Wheat time when Fertile Cresent was being created (Smith

Wheat
is considered as an important part of human staple food since early days due to
its importance in human civilization. A long time ago, when farmers established
their own agriculture, they developed their own wheat from emmer (Triticum
dicoccon) and einkorn (Triticum monococcum) grasses and it was the
time when Fertile Cresent was being created (Smith 1998). In Pakistan, Wheat is
also cultivated as a major staple food crop and its share in our country’s GDP is
2%.  It is of multiple uses and one of
them is value addition. The value addition of wheat accounts approximately 9.9
percent of the total value addition of agriculture. Wheat almost covers most of
the cultivated area and also has the highest share in the production (GOP,
2016).

Due to its nutritional benefits wheat (Triticum aestivum L.) is one of the
important cereal crop cultivated for food purpose and it is because of this
that it attracts the attention of human beings all over the glob. In Pakistan,
the average consumption of wheat per capita is 125 kg annually and the total
national requirements of wheat are approximately 18.64 million tons (Khan,
2003). There are several ways in which the Wheat grain is being consumed. It has
been used commercially and industrially for several purposes such as biscuits, baking
ingredients, burger, pizza, cookies, noodles, pastry, commercial breads and
crackers etc. in Pakistan, the wheat grain is also used as a foundation of
cheap feed for livestock and poultry. Its straw is also of great importance for
paper manufacturing ad cattle feed.

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              In
Pakistan, Wheat (Triticum aestivum
L.) is not only one of the important staple food for majority of the people, it
also plays a central role in the national economy of the country. The area under
wheat cultivation in 2011-12 was 8650 thousand hectares and showed an improvement
of 0.5% (8693 thousand hectares) in the last year data (Pakistan
Bureau of statistics, 2012-13). The
production of wheat grain in 2012-13 was 24.2 million tons while the target of
wheat grain for this year was 25.5 million tons. This achieved grain yield was
5.1% less then the targer but there was an increase in grain yield (3.2 %) over
the grain yield of last year which was 23.5 million tons (Pakistan
Bureau of statistics, 2012-13). The grain
production in 2012-13 raised upto 2787 kg ha-1 and it showed a progressive
growth of 2.7% as related to negative progress of 4.2% last year (Pakistan
Bureau of statistics, 2012-13). In Pakistan, wheat has
attained its importance as one of the principal cereal crop and its
contribution in GDP was 2.2% and in value addition in agriculture was 10.1% (Pakistan
Bureau of statistics, 2012-13).

              There
are many factors which contributes to the lesser grain yield of wheat such as
improper irrigation and fertilizer (Kibe et al., 2006), differences in varietal
prospective (Hussain et al., 1998), deprived seed quality (Farooq et
al., 2008) and lack or absence of suitable weed management practices (Abouziena
et al., 2008). Improper use of inorganic fertilizers is one of the major
cause of water contamination and if this contaminated water is consumed by
animals and humans, it badly affect their health (Soltanpour, 1985). The main
causes of low wheat production are the high prices or rates of inputs, and
their unavailability when needed, uncertainty or non-availability of irrigation
water, deprived plant protection measures and ignorance of farmers etc. Mostly
farmers are not aware of or do not intend to use the plant nutrients available
naturally such as green manuring, application of micronutrients and the use of
natural and commercial plant growth biostimulators / regulators. Plant growth biostimulators
/ regulators are of great importance when it comes to attain higher yield
production in wheat. Among different approaches for thr growth promotion, the exogenous
use of plant growth biostimulators / regulators enhances the plant growth and
development both under stressed and normal conditions (Brathe et al.,
2002). With the exogenous application of natural and commercial growth
regulators or biostimulatrs, the yield and growth of wheat crop can be
improved/ enhanced. By
using commercial fertilizers / nutrients the yield of the crop can be enhanced
upto 30-35% (Stewart et al., 2005).

Allelopathy
is a process that goes on naturally and in this process some fungi, plants, viruses
and bacteria discharge some secondary metabolites in their surroundings that has
a stimulus effect on the growth and development of other entities in their locality
and it consists of two aspects, one of them is growth promotion and other one
is growth inhibition (Ashrafi et al., 2008). Allelopathy can also be viewed as the process
in which micro-organisms such as plants, bacteria abd viruses produce secondary
metabolites which in return has an impact on the agriculturalad biological
systems and this impact can be negative (suppressive) or positive (promotive)
(Farooq et al., 2011). Some plants release the metabolites into their
surroundings via leaching, root exudation, volatilization and also by
decomposition of plant dead material, and these metabolites are called
Allelochemicals (Putnam, 1983). These substances when applied at low concentrations
have an influencial impact on plant activity and physiological processes
(Frankenberger and Arshad, 1995).

