How to prevent yellowing of rice seedlings

During the period of rice seedling cultivation, it is very easy to yellowing, slow growth and weak growth, which is not conducive to the cultivation of strong seedlings, and has a serious impact on the field production seedlings and even the improvement of rice yield.

1. Yellowing caused by insufficient base fertilizer

The growth of seedlings before the third leaf mainly depends on the endosperm, and after the third leaf mainly depends on the root system to absorb nutrients from the soil. However, many people think that during the seedling period, rice seedlings are small and do not need much fertilizer, so the insufficient application of base fertilizer and the lack of ammonia has become the main reason for the etiolation of seedlings.

Countermeasures: urea 60-75 kg per hectare of seedling field, evenly sprinkled on the border surface, or 1% urea solution, foliar spray in the morning or afternoon, 800 kg per hectare.

2. Yellowing caused by uneven application of chemical fertilizer

The area of the seedling field is small, which is not conducive to repeated sugar raking operation, and the application of chemical fertilizer is mostly scattered, which is uneven, and it is easy to form "looped baldness". When the seedlings first germinated, the leaf color was basically the same, and began to differentiate after the three-leaf stage, and the yellow, green, yellow and green appeared obviously. With the increase of seedling age, yellowing became more serious, the plant had no tillers or few tillers, the leaves were narrow and short, the plants were thin and small, and the leaves dried up from the bottom to top from the leaf tip.

Countermeasure: use quick-acting ternary compound fertilizer containing nitrogen, phosphorus and potassium, 150-225 kg per hectare, scattered around the rhizosphere, the principle is which piece of yellow sprinkles which piece. At the same time, etiolated seedlings were sprayed with 1% urea solution.

Third, yellowing caused by high pH value

Soil pH has a direct effect on the growth of rice, and pH has a great influence on the transformation of soil nutrients, especially on the availability of phosphorus and trace elements. ⑦ suitable for rice growth: the pH of the soil is close to neutral, the seedlings prefer acidic soil, and the pH value is high, which affects the nutrient absorption of seedlings and makes the seedlings yellowing due to malnutrition.

Countermeasures: for the soil with high pH value, the pH value should be reduced by adjusting acid, applying 10 grams of zinc sulfate or ferric sulfate per square meter, and adjusting the pH value to 4.5-5.0, so as to inhibit fungal activity, alleviate the deficiency of trace elements in the soil and promote the formation of chlorophyll.

4. Yellowing caused by shallow covering of seeds

When sowing, the seeds are less covered with soil, some of the grains are exposed, the soil grains are dry after the field is slightly dry, the roots can not be tied down, and the yellow seedlings are formed due to the inability to absorb nutrients and water.

Countermeasures: one is to use sifted compost 1500kg to 2000kg per hectare and sprinkle it gently on the border surface; the second is to gently paddle the seedlings with a loose soil shovel about 1.5cm in width, so that the seeds and root necks are buried; third, every 1-2 days, spray water into the seedling field with instruments such as sprayers to keep the field moist, accelerate root growth, and promote weak and strong as soon as possible.

5. Yellowing caused by sudden drop in temperature

The weather in early spring is changeable, and the seedlings at the three-leaf stage have low sugar content and weak cold resistance. After the sudden drop of temperature, the cell membrane of the root cells of the seedling was destroyed, the permeability was enhanced, and the exudation of amino acids and other contents increased. It causes the rhizosphere rot mold to propagate rapidly and invade the roots, which weakens the root absorption function and leads to the yellowing of seedlings.

Countermeasures: cultivate strong seedlings and increase the sugar content of seedlings at three-leaf stage; Dixong has a special effect on Pythium, promotes the root development of seedlings, and has a good rescue effect on etiolated seedlings. When the seedlings are of one leaf, spray with 700 times of dimethazone, spray wine with 300 to 500 times of liquid during rescue, and do not water within 3 days after spraying.