**5.1 Water-dispersible clay**

Water-dispersible clay is the fraction of clay that disperses in water, and dispersive soils are common problematic soils in many parts of the world [14]. Due to fact that dispersible clay blocked soil porous system and compromise the water and gas movement, this soil property has been used in studies of hydric erosion and soil management.

In a long-term experiment conducted at experimental station of the IAPAR in Londrina, PR submitted to seven different weed management in the interrow area (between coffee row), weed managements in the interrow area did not affect the point of zero charge. The experiment was installed in randomized complete block design, seven treatments with four replicates. The soil in the experiment site is classified as Typical Dystroferric Red Latosol, very clayey texture (80 dag kg<sup>−</sup><sup>1</sup> clay) with kaolinitic mineralogy derived from the saprolites from basaltic rocks. The weed management were as follows: T1, hand-hoe weeding (HAWE); T2, portable mechanical mower (PMOW); T3, herbicides (HERB); T4, cover crop peanut horse (CCPH); T5, cover crop dwarf mucuna (CCDM); T6, no-weeding control in the interrow area (SCAP); and T7, weed check (CHECK) (no-weed control in the row and interrow area). Soil samples were collected at 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm depths. Soil electrochemical properties were determined: pH in relation 1:2.5 soil/solution in a 0.01 mol L<sup>−</sup><sup>1</sup> CaCl2, KCl, and water and point of zero charge (PZC). Water-dispersible clay was determined by pipette method without chemical dispersion shaker for 2 h.

However, the estimated point of zero charge changed among the soil sample depths (**Figure 2**). The estimated PCZ values were 4.2 (StDv. 0.54), 3.6 (0.54), 3.7 (0.29), and 3.7 (0.37) lower than the pH in all depths which contribute to excess in negative charge. When soil pH is higher than PZC, there were electrostatic repulsion and drop in clay flocculation [7].

For soil samples collected at county Londrina, Northern Paraná in Native Forest at 0–20 cm depth of a Red Latosol with very clayey texture (72 dag kg<sup>−</sup><sup>1</sup> ), incubated with limed sludge with doses 1.5–24 g kg<sup>−</sup><sup>1</sup> , Tavares Filho et al. [7] observed after 180 days incubation in pots in the greenhouse PZC 4.8–5.03; delta pH −0.22 to −0.15; and water-dispersible clay 66–128 dag kg<sup>−</sup><sup>1</sup> ; soil samples were shacked in an orbital shaker at 300 rpm for 3 h.

Weed management in the interrow area of coffee crop changes delta pH (p < 0.001) for a Dystroferric Red Latosol, very clayey at 0–10 cm depth. The highest values were found for T6 no-weed control between coffee rows (∆pH = −0.57) = T1 hand weeding (∆pH = −0.68) = T7 weed check (∆pH = −0.72) and lowest for T2 portable mechanical mower (∆pH = −0.80) = T3 herbicides (∆pH = −0.93) = T4 cover crop peanut horse (∆pH = −0.80) = T5 cover crop dwarf mucuna (∆pH = −0.78).

Changes in ∆pH affected the water-dispersible clay (**Figure 3**).

With the aim of to investigate the effect of liming on chemical and physical properties of three very fine, ferruginous, isothermic Rhodic Hapludox with different levels of organic carbon, Castro Filho [6] observed that pH affects positively the aggregate stability indexes. This author also suggested that aggregate stability depends on the soil mineralogical composition and the highest aggregation occurred nearly 100% of Al neutralization.

**51**

aggregates [6].

**Figure 3.**

**Figure 2.**

*Soil Electrochemical and Physical Properties in Coffee Crops in the State of Paraná, Brazil*

As can be observed in **Figure 4**, mean weight diameter increased as soil pH. Mean weight diameter (MWD) is large if the soil has a high percentage of large

*Water-dispersible clay in relation to delta pH of a Dystroferric Red Latosol cultivated with coffee crop submitted to weed management in the interrow area. HAWE, hand weeding; PMOW, portable mechanical mower; HERB, herbicides; CCPH, cover crop peanut horse; CCDM, cover crop dwarf mucuna; SCAP,* 

*no-weed between coffee rows; CHECK, no-weeding in the interrow and row areas.*

*DOI: http://dx.doi.org/10.5772/intechopen.91352*

*Point of zero charge (PZC) in four layers of a Red Latosol cultivate coffee.*

*Soil Electrochemical and Physical Properties in Coffee Crops in the State of Paraná, Brazil DOI: http://dx.doi.org/10.5772/intechopen.91352*

**Figure 2.**

*Coffee - Production and Research*

**5.1 Water-dispersible clay**

relation 1:2.5 soil/solution in a 0.01 mol L<sup>−</sup><sup>1</sup>

chemical dispersion shaker for 2 h.

sion and drop in clay flocculation [7].

orbital shaker at 300 rpm for 3 h.

with limed sludge with doses 1.5–24 g kg<sup>−</sup><sup>1</sup>

occurred nearly 100% of Al neutralization.

