What is the significance of applying NPK fertilizer in winter?

In winter, the temperature is low and the rainfall is too little. In the application of chemical fertilizers, we should pay attention to the effective selection and suitable application methods of chemical fertilizers in order to give full play to fertility and meet the needs of winter crop growth and development.

Apply base fertilizer in winter. In the working temperature range of 0-32℃, the total amount of fertilizer digested and absorbed by crops is directly proportional to the ground temperature, and the absorption capacity will gradually decrease when it is lower than 0℃ or higher than 32℃. Therefore, when selecting fertilizers, quick-acting fertilizers should be selected for fertilization. Nutrient organic fertilizer can be potassium nitrate, which can dissolve ammonium ions and carbonate positive ions immediately digested and absorbed by crops even below 5℃ after being applied to the soil layer, so potassium nitrate applied at ultra-low temperature in winter and spring can be quickly digested and absorbed by crops.

The test shows that the utilization rate of the filled soil after potassium nitrate furrow application can reach about 54%, and the fertility can be brought into full play quickly. However, urea is a fluorophenyl fertilizer, which can not be digested and absorbed immediately after being applied to the soil layer, and can only be digested and absorbed after being converted into ammonium nitrogen, and the conversion speed is endangered by temperature. When the local temperature is 10℃, urea conversion must take 7- 10 days, and with the decrease of temperature, the longer it takes to convert urea. Therefore, the actual effect of applying urea in winter and early spring is not as good as that of potassium nitrate.

Apply phosphorus and potassium fertilizer in winter. It is best to use calcium superphosphate and apply phosphorus and potassium fertilizer in winter. Calcium superphosphate contains 14%-20% phosphorus pentoxide, of which 80%-95% is soluble phosphorus with strong electrolyte, and its fertility is faster than that of calcium magnesium phosphate. Calcium superphosphate should be applied to wheat, rape, cowpea and green manure crops in winter, in which soluble available phosphorus can be quickly digested, absorbed and utilized by crops to improve the drought resistance of winter crops. If superphosphate and organic fertilizer are applied in heaps, the contact between phosphorus and potassium fertilizer and soil environment can be reduced.

Reduce the fixation of phosphorus and improve the efficiency of phosphorus application. It is important to note that calcium superphosphate cannot be applied to winter crops with tap water. This is because when running water is used, it will stay on the ground and be immobilized with calcium, magnesium, iron and aluminum in the soil environment, and it will be transformed into water-insoluble sediment, which cannot be digested and absorbed by crops, so that the water-soluble phosphorus and potassium fertilizer will be immobilized by organic chemistry and the fertility will be greatly reduced.

Apply potash fertilizer in winter. Potassium chloride can be used as potassium fertilizer in winter (but ammonium sulfate should be used in the second half of chlorine-free crops such as tomatoes and potatoes), and 45% ternary compound fertilizer can be used as compound fertilizer. To apply potassium fertilizer in greenhouse in winter, potassium-containing plant ash can be used as root fertilizer, with plant ash 15-20KG per mu and cold water 50KG, and the leaves are soaked and filtered and then sprayed with soil solution. Or applying plant ash to rows of vegetables and fruits in the greenhouse can not only supplement potassium, but also absorb water to reduce the environmental humidity in the plastic greenhouse and prevent diseases.

When the temperature is low in winter, organic fertilizers such as compost, river mud, farm manure and human and animal manure can be selected as wax fertilizers, which can increase the soil temperature. When the temperature is high, apply potassium nitrate, ammonium chloride, etc. Cooperate with each other in sunny days to ensure the coordinated application of organic fertilizers. If peanut bran is used as wax fertilizer, it is appropriate to apply 40-50 kg per mu. In case of winter drought, water and fertilizer regulation should be combined with drought-tolerant irrigation, and the actual effect is stronger.