The means and standard deviation of the variables related to the yield of grass cultivars grown at different tree densities are shown in Table 3. There was a significant effect of cultivar, cultivar density and interaction, and density for all variables (p<0.01).
Table 3. Means and standard deviations of yield of cultivars in systems with different tree densities in four sections, regardless of the cultivar
Variable
|
DM content in biomass (%)
|
Daily forage accumulation (kg/day)
|
DM yield (kg/ha)
|
Stem Leaf Ratio
|
Cut
|
1
|
2
|
3
|
2
|
3
|
3
|
4
|
Tree Density
|
0
|
16.73 B
|
17.80 A
|
20.95 A
|
46.08 A
|
57.10 A
|
2455.31 A
|
6.32A
|
83
|
17.56 AB
|
17.38 A
|
18.22 B
|
46.51 A
|
65.91 A
|
3215,04 A
|
3.54B
|
168
|
18.82 A
|
17.12 A
|
18.92 B
|
32.27 B
|
37.47 B
|
1611.27 B
|
3.45B
|
333
|
17.85 AB
|
17.36 A
|
17.67 B
|
36.97 B
|
37.32 B
|
1604,96 B
|
2.82B
|
P-value 1
|
C 2
|
0,88
|
<0.01
|
<0.01
|
<0.05
|
0,138
|
0,07
|
<0.05
|
D 3
|
<0.01
|
0,21
|
<0.01
|
<0.05
|
<0.01
|
<0.01
|
<0.01
|
C x D 4
|
0,24
|
0,11
|
0,56
|
0,44
|
0,10
|
0,34
|
0,06
|
DP 5
|
|
0,37
|
0,23
|
0,53
|
4,05
|
3,95
|
161,94
|
0,48
|
1 Means followed by distinct letters on the same line differ statistically based on the Tukey’s testy (p<0.05); 2 Cultivate; 3 Density of trees per hectare; 4 Interaction between Cultivar and Tree Density; 5 Standard deviation
The total dry matter production (TDMP) of forage cultivars, after 168 days of experimentation, is shown in tables 4 and 5, where it is observed the absence of significant interaction between the treatments (p>0.05), where the monoculture and the density of 84 trees/ha presented higher productivity (approximately 35%) when compared to the other arrangements.
Table 4. Means and standard deviations of productivity variables accumulated in four sections, in systems with different tree densities, regardless of cultivar
Variable
|
Total Dry Matter Production (kg/ha)
|
Daily forage accumulation rate (kg/day)
|
Tree Density
|
0
|
8428,42 A
|
50.16 A
|
84
|
9402.28 A
|
55.96 A
|
168
|
5735,04 B
|
34.13 B
|
333
|
5933,50 B
|
35.31 B
|
P-value 1
|
C 2
|
<0.01
|
<0.01
|
D 3
|
<0.01
|
<0.01
|
C x D 4
|
0,18
|
0,18
|
DP 5
|
|
455,15
|
2,71
|
1 Means followed by distinct letters on the same line differ statistically based on the Tukey’s testy (p<0.05); 2 Cultivate; 3 Density of trees per hectare; 4 Interaction between Cultivar and Tree Density; 5 Standard deviation
The cv. Zuri obtained the highest TDMP (9013.68 kg/ha) and the highest forage accumulation rate (53.65 kg/day) among those analyzed, which reveals the highest production potential. On the other hand, the Tamani and Piatã grasses did not show significant differences in the different densities of trees.
Table 5. Means and standard deviations of yield variables accumulated in the four cultivars' cuts, regardless of tree density
Variable
|
Total Dry Matter Production (kg/ha)
|
Daily forage accumulation rate (kg/day)
|
Cultivate
|
Tamani
|
6869,13 B
|
40.88 B
|
Piatã
|
6241,63 B
|
37.15 B
|
Zuri
|
9013,68 A
|
53.65 A
|
P-value 1
|
C 2
|
<0.01
|
<0.01
|
D 3
|
<0.01
|
<0.01
|
C x D 4
|
0,18
|
0,18
|
DP 5
|
|
380,74
|
2,27
|
1 Means followed by distinct letters on the same line differ statistically based on the Tukey’s testy (p<0.05); 2 Cultivate; 3 Density of trees per hectare; 4 Interaction between Cultivar and Tree Density; 5 Standard deviation
The means and standard deviation of the variables related to the yield of grass cultivars cultivated at different tree densities are shown in Table 6 and Table 7. There was a significant effect of cultivar, cultivar density and interaction, and density for all variables (p<0.01).