The plant growth stimulators / regulators are
natural or synthetic or commercial compounds that are applied exogenously directly
to the target plant to improveits quality and enhance yield (Nickell, 1982). The
proper application of these Plant Growth Biostimulators / Regulators, antioxidant,
nutrients, inorganic and organic compounds / chemicals when applied exogenously
had beneficial impact on plant growth and development and also enhanced crop
production and net returns (Hall and Bingham, 1993; Arteca, 1996; Farooq et
al., 2009). Allelopathy
is a process in which plants release some secondary allelochemicals due to bio-chemical
contacts among plants and these released metabolites may have a stimulatory of
inhibitory impact on other plants in their vicinity (Kohli et al. 1998).
Among these naturally
occurring Plant Growth Biostimulants / Regulators, the hormones attained from
plants are considered to be safe, efficient and commonly found. These
allelochemicals when applied at high concentration may inhibit / suppress the
growth of plants and when applied at low concentrations may stimulate / enhance
the growth (Narwal, 1994).  

In
sustainable agriculture, the application of different natural allelopathic
extracts / biostimulants has been greater than before due to environmental
concerns. In addition the allelopathic interfaces with plant nutrients are also
of great significance in modern day agriculture. So, it is required to
establish some eco-friendly systems by utilizing these Allelochemicals to
overcome environmental concerns.

Regarding environmental concerns, bio-stimulants
are of greater importance and in these growth stimulants there are microorganisms,
trace elements, macro algal extracts, enzymes, plant growth biostimulators /
regulators and polyamines vitamins. Thses biostimulnts are used either on soils
or on plants to enhance the functional developments of the crop plants and consequently
improve their efficiency. These growth bio-stimulants have a positive impact on
the quality, yield and vigor of the crop, boost root growth and alo improve stress
resistance due to their influence on plant physiology (Sami et al.,
2016). Anna et al., in 2017 laid out an experiment in which exogenously
application of a commercial biostimulant (nitro-phenolate based) (Atonik) was done
at two different Bean cultivars. It was informed that the use of this
biostimulant improved efficiently the yield of Bean without worsening its
quality. Tandon and Dubey in 2015 conducted an experiment on soybean crop to
monitor the influence of a commercial biostimulant (biozyme) and it was recorded
that the exogenously application of 500 ml ha-1 of this biostimulant
in combination with half of the recommended amount of NPK showed overall the
best outcome in all aspects. In the member countries of EU, there is concern
regarding the use of plant growth promotors / strengtheners (biostimulants) for
improved production of crop plants. There are some major concerns about the use
of these growth regulators / biostimulants and the most important one of them
is the injurious influence of these growth regulators / biostimulants on human
health (Torre et al. 2013).

In
the last few decades sorghum has been studied and documented for its
allelopathic potential and these studies showed that the phytotoxicity of
sorghum differs with plant age, plant part and the environmental factors. The
impact of sorghum extract (sorgaab) on a number of crops, especially wheat,
maize, mustard and Mungbean has been studied. These studies showed a
significant increase in the yield of these crops when sorghum water extract was
applied at different time intervals after sowing. This increase in wheat yield was
directly related to the number of applications and the concentration of sorghum
extract (Weston et al., 2013). Zhou et al., in 2007 conducted an
experiment to check the impact of garlic water extract on growth of tomato and
hot pepper and the results of this experiment showed that the application of
garlic extract enhanced the growth of tomato and hot pepper and in case of hot
pepper it was much more significant than tomato. Hammad and Ali in 2014
conducted an experiment in which they applied biostimulants to wheat under
drought stress and reported that the efficiency of wheat was enhanced
significantly due to the application of these biostimulants.

In
previous studies, the scientists have conducted experiments to evaluate the
impact of different natural and commercial biostimulants and reported that
these biostimulants significantly enhanced crop yields. But there are some
concerns regarding the use of commercial biostimulants like high prices and its
effect on human health. The present study was carried out to study the impact
of different natural and commercial growth biostimulants on growth and
productivity of wheat. It will be evaluated by economic analysis whether we can
use natural growth
biostimulants instead of commercial biostimulants as natural growth
biostimulants are cost effective and more environmental friendly as compared to
commercial growth biostimulants.

In
this experiment different commercial and natural biostimulants were used to
enhace the productivity of wheat. Foliar application of these commercial and
natural biostimulants was done to determine their effects on wheat yield.

