 0.059
Sugar graze 12.95 ± 0.09d 15.24 ± 0.35abc 18.88 ± 0.07a V × H 0.085

Annual dry matter yield (t/ha) CO-3 13.63 ± 0.35e 34.24 ± 0.65c 40.87 ± 1.56b V 0.000
CO-4 13.04 ± 0.72e 26.92 ± 0.74d 38.96 ± 1.75b H 0.000
Sugar graze 3.24 ± 0.32f 27.85 ± 0.82d 44.35 ± 1.32a V × H 0.000

Crude protein (%) CO-3 20.37 ± 0.45b 14.15 ± 0.18e 13.43 ± 0.11e V 0.000
CO-4 20.25 ± 0.21b 13.57 ± 0.23f 12.78 ± 0.05g H 0.000
Sugar graze 21.55 ± 0.32a 19.23 ± 0.05c 14.68 ± 0.14d V × H 0.000

Annual crude protein yield (t/ha) CO-3 2.77 ± 0.34de 4.84 ± 0.23c 5.48 ± 0.13b V 0.000
CO-4 2.64 ± 0.11e 3.65 ± 0.12d 4.98 ± 0.32b H 0.000
Sugar graze 0.69 ± 0.18f 5.35 ± 0.15b 6.51 ± 0.15a V × H 0.000

Crude fiber (%) CO-3 26.75 ± 0.23d 28.65 ± 0.35c 29.55 ± 0.19b V 0.000
CO-4 26.75 ± 0.25d 29.10 ± 0.19c 31.25 ± 0.1a H 0.000
Sugar graze 22.58 ± 0.05e 26.26 ± 0.14d 28.86 ± 0.15c V × H 0.000

Interaction effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the second harvesting year (2018–2019) Means ± standard error followed by different letters within columns show statistically significant differences (p < 0.05). V: variety, H: harvesting interval.

Tabelle 7. Interaktionseffekte von Sorte und Schnittintervall auf den jährlichen Trockenmasseertrag, den Trockenmassegehalt, das Rohprotein, den jährlichen Rohproteinertrag und den Rohfasergehalt im zweiten Erntejahr (2018–2019). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Cutting interval p-Value
4 weeks 6 weeks 8 weeks
Dry matter (%) CO-3 11.67 ± 0.41cd 13.01 ± 0.04cd 15.21 ± 0.92abc V 0.000
CO-4 12.86 ± 0.36cd 13.84 ± 0.71bcd 16.53 ± 2.03ab H 0.059
Sugar graze 12.95 ± 0.09d 15.24 ± 0.35abc 18.88 ± 0.07a V × H 0.085

Annual dry matter yield (t/ha) CO-3 13.63 ± 0.35e 34.24 ± 0.65c 40.87 ± 1.56b V 0.000
CO-4 13.04 ± 0.72e 26.92 ± 0.74d 38.96 ± 1.75b H 0.000
Sugar graze 3.24 ± 0.32f 27.85 ± 0.82d 44.35 ± 1.32a V × H 0.000

Crude protein (%) CO-3 20.37 ± 0.45b 14.15 ± 0.18e 13.43 ± 0.11e V 0.000
CO-4 20.25 ± 0.21b 13.57 ± 0.23f 12.78 ± 0.05g H 0.000
Sugar graze 21.55 ± 0.32a 19.23 ± 0.05c 14.68 ± 0.14d V × H 0.000

Annual crude protein yield (t/ha) CO-3 2.77 ± 0.34de 4.84 ± 0.23c 5.48 ± 0.13b V 0.000
CO-4 2.64 ± 0.11e 3.65 ± 0.12d 4.98 ± 0.32b H 0.000
Sugar graze 0.69 ± 0.18f 5.35 ± 0.15b 6.51 ± 0.15a V × H 0.000

