ARS | Publication request: POTASSIUM MANAGEMENT FOR OPTIMIZING CITRUS PRODUCTION AND QUALITY

Submitted to: International Journal of Fruit Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2006
Publication Date: July 1, 2006
Citation: Alva, A.K., Mattos, Jr, D., Paramasivam, S., Patil, B., Dou, H., Sajwan, K.S. 2006. Potassium management for optimizing citrus production and quality. International Journal of Fruit Science. 6: 3-43, 2006.

Interpretive Summary: Potassium is an important essential element for plant growth and production, and is required in large quantities, next only to that of nitrogen. Potassium is a highly mobile element in the soil as well as in the plants. Potassium fertilization plays an important role for sustainable citrus production worldwide. Fruit quality is more sensitive to potassium fertilization compared with tree growth and/or leaf nutritional status. Quality of fruit destined for the fresh fruit market is judged by the fruit size, peel thickness as well as peel texture. Deficiency of potassium leads to production of small fruit with thin peel, while high potassium availability results in large fruit with thick and coarse peel. With regard to juice quality, high potassium availability results in high juice acidity. Careful management of potassium fertilization is important for optimizing fruit as well as juice quality.

Technical Abstract: Potassium (K) is highly mobile in plants at all levels, i.e. from individual cell to xylem and phloem transport. This cation plays a major role in: (i) enzyme activation; (ii) protein synthesis; (iii) stomatal function; (iv) stabilization of internal pH; (v) photosynthesis; (vi) turgor related processes; and (vii) transport of metabolites. Citrus trees generally do not show visible deficiency symptoms across a wide range of K status in the leaves, except when the leaf concentrations drop below 3 to 4 mg/kg. However, fruit quality is quite sensitive to varying levels of K availability. High levels of K cause large fruit size with thick and coarse peel. In contrast, K deficiency produces smaller fruits with thin peel. With regard to juice properties, K nutrition has a significant role in juice acidity; i.e. high juice acidity with high K availability, while low K availability causes decrease in juice acidity. High K availability in the soil can reduce the uptake of other cations, primarily magnesium, calcium, and ammonium_N. In this paper, the available information on the effects of varying availability of K on the fruit yield, postharvest quality of fruit, as well as juice quality is summarized. The current recommendations on the application of soil and leaf analysis for evaluation of the K nutritional status, and guidelines for K fertilization are also discussed.