Fine classification of wheat seedlings for skillful management of diseases

After emergence, different types of weak seedlings are often formed due to the influence of natural conditions and cultivation measures. Prevention of weak vaccine and symptomatic management are introduced as follows:

The weak seedlings caused by soil drought mostly occur in the wheat fields where the soil moisture is insufficient or ventilated, which is characterized by slow tillering, gray-green leaves, short heart leaves, slow growth or stagnation (called by the masses as "shrinking seedlings"), and the middle and lower leaves gradually turn yellow and dry, and the roots are few and thin. Key points of management: combined with watering, 15 kg ammonium bicarbonate per mu.

The weak seedlings caused by soil nitrogen deficiency were erect, the tillers decreased, the leaves were narrow and short, and the lower leaves began from the leaf tip, gradually yellowed and withered, and developed to the upper leaves. Key points of management: use urea 7mura 8kg per mu, or ammonium bicarbonate 20mu 25kg, apply it in the furrow between rows or pour it with water.

The weak seedlings caused by phosphorus deficiency in soil showed poor root development, few and weak secondary roots, dark green leaves, purplish red leaf tip and leaf sheath, thin plants and reduced tillers. Key points of management: combined with watering and hoeing, 30kg calcium superphosphate is used per mu and ditched between rows. The earlier the topdressing, the better.

The weak seedlings caused by soil wet board or saline-alkali damage are usually characterized by poor root development, weak absorptive capacity, slow tiller birth, and often accompanied by desalination; patches of purplish-red "little old seedlings" often appear in the land with heavy saline-alkali damage. At the base of the seedlings, two leaves yellowed and withered, and when serious, the seedlings withered. Key points of management: combined with deep ploughing, trenching and topdressing nitrogen and phosphorus mixed fertilizer; land with serious saline-alkali hazards, irrigating water and pressing salt after topdressing, and timely hoeing to loosen the soil to break the consolidation.

Due to the lack of soil moisture and air, the root system is difficult to stretch, so the wheat leaves are yellow and short, and the tillers can not appear on time. Management points: first timely watering, and then deep ploughing and loosening soil, in order to break the rigid layer.

The weak seedlings caused by too wet soil usually show lilac leaves, slow tiller birth, and when serious, the leaf tips become white and dry. Key points of management: first, timely deep ploughing and dispersing moisture ventilation, and then topdressing a small amount of available chemical fertilizer to promote the early development of seedlings.

The weak seedlings caused by excessive sowing rate are as follows: the seedlings are crowded, and the plants are thin and slender. Key points of management: first, we should pay close attention to thinning seedlings, especially the "pimple seedlings" in the land, the edge of the ground, and in the field, and then combine with watering, and apply a small amount of nitrogen and phosphorus fertilizer to make up for the excessive consumption of soil nutrients and promote the wheat seedlings to change from weak to strong.

The weak seedlings caused by sowing too deeply are as follows: slow emergence, slender leaf sheath, delayed tillering and no long rooting. Key points of management: first pick the soil and clear the trees, and then topdressing in time (15kg ammonium bicarbonate per mu), in order to promote the development of roots and seedlings.

Because the tiller node is too close to the surface and the water and nutrient conditions are poor, the root growth and tiller bud development of the weak seedlings caused by shallow sowing are inhibited, so the roots and tillers are usually reduced, the plants are yellow and weak, and are easy to die by freezing. Key points of management: combined with hoe, obstructing the soil around the root; when the aboveground part of the plant basically stops growing, break the ridge to cover the soil. It is appropriate to cover the soil thickness so that the tiller node is about 3 cm below the surface; if it is covered with guest soil, that is, using clay to cover sand and sand to cover clay, the soil can also be improved.

The weak seedlings caused by sowing too late are mostly due to the short growth period before winter and the lack of accumulated temperature, resulting in thin growth and few tillers of wheat seedlings. Main points of management: mainly paddling hoe and replenishing fertilizer and water, applying 15 kg ammonium bicarbonate per mu in the three-leaf period; wheat fields with poor soil moisture and fast water seepage, watering tillers in time after the three-leaf stage (but the land with suitable soil moisture or soil viscosity and poor water permeability should not be watered before winter), and the last hoe before freezing should pay attention to choking the soil around the roots to protect the seedlings safely through the winter.