Table 6. Means and standard deviations of yield variables of cultivars in systems with different tree densities in the four sections
|
|
|
Tree density/hectare
|
DP2
|
|
P- value1
|
Variable
|
Cut
|
Cultivate
|
0
|
84
|
168
|
333
|
|
C3
|
D4
|
CxD 5
|
Dry Matter Production (kg/ha)
|
1
|
Tamani
|
3410,98 Ba
|
2283,30Bb
|
3097.89 Aa
|
1884,37Bb
|
431,38
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
2349,92 Ba
|
2716,77 Ba
|
1514,33Bc
|
2008,37Bb
|
Zuri
|
4880.74 Aa
|
5378.34 Aa
|
2656,85ABC
|
4280,89Ab
|
2
|
Tamani
|
1083,39 ABa
|
1108.19 Aa
|
1003.56 Aa
|
870.72 Aa
|
142,64
|
0,96
|
<0.01
|
<0.05
|
Piatã
|
1310.06 Aa
|
1027,54 Aab
|
714,00 Ab
|
969,63 Aab
|
Zuri
|
764,52 Bb
|
1352.52 Aa
|
703,30 Ab
|
1094,48Aab
|
4
|
Tamani
|
2068.36 Aa
|
1214,87 Bb
|
719,95 Bbc
|
587.62 Ac
|
162,78
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
696,00 Ba
|
937,55 Ba
|
719,10 Ba
|
612.73 Aa
|
Zuri
|
1056,60 Bb
|
1943.96 AA
|
1242,31 Ab
|
838,39Ab
|
Daily forage accumulation rate (kg/day)
|
1
|
Tamani
|
77,52 Ba
|
51,89 Ba
|
70.40 Aa
|
42,82Bb
|
3,38
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
53,40 Ba
|
61,74 Ba
|
34,41 Bb
|
45,64 Ba
|
Zuri
|
110.92 Aa
|
122.23 Aa
|
60,38Abb
|
97.29 Aa
|
4
|
Tamani
|
36.93 Aa
|
21,69 Bb
|
12,85 Abb
|
10,49 Ab
|
3,32
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
12.42 Ba
|
16,74 Ba
|
12,84 Ba
|
10.94 Aa
|
Zuri
|
18,86 Bb
|
34.71 Aa
|
22,18 Ab
|
14,97 Ab
|
Dry Matter Content (%)
|
4
|
Tamani
|
33,69 ABa
|
22,34 Bc
|
24.30 Ac
|
28,06 Ab
|
0,84
|
<0.01
|
<0.01
|
<0.05
|
Piatã
|
35.42 Aa
|
27.73 ABC
|
24.58 Ac
|
28,06 Ab
|
Zuri
|
32,53 Ba
|
22,83 Bb
|
22,04 Ab
|
24,57 Bb
|
¹ Means followed by distinct letters per section, lowercase in the row and uppercase in the column, differ statistically based on the Tukey’s testy (p<0.05); ² Standard Deviation; 3 Cultivate; 4 Tree density; 5 Interaction between Cultivate and Tree Density.
Cv. Zuri showed the best results in relation to DM production and daily forage accumulation rate. On the other hand, cv. Tamani had the highest leaf/stem ratio, which indicates a higher proportion of leaves in relation to the stem. It was also noted that the daily forage accumulation rate showed no significant difference between PS and density of 84 trees/ha, and the worst performances occurred at tree density of 168 arv/ha.
