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DOI: http://dx.doi.org/10.20534/ESR-16-11.12-13-15
Urazbaev Ismatulla Ummatovich, Gulistan State University, Department of Soil Sciences, Docent E-mail: ismatullaurazboev@gmail.com Kurvantaev Rahmon, Doctor Agricultural Sciences, Department of Soil Physics Scientific Research Institute of Soil Sciences and Agrochemistry
E-mail: kurvontoev@mail.ru
Productivity survey of gypsiferous soils in golodnaya steppe of Mirzachul Oasis
Abstract: The article presents the discussion of the research data obtained from survey of gypsiferous soils in Golodnaya Steppe of Mirzachus oasis. As a result of the research there were developed survey factors for cultivated vegetable crops such as potato, onion, tomato and cabbage and the content of gypsum in the soils of Golodnaya steppe.
Keywords: irrigation, soil survey, sierozem meadow, carbonates, yield total nitrogen, phosphorus, potato, cabbage, tomato, onion, gypsum.
Introduction. Cultivation limits have already gone beyond traditional cultivated lands. Practically all flat lands have been assimilated. At present within the contours of irrigated assimilation of lands there are the lowest lying lands with drained swamps, lakes and near mountain lands with undeveloped soils. Various soil types from various geomorphological elements are under cultivation nowadays. Before the science of soil-melioration there a number of problems which require solutions. Soil scientists are facing great challenges in mapping and surveying the quality of newly assimilated lands and improving the quality of irrigated arrays. Traditional methods of soil survey mapping of gypsiferous soils do not fit the requirements of present, therefore there is a need for the development of survey factors on occurrence of gypsiferous horizons.
Gypsiferous horizons are spread across desert and light sierozem zones. Vast areas of gypsiferous soils are found in Ferghana valley, Djizzak, Golodnaya Steppe, Malikchul, Sherabad deserts and Ustyurt plateau. With the purpose of surveying the fertility of these massifs there is a need for the development of survey factors. Gypsiferous level and the form of gypsum accumulation and its location in their profile determined production capacity of these soils.
Methodology of the research. According to the soil climatic conditions object of the research belongs to Golodnaya Steppe district. On thermal resources the region belongs to moderately warm and hot zones. Average temperature in January is equal to — 1.4-2.5°. Bare minimum is equal to 32.3°. Snow covering is unstable. Number of days with snow covering are 33-36 days per year. Frost-free season is 192-21° days per year. Precipitations are in few amounts — on average 3°°-32° mm a year. The summer is very hot and dry. Bare maximum is 44-45 ° Agriculture is possible only in cultivated lands. Thermal resources of the region provide development and maturing mid-ripening variety of cotton, vegetable and melon crops [1]. According to the soil covering the region belongs to cultivated meadow and sierozem-meadow lands of Central Asian provinces of mountainous and near mountain, semidesertic zones.
In 2°1°-2°13 field studies were carried out in 2° key areas and 2°° areas were chosen for calculation of crop capacity. Areas in dimension of 1°X1° meters were located in such a way that they could cover all main soil varieties. Calculation of crop capacity was made employing the method developed by Dospehov [1, 117-29°]. Then the statistical data processing obtained from crop capacity
calculation was done in order to compute average yields and search of correlation dependencies between certain properties of soil and productivity of vegetable crops.
Research results and their discussion. Presence of gypsum in loamy soil and clay up to 1°-3°% sharply increases density of soil composition. Weak and hardly soluble salts (gypsum, carbohydrates of calcium and magnesium) are physiologically not harmful but in high level of presence as well as readily soluble salts present land-reclamation difficulties. Accumulation of gypsum and carbonates in soils proceeds along with the decrease of interstices of soil and increase in the soil density and carbonization of horizons into blended mass. At the same time change in the water physical properties of soil depends on depth ofbedding and accumulation of gypsum horizons. Volume weight in superficial accumulation ofpowdery gypsum equals to 1.31-1.41 g/cm 3, porosity 42-47%, in the bedding on the middle and lower layers of soil profile in the form of falky and coarse gypsum 1.6°-1.74 g/cm 3 and 31-4°% respectively [3].
