INFLUENCE OF DIFFERENT IRRIGATION REGIMES OF COTTON PLANTS ON THE SALT REGIME OF THE SOIL

АННОТАЦИЯ

По результатам наших многолетних исследований впервые выявлен рост и развитие тонковолокнистого хлопчатника и получение ранних обильных урожаев в условиях светлоокрашенных сероземов при глубине фильтрационной воды 1,5- 2,0 м и 3,5-4,0 м, также разработаны оптимальные сроки, количество и нормы поливов, обеспечивающие поддержание мелиоративных земель в устойчивом состоянии. Изучено водопотребление хлопчатника, нормы и режим орошения, климатические условия, свойства почвы, глубина инфильтрации, биологические особенности сорта и фазы роста растений, гидромодули хлопчатника и других культур в речных условиях в севообороте. Нижние районы оазиса реализовывались районами, разрабатывались и внедрялись в практику режимы орошения.

ABSTRACT

According to the results of our long-term research, for the first time, the growth and development of fine-staple cotton and the receipt of early abundant crops in conditions of light-colored gray soils with a depth of seepage water of 1.5-2.0 m and 3.5-4.0 m were revealed. Optimal timing, quantity and rates of irrigation were also developed to ensure the maintenance of reclamation lands in a stable state. The water consumption of cotton, norms and irrigation regime, climatic conditions, soil properties, infiltration depth, biological characteristics of the variety and plant growth phases, hydro modules of cotton and other crops in river conditions in crop rotation have been studied. The lower regions of the oasis were implemented by regions, irrigation regimes were developed and put into practice.

Keywords: irrigation regime, watering, ground water, salting, ion chlorine, saline regime.

Ключевые слова: режим орошения, полив, грунтовая вода, засоление, ионы хлора, солевой режим.

This is due not only to the toxic effect of salts, but also to the increase in the concentration of the soil solution and, accordingly, the osmotic pressure. As a result, the root hairs cannot absorb the water they need, and eventually the plant sprouts may die. In order to describe the degree of salinity of the soils of the experimental fields, the initial amount of salt in them was studied.

The obtained results showed that the soils of the first experimental field have a heavy mechanical composition and because of the location of mineralized syzob waters near the surface of the earth, they are somewhat more saline than the soil of the second field. The top 1 m layer of the first experimental field contains 0.590% dry residue and 0.046% chlorine ion. Under a one-meter layer, the amount of salt is even higher - dry residue is 0.725%, and chlorine ion is 0.063%.

Table 1.

The degree of mineralization of syzob waters in experimental fields

In the second experimental field, indicators of salt accumulation have different values. The 0-100 and 200-300 cm layers of this field soil contained 0.121 and 0.171% dry residue and 0.025 and 0.015% chlorine ion, respectively. In the middle part of the aeration layer, i.e., in the layer of 100-200 cm, salts accumulate relatively more, their amount reaches 0.5%. According to the initial number of salts, the soils of the first experimental field can be considered weakly saline. The 0-100 and 200-300 cm layers of the second experimental field were practically not saline, and the 100-200 cm layer was subjected to weak salinization. In our opinion, the reason for this may be the rise of weakly mineralized groundwater to the 150-160 cm layer of the aeration layer and the accumulation of salts in the capillary bed over the years. Chloride-sulfate type of salinity is characteristic of the soils of the experimental fields. Among the salts, sulfates predominate and account for more than half of the dry residue.

Table 2.

