Effect of microelements (B, Zn) on Cotton plant's productivity, its leaf area and plant height. Abstract

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Effect of microelements (B, Zn) on Cotton plant's productivity, its leaf area and plant height. 
Abstract. 
This article presents the results of the study of the effect of microelements on the leaf area, plant height formation and 
yield of cotton in the conditions of the gray soil of the Zarafshan Valley.
The optimal rate of using microelements had a positive effect on the leaf area and dry mass of cotton plants.The 
highest result was observed when N
250
P1
75
K
125 
+KUPRUMHITE+NANOSEREBRO kg/ha was applied with mineral 
fertilizer. 
Key words: fertility, cotton, organic fertilizers, physiological process, biometrical measures, micronutrient, productivity. 
1.Introduction. 
Today famine is becoming one of the most serious global problems. The reason for that is the increase in the number of the 
world population, moreover the weather and soil conditions are changing dramatically. Also, the lack of micronutrients in plants 
causes a decrease in the yield of plants [23].In order to meet the demand for food, it is necessary to increase the producti vity of 
agricultural crops on the available land, to achieve more food production more crops should be planted on per unit of the 
currently available cropland [3].As a result of the positive effect of microelements, the amount of chlorophyll in the leaves

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increases, photosynthesis increases, and the assimilative activity of the whole plant increases. [38]. Deficiency of microelements 
causes defects in the growth and development of agricultural crops, their development is delayed, resistance to adverse conditions 
decreases, and they are often damaged by diseases and pests [35]. 
To meet the food demand of the growing world population, food production needs to be greatly increased. At the same time, 
the increase in the world's population due to urbanization and intensive farming puts serious pressure on the available agricultural 
land [1]. The rapid growth of the population and the reduction of arable land to a certain extent create the need for the 
development and scientific justification of measures to increase soil fertility, improve the weight and quality of crops obtained 
from agricultural crops [8]. 
Taking into account the ecological problems, the use of micronutrients in combination with proper agrotechnical methods 
appears to be the most sustainable and cost-effective solution for alleviating food shortages. Reducing the use of macrofertilizers 
can provide a number of advantages, such as tolerance to abiotic and biotic stresses. The use of microfertilizers which are rich in 
biologically available microelements is the most optimal way to improve the nutritional status of the land [2]. 
To meet the demand for food, it is necessary to increase the agricultural production on the available land. This means that to 
achieve more food production, to produce more agricultural products on per unit of currently available cropland is very crucial 
[3]. After increasing the amount of fertilizer, higher yields on per unit area led to greater depletion of micronutrients in the soil, 
and less attention was paid to micronutrient fertilization. 
Currently, micronutrient deficiency has become a limiting factor in the productivity of many agricultural lands around the 
world. (12) Currently, intensive crop cultivation, high yield production, improvement of agricultural mechanization, and 

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micronutrients with low mixtures of macronutrients, the production of fertilizers and the use of modern irrigation systems have 
increased crop production per unit area and the amount of trace elements in the soil increased [7]. 
Erosion, dehydration, loss of trace elements as a result of liming of acidic soils are factors for reduction of agricultural 
manure compared to chemical fertilizers and increase in the level of trace element deficiency in agricultural soils [28]. (Fageria et 
al., 2002). The problems of micronutrient deficiency have been exacerbated by the high demand for modern crop varieties. 
Accordingly, low levels of micronutrients have been reported in many crops grown in different countries [29]. Fageria, 2000; 
Martens and Lindsay. ) Micronutrient deficiency has become a limiting factor in crop productivity in many agricultural soils. To 
increase the productivity of crops, it is necessary to solve the deficiency of microelements [30]. 
In developing countries, there are several solutions, including soil and foliar fertilization, cropping systems, correcting 
micronutrient deficiencies, and applying organic amendments to increase their density in the digestible parts of plants [13]. 
Agricultural practices are almost always aimed at maximizing crop yields while minimizing costs. Thus, as a result of the 
use of chemical fertilizers, the increase in productivity in many agricultural systems occurred as a result of their use in 
combination with micronutrients in various crops [14]. 
There are two strategies for increasing food production: (a) expanding agricultural area and (b) increasing productivity per unit 
area [30]. Agricultural expansion is limited by lack of suitable land, urbanization, soil degradation, and increasing water scarcity 
[27]. Focusing on improving the amount of micronutrients in crops, increasing the amount of bioavailable micronutrients in crops 
to take into account plant factors that increase or decrease the bioavailability of plant micronutrients.[32] 
To correct micronutrient deficiencies and increase their concentration in plant parts that can absorb them, a variety of meth ods 
such as soil and foliar fertilization, improved cropping systems, application of soil amendments, and organic nutrient sources are 

