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Rakhmatov Zoyir Umirzokovich, Postgraduate Student Department of Soil Science, National University of Uzbekistan named after Mirzo Ulugbek, Faculty of Biology Abdullayev Sagdulla, doctor of agricultural sciences, professor Department of Soil Science, National University of Uzbekistan named after Mirzo Ulugbek, Faculty of Biology E-mail: zoirrakhmatov@gmail.com
DYNAMICS OF ALTERATIONS IN SIEROZEM-MEADOW SOILS FERTILITY OF THE DJIZAK STEPPE UNDER THE INFLUENCE OF IRRIGATION
Abstract: In this article has based scientifically on soils generating, their development, forming soil nutrients, humus, distribution to soil layers and their correlation with each other and soil changing effect of irrigation area.
Keywords: soil fertility, nutrients, light brown soil, brown-meadow soil, humus, cultivated layer, under cultivated layer, ground water, mineral substances.
Introduction. In the soil-climatic conditions of many regions in the Republic of Uzbekistan, it is impossible to obtain a crop without artificial irrigation of agricultural crops. Because, a very small amount of precipitation in the plains and foothills of our republic and having a seasonal character leads to a lower accumulation of moisture in different soil layers. Therefore, because of large-scale irrigational measures, the appearance of soil fertility and its formation undergo peculiar changes. One of these territories is the Djizak steppe (this includes the territories of the Mirzachul, Arnasay, Zafarobod, Dostlik, Pakhtakor and partially Zarbdor). Most of the soil in these areas because of irrigation periodically turns from one type of soil to another and, due to the exposure to salinity of varying degrees and erosion, the level of fertility has changed and to date, improving their reclamation state is one of the urgent problems.
Materials and methods. Field experimental works in the soils of the Djizak steppe were carried out at certain strong points. Morphogenetic details of soils, sampling and work on the determination of soil nutrients in laboratory conditions were carried out based on methods developed by scientists of the Institute of Selection, Seed Growing and Cotton, the Research Institute of Soil Science and Agrochemistry, and methodological manuals published in 1963-2004.
Results and discussion. The study ofthe state offertility of irrigated soils of the Djizak steppe, in general, the study of agro-chemical features and properties, including the content of nutrients and their dynamics, is of great importance in the regulation ofsoil processes. Analysis ofthe collected scientific materials and obtained data showed that the studied soils of the Djizak steppe 35-40 years ago were light gray soils and up to the development
of humus content on the upper soil layers were 1-1.5%, on saline soils it was about 1%. That is why, the unblocked soils in these territories were considered the most fertile.
O. Komilov [3], N. F. Bespalov [1], Zimina [2], M. U. Uma-rov [5], L. Tursunov, S. Abdullaev and others studied in detail the agrophysical and water-physical properties of soils of these territories and came to the conclusion that these soils had a propensity for processing and active scientific research is currently underway to study the properties of these soils.
Because of the development and irrigation of soils over the past 15-20 years, one can see that the process of their formation and the component part has undergone drastic changes. For example, the content of humus and the mechanical composition of modern sierozem-meadow soils in 1958 averaged 1.45% humus and 38.39% physical clay (data of S. K. Ochilov and others, 2014), with the passage of time as a result of the continuation of the process of land development in these soils in the last 15-16 years the humus content decreased by 0.97%, and the content of physical clay decreased by 29%.
It should be specially noted that the above processes on these soils have been studied in the scientific studies of Uzbek scientists such as S. N. Ryzhov, B. V. Gorbunov, S. P. Suchkov, N. F. Bespalov, M. Umarov, O. Komilov and others; they studied the agrophysical properties of soils in their studies and came to the following conclusion: on the upper half-meter layer ofbright sierozem-meadow soils prevalent on Mirzachul territory, the supply of such substances as humus, phosphorus, nitrogen turned out to be relatively higher than other layers of the same soils and their production ability in comparison with other irrigated soils and came to the conclusion that they can be mastered on a large scale.
Very important is the data obtained on soil humus by O. K. Komilov [3], and it was found that the humus content on the upper half-meter layer is almost uniformly distributed, and in some places in the lower seed layer its content was larger than the upper seed layer and the reason for this is the exchange of layers during the leveling of the earth. The data presented partly found its reflection in the areas studied by us.
