LEAF ANALYSIS AS AN INDICATOR OF POTASSIUM REQUIREMENT OF CANE FRUITS

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Abstract
The study was made of the value of leaf analyses as compared to that of soil and fruit for indicating K requirements, and with the hope of establishing the normal and critical K level for foliage of certain crop plants. Field plot fertilizer trials were conducted with Cuthbert raspberries, boysenberries, and black raspberries where leaf "scorch" and "crumbly" berries had been observed. Soils used were Powell and Olympic 6ilt loams. Characteristics of the soils were detd., and Neu-bauer tests made on soil samples taken from the fertilizer trial plots and from adjoining fields. Cane fruit leaves and fruits from the 3 exptl. areas were analyzed for K contents. Use of K salts increased available K in soils low in this nutrient; caused increased growth of cover crops; larger cane diam.; increased K in foliage; and was related to larger, firmer berries, and greater yields from black raspberries and boysenberries. The critical level of K in black raspberry and boysenberry leaves was found to be 0.2 and 0.5%, respectively, under conditions for which the leaf composition was studied. Thrifty black raspberry leaves had 0.47, boysenberry leaves 1, and red raspberry leaves 1.2% K. The Neubauer test is longer, yet may give somewhat more consistent indication of K used than leaf analysis. Application of K carriers appears to increase the K content of leaves more than it does that of the fruit.