Recommendations of Scientists and Specialists from the Institute of Soil Science and Agrochemistry
“Primary Soil Tillage”
Almost half of the irrigated lands in the republic are located on plots with a stable crop rotation system. Under such conditions, the high efficiency of all agrotechnical practices, including soil tillage, is most fully achieved.
Scientists from the Academy of Agricultural Sciences of Tajikistan (AAST) have conducted extensive research to develop methods of rotational soil tillage in cotton and alfalfa crop rotations in the Vakhsh and Gissar valleys.
It was established that plowing and deep incorporation of perennial grasses helps the soil to retain its formed fertility and positive water-physical properties for a long time. Additionally, alfalfa regenerates, and perennial weeds are suppressed in crop rotations.
Based on these results, in the Vakhsh valley on irrigated gray soils, deep plowing of alfalfa residues with a plantation-type plow to a depth of 60 cm is recommended, while on other soil types (including loams), regardless of the region, a depth of 45-50 cm is advised. For the second year of cotton cultivation following deep plowing and incorporation of perennial grasses, plowing to a depth of 23-25 cm is necessary. For crop rotations 1:4:1:4 and 1:3:1:3, as well as for long-term cotton-growing lands, a different plowing approach should be applied. In these cases, the timing of tillage plays a crucial role. It was found that if plowing of the chernozem meadow soils of the Gissar valley shifts from the autumn to the spring season, cotton yields decrease by up to 4.5 quintals per hectare. Therefore, plowing should be conducted in October-November and no later than mid-December.
The importance of plowing lies in significantly improving the physical properties of the soil, its moisture retention capacity, and biological activity. Furthermore, timely deep soil tillage enhances the beneficial functions of the soil and ensures active cotton growth.
An essential condition is plowing with the use of subsoilers, which ensures better soil loosening, incorporation of fertilizers into the active root zone of cotton, destruction of spreading weed roots, overwintering pests, and suppression of pathogenic microorganisms.
In the republic, plowing is carried out both by standard methods and with two-furrow plows. On plots heavily infested with weeds, especially perennial ones, it is recommended to use only two-furrow plows, which provide complete soil inversion and deep incorporation of weeds, creating unfavorable conditions for their germination.
It is important to ensure optimal soil density, at which the root system operates actively; the optimal soil density is 1.1–1.2 g/cm³. Since multiple tractor passes (up to 20 times) are inevitable when growing cotton, soil density often exceeds the permissible limit of 1.5 g/cm³ in the second half of the growing season.
Also, long-term plowing at the same depth (about 30 cm) increases the density below the plowed layer due to the formation of a plow pan, which negatively affects soil condition.
Research has shown that the root systems of cereals (wheat, barley, oats) penetrate to a depth of 0-20 cm, whereas cotton, alfalfa, and maize roots reach 50-60 cm. Therefore, plowing to the standard depth (30 cm) should be complemented by deep loosening with soil inversion (30 cm plowing + 15 cm loosening). Deep soil tillage is more effective and can increase cotton yield by 2.4 quintals per hectare on hydromorphic soils (chernozems of meadow type, etc.).
Deep soil loosening is also effective on areas allocated for alfalfa and significantly increases its yield. Additionally, this treatment improves soil permeability and biological activity at depths of 30-60 cm, allowing cotton and alfalfa roots to penetrate deeper.
The following measures are recommended for agricultural producers:
In areas with strong winds and low humidity, as well as on soils requiring washing irrigation, spring harrowing combined with plowing is recommended. This improves moisture retention and promotes even grass stand.
For leveling fields, plowing is done with the creation of furrows and ridges.
After completing the treatment of the entire field, repeat harrowing is recommended.
A common drawback observed in farms is the one-sided tillage of tractor turning areas, which leads to soil displacement from the edges of the field and the formation of depressions, causing the need to construct additional drainage ditches 10-15 meters from the field edge.
The direction of tillage in the turning areas should ensure field evenness and uniformity.
