Technical Problems and Solutions for the "Two No" Cotton Cultivation Technique

The "Two No" cotton cultivation technique refers to cotton seedling raising in soilless substrate and transplanting of bare-root seedlings without carrier. From 2004 to 2005, after demonstrations at more than 80 county sites across the country, some technical problems were found, and the following solutions are proposed:

1. Excessive seedbed density

Main causes: First, rows were not marked out at 10 cm row spacing and 3 cm plant spacing; second, the sowing rate was too high with too many seeds; third, after emergence, seedlings were not thinned in time, resulting in leggy or spindly seedlings.

Solutions: First, mark out rows at 10 cm row spacing and 3 cm plant spacing; second, sow according to plant spacing, one seed per hole; third, after emergence, thin seedlings in time according to plant spacing.

2. Weak, thin and non-sturdy seedlings

Main causes: First, in some places, to reduce costs, too much sand was added to the substrate; second, the substrate and sand were not mixed evenly.

Solutions: First, add river sand to the substrate according to the ratio, with a volume ratio of 1:1 and a weight ratio of 1:8-1:9; second, the substrate and sand must be mixed evenly; third, the moisture content of the sand is required not to exceed 5%, with no industrial or domestic pollution.

3. What are the characteristics of the substrate?

First, the soilless substrate seedbed has the characteristics of rapid emergence and rapid growth. For seedlings of the same seedling age, the time is 4-5 days earlier.

Second, the suitable seedling age for transplanting bare-root seedlings is 2 true leaves per plant; at this time, transplanting to the field will not cause seedling disease and death. At the same time, the transplanting survival rate is high, the plants grow quickly, and they clearly start growing early.

4. How to sow at the right time and accurately grasp the suitable seedling age

Sowing at the right time is one of the keys to ensuring a high survival rate when transplanting bare-root seedlings. Methods for sowing at the right time and grasping the suitable seedling age: First, calculate the seedling raising and sowing time backward from the transplanting date. According to the seedling age of 2 true leaves per plant, early sowing generally requires 25 days, and late sowing requires 20 days. If transplanting is at the end of April, sow in early April; if transplanting is in early May, sow in mid-April. In the middle reaches of the Yangtze River, after rapeseed harvest, transplanting is in mid-May, and the sowing period is in late April; for short-season cotton in the Yellow River region, transplanting is in early to mid-June, and the sowing period is in late May. Second, large-scale seedling raising emphasizes continuous sowing, or sowing in stages and batches; centralized seedling raising requires continuous sowing for 2-3 days. Third, bare-root seedling transplanting emphasizes that "when the seedlings are ready, do not wait for the time"; the technical regulations require controlling the transplanted seedling age to no more than 3 true leaves, and when the seedling grows to 2 true leaves per plant, it should be transplanted.

5. How to control overage seedlings

Use the "seedling hardening" method. If transplanting cannot be carried out on time due to special weather or other reasons, there are two methods of "seedling hardening": First, take seedlings from the seedbed and replant them in the seedbed (also called "temporary planting"), which can stop growth. Second, spray the seedbed with a low concentration of mepiquat chloride (0.1 g diluted in 1000 kg water), controlling for 7-8 days.

6. How to ensure the survival rate of bare-root seedling transplanting

The key to a high survival rate in bare-root seedling transplanting is water. "Transplanting cotton is like transplanting vegetables" also requires sufficient water, and water is also one of the factors for early plant growth and early development. First, the bottom moisture must be sufficient. Water before transplanting to ensure sufficient bottom moisture. Second, the surface moisture should be good; while transplanting, water with "root-settling water". Third, control the use in areas without irrigation conditions. "Transplanting cotton is like transplanting vegetables" requires water as a basic guarantee condition, and large-scale demonstrations should not be carried out in areas without irrigation conditions.

7. How to promote plant growth after transplanting bare-root cotton seedlings

In addition to sufficient moisture, temperature is also one of the factors for plant growth after bare-root seedling transplanting, and plastic film mulching is recommended. First, cover with plastic film first, then transplant. Second, while transplanting, water with "root-settling water" and cover with plastic film at the same time. It should be emphasized that the "Two No" technique is a successor technique to transplanting seedlings raised in nutritional pots, and it cannot replace plastic film mulching.