Acknowledgments
The work is done within the "Introduction assessment and biology of seed multiplication of promising new species of ornamental and medicinal plants" project (№ F.5 — F A-O-12154, Academy of Sciences of Uzbekistan).
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DOI: http://dx.doi.org/10.20534/ESR-16-9.10-24-26
Urazbaev Ismatulla Ummatovich, Gulistan State University, Department of Soil Sciences, Docent E-mail: ismatullaurazboev@gmail.com
Saline resistance of vegetable and melon crops and valuation factors on the degree of soil salinity
Abstract: The article is devoted to the discussion of results obtained from the valuation of saline soils in Golodnaya steppe of Mirzachul oasis, correlation between the crop capacity of vegetable melon crops and salinity degree of soil. As a result of the research there were developed valuation factors for cultivated crops such as potato, onion, tomato and cabbage. Keywords: Golodnaya steppe, valuation, salinity, vegetable crop, crop capacity.
Introduction. Practical works on soil evaluation carried out in the Republic revealed that the transition in conditions of market economy requires effective use of every hectare of land. In order to achieve this there is a need in developing bonitation methods which take into account natural, economical and agricultural conditions in the process of evaluating soils used in producing vegetable and melon crops.
At present, soil valuation and assessment of soil's fertility in scoring units in the Republic of Uzbekistan are carried out by the Institute of Soil Sciences and Agricultural Chemistry and regional branches of the land Registry "Uzdavyerloyiha". It is generally known that the data obtained from soil valuation procedures is widely employed by agriculture planning institutions and tax inspections with the aim of planning the productivity of vegetable and melon crops and identifying the amount of tax on land.
Objective of the study was to develop valuation factors on the degree of soil salinity for the vegetable crops such as potato, tomato, onion and cabbage.
Material of the research. The research was carried out in Golodnaya steppe in developing methodological fundamentals of bonitation of soil found in the Steppe and used for growing main vegetable crops. Thus, irrigated meadow soils of Golodnaya steppe was taken as an object of the present study.
In 2010-2013 field studies were carried out in 20 key areas and 200 areas were chosen for calculation of crop capacity. Areas in dimension of10X10 meters were located in such a way that they could cover all main soil varieties. Calculation of crop capacity was carried out employing the method developed by Dospehov [1, 117-290]. 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.
Soils of Golodnaya steppe are saline in diverse levels where content of chloride sulfate type of salinity prevails. With the increase of salinity, the approach of soil horizons with the content of Mg and Na to the surface occurs.
Results of the research. Results of analysis of aqueous extracts obtained from studied soil types revealed (Table 1) that amount of solid residue in the upper horizons is insignificant. In non-saline soils content of water soluble salts is equal to 0.1% whereas in mid-saline soils the content is equal to 1%. Weak saline soils have intermediate position. Up to 1% of salt is concentrated in morphologically observed soil horizon. Formation of the horizon is due to the maneuvering of soil from overlying strata and possibly due to the capillary pulling up from the bottom salt solutions due to evaporation during subsurface soil desiccation after spring rain.
Saline resistance of vegetable and melon crops and valuation factors on the degree of soil salinity
Table 1. - Results of analysis of aqueous extract obtained from cultivated meadow soils of Golodnaya steppe
Depth, Cm Dry residue, % Alkalinity overall in HCO3 Cl- so4- Ca++ Mg++ Na+ K
Nonsaline
0-37 0,095* 0,037** 0,007 0,017 0,015 1,16 0,16
0,61 0,20 0,35 0,73 1,00 0,003
37-55 0,080 0,030 0,007 0,017 0,010 1,06 0,31
0,51 0,20 0,35 0,50 0,75 0,007
80-100 0,165 0,024 0,007 0,085 0,040 2,36 0,11
0,39 0,20 0,085 2,00 2,25 0,002
120-130 0,180 0,021 0,014 1,77 0,040 2,50 0,25
0,34 0,39 0,085 2,00 2,25 0,006
Weak saline
0-36 0,100 0,040 0,010 0,017 0,020 1,29 0,04
0,66 0,28 0,35 1,00 1,25 0,001
36-54 0,475 0,033 0,024 0,272 0,075 6,87 1,90
0,54 0,68 5,65 3,74 4,97 0,043
54-80 1,105 0,018 0,040 0,717 0,275 0,009 1,04
0,30 0,28 14,92 13,72 0,74 0,024
90-100 0,320 0,018 0,031 0,174 0,075 0,012 0,16
0,30 0,87 3,62 3,74 0,99 0,004
Mid saline
0-33 0,560 0,024 0,017 0,355 0,135 0,018 0,03
0,39 0,48 7,38 6,47 1,48 0,0006
33-45 1,125 0,021 0,007 0,760 0,275 0,015 1,42
0,34 0,20 15,83 13,72 1,23 0,033
55-65 1,160 0,024 0,010 0,780 0,260 0,015 2,75
0,39 0,28 16,28 12,97 1,23 0,063
75-90 0,545 0,021 0,014 0348 0,135 0,006 0,73
0,34 0,39 7,23 6,74 0,49 0,017
110-125 1,050 0,021 0,017 0,696 0,275 0,015 0,33
0,34 0,48 14,47 13,72 1,23 0,007
* In numerator - %
** In denominator - mg/eq
Discussion and analysis of results. Content of alkali is minor and chlorine is below toxic level — 0.007%. In weak and medium saline soils the content of alkali and chlorine exceed 0.010%. Amount of chlorine on the profile is divided unevenly.