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used [25]. Taking into consideration the environmental concerns, sustainable agriculture is looking for environmentally friendly 
and more cost-effective approaches that use less energy and chemicals. Among the various strategies used to correct 
micronutrient deficiencies in plants, the most sustainable solution, especially for developing countries, is to reduce micron utrient 
deficiencies in combination with proper agronomic practices[26]. 
Today, the main directions of the world's cotton production are aimed at obtaining a high and high-quality cotton crop due 
to the introduction of resource and energy-saving technologies. Because 30-40 percent of the world's land areas are depleted of 
humus, nutrients, and the process of erosion is observed, which leads to a decrease in soil fertility and crop yield. Eliminating 
these situations is achieved by using microfertilizers in feeding agricultural crops in the USA, Germany, Austria and other 
countries [19].
In the practice of cotton growing in the world (USA, Egypt, Israel, Turkey, India, etc.), it is possible to increase 
productivity by 14-17 percent by using microfertilizers, taking into account the fact that the soil is supplied with micronutrients. 
In addition, it is observed that the application of various forms of microfertilizers to the soil optimizes the nutritional regime and 
increases the tolerance of plants to external extreme conditions [4]. 
From this point of view, the development of the technology of applying macro- and micro-fertilizers in appropriate proportions, 
in convenient terms, standards and methods for the cultivation of high-quality cotton crops in the conditions of the soils of our 
Republic with a shortage of microelements is considered one of the urgent issues of agrochemistry and cotton growing. [16]. 
Boron not only affects the formation and development of reproductive organs of plants [13;24], but also plays an important 
role in the vegetative development of plants [10;18]. This element affects the transport and metabolism of photosynthetic 

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products in plants[6;17] and also participates in the structural composition of cell walls and [24;31] indirectly affects the
metabolism of proteins and nucleic acids [31;9]. 
B deficiency inhibits root elongation [17;19] and affects leaf growth and development [11;21]. The important reason is that the 
root and leaf are the important organs of plants for obtaining nutrients. 
Several studies have examined leaf vascular bundles under B deficiency and found that B deficiency affects growth and 
causes increased vascular tissue in plants[20]. Therefore, B deficiency can inhibit the growth and development of cotton, which 
can disrupt the transport function of stems, prevent the transport of nutrients, reduce the photosynthetic capacity of plants, and 
reduce the transport of photosynthetic products. 
Kumar V. (2011) reported the emergence of nano-fertilizers. Although fertilizers are very important for plant growth and 
development, most of the applied fertilizers are not readily absorbed by plants due to many factors. Therefore, it is necessary to 
minimize the loss of nutrients in fertilizing and increase the yield by using new nanofertilizers. (Siddiqui et al., 2015) [5]. 
Nanoparticles have become a valuable material in agricultural research today because of their unique physicochemical properties. 
Nanoparticles growth variables (plant height, leaf area, fresh and dry weight of shoots and roots) significantly increased. Chitosan 
is derived from natural chitin, used in agriculture as a plant growth promoter (Katiyar et al., 
2014) is being used. Chitosan increased root and leaf length, and chitosan-treated seeds also showed higher growth. (Mahdavi 
and Rahimi, 2013)[22].