123Foliar application of N is also an option in dryland soils because the farmers
apply fertilizer when rain occurs which are often delayed. Foliar application of con-
centrated urea solution enhanced the dryland wheat yield by 31 % (FAO 1988 ). In
dryland cotton (Gossypium hirsutum L.), application of urea at the rate of 25–30 kg
ha−^1 through soil and foliar application enhanced the yield by 13–51 % than sole
soil application (Rao et al. 1973 ). Foliar application is usually pragmatic when the
fertilizers are not applied as basal dose and the onward soil applications are also not
possible due to some operational difficulties (Dargan et al. 1973 ).
Some other factors like fertilizer and cash availability, the relative return from
other inputs used for crop production, and the environmental risk may affect the
choice of fertilizer application to crops in drylands. Various site specific character-
istic such as soil texture, soil organic matter, rainfall, soil tests for different nutri-
ents, the crop type and tillage method may affect the efficiency of nutrient use in
dryland areas (Ryan et al. 2010 ). In dryland soils, less rainfall and leaching losses
necessities the same amount of N applications in spring and fall, top dressing in
spring being better in relation to flexibility with rainfall. The responses to applied N
increases with increase in rainfall and soil moisture availability in dryland regions.
For example, response to N were highest at rainfall level of 350–550 mm in Syria,
and they were lowest when rainfall was less than 250 mm. Likewise, the responses
of N are more when applied after fallow than applied after cereal crop (Ryan and
Sommer 2010 ). Deficiency of Zn and Fe, and the toxicity of B may affect the
responses of crops towards applied N and P. Level of soil organic matter and the
type of crop rotation in a specific dryland region also affects the responses of crops
to N fertilization (Ryan et al., 2010 ), which should be taken care while devising the
N application schedules for dryland crops. In the dryland areas, where urea is used
as N fertilizer source, it should be mixed into soil, or should be applied under cooler
conditions, or may be top-dressed before or during spring rains to avoid the losses
through volatilization (Abdel Monem et al. 2010 ).
In calcareous soil, most of the soluble P sources become fixed. Under such con-
ditions, long-term band placement of P is beneficial (Ryan and Sommer 2010 ). The
N fertilizer use efficiency in dryland crops can be enhanced through innovative
placement techniques and timing of application. For example, application of ammo-
nia based N fertilizers in concentrated bands may restrict nitrification and leaching.
Top dressing of N based fertilizers in favorable season or before a forecasted rainfall
event can enhance crop yield and quality (Angus et al. 1994 ). Leaching losses of
urea are usually less in dryland losses due to less soil moisture.
In dryland areas of Africa, the losses of N from applied N, regardless of N
sources in gaseous form has been reported with increasing application rate (Bekunda
et al. 1997 ). However, certain sources may yield better for some crops. For instance,
the use of calcium ammonium nitrate was better than urea regarding the plant N
uptake, and it eventually enhanced the yield of pearl millet (Mughogho et al. 1986 ).
In West Africa, the N uptake by millet crop was about three times more from point-
placed calcium ammonium nitrate against point-placed urea fertilizer, and the N
uptake was 57 % less from the broadcasted calcium ammonium nitrate than the
Nutrient Management in Dryland Agriculture Systems