Reducing potassium deficiency by using sodium fertilisation

Abstract

Potassium (K) is the most abundant cation in the vast majority of plants. It is required in large quantities which, in an agronomic context, typically necessitates application of K in the form of potash or other K fertilisers. Recently, the price of K fertiliser has risen dramatically, a situation that is paralleled by increasing K deficiency of soils around the globe. A potential solution to this problem is to reduce crop K fertiliser dependency by replacing it with sodium (Na) fertiliser which carries a much smaller price tag. In this paper we discuss the physiological roles of K and Na and the implications of Na fertilisation for crop cultivation and soil management. By using greenhouse growth assays we show distinct growth promotion after Na fertilisation in wheat, tomato, oilseed and sorghum. Our results also show that up to 60% of tissue K can be substituted by Na without growth penalty. Based on these data, simple economic models suggest that (part) replacement of K fertiliser with Na fertiliser leads to considerable savings.

Keywords: Deficiency; Fertiliser; Nutrient; Potassium; Salinity; Sodium.

Fig. 1

Relative growth rate (RGR) after 4 weeks of treatment with varying levels of K in the presence or absence of Na for wheat, tomato, oilseed, maize, and sorghum. Shown are the means ± SE of six replicates. Stars show significant differences between treatments with and without Na at each level of K as determined using t-tests. * p < 0.05, *** p < 0.001

Fig. 2

Relative growth rate (RGR) after treatment with varying levels of Na for wheat, tomato, oilseed, maize, and sorghum. Plants were harvested after 6 weeks of treatment (4 weeks for oilseed). Plants were grown with 0.02 mM K (0.2 mM for wheat). Shown are the means ± SE of three replicates. Different letters represent statistically different results (p < 0.05) between treatments as determined by one-way ANOVA followed by Tukey’s post-hoc test

Fig. 3

Tissue K and Na content of wheat, oilseed, sorghum, and tomato grown at different levels of K and Na. Shown are the means ± SE of three biological replicates per species. Different letters represent statistically different results (p < 0.05) between treatments as determined by two-way ANOVA followed by Tukey’s post-hoc test