3.2. Dynamics of Soil Chemical Properties
The interactions between mechanical scarification and the cover crops were significant in the 0–5 cm layer for P, Ca, SB, and CEC; in the 5–10 cm layer for S, Mg, H + Al, and V; in the 10–20 cm layer for P, S, H + Al, CEC, and Al; and in the 20–40 cm layer for H + Al and Al in the first and second years, respectively (
Table 4,
Table 5,
Table 6,
Table 7,
Table 8,
Table 9,
Table 10 and
Table 11).
In the 0–5 cm layer (
Table 4 and
Table 5), mechanical soil scarification significantly affected the soil properties in terms of S, pH, K, Ca, CEC, and V (%). In general, the values were greater under NTS, except for S.
Urochloa ruziziensis, which had a greater soil K content (3.76 mmol
c dm
−3) than did
C. cajans (2.79 mmol
c dm
−3) in the first year. In the second year, a significant effect of MSC on S, pH, Mg, H + Al, and V% in the 0–5 cm layer was observed (
Table 4 and
Table 5). Among the studied CCs, those previously cultivated with
P. glaucum exhibited the greatest increases in soil organic matter, K, Mg, and V (26 g dm
−3, 2.36 mmol
c dm
−3, 35 mmol
c dm
−3, and 82%, respectively).
Table 4.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 0–5 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 4.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 0–5 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (0–5 cm) |
---|
| MO | P | S | K+ | Ca2+ | Mg2+ |
---|
| g dm−3 | ---------- mg dm−3 ------- | ------------------- mmolc dm−3 ----------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 28 | 24 | 29 | 35 | 6 b | 8 b | 3.5 a | 2.0 | 57 a | 40 | 35 | 29 a |
With | 26 | 23 | 36 | 35 | 8 a | 10 a | 3.0 b | 2.1 | 44 b | 35 | 33 | 26 b |
Cover Crops (CCs) |
Fallow | 27 | 22 b | 32 | 26 | 7 | 10 ab | 2.9 ab | 1.9 ab | 53 | 35 | 34 | 24 b |
U. ruziziensis | 27 | 24 ab | 35 | 33 | 8 | 9 ab | 3.8 a | 2.0 ab | 50 | 35 | 35 | 24 b |
C. juncea | 27 | 24 ab | 31 | 38 | 6 | 11 a | 3.2 ab | 1.9 b | 51 | 41 | 36 | 27 b |
C. cajan | 27 | 22 b | 33 | 36 | 6 | 7 b | 2.8 b | 2.2 ab | 47 | 34 | 30 | 24 b |
P. glaucum | 26 | 26 a | 31 | 42 | 7 | 9 ab | 3.7 ab | 2.3 a | 54 | 44 | 35 | 35 a |
F-Value (5%) |
MSC | 3.83 ns | 1.70 ns | 32.70 * | 0.0 ns | 7.97 * | 24.59 * | 4.78 * | 2.11 ns | 11.05 * | 18.89 * | 0.36 ns | 4.37 * |
CC | 0.36 ns | 4.81 * | 1.10 ns | 8.13 * | 1.33 ns | 3.44 * | 3.73 * | 3.59 * | 0.44 ns | 11.75 * | 0.64 ns | 7.63 * |
MSC × CC | 0.59 ns | 1.68 ns | 4.90 * | 3.14 * | 0.74 ns | 1.85 ns | 0.46 ns | 0.41 ns | 0.38 ns | 8.39 * | 2.13 ns | 2.56 ns |
Minimum significant difference (5%) |
MSC | -- | -- | 2.75 | -- | 3.11 | 1.32 | 0.42 | -- | 7.99 | -- | -- | 2.99 |
CC | -- | -- | -- | -- | -- | 2.98 | 0.94 | 0.45 | -- | -- | -- | 6.74 |
CV (%) | 8.74 | 9.26 | 13.05 | 17.34 | 30.4 | 22.42 | 19.7 | 14.65 | 24.28 | 9.57 | 22.57 | 16.72 |
IC | 24 | 24 | 29 | 29 | 3 | 3 | 3.5 | 3.5 | 41 | 41 | 25 | 25 |
Table 5.
Mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% in the 0–5 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 5.
Mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% in the 0–5 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (0–5 cm) |
---|
| pH | H + Al | Al3+ (1) | SB | CEC | V(%) |
---|
| CaCl2 | -------------------------------------------- mmolc dm−3 ---------------------------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 6.3 a | 6.0 a | 18 | 17 b | 0.0 | 0.0 | 99.5 a | 71.3 | 113.6 a | 88.3 | 84 a | 80 a |
With | 6.2 b | 5.8 b | 19 | 19 a | 0.0 | 0.0 | 80.7 b | 63.4 | 99.9 b | 82.6 | 80 b | 77 b |
Cover Crops (CCs) |
Fallow | 6.1 | 5.8 | 19 | 18 | 0.0 | 0.0 | 90.1 | 61.4 | 108.9 | 79.1 | 83 | 77 b |
U. ruziziensis | 6.1 | 5.9 | 20 | 19 | 0.0 | 0.0 | 88.3 | 64.6 | 107.9 | 83.3 | 81 | 77 b |
C. juncea | 6.3 | 5.8 | 19 | 18 | 0.0 | 0.0 | 92.3 | 70.0 | 107.8 | 87.9 | 83 | 79 ab |
C. cajan | 6.2 | 5.8 | 19 | 19 | 0.0 | 0.0 | 89.9 | 58.9 | 98.3 | 78.5 | 79 | 76 b |
P. glaucum | 6.2 | 6.1 | 19 | 17 | 0.0 | 0.0 | 92.3 | 80.9 | 110.8 | 98.2 | 83 | 82 a |
F-Value (5%) |
MSC | 4.52 * | 4.93 * | 1.59 ns | 10.36 * | -- | -- | 7.45 * | 10.84 * | 7.03 * | 6.38 * | 5.28 * | 13.1 * |
CC | 1.42 ns | 1.87 ns | 0.31 ns | 0.68 ns | -- | -- | 0.65ns | 9.99 * | 0.71 ns | 9.83 * | 0.83 ns | 4.55 * |
MSC × CC | 2.48 ns | 0.66 ns | 2.51 ns | 0.65 ns | -- | -- | 0.55ns | 5.45 * | 0.56 ns | 5.32 * | 0.40 ns | 2.71 ns |
Minimum significant difference (5%) |
MSC | 0.11 | 0.16 | -- | 1.37 | -- | -- | 11.16 | -- | 10.68 | -- | 3.63 | 2.02 |
CC | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | 4.55 |
CV (%) | 2.76 | 4.13 | 11.33 | 11.69 | - | - | 19.53 | 11.34 | 15.41 | 8.51 | 6.82 | 3.93 |
IC | 5.9 | 5.9 | 19 | 19 | 0 | 0 | 69.5 | 69.5 | 88.5 | 88.5 | 79 | 79 |
With respect to the interaction between the cover crops subjected to mechanical soil scarification and the available soil P in the 0–5 cm layer (
Figure 5a and
Figure 6a) in the first year, the
P. glaucum, U.
ruziziensis,
C. juncea, and fallow land soils subjected to mechanical soil scarification exhibited increased soil P contents. Fertilization at rice sowing may have contributed to the increase in the available soil P. Regarding the dry matter yield of the CCs, the scarified soil under
U. ruziziensis again had a greater P content (42 mg dm
−3) than that under
C. juncea (33 mg dm
−3). In the second year, there was a significant effect on soil P, SB, and CEC under the CCs, with 38 mg dm
−3, 57 mg dm
−3, and 80 mmol
c dm
−3, respectively. In particular,
P. glaucum induced higher values of these soil properties (
Figure 5a and
Figure 6a,c,d).