During the past 30-40 years the reserve of humus in the cultivated irrigated soils is mainly distributed more than the subsoil layer, in our studies for 10-15 years this process has changed partially and it can be seen that the main content of humus has increased in the upper sowing layers of the earth. For
example, in the upper arable and sub-cultivated layers of newly cultivated and irrigated slightly saline sierozem-meadow soils
30-40 years ago in the fields where various technical plants were grown humus was 0.24-0.60% and its total reserve in the 30-50 cm soil layer was 25-45 tons, during the last 15 years the humus content in the upper seed layers of these soils was 0.70-0.97%, and in the 0-30 cm layer the total reserve of humus reached
31-40 tons, and in the 0-50 cm layer it is 45-60 t ha (table). Hence, over the past years, depending on irrigation, tillage, fertilization, and depending on the agro technical measures applied and the type of crops grown, the reserve of humus in these soils has increased several times.
Table 1.- Agrochemical properties of the soils of the Djizak steppe (in% with respect to absolutely dry soil)
№ section Years depth, cm Content ^ N Total content,% Reserve, t/ha
Humus Nitrogen P2O5 K2O section, cm Humus Nitrogen
Th ie newly deve oped sierozem-meadow soils
1 2015 0-30 30-35 35-55 55-80 0.637 0.521 0.429 0.362 0.059 0.044 0.037 0.034 6 7 7 6 0.140 1.085 0-30 0-50 26.7 39.3 2.4 3.4
2016 0-34 34-40 40-65 0.701 0.610 0.510 0.060 0.058 0.045 7 6 6 0.115 0.939 0-30 0-50 29.4 45.5 2.4 4.0
3 2015 0-25 25-47 47-75 0.694 0.245 0.205 0.059 0.021 0.018 7 7 7 0-30 0-50 25.9 32.6 1.8 2.47
2016 0-29 29-40 40-60 0.673 0.653 0.224 0.059 0.053 0.017 7 7 7 0.156 0.06 0-30 0-50 28.7 40.4 2.55 3.1
Irrigated sierozem-meadow soils
7 2015 0-30 30-42 42-60 0.736 0.761 0.583 b.072 0.061 0.049 6 7 7 0.175 0.140 0.110 1.883 1.902 1.900 0-30 0-50 30.9 50.2 3.0 5.2
2016 0-30 30-50 50-70 0.926 0.749 0.403 0.069 0.051 0.036 8 8.5 6 0.177 0.152 0.140 1.850 1.912 1.902 0-30 0-50 38.3 59.9 0.8 1.4
2 2015 0-26 26-38 38-50 50-78 0.901 0.710 0.510 0.394 0.070 0.050 0.058 0.047 7 8 5 5 0.185 0.162 0.120 1.939 2.041 2.102 0-30 0-50 36.8 53.4 2.4 4.0
2016 0-30 30-40 40-85 0.975 0.649 0.349 0.074 0.062 0.040 8 6 5 0.160 0.142 0.101 1.822 1.800 1.921 0-30 0-50 40.9 54.8 1.6 2.2
5 2015 0-10 10-21 21-50 0.952 0.807 0.497 0.070 0.069 0.046 8 7 6 0.145 0.120 0.102 2.746 2.548 2.516 0-30 0-50 32.0 45.9 2.7 3.9
2016 0-25 25-45 0.901 0.805 0.072 0.062 7 7 0.164 0.120 2.770 2.712 0-30 0-50 37.5 59.9 2.5 3.5
45-70 0.771 0.053 8 0.100 2.701
Particularly, in our collected biennial data, it partially confirmed this process and it can be seen that due to changes in groundwater level, agrotechnical measures, and the use of organic fertilizers in some fields, the content of humus in various soil layers has undergone a partial change. As it can be seen from the data given in the table, in 2015-2017, in fields where cotton was grown and partly intermediate plants in fertilized lands, the humus content increased by 0.05-0.2% within 2 years, as a result of an increase in the level of salinity or in fields that did not receive organic fertilizers, the humus content decreased to 0.05%. However, in their sub-plow layers, the total reserve of humus was not almost not undergoing tangible changes. Hence, as it was said above, the content of humus could be increased by fertilizing the soil with 6-8 t / ha manure. However, it should be specially noted that in some saline layers, by increasing the content of mobile cations of water-soluble salts, the content of humus might partly increase.
In sierozem-meadow soils, where the studies were carried out, the content of nitrogen corresponds to the content of humus. The content of total nitrogen in the soils of the investigated territories is very low and an acute insufficiency of organic fertilizer is felt in the system of alternating cultivation of cotton-wheat. Because the scarcity of humus in the soil as compared to humic acids due to the reduction of organic compounds in their formation in soils, less nitrogen accumulates. In irrigated soils, where wheat is grown, the content of total nitrogen was much higher. It may be thought that the manifestation of such a case led to the activation of nutrients in the soil under the influence of mineral substances and irrigation in the fields under wheat. Exactly the same state can be observed in the carbon ratio of nitrogen. Because, in the fields that have received fertilizers, the nitrogen content is relatively large, and in the remaining areas, one can observe the opposite state.