Crude fiber (%) CO-3 26.75 ± 0.23d 28.65 ± 0.35c 29.55 ± 0.19b V 0.000
CO-4 26.75 ± 0.25d 29.10 ± 0.19c 31.25 ± 0.1a H 0.000
Sugar graze 22.58 ± 0.05e 26.26 ± 0.14d 28.86 ± 0.15c V × H 0.000
Discussion
Growth characteristics

Growth characteristics of the two Napier grass cultivars and sugar graze responded to the varying cutting intervals, demonstrating that defoliation impacts the morphological development and forage quality (Manyawu et al., 2003). Sugar graze had the highest plant height, which is a result of elongation of stem internodes due to narrow spacing as suggested by Pushparajah and Sinniah (2018). Generally, stem elongation occurs due to narrow spacing as a result of competition to obtain sunlight (Pushparajah and Sinniah, 2018; Lamana, 2003). Taller plants lead to narrower stem diameter as well. The plant height of sugar graze at 8 weeks of growth in the present study was slightly deviated from the findings of Epasinghe et al. (2012) who reported 218 cm at the 9th week of growth when grown in a wet zone in Sri Lanka. Furthermore, Samini and Premaratne (2017) reported 231 cm of plant height in sugar graze and 145 cm of plant height in CO-3 at the 8th week of growth when grown in a northern region of Sri Lanka. This variability may be due to the diverse climatic and soil conditions of the different regions of Sri Lanka. According to Ekemini et al. (2012), there is a positive correlation between plant height and fodder yield. However, greater height of sugar graze compared to CO-3 at the 8th week verified the suitability of sugar graze as good forage. According to Amin (2011), leaf area of forage increases with the leaf length and leads to higher forage yield attributing to efficient photosynthesis. Pahuja et al. (2016) reported a leaf length of 95 cm for sugar graze in India for the first cut at 50% of flowering and a spacing of 15 × 45 cm. Leaf length of CO-3 is higher compared with the findings of Samini and Premaratne (2017) at the 8th week and Mounika et al. (2015) at the 13th week of growth (85.6 and 82.3 cm, respectively). The variability of the leaf length in the current study may be attributed to growth due to maturity and the climatic conditions in different agro ecological zones.

Higher number of tillers and leaves in hybrid Napier varieties demonstrates the profuse tillering capacity of hybrid Napier varieties (Premaratne and Premalal, 2006). By confirming the findings of the present study, Mounika et al. (2015) reported that number of tillers and number of leaves per plant were always higher in CO-4 compared to CO-3 at all growth stages. According to literature, when plants have more number of tillers per plant, it has a positive relationship with DM yield (Bandara et al., 2016). Ibrahim et al. (2014) stated that the number of leaves per plant is a very important parameter for calculating the growth and forage yield of fodder species. Furthermore, leaves have higher nutritive values compared with the stem of the plant. Variation in results may be due to the differences in maturity level, plant spacing, and climatic conditions. The higher stem diameter and profuse tillering suggested that lower plant densities should be employed for the cultivar CO-3.

ADM yield and nutritive composition

DM yield is the basic component related to forage production. Based on the results obtained at all harvesting intervals, it may be envisaged that all tested fodder species can produce higher DM yield than traditional fodder species. The lower ADM yields of hybrid Napier varieties at 4 weeks during the second harvesting year may be attributed to immature tillers of hybrid Napier varieties at early growth stages. The higher ADM yield of hybrid Napier varieties at 8 weeks confirms the statement of Wadi et al. (2004) that the number of regrown tillers tends to be higher in Napier plants cut at 60-day interval. However, the present study results agree with the statement of Premaratne and Premalal (2006) that higher production could be obtained from hybrid Napier up to 2 years under good management practices. The present study observed no significant difference in DM yields of CO-3 and CO-4, as evidenced by the absence of significant differences in tiller number and leaf number. In contrast, Singh and Garg (2015) observed that CO-4 had higher DM yield compared with CO-3 in Central Gujarat, India. The highest ADM yield of sugar graze at 8 weeks cutting interval of second year may be due to the ability to produce very high DM yield in sorghum. The DM content of sugar graze at 8 weeks was higher than the results of Pushparajah and Sinniah (2018), that is, 17.9 of DM content at 60 days after planting, and of Samini and Premaratne (2017), that is, 15.6 of DM content at 8 weeks of growth. This may be attributed to the variation in rainfall of different climatic zones.