−0.15; and water-dispersible clay 66–128 dag kg<sup>−</sup><sup>1</sup>

**aggregates**

management.

**5. Electrochemical properties of an Oxisol cultivated with coffee crop and its relationship with flocculation-dispersion of colloids and** 

Water-dispersible clay is the fraction of clay that disperses in water, and dispersive soils are common problematic soils in many parts of the world [14]. Due to fact that dispersible clay blocked soil porous system and compromise the water and gas movement, this soil property has been used in studies of hydric erosion and soil

In a long-term experiment conducted at experimental station of the IAPAR in Londrina, PR submitted to seven different weed management in the interrow area (between coffee row), weed managements in the interrow area did not affect the point of zero charge. The experiment was installed in randomized complete block design, seven treatments with four replicates. The soil in the experiment site is classified as Typical Dystroferric Red Latosol, very clayey texture (80 dag kg<sup>−</sup><sup>1</sup>

with kaolinitic mineralogy derived from the saprolites from basaltic rocks. The weed management were as follows: T1, hand-hoe weeding (HAWE); T2, portable mechanical mower (PMOW); T3, herbicides (HERB); T4, cover crop peanut horse (CCPH); T5, cover crop dwarf mucuna (CCDM); T6, no-weeding control in the interrow area (SCAP); and T7, weed check (CHECK) (no-weed control in the row and interrow area). Soil samples were collected at 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm depths. Soil electrochemical properties were determined: pH in

charge (PZC). Water-dispersible clay was determined by pipette method without

However, the estimated point of zero charge changed among the soil sample depths (**Figure 2**). The estimated PCZ values were 4.2 (StDv. 0.54), 3.6 (0.54), 3.7 (0.29), and 3.7 (0.37) lower than the pH in all depths which contribute to excess in negative charge. When soil pH is higher than PZC, there were electrostatic repul-

For soil samples collected at county Londrina, Northern Paraná in Native Forest

at 0–20 cm depth of a Red Latosol with very clayey texture (72 dag kg<sup>−</sup><sup>1</sup>

Changes in ∆pH affected the water-dispersible clay (**Figure 3**).

180 days incubation in pots in the greenhouse PZC 4.8–5.03; delta pH −0.22 to

Weed management in the interrow area of coffee crop changes delta pH (p < 0.001) for a Dystroferric Red Latosol, very clayey at 0–10 cm depth. The highest values were found for T6 no-weed control between coffee rows (∆pH = −0.57) = T1 hand weeding (∆pH = −0.68) = T7 weed check (∆pH = −0.72) and lowest for T2 portable mechanical mower (∆pH = −0.80) = T3 herbicides (∆pH = −0.93) = T4 cover crop peanut horse (∆pH = −0.80) = T5 cover crop dwarf mucuna (∆pH =

With the aim of to investigate the effect of liming on chemical and physical properties of three very fine, ferruginous, isothermic Rhodic Hapludox with different levels of organic carbon, Castro Filho [6] observed that pH affects positively the aggregate stability indexes. This author also suggested that aggregate stability depends on the soil mineralogical composition and the highest aggregation

clay)

), incubated

CaCl2, KCl, and water and point of zero

, Tavares Filho et al. [7] observed after

; soil samples were shacked in an

**50**

−0.78).

*Point of zero charge (PZC) in four layers of a Red Latosol cultivate coffee.*

#### **Figure 3.**

*Water-dispersible clay in relation to delta pH of a Dystroferric Red Latosol cultivated with coffee crop submitted to weed management in the interrow area. HAWE, hand weeding; PMOW, portable mechanical mower; HERB, herbicides; CCPH, cover crop peanut horse; CCDM, cover crop dwarf mucuna; SCAP, no-weed between coffee rows; CHECK, no-weeding in the interrow and row areas.*

As can be observed in **Figure 4**, mean weight diameter increased as soil pH. Mean weight diameter (MWD) is large if the soil has a high percentage of large aggregates [6].

**Figure 4.** *Mean weight diameter (MWD) of the aggregates of a Red Latosol cultivate coffee 6 months after liming. Source: From Roth et al. [21].*

Soil organic matter and soil pH (**Figure 3**), whose mechanisms involved depend on the substitution of aluminum by calcium in the sortive complex, participate in the soil aggregation whose formation and stabilization of the different classes of soil aggregate sizes will allow more or less lower aggregation, resulting in greater or lesser soil loss [9].

In a field experiment conducted in a Rhodic Hapludox cultivated with coffee, 2 years after the surface liming, Roth et al. [21] highlighted that the aggregation of solid particles exerts a significant action on soil susceptibility to accelerated water erosion for uncovered soil conditions. This study showed that after 60 min of simulated rainfall at an intensity of 60 mm per hour, soil maintained without soil correction with pH = 5.2 provided total infiltration of 56% of the total precipitation [21]. On the other hand, the authors observed that the best liming treatment to increase pH 7.0 provided 83% of total infiltration. In soil with pH 6.0 and with the application of plaster, the total infiltration was 67% of the total precipitation.