The initial number of salts in the soils of the first experimental field

Taking into account the weak salinity of the soils of the first experimental field and the weak salinity of the soils of the second experimental field only in the 100-200 cm layer, then it becomes clear that these salts rise to the upper layers of the soil after a certain period of time and pose a danger to plants. Of course, the regime of crop irrigation has a great influence on the occurrence of this situation. According to the results of the three-year research, the data on the effect of the irrigation regime of thin fiber cotton on the change of the salt regime of the soils of the experimental fields are presented in Tables 1 and 2 In the field where seepage waters are located at a depth of 1.5-2.0 m, a significant change in the salt regime of the soil was observed under the influence of the cotton irrigation regime. For example, in 1988, when the irrigated soil moisture was equal to 70-70-65% of the limited field moisture capacity (option 2), the amount of dry residue in the 0-60 cm layer in the spring, that is, before the start of irrigation while it was 1.153% in the period by autumn, it was found that its amount decreased to 1.121%. A similar situation was observed in the 60-100 cm layer. However, salt accumulation occurred in the 100-200 cm layer of the soil from spring to autumn. For example, in the spring, this layer contained 1.019% of dry residue, and by autumn, its amount increased to 1.240%. In the experiment, it was found that the amount of chlorine ion increased from spring to autumn in all layers. In the first option (60-70-65%), the amount of salt in the soil increased significantly from spring to autumn. A similar scenario was observed in options 3 and 4.

For example, at the beginning of the growing season, the amount of dry residue in the 0-60 cm layer was 1.153%, by the fall this indicator increased to 1.270% in the 3rd option, and up to 1.261% in the 4th option.

However, it was found that the number of salts in the 100-200 cm layer is slightly less (1.227-1.262%) than in option 1 (1.328%). The best land reclamation was observed in the 2nd and 3rd options with 70-70-65% and 70-75-65% compared to ChDNS with irrigation.

Table 3.

The initial number of salts in the soils of the second experimental field

Data on the salt regime of the soil of the second experimental field are presented in Table 3. The results of the research showed that the amount of dry residue and chlorine ion in the 1-meter layer of the soil remained almost unchanged and stable from spring to autumn according to different watering regimes. A significant change in the salt regime was observed in the 100-200 cm layer, which has more salinity than the upper layer. In all years of research and in all modes of irrigation, it was found that salts were washed from the 100-200 cm layer and fell to the lower 200-300 cm layer.

Table 4.

Changes in the amount of salt in the soil depending on the cotton irrigation regime, % (First experimental field)

At the beginning of the growing season, the amount of dry residue in the 100-200 cm layer of the soil was equal to 0.588%, and by autumn, this indicator was 0.235-0.539% according to the experimental options. The same indicator decreased from spring (0.600%) to autumn (0.231-0.408%).

In the option with 60-70-65% moisture regime with irrigation, a slight accumulation of salt in the soil was observed in autumn, in option 2, where cotton was irrigated according to 70-70-65% moisture, these indicators took an intermediate place. From the data presented in Table 4, it is possible to see the accumulation of salts in the 200-300 cm layer of the soil due to the leaching of easily soluble salts from the upper layers, especially from the 100-200 cm layer. It was found that the amount of chlorine ion remained unchanged in the layers of 100-200 and 200-300 cm in all experimental options. Salinity of the 100-200 cm layer of the soil occurs under the influence of backup irrigation in spring and irrigation during the growing season. V.A. Kovda believed that preventive irrigation in spring enhances the seasonal desalination of soil, reduces the strength of salinization in the summer season, and curbs the annual dynamics (change) of salts in saline soils. In addition to desalination of the 1.5-2.0 m layer of the soil with the help of preventive irrigation, it is necessary not to exceed the reserve irrigation rate by 1500-2000 m³ per hectare in order not to raise the level of seepage.

The effect of preventive, i.e., backup irrigation in soil desalination is enhanced by irrigation during the growing season. In our studies, we carried out preventive irrigation 10-12 days before planting seeds at the rate of 1200-1500 m³ per hectare. If it is taken into account that the soil of the field with deep seepage water is composed of loamy and light sand starting from the bottom of the arable layer and that the soil- has a joint that becomes lighter from top to bottom, in that case, it is not difficult to make sure that the water standard set for the reserve can desalinate the 2 m layer of the soil.

Thus, it is necessary to carry out reserve (prophylactic) irrigation as a very important agrotechnical measure in the lands of the Karshi steppe with weak salinity. The effectiveness of preventive irrigation is increased during the growing season by combining it with other agrotechnical measures such as feeding, inter-row cultivation, weed control, etc. Coordination of measures prevents the rising of salts from the lower layers and allows maintaining the upper active layer of the soil during the growing season in an amelioration condition favorable for agriculture.

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