THE INTERACTION EFFECTS OF POTASSIUM AND DROUGHT IN FIELD-GROWN BARLEY .2. NUTRIENT RELATIONS, TISSUE WATER-CONTENT AND MORPHOLOGICAL DEVELOPMENT

The effect of K supplied at rates of 50 (K-level 1), 125 (K-level 2), and 200 (K-level 3) kg K/ha as KCl on nutrient uptake and concentration, tissue water content and morphological development of field-grown spring barley (Hordeum distichum L. cv. Gunnar) was studied during three growing seasons. Also the interaction of K application and drought during the early grain-filling period was studied. The soil was coarse-textured and low in K content and water holding capacity. Maximum accumulation of K occurred at the end of heading and was 140 to 200 kg/ha at K-level 1 and 210 to 280 kg/ha at K-levels 2 and 3. In the shoot solution, the K concentration increased by increasing K application and varied from 200 to 250 mM in non-maturing plants. The shoot tissue water content also increased by increasing K application and was 5-20% higher at K-level 3 than at K-level 1. At the tillering stage of growth an increasing number of shoots were established by increasing K application. which resulted in a higher number of ears at high K-levels. Differences in the effect of K on shoot initiation were noticed between dry and 'wet' years, as high K application did not increase the number of shoots under the latter conditions. High K application increased the leaf size and the leaf area index (LAI) of the upper leaves, resulting in a larger LAI than at low K application during the grain-filling period and under drought. The specific leaf area (SLA) increased with the level of K application, probably caused by increase of water content and cell size. SLA decreased during a season with high light intensity and increased with low intensity.