[154]. Some authors also reported the additional advantages of mulching with
leguminous crops like greater flowering and obvious vegetative growth of coffee
plant and weed control function [155]. The degree of effectiveness of mulching is
site specific and depends upon soil permeability, soil organic carbon (SOC), percentage of soil surface cover, interaction among these variables, and other agroecological conditions. The mulching improves the SOC and water aggregate stability
index (WAS) and reduces the soil bulk density (BD) and Interrill and rill erodibility
of coffee fields at high altitudes [154]. The increase in BD following mulching as
reported by some author [152] may be due to incorporating the mulch material with
soil instead of layering which affects the porosity and hence the BD of soil.
Tumwebaze and Byakagaba [135] also reported that BD has a positive linkage
with pH and N and P contents of soil. The authors also noted BD is highly crop
and crop production system dependent. BD is higher in mono-crop systems than
agroforestry or intercropped systems, and Robusta coffee soils also have greater BD
values than Arabica coffee soils which may be due to their cultivation at lower
altitudes.
The outcomes of mulching in coffee fields largely found to be depended upon the
type of its application, superficial or buried mulching. Superficial mulching gives
delayed results (e.g., soil physical properties improvement, increasing SOC), while
buried mulching resulted in fast improvement in soil but less soil protecting capability in the starting [156]. Buried mulching also reduced the runoff depth by 40.2%
as compared to superficial mulching which exhibited (50–87%) rise in infiltration
rate and runoff values are smaller in both types of mulching [157]. Crusted soils
promote runoff rate and superficial mulching does not leave positive effect on crust
soils over runoff rate. In addition, soil conditions significantly affect the runoff and
infiltration in comparison to poor relation of soil class with them. Both kind of
mulching give rise to 53–87% reduction in soil losses, whereas highest soil losses
were achieved with smallest particle size mulch material. The highest rate of
erodibility was seen in sandy and very fine sandy soils due to their ease of detachment because of weak association with organo-clay complex. Thus, sandy and silty
soil (i.e., silt, silty loam, loam, silt clay loam) soils are highly vulnerable to runoff
and acts of mulching offer resistance to erosion by strengthen the bond between finer
particles and organo-clay complex [154].
Besides mulching, high density planting was also proposed as counter measurement for soil erosion and its detrimental consequences. Soil erosion is mainly
considered responsible for soil acidification in coffee fields along nutrient leaching.
Soil erosion was found to be more obvious in less denser planting systems, whereas
high density planting systems contributed in enhancing the soil OM contents,
exchangeable cations (Ca, Mg, K), CEC, extractable P, water storage soil crust and
lowering the soil acidity, Al and Fe toxicity, and microbial population [158]. The
control of soil erosion is also differing with respect to the cropping or plantation
system. In agroforestry system, litter size is found to be more important erodibility
factor [14] as compared to intercropped system where gradient slope has marked
influence on both shaded and sun coffee plantations [148]. In agroforestry system of
coffee, the threshold levels of litter cover and slope gradients are 30% and 60–65%,
668
A. Hameed et al.
leguminous crops like greater flowering and obvious vegetative growth of coffee
plant and weed control function [155]. The degree of effectiveness of mulching is
site specific and depends upon soil permeability, soil organic carbon (SOC), percentage of soil surface cover, interaction among these variables, and other agroecological conditions. The mulching improves the SOC and water aggregate stability
index (WAS) and reduces the soil bulk density (BD) and Interrill and rill erodibility
of coffee fields at high altitudes [154]. The increase in BD following mulching as
reported by some author [152] may be due to incorporating the mulch material with
soil instead of layering which affects the porosity and hence the BD of soil.
Tumwebaze and Byakagaba [135] also reported that BD has a positive linkage
with pH and N and P contents of soil. The authors also noted BD is highly crop
and crop production system dependent. BD is higher in mono-crop systems than
agroforestry or intercropped systems, and Robusta coffee soils also have greater BD
values than Arabica coffee soils which may be due to their cultivation at lower
altitudes.
The outcomes of mulching in coffee fields largely found to be depended upon the
type of its application, superficial or buried mulching. Superficial mulching gives
delayed results (e.g., soil physical properties improvement, increasing SOC), while
buried mulching resulted in fast improvement in soil but less soil protecting capability in the starting [156]. Buried mulching also reduced the runoff depth by 40.2%
as compared to superficial mulching which exhibited (50–87%) rise in infiltration
rate and runoff values are smaller in both types of mulching [157]. Crusted soils
promote runoff rate and superficial mulching does not leave positive effect on crust
soils over runoff rate. In addition, soil conditions significantly affect the runoff and
infiltration in comparison to poor relation of soil class with them. Both kind of
mulching give rise to 53–87% reduction in soil losses, whereas highest soil losses
were achieved with smallest particle size mulch material. The highest rate of
erodibility was seen in sandy and very fine sandy soils due to their ease of detachment because of weak association with organo-clay complex. Thus, sandy and silty
soil (i.e., silt, silty loam, loam, silt clay loam) soils are highly vulnerable to runoff
and acts of mulching offer resistance to erosion by strengthen the bond between finer
particles and organo-clay complex [154].
Besides mulching, high density planting was also proposed as counter measurement for soil erosion and its detrimental consequences. Soil erosion is mainly
considered responsible for soil acidification in coffee fields along nutrient leaching.
Soil erosion was found to be more obvious in less denser planting systems, whereas
high density planting systems contributed in enhancing the soil OM contents,
exchangeable cations (Ca, Mg, K), CEC, extractable P, water storage soil crust and
lowering the soil acidity, Al and Fe toxicity, and microbial population [158]. The
control of soil erosion is also differing with respect to the cropping or plantation
system. In agroforestry system, litter size is found to be more important erodibility
factor [14] as compared to intercropped system where gradient slope has marked
influence on both shaded and sun coffee plantations [148]. In agroforestry system of
coffee, the threshold levels of litter cover and slope gradients are 30% and 60–65%,
668
A. Hameed et al.