5.2 Soil Limiting Factors
As mentioned in Chaps. 3 and 4, the majority of areas in
Libya are characterized by dry and hot climatic conditions
and the absence of vegetative cover. This leads mainly to the
formation of Entisols, Aridisols. Mollisols, Alfisols, and
Vertisols, which are only found in Al-Jabal Al-Akhdar,
Inceptisols are also found in the Al-Jabal Al-Akhdar and in a
small area of the Tripoli Mountains (Jabal Nafusa), where
the Mediterranean climate is dominating. Such soils have a
low content of organic matter (O.M %) and low nutrient
content. In addition, soil physical attributes, for example,
soil texture, infiltration rates, cannot support plant production well (Nwer 2005). There are many soil limiting factors
in the agriculture system. Available water is essential for
plant growth. The water storage capacity of the soil is one of
the most important soil properties for soil functions including productivity (Shaxson 2006; Jones et al. 2009). The
other group of limitations include other internal soil deficiencies mainly due to an improper substratum, limiting
rooting and nutrition of plants. These include shallow soils,
stoniness, hardpans, anaerobic horizons, or soils with
adverse chemistry such as salinity, sodicity, alkalinity,
nutrient depletion, or contamination, which may cause severe restrictions to plant growth or utilization of biomass
(Murray et al. 1983; Louwagie et al. 2009; Ben Mahmoud
2013). Other soil constraints to agricultural use are the depth
of the water table, internal drainage, and soil erosion by
wind or water (Ben Mahmoud 1995). The following sections
will address soil properties that are believed to have a greater
impact on agriculture production in the Libyan context.
According to Ben Mahmoud (2013), these problems and
obstacles can be summarized as follows.
5.2.1 Soil Texture
Texture is the most permanent characteristic of soil. It
decisively influences a number of soil attributes such as soil
moisture regime, permeability, infiltration rate, runoff rate,
erodibility, workability, root penetration, and fertility
(ILACO 1989). Soil texture is the most important property to
be determined, and it is critical for understanding soil
behavior and management. From the soil texture, many
conclusions can be drawn. Soil texture governs moisture and
nutrient storage capacity. It provides a measure for permeability, and to some extent, for water retention capacity
(Brady and Weil 1999). With the exception of some Libyan
soils that have relatively suitable texture, the majority of
these soils are Coarse sandy soils, compact clay soils, and
gravel and stony soils that are unsuitable for agricultural use.
This is because they reduce the chance of crop growth, cause
difficulties in agricultural activities, and have negative effects
on soil-water properties (Fig. 5.1).
5.2.2 Soil Depth
Soil depth can greatly influence the types of plants that can
grow. Soil depth is a very important parameter in determining the quantity of water and nutrients that can be stored
in the soil profile, as well as the ability to support plant
growth, during periods of no rainfall or when irrigation
ceases. Soil depth is also important in determining the ability
of the profile to support plant roots and the ability of the crop
to withstand wind damage. Under irrigated conditions, soil
depth affects drainage, aeration, and water retention properties. The available storage capacity of the soil and consequently the water application depth and irrigation frequency
are determined by root depth and root distribution, as well as
by the moisture characteristics of the soil (ILACO 1989;
Nwer 2005). Deeper soils can provide more water and
nutrients to plants than more shallow soils. Furthermore,
Fig. 5.1 Stony gravel soils (Ben Mahmoud 2013)
66
B. A. Nwer et al.
As mentioned in Chaps. 3 and 4, the majority of areas in
Libya are characterized by dry and hot climatic conditions
and the absence of vegetative cover. This leads mainly to the
formation of Entisols, Aridisols. Mollisols, Alfisols, and
Vertisols, which are only found in Al-Jabal Al-Akhdar,
Inceptisols are also found in the Al-Jabal Al-Akhdar and in a
small area of the Tripoli Mountains (Jabal Nafusa), where
the Mediterranean climate is dominating. Such soils have a
low content of organic matter (O.M %) and low nutrient
content. In addition, soil physical attributes, for example,
soil texture, infiltration rates, cannot support plant production well (Nwer 2005). There are many soil limiting factors
in the agriculture system. Available water is essential for
plant growth. The water storage capacity of the soil is one of
the most important soil properties for soil functions including productivity (Shaxson 2006; Jones et al. 2009). The
other group of limitations include other internal soil deficiencies mainly due to an improper substratum, limiting
rooting and nutrition of plants. These include shallow soils,
stoniness, hardpans, anaerobic horizons, or soils with
adverse chemistry such as salinity, sodicity, alkalinity,
nutrient depletion, or contamination, which may cause severe restrictions to plant growth or utilization of biomass
(Murray et al. 1983; Louwagie et al. 2009; Ben Mahmoud
2013). Other soil constraints to agricultural use are the depth
of the water table, internal drainage, and soil erosion by
wind or water (Ben Mahmoud 1995). The following sections
will address soil properties that are believed to have a greater
impact on agriculture production in the Libyan context.
According to Ben Mahmoud (2013), these problems and
obstacles can be summarized as follows.
5.2.1 Soil Texture
Texture is the most permanent characteristic of soil. It
decisively influences a number of soil attributes such as soil
moisture regime, permeability, infiltration rate, runoff rate,
erodibility, workability, root penetration, and fertility
(ILACO 1989). Soil texture is the most important property to
be determined, and it is critical for understanding soil
behavior and management. From the soil texture, many
conclusions can be drawn. Soil texture governs moisture and
nutrient storage capacity. It provides a measure for permeability, and to some extent, for water retention capacity
(Brady and Weil 1999). With the exception of some Libyan
soils that have relatively suitable texture, the majority of
these soils are Coarse sandy soils, compact clay soils, and
gravel and stony soils that are unsuitable for agricultural use.
This is because they reduce the chance of crop growth, cause
difficulties in agricultural activities, and have negative effects
on soil-water properties (Fig. 5.1).
5.2.2 Soil Depth
Soil depth can greatly influence the types of plants that can
grow. Soil depth is a very important parameter in determining the quantity of water and nutrients that can be stored
in the soil profile, as well as the ability to support plant
growth, during periods of no rainfall or when irrigation
ceases. Soil depth is also important in determining the ability
of the profile to support plant roots and the ability of the crop
to withstand wind damage. Under irrigated conditions, soil
depth affects drainage, aeration, and water retention properties. The available storage capacity of the soil and consequently the water application depth and irrigation frequency
are determined by root depth and root distribution, as well as
by the moisture characteristics of the soil (ILACO 1989;
Nwer 2005). Deeper soils can provide more water and
nutrients to plants than more shallow soils. Furthermore,
Fig. 5.1 Stony gravel soils (Ben Mahmoud 2013)
66
B. A. Nwer et al.