According to the content of solid residue in the depths of 0-05 cm the coefficient ofvariation show a discrepancy from 14.3 to 24.1. The most amount of solid residue is found in non-saline soils M=0.12, and in weak saline soils M is equal to 0.37% whereas in mid-saline lands M is equal to 0.63% respectively.
Confidence limits of variation (0.95) according to the content of solid residue in non-saline lands are beyond the limits of 0.10-0.14, in weak saline soils 0.30-0.34 and in mid-saline soils 0.59-0.67% respectively.
The soils under study mostly consist of anions and cations. Among the cations which take part in the formation of salts are Na+, Mg++ and Ca++. Anions which form salts are — Cl-, S04-C03- - u HC03-. Various combinations of these cations and anions form salts, many ofwhich are found in the soils under investigation.
Noxiousness degree of definite salts for the cultivated plants is not equal. The most harmful among them is considered to be the plain soda (Na2CO3). In aqueous solution it produces caustic soda (NaOH), hydroxyl ion of which is extremely hazardous for plants.
Noxiousness of salts considerably depends on their solubility. Plants are mainly affected by salts which occur in soil tincture e. g. in soluble condition. Additionally, a number of salt types are found in
solid phase of soil in the form of crystals and they do not cause any harm to cultivated plants.
Some soil scientists and specialist in land-reclamation suggested identifying the degree of salification of not soil but of soil tincture, considering that aqueous extract contains marginally soluble salts from the solid phase as well. In natural conditions during temperature variation and change of other conditions salts which occur in soil mass may enter into the tincture.
Li [4, 51-52] suggests that it is better to identify soil salinity degree in total sum of all salts which are found in solid and liquid phase. In this case more accurate results concerning the quantity of salts in soil are indubitably obtained from the analysis of aqueous extract.
It is important to take into account that in various regions depending on natural conditions (quality of soil, content of salts in it and etc.) acceptable limit of soil salinity level for the normal development of cultivated plants varies considerably.
Salinity resistance is a plant property which is genetically acquired and fixed in phylogenesis. In practice, salinity resistance of cultivated plants is explained by the limit values of salt content in soil and their concentration in soil tincture which do not affect normal development of plants and yielding sufficient crop.
In majority of cultivated plants salinity resistance property in various phases is considerably varied. This property is minimal in the early phases of plant development and reaches its maximum level in full-grown plants. Increasing of salinity resistance in definite phases of plant life is stipulated by the growth of sorptive
capacity of cytoplasm for salt ions and the decrease of ion solubility in cellular fluid.
Study of salinity resistance of vegetables, melons and grounds in Golodnaya steppe was carried out by Kabaev [3, 35-38]. As a result of the research Kabaev [3, 35-38] suggested marginal rates of chlorine in soil. Among the studied plants the most saline resistant, normal developing and yielding sufficient crop in conditions which contain 0.007-0.020% chlorine in soil and 0.3-1.4 g/l chlorine in soil tincture is appeared to be cucurbit, tomato, and cabbage. The least saline resistant of them is cucumber [3, 38] for which the rejection number of chlorine is equal to 0.005-0.007% in soil and 0.2-0.3 g/l in soil tincture respectively [3]. Melon, onion and watermelon were in intermediate position and the content of chlorine was 0.007-0.015% and 0.3-0.5 g/l respectively.
In a number of studies of foreign scientists there is a common pattern of relationship concerning vegetable crops — in conditions of growing level of soil salinity there was observed a decrease in productivity and weakening of growth.