The CP content of sugar graze harvested at 6th week in the present study was relatively higher than that reported in some other studies. Epasinghe et al. (2012) and Moran (2005) reported a CP content of 17.1% and 12.2%, respectively, for sorghum harvested at the 7th week of maturity.

The CP content generally declines with maturity; this could be the reason for the lower CP content reported by Samini and Premaratne (2017), that is, 14.3% of CP at the 10th week of harvest, and Bandara et al. (2016) demonstrated a CP content of 11.6% at 50% of flowering. The CP content of CO-3 at 8 weeks in the present study was comparable with the findings of Bandara et al. (2016) who indicated 13.3% at 50% of flower initiation after establishment. Whereas Premaratne and Premalal (2006) reported a CP content of 15%–16% for CO-3 when harvested at the pre-blooming stage. The variations in the present values may be attributed to the different stages of maturity and variations in soil and climatic conditions. Among several nutrients, CP is an important nutrient, and according to Qureshi (1992), forage with higher CP has superior feeding quality. Thus, CP content of forages can be used as a good indicator to measure the quality of fodder (Bogdan, 1977).

The CF content the in present study was incomparable with the results of Premaratne and Premalal (2006), who reported 34%–37% for CO-3 when harvested at the pre-blooming stage. Bandara et al. (2016) reported a CF content of 37.8% for CO-3 and 36.8% for sugar graze when harvested at 45 days. However, Pushparajah and Sinniah (2018) reported comparable results with the present study, that is, 29.22% of CF for sugar graze when harvested at 60 days after planting. The deviations may be attributed to the differences in soil fertility, climatic conditions, and stage of maturity of forages. Relatively lower CF content together with higher CP of sugar graze could be having comparatively higher digestibility than CO-3 and CO-4.

In accordance with the reports of Wangchuk et al. (2015) and Tessema et al. (2010), we found that a short cutting interval of 4 weeks seriously reduced the DM yields of both hybrid Napier cultivars. While the protein concentration was very high, this would scarcely compensate for the greatly reduced forage production. Similar patterns for DM and CP were observed for sugar graze as well. General decline in CP concentration with increasing cutting interval found in the present study is in agreement with numerous works (Manyawu et al., 2003; Peiretti et al., 2015). We consider that cutting interval of 8 weeks appears optimal for the environmental conditions in the southern low country of Sri Lanka. This is supported by our results revealing DM and CP yields and acceptable CP and crude fiber concentrations at 8 week cutting interval for all three cultivars.

Conclusions

While two Napier hybrids and sugar graze cultivars performed well in the low country wet zone of Sri Lanka, they varied in terms of growth characteristics, forage yield, and quality. Cultivars CO-3 and CO-4 were superior in the overall DM and CP yields, while sugar graze performed equally well with highest CP, CP yields, and lowest CF concentrations. From the forage standpoint under the environmental conditions of the southern wet zone of Sri Lanka, CO-3, CO-4, and sugar graze can be recommended as beneficial forages for higher animal production. While a cutting interval of 8 weeks appears optimal for the environmental conditions in the southern low country of Sri Lanka.

Figure 1

Total rainfall during 2017 and 2018. Data extracted from the records of the meteorological station, Department of Agricultural Engineering, Mapalana, Kamburupitiya, Sri Lanka.Abbildung 1. Gesamtniederschlag in den Jahren 2017 und 2018 aus den Aufzeichnungen der Wetterstation, Abteilung für Agrartechnik, Mapalana, Kamburupitiya, Sri Lanka.
Total rainfall during 2017 and 2018. Data extracted from the records of the meteorological station, Department of Agricultural Engineering, Mapalana, Kamburupitiya, Sri Lanka.Abbildung 1. Gesamtniederschlag in den Jahren 2017 und 2018 aus den Aufzeichnungen der Wetterstation, Abteilung für Agrartechnik, Mapalana, Kamburupitiya, Sri Lanka.

