L.C. Gonçalves, N.M. Rodriguez, I. Borges, |
J.A.S. Rodrigues |
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Departamento de Zootecnia |
EMBRAPA-Centro Nacional de Milho e Sorgo |
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L.G.R. Pereira |
INTRODUCTION
In recent years, the sowing of fodder crops during the rainy season (January to March) has become very popular. Generally, corn [maize] and sorghum are used, because they produce a well-preserved silage of good nutritive value. However, their DM yields and quality are uncertain from year to year, because of frequent drought stress.
Sunflower stands out as an alternative for forage production and conservation as silage because of its drought tolerance, its high DM yields, its resistance to cold and heat, its adaptability to different edaphoclimatic conditions and its relative independence of latitude, altitude and photoperiod (Cotte, 1959; Tomich, 1999).
To obtain silage of good quality and of high nutritive value, the material should be cut at the appropriate stage of maturity. Tan and Tumer (1996) ensiled sunflower at several stages of maturity and concluded that the final flowering stage was the best for silage making.
The present study was carried out at the EMBRAPA National Centre of Research in Corn and Sorghum. The objectives were to evaluate sunflower cultivars V2000, DK180, M734 and Rumbossol-91 grown in a completely randomized block with 3 replications and cut and ensiled 30, 37, 44 and 51 days after flowering.
RESULTS
Table 1 shows that many of the plots had inferior stands compared to those recommended by Castro et al. (1996) of 40 to 50 thousand plants per hectare. Rumbosol-91 was significantly taller than the other cultivars, but had the lowest percentage heads and the highest percentage stem. DM yield of V2000 was inferior to the others, except at the first harvest date (Table 2). The DM concentration of the material is the most important factor for the quality of the ensiling process (McDonald et al., 1991) and it is recommended that it be between 30 and 35%.
Laboratory silos of PVC, 40 cm long by 10 cm in diameter, were used, and the silos were opened after 56 days.
Table 1. Stand density, height, head diameter and percentages of heads, stems and leaves at four maturities
Days after flowering |
Stand density |
Height |
Diameter |
Head |
Stem |
Leaf |
|
V2000 |
|||||
30 |
39.59ABa |
195.00Ba |
16.84Aa |
46.34Aa |
35.56Ba |
18.12Aab |
37 |
26.74Ba |
190.00Ba |
20.44Aa |
42.17Aa |
37.34Aba |
20.49Aa |
44 |
33.34Aa |
178.33Ba |
17.56Aa |
47.22Aa |
37.16Aba |
15.61Bab |
51 |
19.44Aa |
176.67Ba |
15.55Aa |
51.85Aa |
37.68Ba |
10.47Ab |
|
DK180 |
|||||
30 |
31.60Ba |
205.00Ba |
17.56Aa |
44.38Aa |
35.46Ba |
20.16Aa |
37 |
39.58Aba |
190.00Ba |
15.56Aba |
52.00Aa |
35.03Ba |
12.97Ba |
44 |
25.35Aa |
200.00Ba |
17.67Aa |
45.63Aa |
38.32Ba |
16.05Ba |
51 |
38.19Aa |
203.33Ba |
12.22Aa |
41.16Ba |
42.41Ba |
16.43Aa |
|
M734 |
|||||
30 |
30.56Ba |
193.33Ba |
19.67Aa |
48.83Aa |
32.68Ba |
18.49Aa |
37 |
42.71ABa |
181.78Ba |
14.78ABa |
48.99Aa |
33.30Ba |
17.71ABa |
44 |
46.53Aa |
198.33Ba |
15.11Aa |
50.67Aa |
31.25Ba |
18.08ABa |
51 |
39.58Aa |
191.67Ba |
13.22Aa |
48.58ABa |
35.62Ba |
15.79Aa |
