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Title: What are the unique attributes of potassium that challenge existing nutrient uptake models?

item Kovar, John
item BROUDER, SYLVIE - Purdue University

Submitted to: Meeting Proceedings
Publication Type: Research Technical Update
Publication Acceptance Date: 1/26/2015
Publication Date: 3/1/2015
Citation: Kovar, J.L., Brouder, S.M. 2015. What are the unique attributes of potassium that challenge existing nutrient uptake models? In: Murrell, T.S., editors. Frontiers in Potassium Science Workshop Proceedings. ISSPA, January 26-30, 2015, Kona, HI. Available:$FILE/K%20Frontiers%20Summary.pdf.

Interpretive Summary:

Technical Abstract: Soil potassium (K) availability and acquisition by plant root systems are controlled by complex, interacting processes that make it difficult to assess their individual impacts on crop growth. Mechanistic, mathematical models provide an important tool to enhance understanding of these processes, and can enable better management of crop K nutrition. Current mechanistic models describe soil K supply by mass flow and diffusion to root surfaces. Root surface absorption of K follows Michaelis-Menten kinetics. Root growth rate is considered; however, model calculations have generally been based on a single, cylindrical root, rather than a three dimensional root system. Recent advances have allowed for consideration of water and nutrient uptake by root hairs and mycorrhizal hyphae. Under controlled conditions, existing models can adequately calculate K uptake by growing roots. Problems generally arise when a biotic or abiotic process affects root system function, thus violating the assumptions built into the models. For example, research suggests that root exudates can mobilize soil K or influence release of non-exchangeable K. Upscaling from a single root to whole-plant or field scales also presents problems. Roots do not grow uniformly in soil, and water and K are not distributed evenly in the soil profile. Further, many functions of K within plant tissues and organs are at least partially substitutable. Potassium has a predominant role in osmoregulation and in maintaining cation-anion balance within cytoplasm, and these functions can be partially replaced by other cations and/or organic compounds. Such substitutions pose significant challenges to mechanistic representation of plant demand. As demand for food, feed, and fiber increase, and climate change affects productivity, improved understanding of crop K nutrition becomes more important. Quantitative mechanistic models can help us advance, but upscaling from a single root to full-season crop growth requires thoughtful adaptation of existing crop growth and nutrient uptake models.