Figure 2

Effect of variety and cutting interval on ADM yield, CP content, and ACP yield of three varieties during the first (2017–2018) and the second (2018–2019) harvesting years, respectively. abcdefg Interactions means with different superscripts in bars are significantly different at (p > 0.05). ACP: annual crude protein, ADM: annual dry matter, CP: crude protein.Abbildung 2. Auswirkung von Sorte und Schnittintervall auf den jährlichen Ertrag an Trockenmasse (ADM), den Gehalt an Rohprotein (CP) und den jährlichen Ertrag an Rohprotein (ACP) von drei Sorten während des 1. (2017–2018) bzw. 2. (2018–2019) Erntejahres. Interakton mittel mit unterschiedlichen hochstellungen in takten unterscheiden sich signifikant bei (p > 0.05).
Effect of variety and cutting interval on ADM yield, CP content, and ACP yield of three varieties during the first (2017–2018) and the second (2018–2019) harvesting years, respectively. abcdefg Interactions means with different superscripts in bars are significantly different at (p > 0.05). ACP: annual crude protein, ADM: annual dry matter, CP: crude protein.Abbildung 2. Auswirkung von Sorte und Schnittintervall auf den jährlichen Ertrag an Trockenmasse (ADM), den Gehalt an Rohprotein (CP) und den jährlichen Ertrag an Rohprotein (ACP) von drei Sorten während des 1. (2017–2018) bzw. 2. (2018–2019) Erntejahres. Interakton mittel mit unterschiedlichen hochstellungen in takten unterscheiden sich signifikant bei (p > 0.05).

Interaction effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the second harvesting year (2018–2019) Means ± standard error followed by different letters within columns show statistically significant differences (p < 0.05). V: variety, H: harvesting interval.Tabelle 7. Interaktionseffekte von Sorte und Schnittintervall auf den jährlichen Trockenmasseertrag, den Trockenmassegehalt, das Rohprotein, den jährlichen Rohproteinertrag und den Rohfasergehalt im zweiten Erntejahr (2018–2019). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Cutting interval p-Value
4 weeks 6 weeks 8 weeks
Dry matter (%) CO-3 11.67 ± 0.41cd 13.01 ± 0.04cd 15.21 ± 0.92abc V 0.000
CO-4 12.86 ± 0.36cd 13.84 ± 0.71bcd 16.53 ± 2.03ab H 0.059
Sugar graze 12.95 ± 0.09d 15.24 ± 0.35abc 18.88 ± 0.07a V × H 0.085

Annual dry matter yield (t/ha) CO-3 13.63 ± 0.35e 34.24 ± 0.65c 40.87 ± 1.56b V 0.000
CO-4 13.04 ± 0.72e 26.92 ± 0.74d 38.96 ± 1.75b H 0.000
Sugar graze 3.24 ± 0.32f 27.85 ± 0.82d 44.35 ± 1.32a V × H 0.000

Crude protein (%) CO-3 20.37 ± 0.45b 14.15 ± 0.18e 13.43 ± 0.11e V 0.000
CO-4 20.25 ± 0.21b 13.57 ± 0.23f 12.78 ± 0.05g H 0.000
Sugar graze 21.55 ± 0.32a 19.23 ± 0.05c 14.68 ± 0.14d V × H 0.000

Annual crude protein yield (t/ha) CO-3 2.77 ± 0.34de 4.84 ± 0.23c 5.48 ± 0.13b V 0.000
CO-4 2.64 ± 0.11e 3.65 ± 0.12d 4.98 ± 0.32b H 0.000
Sugar graze 0.69 ± 0.18f 5.35 ± 0.15b 6.51 ± 0.15a V × H 0.000

Crude fiber (%) CO-3 26.75 ± 0.23d 28.65 ± 0.35c 29.55 ± 0.19b V 0.000
CO-4 26.75 ± 0.25d 29.10 ± 0.19c 31.25 ± 0.1a H 0.000
Sugar graze 22.58 ± 0.05e 26.26 ± 0.14d 28.86 ± 0.15c V × H 0.000

Harvest dates for cutting treatments in 2017 and 2018.Tabelle 1. Erntedaten für Schnittbehandlungen in den Jahren 2017 und 2018.