|
RUMBOSOL 91 |
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30 |
58.33Aa |
235.00Aa |
16.67Aa |
26.52Ba |
50.27Aab |
23.21Aa |
37 |
57.64Aa |
226.67Aa |
13.68Ba |
33.38Ba |
44.20Ab |
22.43Aa |
44 |
25.35Ab |
228.33Aa |
17.78Aa |
29.95Ba |
46.05Ab |
24.01Aa |
51 |
42.36Aab |
228.33Aa |
15.00Aa |
24.78Ca |
57.20Aa |
18.01Aa |
Coefficient of variation |
32.80 |
6.616 |
18.42 |
11.90 |
11.23 |
20.01 |
Notes: Capital letters compare harvest times among cultivars. Small letters compare harvest times within each cultivar
The largest silage densities were observed for V2000, which may be explained by its having the lowest DM concentration. Within each cultivar, the densities decreased with time, due to the higher DM concentrations as plants matured, with the exception of V2000. These results are superior to those reported by Tomich (1999), who studied 13 genotypes with an average density of 677.4 kg/m3, and they are also above those found for farm silos, with values of around 600 to 800 kg/m3 for a good compression (Nussio, 1992). The quality of the preservation decreased with age of the plants, as shown by increasing pH, particularly for V2000, which also had high ammonia-nitrogen (NH3-N) levels. In another experiment done at our laboratory with 13 genotypes (Tomich, 1999), the mean values of ether extract and in vitro DM digestibility of the silages were 13.7% and 50%, respectively, and showed normal profiles of lactic acid and AGV production.
Table 2. Production of fresh matter, DM, and DM of plants, heads, leaves and stems at four maturities
Days after flowering |
Fresh matter |
DM |
DM as percentage of |
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Plants |
Heads |
Leaves |
Stems |
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|
V2000 |
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30 |
30.94Aa |
5.63Aa |
17.85Aa |
23.45Aa |
20.35Ab |
22.45Aa |
37 |
16.31Ab |
3.05Bb |
19.13Ba |
6.23Aa |
29.27Bb |
16.17Ba |
44 |
10.28Ab |
3.27Bb |
32.80Ba |
26.77Aa |
48.43Aab |
21.37Ba |
51 |
7.57Ab |
2.73Bb |
35.17Ba |
30.30Ba |
58.13Aa |
22.73Ba |
|
DK180 |
|||||
30 |
24.58Aa |
6.03Aa |
24.53Ab |
24.20Ab |
31.77Ab |
21.00Aa |
37 |
21.49Aa |
6.22Aa |
29.30ABb |
27.43Ab |
46.30Bab |
26.47Aba |
44 |
12.85Ab |
5.50Aa |
42.57ABa |
32.10Ab |
60.70Aa |
24.80ABa |
51 |
11.39Ab |
6.40Aa |
59.60Aa |
51.30ABa |
71.97Aa |
31.00Ba |
|
M734 |
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30 |
29.93Aa |
6.53Aa |
22.10Ab |
21.70Ab |
22.27Ab |
19.20Aa |
37 |
20.21Ab |
6.24Aa |
32.27ABb |
25.73Ab |
31.30Bb |
20.80ABa |
44 |
13.51Abc |
7.49Aa |
55.43Aa |
37.30Aab |
68.43Aa |
25.70Ba |
51 |
10.35Ac |
6.57Aa |
67.33Aa |
49.73ABa |
78.10Aa |
32.30Ba |
|
RUMBOSOL-91 |
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30 |
24.38Aa |
6.15Aa |
25.70Ac |
24.77Ab |
38.43Ab |
31.60Ab |
37 |
12.57Ab |
5.32Aa |
43.20Ab |
39.83Ab |
70.10Aa |
37.90Aab |
44 |
15.77Ab |
6.95Aa |
49.23ABb |
42.40Ab |
76.43Aa |
41.80Aab |
51 |
7.43Ab |
4.79Aa |
68.57Aa |
68.97Aa |
84.50Aa |
55.13Aa |
Coefficient of variation |
26.50 |
19.97 |
26.60 |
32.62 |
24.59 |
31.88 |
Notes: Capital letters compare cutting times among genotypes. Small letters compare cutting times within each genotype.
