Potassium-salinity interactions in irrigated corn

Abstract

Potassium uptake by plants can be affected by high salinity and the Na concentration in the soil solution. There is abundant evidence that Na and the Na/Ca ratio affects K uptake and accumulation within plant cells and organs and that salt tolerance is correlated with selectivity for K uptake over Na. This provides the basis for hypothesis which exists in the literature and was examined in this study, that K application can reduce salinity damage to plants. The main objectives of this study were to: (i) study the effects of salinity and K fertilization interactions on corn yield and nutrient uptake; (ii) test the possibility that salinity damage can be reduced by elevating K fertilization rate; and (iii) study K dynamics in soil as a function of the salinity of the irrigation water, in soils with high and low indigenous potassium. The response of corn (Zea mays (L.) cv. ‘Jubilee’) to K fertilization under saline and non-saline conditions was studied by growing corn in two soil types in a pot experiment. Rates of K application to a 3 kg pot were: 0, 15 and 30 mmol K to the Gilat soil and 7.5, 15 and 30 mmol K to the Nordiya soil as KCl. The desired quantity of K was applied in one dose after seedling emergence. The salinity levels of the irrigation water were 4, 20 and 40 mmol charge 1−1. The irrigation was applied at least every second day and in excess to avoid water stress and to ensure drainage. Increased salinity in the irrigation water significantly decreased yield in both soils. Potassium significantly increased yield at all salinity levels only in the sandy soil which had a low natural level of K, but there was no difference in the relative yield decrease with salinity increase between the lowest and highest K application rates. Potassium fertilization did not eliminate the deleterious effects of salinity on corn yield despite its beneficial effect of increasing K content and reducing the Na∶K ratio in plant tissue. Potassium uptake by plants was the major factor in K dynamic processes. Potassium adsorption, release and fixation were secondary factors while leaching was an insignificant factor in overall K balance under cropping conditions.