1192.4 Soil Erosion
Soil erosion in dryland regions also causes substantial loss of nutrients. Tillage of
dryland soils degrades the top soil layer (Izaurralde et al. 2006 ), which is followed
by increase in soil bulk density, deterioration of soil structure and alteration in total
soil porosity causing decrease in crop yield (Malhi et al. 1994 ). Soil erosion also
depletes the soil nutrients thus causing nutrient deficiencies, and alters the soil
chemical properties (Larney et al. 2000 ; Izaurralde et al. 2006 ) in dryland regions.
In a study, Baptista et al. ( 2015 ) noted higher concentration of nitrate-N (2.20–
4.83 mg L−^1 ) in runoff, and PO 4 -P (5.27–18.8 mg g−^1 ) in eroded soil, which indi-
cates how nutrients are lost through soil erosion and runoff in dryland regions. Wind
and water erosion has also been major drivers to organic N losses from soil in dry-
land soils in China (Li et al. 2009b).
2.5 Soil Type and Nutrient Deficiencies
Successful crop production in drylands depends upon the soil management of nutri-
ents (macronutrients and micronutrients) in the soil. The macronutrients include N,
P, K, calcium (Ca), magnesium (Mg) and S. The response of crops to N grown in
dryland area depends on the type of the soil, crop rotation and the crop season
(Russell 1967 ; McDonald 1989 ; Mason et al. 1994 ). The main reason of N defi-
ciency in dryland regions include the low soil organic matter as more than 95 % of
the N in the soil exists in soil organic matter. In dryland regions, the losses of applied
N on coarse texture soil are higher than clay soil owing to leaching losses. In many
dryland soils, the deficiency of P is widespread due to P fixation (Russell 1967 ;
Harmsen 1984 ; Impiglia and Ryan 1997 ), which necessities regular application of P
in dryland soils. The K deficiencies in dryland crop production (especially) has
rarely been reported, but may be present where the crop production is intensified
(Ryan et al. 1997 ). The less deficiency of K in dryland soils is attributed to the pres-
ence of K-minerals in these soils which weather very slowly (Sekhon 1983 ).
In Australia, removal of crop nutrients in harvested products, nutrient loss
through soil erosion, denitrification (from waterlogged Vertisols), and leaching
(from light textured soils) has led towards severe deficiencies of N and P in dryland
regions. The Zn and S deficiencies are reported on large area, but the deficiencies of
K, manganese (Mn), copper (Cu) and molybdenum (Mo) (in ferrosols) has been
reported on very small area in Australia (Birch and Bell 2011 ).
In drylands, the most frequently deficient micronutrients are Zn (on alkaline
soil), Fe and Mn. Indeed, the most of the soils in the dryland regions have pH of 8.0
or above, and are highly alkaline and calcareous which reduced the availability of
these trace nutrients. The deficiency of Zn and Mn has mostly been observed in
dryland wheat. Deficiency of Zn in dryland soils (e.g., rice and maize) might be also
attributed to high incident of solar radiations.
Nutrient Management in Dryland Agriculture Systems