Among the soils studied on their basis by the abundant total nitrogen are irrigated sierozem-meadow soils and meadow soils and total nitrogen is 0.01 to 0.10%, but the level of provision of these soils with total nitrogen is low, i.e. The ratio of carbon to nitrogen (C: N) in all soils varies between 5 and 8.5. Taking into account the need of all soils for organic fertilizers, in fields where cotton and wheat are intensively grown, the cultivation of leguminous plants that accumulate nitrogen and the formation of a system of partial crop rotation is, in our opinion, a necessary measure.
The content of total phosphorus among nutrients and the dynamics of its change within 25 to 30 years has attracted the attention of many scientists.
Among the nutrients in the sierozem-meadow soils where our studies were conducted and the study of its dynamics under the influence of its assimilation is of great importance. The change in phosphorus content in soils occurs mainly in
connection with the agro technical measures carried out, the environmental conditions, the norms of organic and mineral fertilizers, the introduction of a crop rotation system and the quality of irrigated waters. In general, this indicator reliably indicates that there is a strong correlation between the accumulation of humus and other nutrients in the soil and the level of assimilation of these substances by plants and this is applicable not only to nitrogen but also to other substances.
The change in the content of total phosphorus in soils under the influence of assimilation is of great importance. According to the data of S. P. Suchkov [4] in the soddy and backing layers of virgin light gray-earth-meadow soils, the content of total phosphorus is 0.14% and decreases downwards by 0.1-0.09%. After the development of virgin lands and their irrigation, according to the literature data 20-25 years ago, the total phosphorus content in irrigated soils was 0.10-0.12%, according to our data, this index reached 0.10-0.18% and its maximum the content was concentrated in the plow and subsoil layers. Because, in these layers, biogenic processes occur more intensively than other layers, but in spite of this the phosphorus content that can be assimilated by plants is only 10-20%. The rest 50-60% of phosphorus is gradually transferred to intractable forms. The reason for this is that soil fertilization with a mobile form of phosphorus depends on its content and the level of soil cultivation. Proceeding from this, it can be said that the change in the content of phosphorus in the studied soils varies depending on the conditions of the agrotechnical measures carried out or used, the norms of organic and mineral fertilizers, the introduction of a system of crop rotation of the quality of irrigated waters. In general, this index reliably indicates that there is a strong correlation between the accumulation of humus and other nutrients in the soil and the level of assimilation of these substances by plants and this applies not only to phosphorus, but also to other substances.
The element of potassium is the most important and necessary nutrient in the nutrition of plants. Crops cannot grow and develop in a timely manner and correctly without potassium. Potassium is found more in plants than in soil.
The main source of potassium in the soil are the minerals of the group of silicates and aluminosilicates. The content of various forms of potassium in soils and the level of provision of soils with this element depends on the primary and secondary minerals. That is why our soils are richer in potassium than other soils, but they are poorly provided. Therefore, knowledge of the composition and properties of minerals is important when properly and effectively using potassium fertilizers.
In irrigated soils, the content of potassium is not high (0.815-2.77%), and this indicator in saline soils cannot regulate the growth and development of plants, as a result, growth decreases and yields drop sharply. Therefore, the question of
the availability of potassium for plants is not only theoretical, fluence of irrigation. Despite this, in recent years a positive
but also practical. change in the content of humus and nutrients can be observed
Conclusion. During the past periods, in the conditions of in different soil layers. These changes, of course, could occur
agriculture in the Djizak steppe, sharp changes in the proper- due to the processing of land and organic fertilizers. How-
ties and specificities of the soils occurred, firstly, a large part ever, these measures are inadequate and we believe that the
of the territory turned into light gray-earth meadow soils, and conservation of the humus condition of the soil and measures
sierozems salinized to varying degrees of soil under the in- for their improvement should be carried out at least twice.
References:
1. Bespalov N. F. Some physical features of light gray soils ofMirzachul / In: Melioration of the Mirzachul.- Tashkent, 1957.-P. 101-167.
2. Zimina N. I. Agrochemical properties of the soil of Mirzachul. In a book "Soils of the Mirzachul and their agronomic characteristics" - Tashkent, 1961.- P. 29-41 p.
3. Komilov O. K. Land reclamation and fertility of newly developed soils of Mirzachul.- Tashkent: Publishing house "Fan", 1980.- 74 p.
4. Suchkov S. P. Change in the light gray soils of Mirzachul under the influence of development. In the collection "Soils of the Mirzachul and Their Agrochemical Characteristics" Izd. MoA Uz. - Tashkent, 1961.- 175 p.
5. Umarov M. U. Physical properties of soils in areas of new and promising irrigation of Uzbek SSR.- Tashkent: Publishing house "Fan", 1974.- 282 p.
