There are many benefits of topdressing fertilizer outside the roots of crops, such as fast fertilizer efficiency, high utilization rate, easy application, significant effect, and fertilizer saving. It is a common application method for everyone, but extra-root fertilization is also skillful, so how can we carry out effective extra-root fertilization?
1. According to the characteristics of fertilizers, select the appropriate type.
Fertilizers with good effect for extra-root fertilization include urea, potassium dihydrogen phosphate, potassium nitrate, potassium sulfate, and ammonium sulfate. Leachate of superphosphate and plant ash, ammonium metaphosphate and most trace element fertilizers, etc. Some highly volatile fertilizers such as ammonia, ammonium bicarbonate, and chloride ion-containing fertilizers such as ammonium chloride, potassium chloride, etc., are not suitable for extra-root fertilization, because some of them cause large fertilizer losses, and some Have an adverse effect.
Second, choose the appropriate amount and concentration of fertilizer solution.
The appropriate concentration of extra-crop fertilization is generally: urea 1-2%, potassium dihydrogen phosphate 0.3-0.5%, calcium superphosphate leachate 3-5%, ammonium molybdate 0.01-0.1%, ammonium metaphosphate 2-3%, Borax 0.1-0.2%, zinc sulfate 1%, 50-60 kg of fertilizer solution per acre, cotton, rape, beans, vegetables and other dicotyledonous crops, large leaf area, thin cuticle, nutrients in solution Absorb, so the concentration of fertilizer spray solution for such crops should be appropriately lower; the leaf area of monocotyledonous crops such as rice, wheat, and corn is relatively small, the level of silicification of the leaves is high, and the nutrients are difficult to be quickly absorbed by the leaves, so spray fertilizer The concentration of fertilizer solution must be properly increased.
3. Choose the appropriate spraying time.
Many tests have proved that extra-root fertilization is carried out in relatively humid weather, and the leaves are kept moist for 30-60 minutes to obtain better fertilizer efficiency. In order to prolong the moisturizing time of the fertilizer solution on the foliage of the plant as much as possible, the extra-root fertilization should be carried out in the morning and evening when the air is humid or dew. The windless cloudy days can be sprayed all day, but the effect of spraying in the evening. If a small amount of adhesive, such as washing powder, neutral soap, or drug synergist is added to the fertilizer solution, the surface tension of the fertilizer solution can be reduced, the contact area between the fertilizer solution and the leaves can be increased, and the effect of spraying fertilizer can be improved.
4. The selected spraying parts.
The green stems and leaves of crops are a reasonable part of spraying fertilizers, especially the green functional leaves that are young and vigorous, and have a fertilizing effect. It is worth noting that in the epidermal tissue on the front of the leaves of dicotyledonous crops, there is a layer of tightly arranged palisade tissue with small cell gaps. The nutrients in the fertilizer solution are difficult to penetrate through the "blockade"; however, the back of the leaves is different. The epidermal tissues are all loosely arranged sponge tissues with large cell gaps. The nutrients in the fertilizer solution are easier to enter and be trapped Quickly absorbed. Therefore, when fertilizing dicotyledonous crops, the front and back of the leaves should be evenly sprayed, and monocotyledonous crops only need to spray the fertilizer solution from the top to the front of the leaves.
5. Determine the number of fertilizer spraying.
According to relevant test reports, nitrogen and potassium fertilizers are highly mobile in crops, so spraying once is the most critical period of crop growth; phosphate fertilizer is less mobile than nitrogen and potassium fertilizers, and must be sprayed continuously according to the growth of the crop. 1-2 times; zinc, molybdenum, manganese, copper fertilizer, and non-moving boron, calcium and other micro-fertilizers that only partially move in the crop body should generally be sprayed continuously for 2-3 times.