Potassium is the most overlooked nutrient for fruit production -- Dr. Thomas Ruehr, Plant Sciences, Cal Poly San Luis Obispo.
 
Each of these supplements have been listed by their manufacturer as meeting the requirements for Califonia Certified Organic Farming -- the strictest requirements in the U.S.

Citra Grow nutrients are chelated with organic citric acid (tricarboxylic acid), a substance manufactured by plants. The entire product -- chelation and nutrient are utilized by the plant. Tricarboxylic acid plays a major role in detoxification of the plant root system and provides carbon for ammonium assimilation in roots and synthesis of amino acids. pH nuetral, for foliar or soil application.   Meets the requirements for California Certified Organic farming.

Price, 1 Quart bottle: $4.50      Price, 2.5 Gallon jug: $28.50

Source of natural potash, sulfur, and magnesium. This mineral (Langbeinite) is mined directly from the ground and mechanically sorted for purity.   Contains 0% Nitrogen, 0% Phosphate, and 22% Potash.   Meets the requirements for California Certified Organic farming.

Price, 4 lb box: $4.00      Price, 15 lb bag: $13.50