150
D. L. N. Rao et al.
3.2 Plant Based Approaches
3.2.1 Foliar Fertilization
Foliar fertilization offers a specific advantage over soil fertilization when plant
demand for nutrients exceeds the capacity of the roots to absorb nutrient and when
environmental conditions limit the effectiveness or prevent the application of nutrients to the soil. Further, soils with high levels of aluminum, calcium, and iron reacts
with soil applied fertilizers to form insoluble compounds which limit the effectiveness
of soil-applied phosphorus (P) fertilisation strategies [38]. Although not commonly
used in dryland cropping systems to date, foliar P fertilisation may allow a tactical
response to prevailing seasonal climatic conditions, with the added benefit of reduced
input costs at sowing. The current knowledge about the factors that influence the
ultimate efficacy of foliar applications are incomplete, however the following key
principles are recognized [66] (a) physiological age of crop—a decreasing response
with increasing crop age, (b) tissue test status—a crop that is very deficient will have
limited potential to overcome deficiency at low foliar application rates, while a crop
that is sufficient will not be responsive, and (c) Leaf area of crop: sets foliar nutrient
uptake potential and depending on physiological age of crop sets photosynthetic
potential for grain filling.
The response of various soybean cultivars to foliar N, P, K, S supply has been
encouraging [12] when applied during the seed-filling period. Foliar N supply to
soybean was found to be an effective means to replenish N in the leaves and resulted
in higher yields in contrast to soil fertilization alone [29]. In wheat (Triticum sp.),
several studies have shown that foliar sprays of N increased grain protein. While
studying mixed foliar sprays, Alston [1] attributed the yield response of wheat to
foliar application of NP to be the result of N rather than the P in the spray. Optimum
timing for N sprays on wheat showed that post-pollination foliar N gave the highest
grain protein [10, 11, 32]. The benefits of late season foliar applications are influenced
by both cultivar and plant N status [99]. Foliar applications of P are the most effective
way to supply P to crops late in-season whenever there is a need [33]. The effectiveness of foliar P application in cereals has been reported in many investigations
[6, 13, 33, 59].
Foliar fertilizers can be used to enhance crop quality both in terms of grain protein
and Zn content [14, 25]. Nitrogen foliar fertilisation can result in increased levels
of amino acids in the young wine and with or without sulphur foliar nutrition can
enhance the aromatic expression in wines [45]. Rabani-Foroutagheh et al. [70] found
that split foliar fertilisation and the fertiliser type significantly increased saffron yield,
number of flowers and crocins (colour), whereas it decreased the picrocrocin (taste)
and safranal (odour) content of the saffron.
D. L. N. Rao et al.
3.2 Plant Based Approaches
3.2.1 Foliar Fertilization
Foliar fertilization offers a specific advantage over soil fertilization when plant
demand for nutrients exceeds the capacity of the roots to absorb nutrient and when
environmental conditions limit the effectiveness or prevent the application of nutrients to the soil. Further, soils with high levels of aluminum, calcium, and iron reacts
with soil applied fertilizers to form insoluble compounds which limit the effectiveness
of soil-applied phosphorus (P) fertilisation strategies [38]. Although not commonly
used in dryland cropping systems to date, foliar P fertilisation may allow a tactical
response to prevailing seasonal climatic conditions, with the added benefit of reduced
input costs at sowing. The current knowledge about the factors that influence the
ultimate efficacy of foliar applications are incomplete, however the following key
principles are recognized [66] (a) physiological age of crop—a decreasing response
with increasing crop age, (b) tissue test status—a crop that is very deficient will have
limited potential to overcome deficiency at low foliar application rates, while a crop
that is sufficient will not be responsive, and (c) Leaf area of crop: sets foliar nutrient
uptake potential and depending on physiological age of crop sets photosynthetic
potential for grain filling.
The response of various soybean cultivars to foliar N, P, K, S supply has been
encouraging [12] when applied during the seed-filling period. Foliar N supply to
soybean was found to be an effective means to replenish N in the leaves and resulted
in higher yields in contrast to soil fertilization alone [29]. In wheat (Triticum sp.),
several studies have shown that foliar sprays of N increased grain protein. While
studying mixed foliar sprays, Alston [1] attributed the yield response of wheat to
foliar application of NP to be the result of N rather than the P in the spray. Optimum
timing for N sprays on wheat showed that post-pollination foliar N gave the highest
grain protein [10, 11, 32]. The benefits of late season foliar applications are influenced
by both cultivar and plant N status [99]. Foliar applications of P are the most effective
way to supply P to crops late in-season whenever there is a need [33]. The effectiveness of foliar P application in cereals has been reported in many investigations
[6, 13, 33, 59].
Foliar fertilizers can be used to enhance crop quality both in terms of grain protein
and Zn content [14, 25]. Nitrogen foliar fertilisation can result in increased levels
of amino acids in the young wine and with or without sulphur foliar nutrition can
enhance the aromatic expression in wines [45]. Rabani-Foroutagheh et al. [70] found
that split foliar fertilisation and the fertiliser type significantly increased saffron yield,
number of flowers and crocins (colour), whereas it decreased the picrocrocin (taste)
and safranal (odour) content of the saffron.