Table 7. Means and standard deviations of Yield of cultivars in systems with different tree densities in the four sections
Variable
|
Cut
|
Cultivate
|
Tree density/hectare
|
DP²
|
P-value¹
|
0
|
84
|
168
|
333
|
|
C
|
D
|
L x D³
|
Stem Leaf Ratio
|
1
|
Tamani
|
4.67 Aa
|
4.68 Aa
|
3,71 Ab
|
5.08 Aa
|
0,38
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
1.90 Ba
|
1.45 Ca
|
2.08 Ba
|
1.58 Ba
|
Zuri
|
3,36 Aab
|
2,17 Bb
|
3.83 Aa
|
2.60 Bab
|
2
|
Tamani
|
3,36 Abb
|
8.78 Aa
|
5.07 Bab
|
8,46 Ba
|
1,61
|
<0.01
|
0,14
|
<0.05
|
Piatã
|
2.71 Ba
|
2,60 Ba
|
3.30 Ba
|
2.55 Ca
|
Zuri
|
7.06 Ac
|
9,74 Ab
|
10,28 Ab
|
12.78 Aa
|
3
|
Tamani
|
10.63 AA
|
3.31 Ac
|
6,81 Ab
|
4.24 Abc
|
0,49
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
1,74 Bbc
|
1,00 Cc
|
2,27 Cb
|
3.52 Aa
|
Zuri
|
8.07 Aa
|
1,66 Bc
|
4,00 Bb
|
1,20 Bc
|
Mass Production Leaf Dry (kg/ha)
|
1
|
Tamani
|
2803,66 ABa
|
1863.83 Bab
|
2505,93 Aab
|
1572,68 Bb
|
312,83
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
1563,29 Ba
|
1590,59 Ba
|
987,05 Bb
|
1193,38Bb
|
Zuri
|
3730.04 Aa
|
4059.49 Aa
|
2048,50 ABC
|
2954,00 Ab
|
2
|
Tamani
|
353,72 Bb
|
997,16 ABa
|
792.72 Aa
|
803.31 Aa
|
102,61
|
0,13
|
<0.01
|
<0.01
|
Piatã
|
942.24 Aa
|
718,01 Bab
|
533,02 Ab
|
690,30Aab
|
Zuri
|
669,28 Abb
|
1173.32 Aa
|
623,73 Ab
|
997,59 Aab
|
4
|
Tamani
|
1645.14 Aa
|
1100,91 Ab
|
656.96 ABC
|
489.44 Ac
|
127,5
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
583,01 Ba
|
605,96 Ba
|
582.65 Aa
|
560.24 Aa
|
Zuri
|
900,86 Bab
|
1377.05 Aa
|
962,71Aab
|
734,10Ab
|
Stem Dry Mass Production (kg/ha)
|
1
|
Tamani
|
607,32 Ba
|
419,47 Ba
|
591.95 Aa
|
311,68 Ba
|
143,63
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
607,04 Bab
|
1126.17 Aa
|
527,27 Ab
|
612,50 Ab
|
Zuri
|
1150,69 Aab
|
1682.35 Aa
|
608,35 Ab
|
932,34 Abab
|
2
|
Tamani
|
285,86 ABa
|
79,06 Bab
|
162.36 Aa
|
35,73 Bb
|
48,58
|
<0.01
|
<0.01
|
<0.05
|
Piatã
|
353.83 Aa
|
281.54 Aa
|
168.21 Aa
|
271.89 Aa
|
Zuri
|
133,55 Ba
|
132,95 Aba
|
61,22 Ba
|
53,69 Ba
|
3
|
Tamani
|
176,93 Bb
|
827.74 Aa
|
160,67 Bb
|
253,98 Bb
|
90,58
|
<0.01
|
<0.01
|
<0.01
|
Piatã
|
1083.50 Aa
|
1169,46 Aab
|
518.51 Ac
|
702,35 ABC
|
Zuri
|
288,92 Bb
|
1034.00 Aa
|
370,73 Abb
|
472,21 Abb
|
4
|
Tamani
|
423.21 Aa
|
113,96 Bb
|
169,84 Ab
|
149,75 Ab
|
69,35
|
<0.05
|
<0.05
|
<0.01
|
Piatã
|
112,98 Ba
|
331,58 Aba
|
236.10 Aa
|
244.05 Aa
|
Zuri
|
114,15 Bb
|
566.90 Aa
|
279,60 Ab
|
254,76 Ab
|
¹ Means followed by distinct letters per section, lowercase in the row and uppercase in the column, differ statistically based on the Tukey’s testy (p<0.05); ² Standard Deviation; ³ Interaction between Cultivar and Tree Density.
The cumulative results in the three ICLF treatments corroborate Paciullo et al. (2017) where they concluded that intense shading (65% shade) reduces forage mass, tiller density and leaf area index of pastures, but moderate shading (35% shade) does not alter these variables, in relation to PS cultivation.
In the evaluation of the first cut, it was observed that height interacted between the cultivar and tree density in the treatments. The cv. Zuri in PS obtained higher results, especially when compared to cv. Tamani at the tree density of 333 trees/ha (a difference of 61% in the average heights). This result is expected, because the morphogenic size of cv. Zuri is the largest among the three cultivars analyzed. This result indicates a trend towards higher productivity of cv. Zuri, being observed in the production of dry matter (kg/ha) and in the rate of forage accumulation (kg/day). The DM content in the biomass did not show a significant interaction between cultivar and density. (p>0.05). There is a higher DM content in silvopastoral systems when compared to PS (about 6% higher). However, Castro et al. (1999) describe that grasses grown in the shade became juicier and had lower DM content.