Cutting interval Harvest dates Number of cuts
4 weeks 2017: June 14, July 12, Aug 9, Sep 6, Oct 4, Nov 1, Nov 29, Dec 27 13
2018: Jan 24, Feb 21, Mar 21, Apr 18, May 16
6 weeks 2017: Jun 25, July 6, Sep 17, Oct 29, Dec 10 9
2018: Jan 21, Mar 4, Apr 15, May 27
8 weeks 2017: Jul 9, Sep 3, Oct 29, Dec 24, 6
2018: Feb 4, Apr 29

Effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the second harvesting year (2018–2019). Means ± standard error followed by different letters within columns shows statistically significant differences (p < 0.05).Tabelle 5. Auswirkungen von Sorte und Schnittintervall auf die jährliche Trockenmasseausbeute, den Trockenmassegehalt, das Rohprotein, die jährliche Rohproteinausbeute und den Rohfasergehalt von drei Futtermitteln während des zweiten Erntejahres (2018–2019). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0.05).

Treatment Dry matter (%) Annual dry matter yield (t/ha) Crude protein (%) Annual crude protein yield (t/ha) Crude fiber (%)
Variety
CO-3 13.29 ±1.03b 29.58 ± 8.20a 15.98 ± 2.20b 4.14 ± 0.81a 28.32 ± 0.82b
CO-4 14.41 ± 1.10ab 26.31 ± 7.49b 15.53 ± 2.37b 3.70 ± 0.79a 29.03 ± 1.29a
Sugar graze 15.69 ± 1.73a 25.96 ± 11.20b 18.49 ± 2.02a 4.22 ± 0.17a 25.89 ± 1.70c
Harvesting interval
4 weeks 12.49 ± 0.41c 10.78 ± 2.56c 20.72 ± 0.82a 1.89 ± 0.56c 25.36 ± 1.39c
6 weeks 14.03 ± 0.65b 29.67 ± 2.30b 15.65 ± 1.80b 4.56 ± 0.51b 28.19 ± 0.69b
8 weeks 16.87 ± 1.07a 39.39 ± 1.58a 13.63 ± 0.56c 5.61 ± 0.41a 29.69 ± 0.86a

Effects of variety and cutting interval on plant height, leaf length, leaf width, number of tillers, number of leaves, and stem diameter of three forages at the first harvesting year. Means ± standard error followed by different letters within columns show statistically significant differences (p < 0.05).Tabelle 2. Auswirkungen von Sorte und Schnittintervall auf Pflanzenhöhe, Blattlänge, Blattbreite, Anzahl der Ackerbauern, Anzahl der Blätter und Stammdurchmesser von drei Futtermitteln. Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05).

Treatment Plant height (cm) Leaf length (cm) Leaf width (cm) No. of tillers No. of leaves Stem diameter (mm)
Variety
CO-3 163.0 ± 19.6b 94.4 ± 6.1a 3.6 ± 0.3c 33.5 ± 0.4a 254.8 ± 13.1a 15.2 ± 1.7a
CO-4 164.7 ± 28.3ab 91.0 ± 6.4b 3.9 ± 0.3b 35.1 ± 0.6a 266.8 ± 15.8a 13.9 ± 1.0b
Sugar graze 169.0 ± 25.9a 66.6 ± 10.2c 7.2 ± 1.3a 0.0b 8.5 ± 0.7b 12.9 ± 0.9c
Harvesting interval
4 weeks 118.3 ± 4.8c 69.3 ± 11.5c 3.6 ± 0.5c 22.2± 0.4 157.8 ± 75.4b 11.6 ± 0.3b
6 weeks 177.8 ± 3.0b 88.3 ± 7.3b 5.3 ± 1.3b 23.2 ± 0.5 188.8 ± 90.0a 15.0 ± 0.9a
8 weeks 200.6 ± 5.5a 94.4 ± 7.4a 5.7 ± 1.6a 23.1 ± 1.1 183.5 ± 88.2ab 15.0 ± 0.9a

