Corn with potassium deficiency loses water and wilts; applying potassium fertilizer can ensure high yield

Corn fertilization

    As yield increases, potassium requirement rises. With the improvement of corn yield levels, the supply of available soil potassium during key growth stages must increase accordingly. Results from many long-term positioning trials on corn have proven that when yield increases by 10%-20%, potassium uptake also increases correspondingly. Appropriately raising the potassium content in corn tissue is necessary to maintain stable high yields. In the northern spring corn region, although soil available potassium content is at a relatively high level (such as 70-130 mg/kg), applying potassium fertilizer still has a yield-increasing effect. Especially in some soils with medium available potassium content and limited slow-release potassium capacity, additional potassium fertilizer should be considered for high-yield fields. Therefore, when using yield targets as the main basis for potassium recommendation, attention must be paid both to the necessity of applying more potassium fertilizer on soils with low available potassium to ensure high yield, and to the fact that even on some soils with medium available potassium levels, applying an appropriate amount of potassium fertilizer also produces good results.

    As planting density increases, potassium requirement rises. In current high-yield cultivation of hybrid corn, yield is often greatly increased by increasing density, and at the same time the potassium uptake of high-density plants from farmland also increases significantly. Therefore, when density increases, if potassium fertilizer is not applied correspondingly more or soil potassium availability is not improved, the crop will struggle to obtain sufficient potassium, and yield may decline or fail to reach the ideal level. However, after applying 5-6 kg/mu of potassium fertilizer, yield does not drop but instead increases somewhat. This is especially true for corn plots with low available potassium content and irrigation conditions. Therefore, when recommending fertilization for corn, in order to adapt to higher density and yield levels, the potassium application rate should be appropriately increased above the conventional amount.

    Nitrogen-potassium balance, potassium requirement rises. In dense-planting high-yield corn cultivation, coordinating the balanced supply of potassium and nitrogen fertilizer is crucial. Normally, to achieve high-yield goals, excessive nitrogen is applied, which increases the infection rate of plant diseases and pests such as stalk rot, root rot, and bacterial wilt. If potassium supply is not increased accordingly, symptoms of nitrogen-potassium imbalance will develop. Potassium deficiency first weakens the breaking strength and epidermal thickness of corn stalks and leaves, which both increases the possibility of lodging and raises corn's sensitivity to pests and diseases. As is well known, among nutrient elements, both nitrogen and potassium have a major influence on corn disease resistance, but their directions of action differ: excessive nitrogen tends to increase corn's sensitivity to diseases, while potassium acts in the opposite way, increasing crop disease resistance.

    So, how should potassium deficiency in the field be diagnosed? How should potassium be supplemented when deficient?

    When spring corn enters the jointing stage, the growth period from the small funnel stage to the large funnel stage is its rapid growth period, and its demand for nitrogen, phosphorus, and potassium all increases. In actual production, it is usually customary to apply only nitrogen fertilizer as a top dressing without paying attention to potassium top dressing. But in high-yield dense-planting cultivation of spring corn, whether top dressing is actually needed can be answered simply by asking the corn growing in the field and observing the plant growth conditions. That is, often around nine or ten in the morning, go to the corn field to look, especially on windy days. If you see spring corn leaves already wilting in the morning, then it is telling you "I am deficient in potassium." Because for farmland that generally does not urgently need irrigation, normal healthy corn plants will not show leaf wilting in the morning; wilting after noon is normal. This is because potassium can affect the closing of leaf stomata and increase the plant's water-retention function. When potassium is deficient, stomatal resistance is high and the stomata cannot close normally, causing severe water loss in the corn plant and the appearance of wilting. At this time, potassium fertilizer must be applied as a top dressing to remedy the situation. The most feasible measure is to apply 5-8 kg of potassium chloride as a top dressing, by furrow application or hole application, then cover with soil.