Why can't potassium fertilizer be replaced by organic fertilizer or compound fertilizer?
In field crop production, excessive application of potassium fertilizer is generally rare, while potassium deficiency in crops is everywhere. In recent years, farmers have gradually come to recognize the role of potassium fertilizer, but some misconceptions remain: first, the belief that once organic fertilizer is applied, potassium fertilizer is no longer needed; second, the reluctance to apply potassium fertilizer after applying compound fertilizer...
In field crop production, excessive application of potassium fertilizer is generally rare, while potassium deficiency in crops is everywhere. In recent years, farmers have gradually come to recognize the role of potassium fertilizer, but some misconceptions remain: first, the belief that once organic fertilizer is applied, potassium fertilizer is no longer needed; second, the reluctance to apply potassium fertilizer after applying compound fertilizer; third, treating biological organic compound fertilizer as a complete-element fertilizer and therefore not wanting to apply potassium fertilizer separately. As a result, crops suffer yield reductions due to insufficient potassium fertilizer, and in some cases the reduction is quite large.
Among the main crops: potassium-deficient rice has leaves that turn from dark green to bronze, upright young leaves, scorched leaf margins on old leaves, stems that lodge and break easily, a high rate of empty and shriveled grains, and susceptibility to brown spot and sheath blight. Potassium-deficient wheat shows old leaf tips and margins gradually scorching yellow, with thin, lodging-prone stems. Potassium-deficient corn shows yellowing young leaves and small, lodging-prone plants. Potassium-deficient peanuts show pale green leaves with scorched margins and inhibited growth. Potassium-deficient cotton shows yellow-white patches on the leaves, brown spots at leaf tips and margins that curl downward, smaller bolls, and poor boll opening. It is clear that potassium fertilizer is crucial in agricultural production.
At present, some farmers still have certain misunderstandings about potassium fertilizer inputs: first, they believe organic fertilizer contains enough potassium; second, they say compound fertilizer already contains potassium, so no additional potassium application is needed. On the other hand, some farmers feel that potassium fertilizer prices have risen too fast in recent years and that investing more is not worthwhile. These misunderstandings hinder the rational application of potassium fertilizer.
According to available scientific and technical data, among organic fertilizers, the potassium oxide content of human excrement and urine is 0.2%-0.3%, that of pig manure is 0.44%, that of cow manure is 0.15%, that of chicken manure is 0.9%, and that of duck manure is 0.6%. In air-dried crop straw, the potassium oxide content is generally about 1%, with the highest being corn stalks at 2.28% and the lowest being barley husks at 0.28%. In high-content compound chemical fertilizers, the potassium oxide content is 15%-16%, equivalent to 12.5-13.45 kg of potassium chloride or potassium sulfate.
In terms of the potassium requirements of field crops, generally 15-20 kg of potassium chloride or potassium sulfate should be applied per mu. For insect-resistant cotton, the potassium requirement is even greater, and no less than 25-30 kg per mu should be applied.
A comprehensive analysis of the above data shows that although organic fertilizers play a very important role in improving farmland soil properties and building soil fertility, their potassium content is limited. In high-content compound chemical fertilizers, the proportion of potassium is still somewhat short of crop potassium requirements. Therefore, in guiding agricultural production, potassium fertilizer must be supplemented in a timely manner according to the potassium requirements of different crops, supplementing exactly as much as is lacking. Organic fertilizer and compound fertilizer cannot be used to replace potassium fertilizer.