Interaction effects of variety and cutting interval on plant height, leaf length, leaf width, number of tillers, number of leaves, and stem diameter of three forages at the first harvesting year. Means ± standard error followed by different letters within columns differ statistically significant (p < 0.05). V: Variety, H: Harvesting interval.Tabelle 3. Interaktionseffekte von Sorte und Schnittintervall auf Pflanzenhöhe, Blattlänge, Blattbreite, Anzahl der Bestocker, Anzahl der Blätter und Stängeldurchmesser von drei Futtermitteln im ersten Erntejahr. Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Harvesting interval p-Value
4 weeks 6 weeks 8 weeks
Plant height CO-3 125.0 ± 6.1e 173.4 ± 4.2d 190.6 ± 0.5bc V 0.038
CO-4 109.0 ± 7.2f 183.6 ± 3.8cd 201.6 ± 2.1ab H 0.000
Sugar graze 120.9 ± 3.2e 176.5 ± 9.3cd 209.6 ± 4.3a V × H 0.000

Leaf length CO-3 82.7 ± 1.6c 96.8 ± 1.5ab 103.6 ± 3.7a V 0.000
CO-4 78.7 ± 1.0cd 94.5 ± 1.5b 99.9 ± 1.2ab H 0.000
Sugar graze 46.4 ± 1.5e 73.7 ± 0.4d 79.7 ± 1.5cd V × H 0.000

Leaf width CO-3 3.0 ± 1.8e 3.8 ± 0.0d 4.0 ± 0.1d V 0.000
CO-4 3.2 ± 0.2e 4.1 ± 0.0d 4.3 ± 0.0cd H 0.000
Sugar graze 4.6 ± 0.6c 8.0 ± 0.4b 8.9 ± 0.0a V × H 0.000

No. of tillers CO-3 32.8 ± 6.1a 34.2 ± 7.1a 33.4 ± 7.4a V 0.000
CO-4 33.8 ± 7.9a 35.5 ± 7.1a 36.0 ± 6.6a H 0.672
Sugar graze 0.0b 0.0b 0.0b V × H 0.969

No. of leaves CO-3 229.4 ± 55.3b 272.9 ± 56.6ab 262.2 ±50.7ab V 0.000
CO-4 237.0 ± 42.7ab 284.4 ± 57.2a 284.4 ± 57.2a H 0.002
Sugar graze 7.1 ± 0.8c 9.0 ± 0.5c 9.3 ± 0.5c V × H 0.240

Stem diameter CO-3 11.7 ± 0.5d 16.5 ± 0.9a 17.2 ± 0.9a V 0.000
CO-4 12.0 ± 0.7cd 15.0 ± 1.2ab 14.8 ± 1.1ab H 0.000
Sugar graze 11.0 ± 0.3d 13.5 ± 1.2bc 14.1 ± 1.3bc V × H 0.009

Interaction effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the first harvesting year (2017–2018). Means ± standard error followed by different letters within columns shows statistically significant differences (p < 0.05). V: Variety, H: Harvesting interval.Tabelle 6. Interaktionseffekte von Sorte und Schnittintervall auf den jährlichen Trockenmasseertrag, den Trockenmassegehalt, das Rohprotein, den jährlichen Rohproteinertrag und den Rohfasergehalt im ersten Erntejahr (2017–2018). Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05). V: Sorte, H: Ernteintervall.

