Key technical points for moving and hardening cotton seedling nutritional blocks
Moving and hardening the blocks is an important measure in the management of seedbeds for cotton nutritional block seedling raising. Its main benefits are: first, it can break off the tip of the cotton seedling's main root so that the upper part grows slowly, stimulate lateral root development, make the plant short with thick stems and many lateral roots, and improve cotton seedling quality; second, after the blocks are moved, air circulates around the roots and water dissipates quickly, which not only can enhance root activity...
Moving and hardening the blocks is an important measure in the management of seedbeds for cotton nutritional block seedling raising. Its main benefits are: first, it can break off the tip of the cotton seedling's main root so that the upper part grows slowly, stimulate lateral root development, make the plant short with thick stems and many lateral roots, and improve cotton seedling quality; second, after the blocks are moved, air circulates around the roots and water dissipates quickly, which not only can enhance root activity, but also, when combined with removing diseased material during block moving, can reduce pathogen infection and effectively control seedbed diseases; third, after moving and hardening the blocks, the cotton seedlings grow robustly with well-developed lateral roots, which can shorten the seedling recovery period after transplanting and speed up the growth process. According to surveys, moved-block seedlings take root 7 days earlier than unmoved seedlings, reach the squaring stage 12 days earlier, and reach the flowering stage 8 days earlier. The methods and precautions for moving and hardening the blocks are introduced below.
1. The timing of moving the blocks should be appropriate. According to research, when cotton has 2 leaves and 1 heart, mid-maturity varieties are about to begin flower bud differentiation. Moving and hardening the blocks at this time can promote top growth and control lower growth, first control and then promote, improve cotton seedling quality, and promote early development. If the blocks are moved when the cotyledons are flat and spread, it will restrict the growth of the cotyledons and root system, affect strong seedlings and early development, and show a high node position for the first fruiting branch, tall plants, reduced leaf area per plant, and reduced yield. If the blocks are moved too late, because the time until transplanting is relatively short, the phenomenon may occur that the cotton seedlings have not yet taken root but must be transplanted, causing continuous hardening and instead prolonging the field seedling period.
2. The seedling blocks should be placed reasonably. Generally, in film seedling raising, the outer rows have lower temperatures, and the seedlings are small and weak. When moving the blocks, they should be rearranged by classification according to large and small seedlings. Small seedlings should be placed in the middle, and large seedlings in the outer rows. Then, through heat-preservation management, the small seedlings can catch up with the large seedlings and promote balanced growth. After moving, the seedling blocks should be placed somewhat more sparsely.
3. Management after moving must be done well. After the seedling blocks are moved, the "three supplements and one increase" management work of supplementing soil, fertilizer, and water and increasing temperature must be done well. After the seedling blocks are arranged, fine soil should immediately be added to fill the gaps between blocks and along the block surface and seedbed edge, so that no gaps are visible between blocks, the block bodies are not exposed, and the seedbed edge is well filled with soil. After supplementing soil, combine with water supplementation, and sprinkle about 2000 kg of clear water and manure per 667 m2 of seedbed to promote recovery of cotton seedling growth. After moving the blocks is completed, film should also be covered to increase temperature, and the seedbed temperature should be kept between 20-25°C.
4. Moving and hardening the blocks should be done on selected days. Moving and hardening the blocks should preferably be carried out on stable sunny days when the temperature outside the film is stable at 18-25°C, to prevent invasion by low temperatures and strong winds. At the same time, attention should also be paid to high-temperature damage, to prevent water loss and root injury. Before removing the film, ventilation should first be used to regulate the temperature inside and outside the seedbed, so as to avoid too large a temperature difference causing the cotton seedlings to be chilled and their leaves to wilt.