The cover crop interactions during mechanical decompaction were significant for the soil P available in the 5–10 cm layer (
Figure 5b and
Table 6). The available P content increased in the soil under
C. juncea and in the scarified soil under fallow vegetation due to soil movement, despite the low mobility of this nutrient. Regarding the dry matter yield of the CCs, the scarified soil had a greater available P content under
C. juncea (48 mg dm
−3) and
C. cajans (42 mg dm
−3) in the first year, both because of the MSC and because both species were Fabaceae, which are more rapidly decomposed after straw incorporation in the soil by mechanical scarification.
The interactions of the cover crops with mechanical decompaction were significant for soil pH and Al in the 5–10 cm layer (
Figure 5c,d). After MSC, the pH values were greatest under
C. cajan and
P. glaucum (5.6 and 5.5, respectively).
Table 6.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 5–10 cm layer after cover crop (CC) cultivation, rice cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 6.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 5–10 cm layer after cover crop (CC) cultivation, rice cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (5–10 cm) |
---|
| MO | P | S | K+ | Ca2+ | Mg2+ |
---|
| g dm−3 | ------------- mg dm−3--------- | ----------------------mmolc dm−3 ----------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 20 | 21 | 32 | 36 a | 12 | 22 | 2.2 | 1.6 | 26 | 28 | 16 b | 20 |
With | 21 | 21 | 37 | 31 b | 14 | 21 | 1.8 | 1.7 | 30 | 29 | 21 a | 21 |
Cover Crops (CCs) |
Fallow | 20 | 20 | 32 | 37 ab | 11 b | 28 | 1.9 | 1.5 | 30 | 25 | 18 | 19 |
U. ruziziensis | 19 | 21 | 31 | 29 b | 20 a | 22 | 1.9 | 1.6 | 21 | 26 | 15 | 21 |
C. juncea | 21 | 21 | 37 | 28 b | 10 b | 24 | 2.1 | 1.5 | 31 | 30 | 21 | 19 |
C. cajan | 21 | 20 | 38 | 36 ab | 11 b | 19 | 1.7 | 1.8 | 33 | 30 | 22 | 20 |
P. glaucum | 21 | 22 | 34 | 38 a | 12 b | 17 | 2.5 | 1.8 | 25 | 32 | 17 | 23 |
F-Value (5%) |
MSC | 0.82 ns | 0.01 ns | 32.70 * | 6.89 * | 1.79 ns | 0.26 ns | 2.54 ns | 2.94 ns | 2.17 ns | 1.02 ns | 5.35 * | 0.11 ns |
CC | 2.38 ns | 1.94 ns | 1.54 ns | 4.68 * | 8.75 * | 5.05 * | 1.03 * | 2.34 ns | 2.86 ns | 2.81 ns | 2.01 ns | 5.07 * |
MSC × CC | 0.88 ns | 0.53 ns | 6.59 * | 1.99 ns | 0.69 ns | 6.34 * | 0.78 ns | 1.72 ns | 1.48 ns | 1.14 ns | 0.94 ns | 3.63 * |
Minimum significant difference (5%) |
MSC | -- | -- | -- | 3.99 | -- | -- | -- | -- | -- | -- | 3.86 | -- |
CC | -- | -- | -- | 8.98 | 5.69 | -- | -- | -- | -- | -- | -- | -- |
CV (%) | 8.64 | 8.03 | 20.99 | 18.26 | 20.66 | 23.99 | 40.0 | 15.90 | 28.55 | 15.40 | 32.03 | 11.91 |
IC | 17 | 17 | 6 | 6 | 6 | 6 | 4.9 | 1.8 | 17 | 17 | 12 | 12 |
The soil Mg content increased in both years of cultivation in the 5–10 cm layer, and the V% increased only in the first year in the soil treated with MSC (
Table 7). This can be explained by the limestone reaction in this soil layer caused by mechanical soil scarification, which promoted a higher Mg content (12–21 mmol
c dm
−3), with a concomitant increase in soil V (48–65%) in the first year. The CCs had a significant effect on soil H + Al, S, and V%. Under
U. ruziziensis, soil H + Al and S increased and V% decreased. Under the other cover crops, V% exceeded 60% in the first year. The previous cultivation of
U. ruziziensis, due to the greater dry matter yield, or of
C. juncea, because it is a legume with a higher S content and had MSC that accelerated decomposition through soil/straw contact, increased the soil S (30 and 29 mg dm
−3, respectively) in this layer in the second year of rice (
Table 7).