CHAPTER
2

REVIEW
OF LITERATURE

1.1.        
Commercial Growth Regulators

The
foliar application of kinetin and abscisic acid reduced the emissions of N2O
(Nitrous Oxide) in wheat due to the changes it brought about in growth and
development and it also enhanced the grain production of wheat (Bordoloi and
Baruah 2017). Pan et al. in 2013 carried out an experiment comprising of four
treatments to evaluate the impact of plant growth stimulants / promoters on
quality of grain, antioxidant movement of enzymes and grain yield in rice. In
this experiment three plant promotors / growth regulators (paclobutrazol,
gibberellic acid and 6-Benzylaminopurine) were used while using water spray as
control. It was evaluated from the experiment that it was paclobutrazol @ 50 mg L-1 or
6-Benzylaminopurine @ 30 mg L-1 which gave the best results
regarding quality and yiel of grain of rice when it was applied at the heading
stage. Javed et al. in the year 2011 conducted an experiment to evaluate the
impact of auxin and cytokinin on the carbohydrates accumulation in rice and it was
recorded that the grain yield and thousand grain weight of rice improved as a
result of these growth promotors / regulators. 
There has been no noteworthy confirmation of the adverse effects of these
plant growth promotors / regulators but in some countries from European Union a
dispute is being discussed on the use of these plant promotors / strengtheners
(commercial biostimulants). There are various concerns regarding the use of
these growth regulators / biostimulants and one of the most important is their destructive
impact on human health (Torre et al. 2013). An experiment was conducted
by Erin et al. in 2008 to examine the adverse impact of gibberellic acid growth
promotor on human health and it was established that the skin and bladder
diseases might be due to the exposure to these growth promoters, and it is due
to this reason that its use must be supervised.

 

1.2.        
Biostimulants

Due to less efficient methods or
techniques, fertilizers or nutrients applied to the plants escape into the
environment and cause environmental degradation. So, to reduce this risk and to enhance the nutrient
uptake efficacy of the plants bio-stimulants are used. When these
bio-stimulants are applied to plants, seeds and other growing media, they
enhance their growth and development (Halpem, M. et al., 2015). Chen, S.
K. et al., in 2002 conducted an experiment to study the effect of two
bio-stimulants on soil microbial and recycling activity and it was reported
that both bio-stimulants stimulated the mineralization and breakdown of soil
organic matter and increases the availability of nitrogen to the plants.

From
above review, it may be concluded that allelopathic extracts may be used as
growth enhancers in field crops if used in diluted concentrations.

1.3.        
Allelopathy

The allelopathy concept grew in popularity
and its importance was recognized when Rice in 1974 wrote the first book on
allelopathy. This idea of allelopathy given by Rice contains both positive and
negative impact of plants or microorganisms on other plants or microorganisms
and is widely recognized and accepted by all scientists. Allelopathy is the
chemical interface among plants which involves production or release of
secondary metabolites that have both inhibitory as well as promotory effect on
adjacent plants. These effects are of great importance when utilized for
suppressing the weeds and pests (Kohli et al., 1998). Narwal in 1996
defined allelopathy as an interface among plants over chemical pathways. These
allele-chemicals are being used to mediate the effects of allelopathy and these
water soluble allelochemicals move into the environment through volatilization,
exudation and residues decomposition. Rice in 1984 experimented and reported
that these allelochemicals are produced through citric acid pathway or shikimic
acid and this interface contains both promotion as well as inhibition
mechanisms. In agriculture, these injurious and adverse effects are encouraged
to control pest and weed population (Kohli et al., 1998).
Allelochemicals are the chemicals which basically formed by living organisms
and effect the vigor, growth, population or activities of other adjacent
organisms (Einhellig, 1995). Allelochemicals have special stimulatory effects
when applied at low concentrations and it has been reported that these
allelochemicals are both inhibitors as well as promotors in nature for
different crops. (Narwal, 1994). The allelo-chemicals can be used to enhance
the growth of some crop plants when applied in smaller concentrations and it is
considered as safe, environment friendly, inexpensive and effective source of
plant growth regulators (Oudhia et al., 1988). Allelochemicals released
by potentially allelo-pathic plants influence the growth and development of
other plants and organisms when these allele-chemicals are applied through
water extracts (El Atta and Basher, 1999; Farooq et al., 2009). Chung
and Miller in 1995 reported that these allelochemicals when applied in higher
concentrations do have suppressive effects like inhibition of growth while this
suppressive effect is less when allelochemicals concentration is low. Research done in this regard point towards
the fact that these allelochemicals when applied at higher concentrations may cause
inhibition in the crop growth but when applied at low concentrations these
allelochemicals may cause stimulation in the process of growth (Narwal, 1994).
Therefore, this stimulatory impact of allelopathic water extracts on
neighboring plants can be utilized to develop eco-friendly, effective and cheap
plant growth promoters (Oudhia et al., 1998).