In the second cut, all variables were found to interactwith bothcultivar and tree density in the treatments (p<0.05), except for the daily forage accumulation rate (kg/day) and DM content (%), which showed a significant difference only for cv. Zuri (approximately 11% lower, when compared to the other cultivars). Another important piece of data is the stem leaf ratio, where the highest data (12.78) was obtained in cv. Zuri with tree density of 333 trees/ha. It was observed that the daily forage accumulation rate (kg/day) did not show interaction between cultivar and tree density (p>0.05), but the density of 84 trees/ha and PS did not show a significant difference, which reflects that in this shading there is no significant reduction in forage mass production during the cutting period.
In the third cut, tree density factor in the daily forage accumulation rate (kg/day) interferes again negatively in the values of the average cultivars in the silvopastoral systems of 168 and 333 trees/ha, where they presented lower averages (p<0.01) when compared to the density of 84 trees/ha and the PS (reduction between 35 and 45% approximately). This fact converges with findings from the literature, where Pereira et al., (2015) point out that in the shading conditions under the forage in the understory, their potential was impaired to the growth and forage production in agrosilvopastoral and silvopastoral systems.
It is noteworthy that the DM yield (kg/ha) in PS and in the tree density of 84 trees/ha does not present statistical difference (p<0.01) (1938.86 A SP and 1985.96 A 88 tree/ha), which may be an important criterion for choosing the strategy for implementing an SSP system. in PS, it obtained higher means (13% p<0.05) when compared to SSP, which contradicts the data of the first cut, but follows the results found by Castro et al. (1999). This result is also reported by Crestani (2017), when evaluating Piatã grass in monoculture and in three shade regimes (0, 18 and 55% shading). He observed that the shading caused by the trees reduced the forage dry mass in the pre-grazing by 36 and 71%, respectively, for the shade regimes of 18 and 55% of shading, when compared to the pasture in PS.
In the fourth cut, specifically for DM production, F/C ratio and daily forage accumulation rate, there were significant differences among cultivars. For leaf and stem DM production, there were also significant differences between cultivars, but the effect of tree density and cultivar-tree density interaction was not significant (p>0.05). The Zuri cultivar showed the highest performance in relation to plant height, dry matter production, a result also reported by Souza et al. 2020, which indicates a trend of pastures under moderate shade showing greater heights when compared to pastures without shade. In the accumulated total DM production and daily forage accumulation rate, cv. Zuri had the highest performance and cv. Tamani and Piatã showed no statistical difference (p>0.01).
Based on the results, it can be seen that cv. Tamani had the smallest size, compared to Piatã and Zuri grasses. In terms of MS production, cv. Zuri showed higher productivity indexes, while the Piatã and Tamani cvs showed similar values. The F/C ratio was higher for the cv. Tamani in SSP compared to PS. The production of DM from leaves, as well as the rate of daily forage accumulation was higher for cv. Zuri.
In the last cut, a different behavior was observed in DM production among the grass cultivars evaluated. A cv. Tamani had a higher mean at PS, while cv. Zuri had a higher mean in the SSP with 84 trees/ha, with this difference being greater than 50% in relation to the PS. Piatã did not show significant difference in the four treatments. Gobbi et al. (2009) did not observe any difference in the forage mass of U. decumbens at 50 and 70% in the levels of artificial shading and in PS during the period of reduced availability of growth resources (climatic conditions). The study also points to a significant effect of tree density on both variables, with higher densities leading to lower production and accumulation rates. However, surprisingly, the production of cultivars at a tree density of 84 tree/ha was statistically equal to the PS, showing a high potential for use, since ICLFS still have several benefits in their use (carbon sequestration, increased animal welfare, improvement in the microbiological profile of the soil, increase in income per hectare with the use of wood).
De Carvalho (2019) also found similar results in a study comparing forage production in different cropping systems in the Brazilian Amazon biome. He analyzed four systems, cattle ranching with U. brizantha Marandu in monoculture, pastures of Marandu grass integrated with eucalyptus (Eucalyptus urograndis) in three rows of rows, grass with two years of cultivation and grass after two years of cultivation with simple rows of eucalyptus spaced apart. The experiment took place from July 2016 to July 2017, and all experimental units were stored continuously, using a variable stocking rate. The results showed that the highest forage accumulation was observed in the systems with signalgrass with two years of cultivation and signalgrass after two years of cultivation with single rows of eucalyptus spaced, with 21,310 kg/DM/ha and 24,050 kg/DM/ha, respectively, compared to Marandu grass in monoculture (19,500 kg/DM/ha) and Marandu grass pastures integrated with eucalyptus in three rows (18,890 kg/DM/ha).