Root system of cotton

Cotton is native to tropical and subtropical regions and is a perennial plant. After long-term artificial selection and cultivation, it gradually moved northward to the temperate zone and evolved into an annual crop. Within a year, sowing, budding, flowering, boll setting, seed maturation, and completion of the growth cycle. In the process of growth and development, cotton still retains some characteristics of the original perennial crops and has unlimited growth habits. Under suitable conditions, fruit branches can constantly proliferate fruit branches, fruit nodes, buds, blossoms and bolls.

Cotton is a straight-root crop with well-developed roots, deep main roots and wide distribution of lateral roots, forming a strong absorption network in the soil. Cotton root system is composed of main root, lateral root, branch root (small root), hairy root (small branch root) and root hair. When the cottonseed germinates, the radicle protrudes, grows downward, and becomes the main root. In the early stage of cotton growth, the first lateral root was born from the main root about 10 cm away from the growth point of the main root, which grew almost horizontally at the beginning, and then grew obliquely to the lower layer. The secondary lateral root is produced at a distance of about 5 cm from the growing point of the primary lateral root. Under suitable conditions, the third, fourth and fifth lateral roots can continue to grow. The huge root system of cotton is composed of main root, lateral root and a large number of root hairs near the root tip. The root of cotton has a strong ability of regeneration, main root injury or transplanting root cutting, will promote a large number of lateral root growth. The smaller the cotton plant is, the stronger the root regeneration ability is.

Under suitable ecological and cultivation conditions, the depth of cotton root can reach about 2 meters, and some can exceed 3 meters. The upper lateral root extends farther, the lateral extension can reach 60 mi 100 cm, and the lower lateral root extends closer. The occurrence of lateral roots sooner or later and the number of the first lateral roots had significant effects on boll setting characters. The deep and loose soil layer is beneficial for cotton to form a strong and robust root system and improve its resistance to soil-borne diseases. Therefore, deep ploughing is very important for root development, and overcompaction of soil should be avoided during soil preparation. These two measures can slow down the occurrence of cotton seedling disease and Verticillium wilt.

The root formation of cotton can be roughly divided into four stages:

1. The development period of root system is from seed germination to budding. At this time, the daily growth of the root system is up to 2 cm, while the aboveground growth is very slow, and the daily growth is only 0.4 cm 0.5 cm. At this time, early and middle ploughing can increase the ground temperature around the root and promote the branch root to come out early. After that, the middle tillage should be deepened in turn, and the root should be rooted down, and the depth of middle tillage before budding should reach 7 Mel 8 cm.

2. the bud stage of root growth is the peak growth period of main root and lateral root, the main root elongates 2.5 cm every day, and the depth can be more than 1 meter. The lateral root also expands horizontally rapidly, up to 50 cm. The maximum depth of ploughing can be reached in this period. For cotton fields with crazy growth trend, deep ploughing can control vegetative growth, which can reach more than 10 cm. At this time, combined with mid-tillage for the first time, it is beneficial to promote root development, drought and drainage, and prolong the functional period of root system.

3. During the peak period of root absorption, the root net of cotton plant was basically built at the flower and boll stage, absorbing the most water and nutrients, but the rooting ability decreased gradually, so the root should not be injured at the flowering and boll stage, and the middle tillage became shallow step by step. Before the ridge is closed, the soil should be further cultivated in combination with mid-tillage. By strengthening the management of water and fertilizer, it can not only meet the needs of flowering and boll setting, but also maintain root activity and delay root senescence.

4. During the period of cotton boll opening, the root system declined, and the ability of absorbing water and nutrients decreased obviously. The premature decline of root system leads to the premature senescence of cotton plant. When the dry land is dry, watering should also be carried out, which can not only meet the needs of autumn peach development, but also prevent premature senility. Foliar fertilizer spraying in the later stage can make up for the deficiency of root fertilizer absorption and make the root system get the necessary nutrition.