Being present on the upper layers of the profile, gypsum horizons sharply decrease productive capacity of soil [7]. Even after 15 years of reclamation of the southern parts of Golodnaya Steppe productivity of cotton remains low, equaling 7-13 c/ha, in comparison in non-gypsum sierozem meadow lands cotton yield equals to 25-35 c/ha. This is explained by the fact that in conditions ofhigh level ofsoil density not only the intrusion of cotton plant roots into the depth is complicated but also it decreases water physical properties of soil and lowers soil's nourishing property. High contains (up to 5°% and above) of crystallized and coarse gypsum and their close to surface bedding leads to piping and other negative phenomena during cultivation periods.
It has been found experimentally that gypsum, which has low water-retaining properties, lowers general deposit of water. In weak gypsiferous lands of Malikchul desert even in high levels of fertilizing cotton productivity is 6 c/ha lower than in non-gypsiferous lands. In high contains of gypsum (4°-5°%) cotton productivity equals only to 3.2 c/ha.
Increase of small-grained gypsum in root layer of cotton (°-7° cm) only to 1% leads to decrease in the productivity of cotton crop up to 1.6-1.7%. This is caused by the deterioration of water-physical properties of soil.
Minashina [6] suggests the following classification of gyp-siferous soils according to the content of gypsum in gypsiferous
Section 1. Biology
horizons: non-gypsiferous soils <10%, weak-10-20%, mid-20-40%, and strongly gypsiferous soils — above 40%.
In gypsiferous soils of Golodnaya Steppe maximum quantity of gypsum is found in dense gypsiferous strata, whereas maximum amount of carbonates is found underneath and even greater quantity of readily soluble salts are found on gypsum strata and above [5].
According to the content of humus as well as nitrogen, meadow lands are richer than light sierozems of Golodnaya steppe and content of them depends on the degree of salinity. On topsoil of nonsaline soils content of humus equals to 1.2-1.6%, in weak saline soils 1.0-1.3%, and in mid saline soils 0.6-0.8%. On the subsurface the content is 0.60.7; 0.4-0.5; and 0.3-0.5% respectively. It is explained by the fact that as the content of salts increase in soil vegetation becomes thinned and respectively there is less availability for the accumulation of organic mass as well as roots. In these soil types content ofhumus is inversely proportional to the degree of soil salinity.
Content of total yield of nitrogen was equal to 0.14-0.18 in arable horizons of non saline soils, in the analogous horizons of weak
Table 1. - Chemical indicators
saline soils it was equal to 0.08-0.10%, in mid saline soils 0.040.07% respectively. В подпахотном горизонте соответственно 0,03-0,06; 0,02-0,05; 0,02-0,03%. In saline soils correlation of C: N is considerably lower rather than in non-saline soils. Due to the low content of carbon on saline soils, correlation of C: N converges and equals to from 5.4 to 7.7 (Table 1).
Content of total yield of phosphorus is equal to 0.06-0.10%. Kamilov [4] considers that there is no correlation between total yield of phosphorus and degree of salinity in previously cultivated as well as newly cultivated lands. Also there is no definite dependence of phosphorus content on the degree of salinity in newly irrigated sierozem meadow soils.
Total yield of potassium on arable and subsurface horizons is equal to on average 1.6-2.8%.
Carbonates according to the profile on the researched soils are evenly distributed. In some cases there is a decrease of CO2 — carbonates down to the profile. Content of CO2 — carbonates is equal to 5.9-8.2% on average.
