Method for preserving and strengthening seedlings in continuous cropped cotton field with soil moisture deficiency in desert oasis

A method for preserving and strengthening seedlings in a continuous cropped cotton field with soil moisture deficiency in a desert oasis, comprising the steps as follows:

• 1) Seedbed establishment:
• in a desert oasis, selecting a cotton field where a groundwater level is greater than or equal to 1.0 m and a soil salt content is less than and equal to 0.8% in a 0-15 cm tillage layer before soil preparation, wherein the cotton field is equipped with a drip irrigation facility compatible with cotton planting;
• and
• within 0-2 days of a sowing period for cotton in a year, completing land plowing, harrowing and smoothing operations to ensure that a relative soil moisture content in a 0-30 cm tillage layer of the cotton field is maintained at 35-50% from the completion of soil preparation to the beginning of cotton sowing;
• wherein, during the operation of harrowing and smoothing, for cotton fields with sandy loam soil, a combined land preparer with a diverting soil leveling frame design that does not comprise any harrow groups is used, and the diverting soil leveling frame comprises a soil leveling frame group, an inward-facing V-shaped soil diverting and guiding group, a soil scraping and leveling plate group, an outward-facing V-shaped soil diverting and guiding group, and a compaction roller group;
• for cotton fields with a high clay content or where the compaction roller group is unable to effectively crush large soil clumps with a maximum length being greater than or equal to 3 cm, a conventional combined land preparer with a harrow group or a power-driven harrow for soil crushing is still used;
• 2) Sowing and drip irrigation tape laying:
• in the absence of weather conditions comprising low temperatures and rainfall, and when the temperature is in a predetermined range, performing sowing immediately after the seedbed is established, wherein a selected sowing machine is a multifunctional precision sowing machine having a function of drip irrigation tape laying and equipped with a Beidou satellite navigation system;
• a drip irrigation tape selected is either a drip irrigation tape with a labyrinth on one side or a drip irrigation tape inlaid with emitters inside, both with a pipe diameter of 16 mm, an emitter spacing of 200 to 300 mm, a working pressure of 0.1 MPa or above, and irrigation uniformity of 90% or above, when the drip irrigation tape is laid, emitters are placed upwards, and flow channels are selected from at least one of a zigzag type and an S-shape type, wherein main parameters of the drip irrigation tape with a labyrinth on one side are:
• an emitter flow rate is 1.5 to 3.2 L/h, and a laying length of a single drip irrigation tape in the field is 50 to 100 m;
• the main parameters of the drip irrigation tape inlaid with emitters inside are:
• an emitter flow rate is 0.8 to 2.8 L/h, and a laying length of a single drip irrigation tape in the field is 70 to 130 m;
• in a wide-narrow row planting pattern, for the cotton fields with sandy loam soil, the drip irrigation tape is laid in the middle of a narrow row having a width of 10-13 cm, while for the cotton fields with a moderate or high clay content, the drip irrigation tape is laid either in the middle or on one side of the narrow row;
• in an equal-row spacing planting pattern, the drip irrigation tape is laid on one side of a planting row;
• in any case, only one drip irrigation tape is laid between two planting rows in the cotton field;
• 3) Soil moisture supply through water dripping after sowing:
• carrying out first drip irrigation for soil moisture supply within 24 hours after sowing, with a drip irrigation volume of 8 to 15 m3/mu, one day after water dripping, stabilizing the relative soil moisture content in the tillage layer where seed holes and surrounding drip irrigation infiltration areas are located at 58% to 73%, performing second water dripping 3 to 5 days later, with a drip irrigation volume of 15 to 30 m3/mu, wherein surface ponding is strictly avoided during each water dripping, and surface water or groundwater with a mineralization degree of 0.5 to 2.2 g/L is used for drip irrigation;
• and
• when water dripping is performed in the cotton field, drip application of monoammonium phosphate dissolved in irrigation water with an application rate of 1 to 2 kg/mu, or potassium dihydrogen phosphate dissolved in irrigation water with an application rate of 500 to 1000 g/mu, or water-soluble diammonium phosphate dissolved in irrigation water with an application rate of 1 to 2 kg/mu, or urea phosphate dissolved in irrigation water with an application rate of 1 to 2 kg/mu, or fully soluble humic acid dissolved in irrigation water with an application rate of 1.2 to 2.5 kg/mu is performed, and a fully soluble soil conditioner is configured to replace humic acid fertilizer;
• and
• 4) Field management after emergence:
• after the cotton emerges to a stage of two leaves and one heart or three leaves and one heart, covering the planting rows by using a soil covering machine that does not compress the seedlings and sealing the seed holes;
• and
• advancing the first irrigation after all the cotton seedlings emerge to the first ten days of May, accompanied by drip application of fully soluble pure nitrogen (N) dissolved in irrigation water with an application rate of 1.2 to 1.5 kg/mu and pure phosphorus pentoxide (P2O5) dissolved in irrigation water with an application rate of 0.5 to 1.0 kg/mu.