Variety Cutting interval p-Value
4 weeks 6 weeks 8 weeks
Dry matter (%) CO-3 11.67 ± 0.41cd 13.01 ± 0.04cd 15.21 ± 0.92abc V 0.000
CO-4 12.86 ± 0.36cd 13.84 ± 0.71bcd 16.53 ± 2.03ab H 0.059
Sugar graze 12.95 ± 0.09d 15.24 ± 0.35abc 18.88 ± 0.07a V × H 0.085

Annual dry matter yield (t/ha) CO-3 13.63 ± 0.35e 34.24 ± 0.65c 40.87 ± 1.56b V 0.000
CO-4 13.04 ± 0.72e 26.92 ± 0.74d 38.96 ± 1.75b H 0.000
Sugar graze 3.24 ± 0.32f 27.85 ± 0.82d 44.35 ± 1.32a V × H 0.000

Crude protein (%) CO-3 20.37 ± 0.45b 14.15 ± 0.18e 13.43 ± 0.11e V 0.000
CO-4 20.25 ± 0.21b 13.57 ± 0.23f 12.78 ± 0.05g H 0.000
Sugar graze 21.55 ± 0.32a 19.23 ± 0.05c 14.68 ± 0.14d V × H 0.000

Annual crude protein yield (t/ha) CO-3 2.77 ± 0.34de 4.84 ± 0.23c 5.48 ± 0.13b V 0.000
CO-4 2.64 ± 0.11e 3.65 ± 0.12d 4.98 ± 0.32b H 0.000
Sugar graze 0.69 ± 0.18f 5.35 ± 0.15b 6.51 ± 0.15a V × H 0.000

Crude fiber (%) CO-3 26.75 ± 0.23d 28.65 ± 0.35c 29.55 ± 0.19b V 0.000
CO-4 26.75 ± 0.25d 29.10 ± 0.19c 31.25 ± 0.1a H 0.000
Sugar graze 22.58 ± 0.05e 26.26 ± 0.14d 28.86 ± 0.15c V × H 0.000

Effects of variety and cutting interval on annual dry matter yield, dry matter content, crude protein, annual crude protein yield, and crude fiber contents during the first harvesting year (2017–2018). Means ± standard error followed by different letters within columns differ statistically significant (p < 0.05).Tabelle 4. Auswirkungen der Sorte und des Schnittintervalls auf die jährliche Trockenmasseausbeute, den Trockenmassegehalt, das Rohprotein, die jährliche Rohproteinausbeute und den Rohfasergehalt von drei Futtermitteln (2017–2018) Mittelwerte ± Standardfehler, gefolgt von unterschiedlichen Buchstaben in den Spalten, unterscheiden sich statistisch signifikant (p < 0,05).

Treatment Dry matter (%) Annual dry matter yield (t/ha) Crude protein (%) Annual crude protein yield (t/ha) Crude fiber (%)
Variety
CO-3 14.25 ± 0.91b 29.30 ± 8.08a 15.89 ± 2.16b 4.31 ± 0.79a 28.88 ± 0.84b
CO-4 15.15 ± 1.39ab 26.02 ± 7.21b 15.96 ± 2.09b 3.87 ± 0.71a 29.45 ± 1.19a
Sugar graze 15.73 ± 2.09a 24.68 ± 11.61b 18.22 ± 1.73a 4.10 ± 0.13a 25.87 ± 2.02c
Harvesting interval
4 weeks 12.66 ± 0.30c 10.04 ± 3.40c 20.35 ± 0.22a 2.02.82 ± 0.68c 25.62 ± 1.79c
6 weeks 14.78 ± 0.61b 29.32 ± 2.22b 15.86 ± 1.54b 4.62.26 ± 0.41b 28.36 ± 0.82b
8 weeks 17.69 ± 0.96a 40.63 ± 1.42a 13.86 ± 0.54c 5.64.47 ± 0.39a 30.22 ± 0.80a

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