Salts' hazardous impact on plants manifests itself in the phase of emergence of seedlings. Swelling seeds absorb water from soil as their osmotic pressure is higher than in soil tincture. In the process of soil tincture concentration increase, matric force advances and the process of water ingress into the seeds weakens or even stops.
Shalkevet and Varon [5], Hoffman and Rawlens [2] observed transpiration intensity under the growth of salinity in vegetable crops.
With the growth of freely soluble salt content, sprouting dates ofvegetable crops and potato are delayed to some extent, germinating capacity of seeds decreases and sowing becomes more thinned.
According to Zuev [6, 35-43] weakening of growth due to the impact of soil salinity in potatoes is determined by the lower-
Among the four vegetable crops the most susceptible to soil salinity is onion and relatively saline resistant is potato. Cabbage and tomato secure intermediate positions.
It is worth mentioning that in weak saline soils crop capacity of potato decreases to 15-20%; cabbage — 15-25%; tomato — 20-30%; and onion 25-30%; in mid-saline soils 35-40%, 40-50%, 40-60%, 50-60% respectively in comparing with nonsaline soils.
ing level of branchiness of caulis and by the decrease in number of leaves. Inhibitory impact of soil salinity on onion is evidenced by the delay in leaves formation and their size loss. It was identified that ions of chlorine are the most toxic according to their impact on crop capacity. Their increase in soil to 0.002-0.003% notable reduces crop capacity of plants and commercial quality of crop.
Soil salinity also influences plants' entering certain phases of development. In onions, leafy vegetables, root vegetables with the increase of content of salt in soil there was observed considerable delay in leaf formation, bulbing, formation of cabbage heads and roots.
Intrusion of salts in the organs of plants accompanied by a number of destructive change, chlorophyll grain are destroyed and in consequence photosynthesis energy decreases, breathing and normal flow carbohydrate metabolism. In cotton plants in saline soils total and protein nitrogen increases and the content of starch in leaves decreases.
Li [4, 76-84] developed bonitation factors on salinity level of soils with reference to cotton plants: weak saline soils — 0.85; mid-saline — 0.60 and strong saline — 0.30. In mid-saline soils by reference to non-saline soils crop capacity of cotton decreases up to 40% and in strong saline soils this index reaches 70%.
Identification of dependencies of crop capacity of vegetable crops with the use of correlation method according to the soil salinity level revealed substantial relation (-0.57-0.71). For potato this index is equal to — 0.71, cabbage — 0.69, tomatoes — 0.58 and onion — 0.57 respectively.
It is established that with the increase of solid residue, crop capacity of plants decrease. Basing on this we have calculated valuation factors on the degree of soil salinity for vegetable crops of Golodnaya steppe. (Table 2).
Relying on the obtained data there were developed valuation factors on the degree of soil salinity for potato and cabbage: nonsaline soils — 1.00; weak-saline soils — 0.85; mid-saline — 0.65; for tomato: nonsaline — 1.00, weak saline — 0.80, mid-saline — 0.55; for onion: nonsaline — 1.00, weak saline — 0.75, mid-saline — 0.50.
Table 2. - Valuation factors on the degree of soil salinity
Salinity degree Potato Cabbage Tomato Onion
Crop capacity, centner/hectare Valuation coef. Crop capacity, centner/hectare Valuation coef. Crop capacity, centner/hectare Valuation coef. Crop capacity, centner/hectare Valuation coef.
Nonsaline 123 1,00 329 1,00 297 1,00 221 1,00
Weak saline 104 0,85 274 0,85 242 0,80 163 0,75
Mid-saline 77 0,65 203 0,65 162 0,55 115 0,50
References:
1. Dospehov B. A. Metodika polevogo opyta. M. Agroprom izdat. - 1985. - P. 117., 268-290.
2. Hoffman Q. J., Rawlens S. L. Crowth and water potental of root crops as influenced by Salinity and relative humumbity «Argon. S» -63. - 1971, - No 6.
3. Kabaev V. E. Solevynoslivost' selskohozyastvennyh kul'tur.//Sotsial. sel'sk. hozyastva. - 1963 (2). - P. 35-38.
4. Li V. N. Plodorodiye oroshaemyh zemel Uzbekistana. - Tashkent, Fan. - 1989. - P. 51-52; 76; 83-84.
5. Shalhevet J., Varon B. Effect of soil and water salinity on tomato growth. "Plant and Soil» - 39, - 1973, - No. 2.
6. Zuev V. I. Osobennosti vozdelyvaniya ovoshnyh kultur na zasolennyh pochvah. - Tashkent, - Fan. - 1997. - P. 35-43.