63
It is considered as one of the most important leguminous forage crops in Egypt in
the winter season, where it could be cultivated as early as in October and it could be
harvested in May. Egyptian clover plays a very vital role in the sustainability of
Egyptian agriculture. The crop can be mowed several times for forage and then
ploughed to be use as green manure, which helps in increasing the organic matter
content of the soil, thus improving soil physical, chemical and biological properties
(El-Nahrawy 2011). Jabbar et al. (2011) indicated that residual soil fertility, residual
soil nitrogen, and residual soil organic matter can be increased by cultivation of
Egyptian clover. Furthermore, Nair (2015) reported that symbiotic relationships
with soil bacterium are established when clover is cultivated and atmospheric nitrogen is fixed, adding significant amounts of nitrogen to the soil. Egyptian clover
nourishes the soils, suppresses weeds and providing a disease break in cerealdominated crop rotations existed in Egypt (El-Nahrawy 2011).
4.2.1 Effect of Water Stress on Egyptian Clover
Limitation of water supply is a major production constraint for this crop (Lazaridou
and Koutroubas 2004). The impact of water stress on crop growth and productivity
depends upon the intensity and duration of drought, growth stage, the genotype and
physiology of the crop species. The effect of water stress on Egyptian clover was
studied by Barzegar et al. (2016), where they stated that water stress resulted in lower
leaf area, stem length and total dry mass. Iannucci et al. (2000) reported a significant
reduction in total dry weight, plant height and proline content due to water stress
treatments. They also reported that water stress influenced clover plant growth and
its components. Furthermore plants subjected to periods of water stress during development stage have a lessened sensitivity to subsequent stress. Therefore, their ability
to survive drought is mainly due to their capacity to avoid dehydration. Lazaridou
and Koutroubas (2004) noted a 75% decrease in biomass; leaf area and transpiration
rate was recorded as a result of water restriction. An average of 91-fold increase in
proline levels in white clover leaves under water deficit was observed (Barker et al.
1993). Similar results have been found in subterranean clover by Socias and Medrano
(1994). In a study done by Hussain et al. (2015) on the effect of water stress on
Egyptian clover, they found significant effects of water restriction on yield, leaf gas
exchange parameters, canopy temperature and osmotic adjustment. They also
reported that most morpho-physiological traits had higher broad sense heritability
than forage yield, both under full irrigation and water restriction conditions.
4.2.2 Effect of Deficit Irrigation on Egyptian Clover
Application of deficit irrigation to Egyptian clover was studied by Abouelenein
et al. (2010), where they showed that application of 70% of full irrigation to Egyptian
clover resulted in 11% yield losses under surface irrigation in clay soil. Furthermore,
4 Field Crops and Deficit Irrigation in Egypt
It is considered as one of the most important leguminous forage crops in Egypt in
the winter season, where it could be cultivated as early as in October and it could be
harvested in May. Egyptian clover plays a very vital role in the sustainability of
Egyptian agriculture. The crop can be mowed several times for forage and then
ploughed to be use as green manure, which helps in increasing the organic matter
content of the soil, thus improving soil physical, chemical and biological properties
(El-Nahrawy 2011). Jabbar et al. (2011) indicated that residual soil fertility, residual
soil nitrogen, and residual soil organic matter can be increased by cultivation of
Egyptian clover. Furthermore, Nair (2015) reported that symbiotic relationships
with soil bacterium are established when clover is cultivated and atmospheric nitrogen is fixed, adding significant amounts of nitrogen to the soil. Egyptian clover
nourishes the soils, suppresses weeds and providing a disease break in cerealdominated crop rotations existed in Egypt (El-Nahrawy 2011).
4.2.1 Effect of Water Stress on Egyptian Clover
Limitation of water supply is a major production constraint for this crop (Lazaridou
and Koutroubas 2004). The impact of water stress on crop growth and productivity
depends upon the intensity and duration of drought, growth stage, the genotype and
physiology of the crop species. The effect of water stress on Egyptian clover was
studied by Barzegar et al. (2016), where they stated that water stress resulted in lower
leaf area, stem length and total dry mass. Iannucci et al. (2000) reported a significant
reduction in total dry weight, plant height and proline content due to water stress
treatments. They also reported that water stress influenced clover plant growth and
its components. Furthermore plants subjected to periods of water stress during development stage have a lessened sensitivity to subsequent stress. Therefore, their ability
to survive drought is mainly due to their capacity to avoid dehydration. Lazaridou
and Koutroubas (2004) noted a 75% decrease in biomass; leaf area and transpiration
rate was recorded as a result of water restriction. An average of 91-fold increase in
proline levels in white clover leaves under water deficit was observed (Barker et al.
1993). Similar results have been found in subterranean clover by Socias and Medrano
(1994). In a study done by Hussain et al. (2015) on the effect of water stress on
Egyptian clover, they found significant effects of water restriction on yield, leaf gas
exchange parameters, canopy temperature and osmotic adjustment. They also
reported that most morpho-physiological traits had higher broad sense heritability
than forage yield, both under full irrigation and water restriction conditions.
4.2.2 Effect of Deficit Irrigation on Egyptian Clover
Application of deficit irrigation to Egyptian clover was studied by Abouelenein
et al. (2010), where they showed that application of 70% of full irrigation to Egyptian
clover resulted in 11% yield losses under surface irrigation in clay soil. Furthermore,
4 Field Crops and Deficit Irrigation in Egypt