Study on the Absorption Rate of Cotton to Different Doses of Mepiquat Chloride

The indeterminate growth habit of cotton and its strong plant-type plasticity determine that multiple mepiquat chloride growth-regulation treatments must be carried out during its growth period. This is especially true under the "early, dense, dwarf, film" cultivation model, where directional induction is used to shape a reasonable field structure and obtain the optimal temporal and spatial distribution of cotton bolls. This article uses large-scale spraying machinery and takes Xinluzao 23 as the subject to study the absorption rate of mepiquat chloride by cotton at different stages of growth and development as follows.

1. Selection of spraying machinery

The traction power is between 30 and 65 horsepower, the tank volume is 1.7 to 2.2 cubic meters, the improved nozzle spacing is 30 cm, the number of nozzles is 35, and during operation the nozzles are 70 cm above the ground. The working pressure is 1.5 MP, the water volume per 667 sq m is 40 to 43 kg, the spray boom width is 1050 cm, and the spray swath width is 1150 m, allowing 7 films to be sprayed at the same time, that is, two sowing widths plus 1 film, totaling 28 sub-rows, with a width of 1050 to 1056 cm.

2. Absorption rate of mepiquat chloride by cotton plants at each growth stage

1. Seedling stage

① At the 3-leaf stage, plant height is 10 to 12 cm, plant width is 8 to 10 cm, plant height is greater than plant width, and the mepiquat chloride dosage is 0.8 g/667 sq m.

For small 3-film 12-row with row spacing configuration 18 + 50 + 18 cm, the sowing width is 450 to 453 cm. Plant width is 3 to 10 cm, the width of two sub-rows is 16 to 20 cm, and the plant width within one spray swath is (16 to 20) x 2 x 7 = 224 to 280 cm. Absorption rate = 224 to 280 cm/1150 cm, and the actual absorption rate is 19.48% to 24.35%; the actual absorbed amount of mepiquat chloride by cotton is 0.16 to 0.2 g/667 sq m.

For machine-picked cotton with row spacing configuration 10 + 66 + 10 cm, the sowing width is 450 to 453 cm, the actual absorption rate is 19.48% to 24.35%, and the actual absorbed amount of mepiquat chloride by cotton at the 3-leaf stage is the same as that of small 3-film 12-row.

② At the 5 to 6-leaf stage, plant height is 25 to 30 cm, plant width is 15 to 20 cm, plant height is greater than plant width, and the mepiquat chloride dosage is 1.5 to 1.8 g/667 sq m.

For small 3-film 12-row, the width of two sub-rows is 40 to 46 cm, and the plant width within one spray swath is (44 to 46) x 2 x 7 = 560 to 644 cm. Absorption rate = 560 to 644 cm/1150 cm, and the actual absorption rate is 48.69% to 56.0%; the actual absorbed amount of mepiquat chloride by cotton is 0.73 to 0.84 g/667 sq m and 0.88 to 1.01 g/667 sq m.

For machine-picked cotton, the width of two sub-rows is 30 to 35 cm, and the plant width within one spray swath is (30 to 35) x 2 x 7 = 420.490 cm, with an absorption rate of 36.5% to 42.61%; the actual absorbed amount of mepiquat chloride by cotton is 0.55 to 0.64 g/667 sq m and 0.66 to 0.77 g/667 sq m.

2. Full bud stage (8 to 9 leaves)

Plant height is 40 to 45 cm, plant width is 25 to 30 cm, plant height is greater than plant width, and the mepiquat chloride dosage is 2.5 to 3.0 g/667 sq m.

① For small 3-film 12-row, the width of two sub-rows is 55 to 60 cm, and the plant width within one spray swath is (55 to 60) x 2 x 7 = 770 to 840 cm, with an absorption rate of 66.95% to 73.04%; the actual absorbed amount of mepiquat chloride by cotton is 1.67 to 1.83 g/667 sq m and 2.01 to 2.19 g/667 sq m.

② For machine-picked cotton, the width of two sub-rows is 50 to 55 cm, and the plant width within one spray swath is (50 to 55) x 2 x 7 = 700 to 770 cm, with an actual absorption rate of 60.87% to 66.95%; the actual absorbed amount of mepiquat chloride by cotton is 1.52 to 1.67 g/667 sq m and 1.83 to 2.19 g/667 sq m.

3. Flower and boll stage (12 to 13 leaves)

Plant height is 55 to 60 cm, plant width is 36 to 40 cm, plant height is greater than plant width, and the mepiquat chloride dosage is 3.5 to 4.0 g/667 sq m.

① For small 3-film 12-row, the width of two sub-rows is 70 to 75 cm, and the plant width within one spray swath is (70 to 75) x 2 x 7 = 980 to 1050 cm, with an absorption rate of 85.22% to 91.30%; the actual absorbed amount of mepiquat chloride by cotton is 2.98 to 3.2 g/667 sq m and 3.41 to 3.65 g/667 sq m.

② For machine-picked cotton, the width of two sub-rows is 65 to 70 cm, and the plant width within one spray swath is (65 to 70) x 2 x 7 = 910 to 980 cm, with an absorption rate of 79.13% to 85.22%; the actual absorbed amount of mepiquat chloride by cotton is 2.77 to 2.93 g/667 sq m and 3.17 to 3.41 g/667 sq m.

4. After topping

For small 3-film 12-row, plant height is 60 to 65 cm, and for machine-picked cotton, plant height is 70 to 75 cm. The mepiquat chloride dosage is 10 to 15.0 g/667 sq m. The large and small ridges have closed, and the actual absorption rate can reach 100%; the actual absorbed amount of mepiquat chloride by cotton is 10 to 15 g/667 sq m.

3. Effects of other factors on the absorption rate of mepiquat chloride by cotton plants.

1. Vehicle speed

Vehicle speed directly affects the absorption rate of mepiquat chloride by cotton plants. If the vehicle speed is too fast, the absorption rate decreases and the purpose of chemical regulation cannot be achieved; if the vehicle speed is too slow, the absorption rate increases, which is equivalent to increasing the dosage of mepiquat chloride. For normally growing cotton fields, normal speed can be used during chemical regulation; for weak seedlings, do not apply chemical regulation or increase the vehicle speed; for vigorously growing cotton fields, reduce the vehicle speed to increase the plant absorption rate of mepiquat chloride, so as to achieve the goal of "one height, one color."

2. Water pump working pressure

Generally adjusted to 1.5 MP. If it is too high, the pipe will burst; if it is too low, the absorption rate of mepiquat chloride by cotton plants will decrease.

3. Air temperature

When the air temperature is high, evaporation is fast, and the absorption rate of mepiquat chloride by cotton plants decreases. Chemical regulation operations should be carried out before 12 o'clock in the morning or after 17 o'clock in the afternoon.