Common misunderstandings to avoid in foliar feeding
Foliar fertilization, also called foliar spraying, refers to spraying an organic or inorganic nutrient solution that is non-toxic and harmless and contains various nutrients, at a certain dose and concentration, onto the leaves of plants to directly or indirectly supply nutrients; this is called foliar spraying, also known as feeding outside the roots.
Spraying fertilizer on leaves is simple and easy to do, uses little fertilizer, acts quickly, and significantly increases yield. According to statistical analysis, generally on medium-fertility soil, timely spraying of the needed nutrients on crop leaves can increase grain crops by an average of 5-10%, fruit trees by 5-15%, and vegetables by 20-30%. However, in some places, due to misunderstanding or improper application, the effect is poor, or people even fall into misunderstandings, which is not only unfavorable to production but also causes losses.
1. Spraying at will
It is mistakenly believed that foliar fertilizer can be sprayed at any growth stage of the crop. Foliar spraying relies on leaf absorption, which requires the crop to have sufficient leaf area; otherwise the spraying effect is poor and the goal cannot be achieved. Therefore, spraying fertilizer should generally be done in the middle and late stages of crop growth to obtain the greatest benefit from foliar spraying.
2. Using any fertilizer
It is mistakenly believed that any fertilizer can be used for foliar spraying. Actually this is not so. Some highly volatile fertilizers, such as ammonia water and ammonium bicarbonate, release ammonia gas after spraying, which can scorch crops. Another category is fertilizers forbidden for certain crops, such as potassium chloride and calcium chloride, which should not be sprayed on crops such as tobacco.
3. Spraying at any time
It is mistakenly believed that spraying can be done at any time. If there are water droplets or dew on the leaves after rain or in the early morning, it is not suitable to spray fertilizer; otherwise the spray concentration will be reduced, the required concentration will not be reached, and the effect will be poor. Spraying is forbidden at noon on clear days when the sun is blazing, because after spraying the leaves cannot remain moist for a long time, absorption is poor, and utilization rate decreases.
4. Higher concentration means better effect
It is mistakenly believed that the higher the spray concentration, the better the effect. Foliar fertilization only plays a supplementary and regulating role and cannot replace soil fertilization. The fertilization concentration must be strictly controlled. Within the suitable range of use, the spray concentration should generally be low rather than high. However, different crops have different fertilizer tolerance and different requirements; fertilizer types differ, and spray concentrations also vary. Too low a concentration will not achieve the spraying effect; too high a concentration often dehydrates the leaves and causes fertilizer damage. This is one of the keys to success or failure in foliar spraying. For example, when urea is used as a foliar fertilizer, the concentration is generally 0.5%-2.0%; superphosphate is 1%-5%; monopotassium phosphate is 0.2%-0.5%; boric acid is 0.1%-0.5%; ammonium molybdate is 0.02%-0.05%; zinc sulfate is 0.05%-0.2%. At the same time, it is necessary to grasp that the concentration for spraying at the seedling stage should be appropriately lower; the concentration for spraying in the middle and late growth stages can be appropriately higher; when crops are growing normally, the concentration should be lower, and when deficiency symptoms appear, the concentration should be appropriately higher; the concentration for trace element fertilizers should be lower; the concentration for macronutrient fertilizers can be appropriately higher; the concentration for dicotyledonous plants should be appropriately lower; the concentration for monocotyledonous plants can be appropriately higher.
5. Mixing and applying at will
It is wrongly believed that no matter what kind of fertilizer or pesticide it is, it can be mixed and sprayed at will.
6. Increasing the number of sprays
It is wrongly believed that the more times foliar spraying is done, the better. For crops with a short whole growth period, generally spray 1-2 times; for those with a long growth period, spray 2-3 times. According to seedling conditions and soil fertility, 1-2 more sprays may also be appropriate. For continuous spraying within the same growth stage, each interval should be about 10 days. For spraying trace element fertilizers, one spray is enough; if a second spray is desired, the interval should be lengthened.