Table 7.
The mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% at 5–10 cm after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) were measured in Selvíria, MS, Brazil, during two growing seasons.
Table 7.
The mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% at 5–10 cm after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) were measured in Selvíria, MS, Brazil, during two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (5–10 cm) |
---|
| pH | H +Al | Al3+ (1) | SB | CEC | V(%) |
---|
| CaCl2 | ----------------------------------------- mmolc dm−3 --------------------------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 5.3 | 5.7 | 28 | 25 | 1.0 | 0.0 | 44.6 | 49.6 | 74.8 | 74.9 | 59 b | 66 |
With | 5.4 | 5.8 | 27 | 23 | 1.0 | 0.0 | 52.2 | 51.4 | 79.2 | 74.0 | 65 a | 69 |
Cover Crops (CCs) |
Fallow | 5.4 | 5.7 | 26 b | 23 | 0.0 | 0.0 | 50.0 | 45.4 b | 77.0 | 68.3 b | 65 a | 66 |
U. ruziziensis | 4.9 | 5.7 | 32 a | 24 | 4.0 | 0.0 | 37.9 | 48.8 ab | 69.8 | 72.4 ab | 53 b | 67 |
C. juncea | 5.6 | 5.8 | 27 ab | 24 | 0.0 | 0.0 | 54.3 | 50.1 ab | 83.3 | 73.5 ab | 65 a | 68 |
C. cajan | 5.5 | 5.6 | 25 b | 23 | 0.0 | 0.0 | 56.1 | 51.3 ab | 82.2 | 77.5 a | 65 a | 66 |
P. glaucum | 5.3 | 5.9 | 28 ab | 26 | 1.0 | 0.0 | 43.9 | 56.8 a | 73.1 | 80.2 a | 60 ab | 70 |
F-Value (5%) |
MSC | 0.27 ns | 2.24 ns | 0.69 ns | 26.02 * | 8.8 ns | -- | 2.89 ns | 0.88 ns | 1.21 ns | 0.25 ns | 4.53 * | 12.30 * |
CC | 17.73 * | 1.12 ns | 5.51 * | 4.31 * | 529.6 * | -- | 2.27 ns | 3.28 * | 1.58 ns | 4.61 * | 3.82 * | 2.30 ns |
MSC × CC | 4.11 * | 0.41 ns | 2.17 ns | 5.10 * | 111.3 * | -- | 1.26 ns | 1.96 ns | 0.92 ns | 1.70 ns | 1.52 ns | 3.07 * |
Minimum significant difference (5%) |
MSC | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | 5.11 | -- |
CC | -- | -- | 4.72 | -- | -- | -- | -- | 8.82 | -- | 8.89 | 11.51 | -- |
CV (%) | 40.0 | 4.25 | 11.63 | 7.13 | 6.88 | -- | 29.3 | 11.96 | 16.61 | 8.18 | 12.7 | 4.79 |
IC | 1.8 | 4.9 | 33 | 33 | 2 | 0 | 30.8 | 30.8 | 63.8 | 633.8 | 3 | 48 |
Regarding the relationships between mechanical soil scarification and the cover crops,
U. ruziziensis on scarified soil promoted a reduction in pH (4.9) and increased the Al content of the soil (2.75 mmol
c dm
−3) in comparison with the other CCs and the fallow treatment (control) in the first year. Regarding the interactions between MSC and the CCs in the second year in the 5–10 cm layer, for soil H + Al and V%,
P. glaucum under the NTS promoted a reduction in potential acidity (23 mmol
c dm
−3) and increased the base saturation (72%), indicating the potential of this species for recycling and the releasing of nutrients into the soil (
Figure 7c,d).
