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Benefits of Potassium for Corn Production

October 12, 2020

Potassium is a macronutrient for corn as the plant takes up large amounts throughout the growing season.  While potassium is not used by pant as a building block for organic compounds, it functions as an activator for many enzymes and metabolic pathways, including those for photosynthesis and protein and starch formation in grain.  Potassium plays a role in the flow of water, nutrients, and carbohydrates within the plant.  It plays a role in the regulation of stomata closing and opening, thus impacting the exchange of water and gases.  Additionally, potassium is key for cell wall strength and cellulose production.  Good potassium fertility is associated with strong cell walls that enhance disease resistance and the ability of the crop to maintain firm, healthy stalks.

As corn production levels increase, balancing the nitrogen level with the level of potassium is important for managing disease occurrence and stalk strength.  When potassium is limiting, the plant will be limited on the amount of nitrogen it can absorb from the soil, thus impacting stalk strength, disease tolerance, and grain yield.

Potassium is considered an immobile nutrient in the soil but is very mobile within the plant.  Potassium that occurs naturally in the soil is, for the most part, unavailable to the plant as it is primarily found in minerals, such as mica, and only becomes available when the mineral degrades.  Corn residue contains a substantial amount of the potassium taken up by the plant during the growing season, over 60%.  A 200 bu/acre corn yield will take up 266 lb. of K2O from the soil; however, only 50 lb./acre of K2O will be removed with the grain component.

Factors that impact potassium uptake include:
  1.  Soil moisture; with increasing soil moisture, potassium availability and movement in the soil increases, as well as plant uptake.  Response to potassium applications is usually higher in dry years.
  2. Soil compaction can decrease the oxygen availability to roots, which will reduce potassium uptake.  While an increase in soil moisture will increase uptake of potassium, a saturated soil will result in decreased uptake as oxygen is depleted.  Additionally, compacted soils can have restricted root growth, thus reducing potassium uptake.  Sidewall compaction can directly impact potassium uptake by limiting root growth.
  3. Root stress can limit potassium uptake to the point of the plant showing deficiency symptoms, even when soil potassium is adequate.  Root stress caused by dry soils, pruned roots, low soil temperature, and compacted soils can contribute to potassium deficiency in the presence of adequate potassium levels.  The symptoms of potassium deficiency usually do not become visible until the V6 growth stage, about 6 weeks after planting, as the coincides with accelerated potassium uptake.  If the plant is under root stress, the symptoms become more obvious at this time.
  4. The tillage system can impact soil potassium availability, but the impact has not ben shown to be consistent.  Though reduced tillage systems, such as no-till and ridge till, can have lower soil potassium availability than conventional tilled systems, it may be related to cooler soils in the spring or stratification of potassium in the soil profile.
Posted: 10/12/2020 2:11:28 PM by Rob Matherly | with 0 comments

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