Potassium induced improvement of yield response in barley exposed to soil water stress

Summary

The interaction of different K status of barley plants (Hordeum vulgare, L.) and water stress on yield and water relations was studied. The plants which were cultivated outdoor in pots and supplied with 0.8, 5.0, 8.5 or 12.0 g K per pot, as KCl, were subjected to increased soil water stress during the early grain filling stage.

The water content of the flag leaf tissue was significantly increased from 3.1 to 4.1 g H₂O/g D.M. (dry matter) by K application resulting in maintenance of similar leaf osmotic potentials (−1.5 MPa) at all K levels prior to onset of water stress (Table 2). At the lowest K level Ca contributed essentially to maintenance of the cell osmotic potential (Fig. 2).

In fully watered plants grain yield at the lowest K level was reduced 20% (Fig. 5 a) due to a decrease in the number of tillers with ears per plant (Fig. 5 b) and to early commencement of maturity processes (Table 3).

Water stress caused grain yield reductions between 15 and 50%. However, by increase of K application yield was maintained to the greatest degree in high K plants (Fig. 5 a) due to improved water status in these plants during the drying cycle (Fig. 4). The production of above ground dry matter (top D.M.) during the grain filling period and the grain yield were highly correlated with the leaf water content at the end of the drying cycles (Fig. 6). The greater yield in high K plants was associated with prolongation of the grain filling period by up to 7 days (Table 3) and with an increase in grain weight by up to 20% (Fig. 5 b) as compared with low K plants. “Preanthesis reserves” contributed up to 52% of grain yield at low K levels (Fig. 5 c) reducing differences in grain yield between the K levels.