In the 10–20 cm layer, in the first year, the CCs influenced the P, K, Mg, H + Al, SB, and V% (
Table 8 and
Table 9). In particular, the soil under
U. ruziziensis had higher levels of P, K, Mg, SB, V%, and H + Al (35 mmol
c dm
−3). On the other hand, under
C. juncea, the levels of K, SB, and V% increased, but H + Al (31 mmol
c dm
−3) decreased. There was an increase in the OM content of this layer in the NTS in the second year (
Table 8 and
Table 9) due to the absence of soil disturbance (no MSC), which preserved the soil OM.
Table 8.
Mean soil chemical properties (OM, P, S, K, Ca, and Mg) at 10–20 cm after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 8.
Mean soil chemical properties (OM, P, S, K, Ca, and Mg) at 10–20 cm after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (10–20 cm) |
---|
| MO | P | S | K+ | Ca2+ | Mg2+ |
---|
| g dm−3 | ------------- mg dm−3---------- | ---------------------- mmolc dm−3 ---------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 18 | 18 a | 29 | 23 | 19 | 43 | 1.3 | 1.5 | 14 | 16 | 10 | 13 |
With | 18 | 17 b | 26 | 22 | 29 | 44 | 1.2 | 1.3 | 16 | 15 | 11 | 13 |
Cover Crops (CCs) |
Fallow | 17 | 17 | 25 b | 24 | 20 | 48 | 0.8 b | 1.5 | 15 | 15 | 10 ab | 13 |
U.ruziziensis | 18 | 17 | 35 a | 21 | 31 | 44 | 1.5 a | 1.2 | 18 | 14 | 13 a | 12 |
C.juncea | 18 | 18 | 28 b | 25 | 24 | 45 | 1.5 a | 1.4 | 17 | 16 | 11 ab | 13 |
C.cajan | 18 | 17 | 24 b | 18 | 21 | 33 | 1.1 b | 1.4 | 14 | 14 | 11 ab | 12 |
P. glaucum | 18 | 18 | 24 b | 24 | 25 | 48 | 1.0 b | 1.5 | 11 | 17 | 8 b | 14 |
F-Value (5%) |
MSC | 0.01 ns | 4.58 * | 2.82 ns | 1.20 ns | 33.64 ns | 0.47 ns | 0.76 ns | 2.78 ns | 2.39 ns | 2.18 ns | 1.50 ns | 0.52 ns |
CC | 0.29 ns | 2.68 ns | 7.72 * | 2.83 ns | 5.59 ns | 5.10 * | 9.58 * | 1.00 ns | 7.52 * | 2.96 ns | 4.76 * | 2.46 ns |
MSC × CC | 0.98 ns | 0.15 ns | 1.25 ns | 3.96 * | 3.02 * | 2.90 | 1.34 ns | 0.86 ns | 4.49 * | 1.47 ns | 0.52 ns | 1.47 ns |
Minimum significant difference (5%) |
MSC | -- | 1.62 | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
CC | -- | -- | 6.74 | -- | -- | -- | 0.40 | -- | -- | -- | 3.39 | -- |
CV (%) | 6.6 | 6.04 | 16.88 | 23.05 | 21.90 | 17.47 | 23.35 | 20.46 | 19.83 | 13.42 | 21.51 | 20.46 |
IC | 15 | 15 | 38 | 38 | 13 | 13 | 1.3 | 1.3 | 13 | 10 | 7 | 1.3 |
Table 9.
The mean soil chemical properties of pH, H + Al, Al, SB, CEC, and V% in layers of 10–20 cm after rice cultivation, cover crop (CC), and mechanical soil scarification (MSC) were measured in two growing seasons in Selvíria, MS, Brazil.
Table 9.
The mean soil chemical properties of pH, H + Al, Al, SB, CEC, and V% in layers of 10–20 cm after rice cultivation, cover crop (CC), and mechanical soil scarification (MSC) were measured in two growing seasons in Selvíria, MS, Brazil.