of cultivated meadow soils,%
Depth, Cm Gross forms,% СО2 carbon-ates% SO4 Gypsum%
Humus Nitrogen С: N Phosphorus Potassium
Non-Saline
0-37 1,41 0,11 6,8 0,10 2,8 7,21 0,18
37-56 0,60 0,04 7,7 0,07 2,1 6,54 0,91
80-100 0,47 0,03 7,0 0,07 7,49 0,42
120-130 0,31 0,02 6,1 0,06 8,24 0,69
Weak Saline
0-36 1,31 0,11 6,9 0,08 2,8 5,90 0,63
36-54 0,50 0,04 6,1 0,06 1,6 6,66 1,03
54-80 0,42 0,04 5,9 0,06 6,77 12,23
90-100 0,23 0,02 5,9 0,06 7,60 11,26
Mid-Saline
0-33 0,73 0,06 6,3 0,08 2,1 6,44 0,41
33-45 0,43 0,04 5,4 0,07 2,0 6,37 8,66
55-65 0,34 0,03 6,4 0,06 6,90 14,18
75-90 0,27 0,02 6,0 0,06 7,11 12,18
110-125 0,22 0,02 6,0 0,05 7,00 13,44
Gypsum in some horizons of weak and mid saline soils can be found in the form of concretion or dense layer in the depth of 40-80 cm. Content of humus on the upper nonsaline soils is equal to 0.18-0.91%, in weak saline soils 0.63-1.03% and in mid saline soils 0.41-8.66% respectively. In the lower horizons of weak and mid saline soils it is equal to 11.26-14.18% (Table 1).
Identification of crop capacity dependence of vegetable crops on the level of gypsification has shown considerable correlation between them (-0.68 -0.75). For a potato this indicator is -0.75, for cabbage -0.76, for tomato -0.68, and for onion — 0.71 respectively (Table 2).
Table 2. - Variational-statistical indicators of correlation between productivity of vegetable crops and gypsiferousness of soils
№ Depth, cm Number of permanent quadrates Content of gypsum,% Х Productivity c/ha У ХУ Х2 У2
1 2 3 4 5 б 7 9
Potato
1 3 3 134 402 9 17956
2 30-50 4 16 118 1888 256 13924
3 30 2 14 95 1330 196 9025
4 50-100 2 26 108 2808 676 11664
5 30-50 2 28 91 2546 784 8281
6 30 2 24 74 1776 576 5476
1 2 3 4 5 6 7 8
S S S S S S
Cabbage
1 3 5 315 1575 25 99225
2 30-50 4 12 296 3552 144 87616
3 30 2 14 268 3752 196 71824
4 50-100 2 23 255 5865 529 65025
5 30-50 3 28 230 6440 784 52900
6 30 2 26 189 4914 676 35721
S S S S S S
Tomato
1 6 0,5 320 160 0,25 102400
2 30-50 2 15 275 3850 196 75625
3 30 3 16 256 4096 256 65536
4 50-100 3 26 240 6240 676 57600
5 30-50 2 25 186 4650 625 34596
6 30 2 30 173 5190 900 29929
S S S S S S
Onion
1 5 0,8 208 166,4 0,64 43264
2 30-50 2 18 189 3402 324 35721
3 30 3 14 166 2324 196 27556
4 50-100 2 23 141 3243 529 19881
5 30-50 2 29 125 3625 841 15624
6 30 2 27 144 3888 729 20736
S S S S S S
As it is shown on Table 3 close bedding of gypsum horizons the these plants. Plants such as onion with superficial root system, shows most greatly influences the decrease ofpotato's productivity and toma- relatively small reaction to the depth ofgypsum bedding. This is espeto which is related to the relatively interpenetratable root systems of cially noticeable in weak degree of gypsiferousness of soil.
Table 3. - Survey factors on gypsiferous horizons and the level of gypsum content
Level of gypsum content Depth, cm Potato Cabbage Tomato Onion
Productivity, c\ha Survey factors Productivity, c\ha Survey factors Productivity, c\ha Survey factors Productivity, c\ha Survey factors
Non gypsified 134 1,00 315 1,00 320 1,00 208 1,00
Weak gypsified 11-20% of gypsum 30-50 118 0,90 296 0,95 275 0,85 189 0,90
30 95 0,70 268 0,85 256 0,80 166 0,80
Mid gipsified 21-40% and above content of gypsum 50-100 108 0,80 255 0,80 240 0,75 141 0,70
0-30 91 0,70 230 0,75 186 0,60 125 0,60
30 74 0,55 189 0,60 173 0,55 114 0,55
Survey factors for non gypsum sierozem meadow soils and veg- With the increase of the content of gypsum on horizons adjustment etable crops (potato, cabbage, tomato and onion) are equal to 1.00. coefficients of gypsiferous soils decrease.
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