SOIL POTASSIUM AND SODIUM, PHYSIOLOGICAL RESPONSES AND YIELDS OF TOMATO AS AFFECTED BY POTASSIUM FELDSPAR IN SOIL CULTURE

Abstract

To assess an alternative to muriate of potash, the effects of ground K-feldspar on the growth and productivity of tomato were investigated under greenhouse conditions at the University of Newcastle, U. K between October 2008 and March 2009. Potassium feldspar was applied at 0, 64, 128, 192 and 256 mg kg-l soil, arranged in a completely randomized design and replicated five times. Soil properties were determined before and after harvest of fruits. Plant physiological parameters, namely, leaf instantaneous water use efficiency (WUEi), photosynthetic rate, transpiration and stomatal conductance were also determined using non- destructive methods. Total and marketable tomato fresh fruit yields were evaluated along with average fruit weight. The results showed that WUEi, photosynthetic rate and transpiration decreased during vegetative growth and at the on-set of fruit formation but increased significantly (p < 0.05) at the peak of fruit setting. Overall, the application of K-feldspar increased the physiological factors but the means were not significantly different (p < 0.05). The exception was leaf stomatal conductance that decreased significantly at 256 mg kg-1 soil, compared with the control treatment. Average fruit weight was significantly (p < 0.05) increased at the application of 64 mg kg-I soil compared with the control and the higher rates of K. Instantaneous water use efficiency was highly positively correlated with soil exchangeable-K (r = 0.90**) but negatively correlated with soil exchangeable-Na (r = -0.62 *). Photosynthetic rate was positively correlated with transpiration (r = 0.49 *), stomatal conductance (r = 0.48 *) and average fruit weight (r = 0.68*). It was concluded that ground potassium feldspar is a potential fertilizer for tomato but there is the need for further studies under field conditions