Soil Chemical Attributes Harvesting Upland Rice (10–20 cm) |
---|
| pH | H + Al | Al 3+ (1) | SB | CEC | V(%) |
---|
| CaCl2 | ----------------------------------------- mmolc dm−3 ---------------------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 4.8 | 5.1 | 34 | 31 | 3.4 | 1.1 | 25.8 | 30 | 59.7 | 60.8 | 43 | 49 |
With | 4.9 | 5.2 | 33 | 30 | 3.3 | 1.7 | 28.2 | 29 | 61.5 | 57.8 | 45 | 50 |
Cover Crops (CCs) |
Fallow | 4.8 | 5.2 ab | 35 a | 29 | 4.0 | 1.3 | 25.8 ab | 29 b | 60.4 | 57.9 | 43 ab | 50 ab |
U. ruziziensis | 4.9 | 5.0 b | 35 a | 32 | 3.5 | 1.8 | 32.8 a | 27 ab | 67.2 | 58.9 | 48 a | 46 b |
C. juncea | 4.9 | 5.3 a | 31 b | 31 | 2.6 | 1.1 | 29.9 a | 30 ab | 60.9 | 60.9 | 49 a | 50 ab |
C. cajan | 4.9 | 5.1 ab | 33 ab | 30 | 2.4 | 2.1 | 26.6 ab | 27 ab | 59.3 | 61.0 | 45 a | 48 ab |
P. glaucum | 4.8 | 5.3 a | 35 a | 28 | 4.1 | 0.6 | 20.0 b | 32 a | 55.1 | 57.3 | 36 b | 54 a |
F-Value (5%) |
MSC | 0.45 ns | 0.30 ns | 0.84 ns | 7.88 * | 0.20 ns | 0.38 ns | 2.56 ns | 0.38 ns | 1.49 ns | 8.52 * | 2.91 ns | 0.76 ns |
CC | 0.27 ns | 4.30 * | 5.47 * | 2.72 ns | 9.73 * | 3.17 * | 7.93 * | 3.17 * | 6.74 * | 2.54 * | 10.0 * | 3.19 * |
MSC × CC | 1.54 ns | 1.42 ns | 1.18 ns | 3.24 * | 5.35 * | 1.05 ns | 2.39 ns | 1.05 ns | 2.67 * | 5.22 * | 1.84 ns | 0.50 ns |
Minimum significant difference (5%) |
MSC | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
CC | -- | 0.25 | 3.02 | -- | -- | 5.26 | 7.1 | 5.26 | -- | -- | 6.62 | 6.60 |
CV (%) | 3.92 | 3.38 | 6.14 | 10.49 | 9.55 | 12.31 | 17.77 | 12.31 | 7.81 | 5.13 | 10.29 | 9.13 |
IC | 4.5 | 4.5 | 38 | 6 | 6 | 18.3 | 18.3 | 18.3 | 56.3 | 56.3 | 33 | 33 |
The interactions between the cover crops and mechanical soil scarification were significant for soil Al at 10–20 cm (
Figure 8c). In the first year, under the
U. ruziziensis and fallow conditions, with scarification (4 mmol
c dm
−3), and under
P. glaucum in the NTS (5 mmol
c dm
−3), the soil Al increased; this was most likely due to greater shoot and root dry matter yields, the decomposition of which generates more organic acids and consequently increases soil acidity. In the second year, P increased in the 10–20 cm layer (
Figure 8a), and higher P levels were noted after the previous cultivation of
C. juncea (27 mg dm
−3) and
P. glaucum (28 mg dm
−3) in the NTS.