Table 3. Density, DM, CP of the silages cut and ensiled at four maturities
Days after flowering |
Density (kg/m3) |
DM (%) |
CP (%) |
pH |
NH3-N |
|
V2000 |
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30 |
2092.50Aa |
18.60Aa |
13.09Aa |
4.43 |
14.76 |
37 |
1821.33Aa |
22.28Aa |
13.37Aa |
5.26 |
24.27 |
44 |
1559.00Aa |
31.10Ba |
13.18Aa |
5.28 |
12.52 |
51 |
1494.33Aa |
32.79Ba |
12.66Aa |
5.24 |
21.59 |
|
DK180 |
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30 |
1673.67Aa |
23.06Ab |
11.17Aba |
4.42 |
11.00 |
37 |
1570.67Abab |
28.70Ab |
10.31Ba |
4.18 |
9.72 |
44 |
1261.00Aab |
39.40Abb |
11.40Ba |
5.14 |
9.51 |
51 |
1050.33Bb |
56.56Aa |
10.69Ba |
* |
* |
|
M734 |
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30 |
1921.00Aa |
21.06Ab |
11.25Ba |
4.42 |
8.46 |
37 |
1575.00Aba |
31.83Ab |
10.62Ba |
4.17 |
14.38 |
44 |
1240.33Ab |
52.05Aa |
11.25Ba |
5.14 |
7.75 |
51 |
914.67Bb |
61.30Aa |
12.06Aba |
* |
* |
|
RUMBOSOL-91 |
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30 |
1615.67Aa |
25.70Ac |
9.18Ca |
4.07 |
8.64 |
37 |
1189.33Ba |
41.24Ab |
9.94Ba |
4.84 |
7.48 |
44 |
1084.00Aa |
44.90Abb |
9.44Ca |
5.25 |
9.35 |
51 |
666.00Bb |
64.57Aa |
7.00Cb |
* |
* |
Coefficient of variation |
18.87 |
24.49 |
8.45 |
|
|
Notes: Capital letters compare harvest times among genotypes. Small letters compare harvest time within each genotype. * = Not determined.
CONCLUSIONS
1. The best harvest time for ensiling varied according to genotype, and was 37 days after flowering for DK180 and M734, more than 51 days for V2000, and about 30 days for Rambosol-91.
2. V2000 had the highest CP concentrations, but even with 35% DM at ensiling it provided silages with undesirable pH and NH3-N. Within each genotype there were no differences between harvest times in the CP concentration, with the exception of Rumbosol-91, which had lower values at 51 days.
REFERENCES
Castro, C., Castiglioni, V.B.R., & Balla, A. 1996. A cultura do girassol: Tecnologia de Producao. Documentos EMBRAPA-CNPSo, n.67. 20 p.
Cotte, A. 1959. Le tournesol-fourrage. Sunflower for fodder. Herb. Abstr., 29: 92.
Nussio, L.G. 1992. Producao de silagem de alta qualidade. p. 155-175, in: Congresso Nacional de Milho e Sorgo 19, 1992, Porto Alegre, Conferencias. Porto Alegre: SSA/SCT/ABMS/EMATER-RS, EMBRAPA/CNPMS, 1992.
McDonald, P., Henderson, A.R., & Heron, S. 1991. The Biochemistry of Silage. 2nd edition. Marlow, UK: Chalcombe Publications.
Tan, A.S., & Tumer, S. 1996. Research on the evaluation of silage quality of sunflowers. Anadolu 6: 45-57 (Abstract)
Tomich, T.R. 1999. Avaliacao das silagens de treze cultivares de girassol (Helianthus annuus L.) participantes do ensaio nacional. Belo Horizonte, UFMG, Escola de Veterinaria. Dissertacao. (Mestrado em Zootecnia).