Foliar uptake of sodium and chloride in barley sprinkler-irrigated with saline water : effect of pre-irrigation with fresh water

Abstract

Crops that are sprinkler irrigated with saline water often suffer greater yield losses than when they are irrigated by soil surface methods, because harmful levels of salts are directly absorbed through the wetted leaves. We investigated whether salt damage to barley, sprinkler irrigated with saline water, was minimized with a short pre-irrigation with fresh water.A triple line-source sprinkler system was used to test the influence of three irrigation treatments on harvested grain yield, leaf water content and Cl and Na concentrations of barley sampled at two different dates. These treatments were compared at five levels of applied water salinity and consisted of : (i) RO (root salt absorption only) : plants were covered to avoid salt spray on leaves and saline water was applied directly to the soil ; (ii) PREW (pre-washing with fresh water) : plants were pre-irrigated for 3 min with fresh water in addition to the regular 30 min irrigation with saline sprinkler water plus the 3 min post-washing with fresh water ; (iii) NOPREW (no pre-washing with fresh water), where the 3 min pre-irrigation was not applied.Exposure to saline spray plus soil salinity (PREW and NOPREW treatments) decreased grain yields more than soil salinity only (RO treatment). Increased salinity decreased grain yields substantially less in the PREW treatment than in the NOPREW treatment. The EC of the applied water that reduced grain yield by 50 per cent was 12.9 dS m-' in the PREW treatment and 10.8 dS m−1 in the NOPREW treatment. Differences in grain yield were associated with lower concentrations of foliar salt in leaves from the PREW treatment. The first several minutes of sprinkler irrigation are, therefore, critical in the foliar absorption of salts. Cl and Na accumulated in the leaves in the same proportion in the first sampling of 16 April, but plants absorbed Cl more readily than Na in the second sampling of 29 May. This preferential accumulation of Cl was greater in the RO treatment, indicating that roots absorbed Cl more readily than did leaves, in comparison with Na absorption.These results have important implications in the management of overhead sprinkler irrigation, since short pre-irrigations with good quality water may substantially reduce the adverse effects of saline sprinkling water.