The interaction effect of cover crops on mechanical soil scarification was significant for soil S at 10–20 cm. In the first year (
Figure 9a), all the CCs treated with MSC, except
P. glaucum, resulted in greater soil S. In the second year, the scarified soil under
U. ruziziensis had a greater sulfur content (51 mg dm
−3). With mechanical decompaction in the cover crops, the previous cultivation of
U. ruziziensis with MSC increased the soil S (39 mg dm
−3) but did not differ from the soil under
C. juncea in the first year.
The interactions of the cover crops with mechanical soil scarification were significant for soil CEC in the 10–20 cm layer (
Figure 9b). Regardless of scarification,
U. ruziziensis promoted an increase in soil CEC, but this increase did not differ from that of the fallow plants under the NTS in the first year. In the second year, the interactions between the cover crops and MSC and between soil H + Al and CEC (
Figure 8b,d) showed that the previous cultivation of
P. glaucum (31 and 64 mmol
c dm
−3) and
U. ruziziensis (35 and 62 mmol
c dm
−3) in the NTS increased soil H + Al and CEC, respectively.
The sulfur content was greatest in the 20–40 cm layer under the NTS (54 mg dm
−3). The cover crops had a significant effect on the soil contents of P, pH, Ca, Al, S, and V% (
Table 10 and
Table 11) in the first year. However,
Urochloa ruziziensis promoted greater P availability, with no significant difference from
C. juncea. However,
P. glaucum and
C. juncea induced a greater increase in soil pH than did
U. ruziziensis.
In the second year, in the 20–40 cm layer, the V value was highest (44%) under the NTS (
Table 10 and
Table 11). The CCs had a significant effect on pH, K, Ca, Mg, SB, and V%. In general, the
C. juncea cultivated previously exhibited an increase in the above chemical properties. The effect of the interactions between the cover crops and mechanical decompaction caused a reduction in soil H + Al (24 mmol
c dm
−3) and Al (0.00 mmol
c dm
−3) under the NTS of
C. juncea (
Figure 10a,b).
Table 10.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 20–40 cm layer after rice cultivation, cover crop (CC) cultivation and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 10.
Mean soil chemical properties OM, P, S, K, Ca, and Mg in the 20–40 cm layer after rice cultivation, cover crop (CC) cultivation and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (20–40 cm) |
---|
| MO | P | S | K+ | Ca2+ | Mg2+ |
---|
| g dm−3 | ------------ mg dm−3 --------- | ----------------------- mmolc dm−3 ----------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 16 | 15 | 9 | 8 | 54 a | 77 | 0.9 | 0.8 | 11 | 11 | 8 | 9 |
With | 16 | 15 | 8 | 9 | 48 b | 78 | 0.8 | 0.8 | 10 | 10 | 8 | 9 |
Cover Crops (CCs) |
Fallow | 16 | 16 | 8 b | 8 | 59 a | 89 | 0.9 | 0.7 ab | 10 ab | 10 b | 8 | 9 ab |
U. ruziziensis | 16 | 15 | 12 a | 9 | 50 ab | 76 | 0.8 | 0.6 b | 10 ab | 9 b | 7 | 8 b |
C. juncea | 16 | 16 | 9 ab | 9 | 47 ab | 70 | 0.9 | 1.0 a | 11 a | 12 a | 9 | 9 ab |
C. cajan | 17 | 15 | 8 b | 8 | 46 b | 78 | 0.9 | 1.0 a | 10 ab | 11 a | 8 | 9 ab |
P. glaucum | 16 | 15 | 6 b | 9 | 55 ab | 75 | 0.7 | 0.8 ab | 9 b | 10 b | 8 | 10 a |
F-Value (5%) |
MSC | 0.52 ns | 1.20 ns | 0.13 ns | 1.53 ns | 3.97 * | 0.13 ns | 2.52 ns | 0.13 ns | 4.18 ns | 4.01 ns | 0.05 ns | 0.07 ns |
CC | 1.58 ns | 0.51 ns | 6.45 * | 1.71 ns | 2.97 * | 2.23 ns | 0.79 * | 2.23 ns | 2.53 * | 6.19 * | 1.42 ns | 4.14 * |
MSC × CC | 1.26 ns | 1.01 ns | 2.56 ns | 1.35 ns | 1.94 ns | 0.11 ns | 0.33 ns | 0.11 ns | 2.36 ns | 1.86 ns | 0.32 ns | 1.33 ns |
Minimum significant difference (5%) |
MSC | -- | -- | -- | -- | 5.81 | -- | -- | -- | -- | -- | -- | -- |
CC | -- | -- | 3.89 | -- | 13.08 | -- | -- | 0.26 | 2.51 | 1.96 | -- | 1.72 |
CV (%) | 5.56 | 7.02 | 31.74 | 19.14 | 17.49 | 16.96 | 29.91 | 22.01 | 14.30 | 13.07 | 17.79 | 13.09 |
IC | 13 | 13 | 7 | 7 | 43 | 43 | 1.4 | 1.4 | 10 | 10 | 8 | 8 |
Table 11.
Mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% in the 20–40 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Table 11.
Mean soil chemical properties pH, H + Al, Al, SB, CEC, and V% in the 20–40 cm layer after rice cultivation, cover crop (CC) cultivation, and mechanical soil scarification (MSC) in Selvíria, MS, Brazil, in two growing seasons.
Soil Chemical Attributes Harvesting Upland Rice (20–40 cm) |
---|
| pH | H + Al | Al3+ (1) | SB | CEC | V(%) |
---|
| CaCl2 | ----------------------------------------- mmolc dm−3 ---------------------------------- |
---|
Mechanical soil scarification (MSC) |
| 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year | 1st Year | 2nd Year |
Without | 4.9 | 5.1 | 31 | 26 | 2.9 | 1.3 | 19.3 | 20.6 | 48.5 | 47.0 | 39 | 44 a |
With | 4.8 | 5.0 | 31 | 28 | 3.1 | 1.5 | 18.7 | 19.6 | 49.8 | 48.0 | 38 | 41 b |
Cover Crops (CCs) |
Fallow | 4.9 ab | 5.0 ab | 30 | 27 | 3.0 b | 1.5 | 18.5 | 19 b | 45.1 | 46.5 | 39 ab | 41 b |
U. ruziziensis | 4.7 b | 4.9 b | 32 | 29 | 4.4 a | 1.5 | 17.9 | 18 b | 50.2 | 46.7 | 36 b | 39 b |
C. juncea | 5.0 a | 5.1 a | 30 | 26 | 2.1 b | 1.0 | 21.0 | 23 a | 51.0 | 50.0 | 41 a | 47 a |
C. cajan | 4.9 ab | 5.0 ab | 32 | 27 | 2.8 b | 1.5 | 19.9 | 21 ab | 52.0 | 47.0 | 38 ab | 44 ab |
P. glaucum | 5.0 a | 5.1 a | 30 | 27 | 4.4 a | 1.6 | 17.8 | 19 b | 47.5 | 46.8 | 38 ab | 42 b |
F-Value (5%) |
MSC | 3.57 ns | 1.52 ns | 0.29 ns | 11.63 * | 0.56 ns | 17.27 * | 0.74 ns | 1.44 ns | 0.43 ns | 0.87 ns | 1.15 ns | 5.19 * |
CC | 4.43 * | 2.64 * | 0.98 ns | 2.62 * | 0.91 * | 14.56 * | 2.29 ns | 5.73 * | 1.53 ns | 2.31 ns | 2.25 * | 6.79 * |
MSC × CC | 0.88 ns | 2.17 * | 0.94 ns | 3.38 * | 0.45 ns | 5.89 * | 1.39 ns | 1.69 ns | 1.35 ns | 2.04 ns | 1.68 ns | 2.20 ns |
Minimum significant difference (5%) |
MSC | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | 2.25 |
CC | 0.21 | 0.19 | -- | -- | 1.37 | -- | -- | 3.58 | -- | -- | 5.35 | 5.07 |
CV (%) | 2.92 | 2.54 | 11.50 | 5.79 | 13.96 | 11.38 | 13.47 | 12.19 | 13.00 | 12.19 | 9.50 | 8.20 |
IC | 4.8 | 4.8 | 29 | 29 | 2 | 2 | 19.4 | 19.4 | 48.4 | 19.4 | 40 | 40 |