Potassium nutrition of the strawberry plant. Effect of potassium treatment and of the rooting media on components of yield and critical leaf potassium concentrations

Strawberry plants, cv. Cambridge Favourite were grown (a) with 5 different levels of potassium from planting to dormancy, followed by a constant level of K in the flowering and fruiting phase; or (b) with a constant level of K from planting to dormancy, followed by 4 different levels of K during the flowering and fruiting phase. The experiment was carried out in 3 different rooting media—sand, peat and rock wool. Application of K ranging from 0.125 to 2 mEq/litre in the nutrient solution over the period from planting to dormancy had no significant effect on any of the components of yield subsequently measured. Application of K ranging from 0.25 to 2 mEq/litre over the flowering and fruiting period produced significant effects on yield, mainly because of increased flower production. Yields for different rooting media, and even between plants grown in the same medium, varied considerably due to factors other than potassium nutrition, but the leaf potassium concentration at the fruit ripening stage associated with maximum yield of fruit (>7 g per berry) was constant at about 1.2% K, irrespective of the actual yield.