Separate and Combined Effects of Silicon and Potassium on Growth and Nitrogen Uptake in Okra Plants as Influenced by Salinity of Irrigation Water

The aim of this pot experiment was to determine the impact of foliar spraying of silicic acid (Si) with or without potassium fertilizer amendment (K) on dry matter (DM), nitrogen uptake (TN), efficient use of N fertilizer (NUE) and pod yield of okra plants (Abelmoschus esculentus L.) as influenced by salinity in the irrigation water (Salt) using 15N isotope. Results showed that salt stress reduced growth and N uptake by okra plants. Si and/or K applications could reduce the negative effect of salinity to a certain extent depending on the way and the type of applied materials (i.e., separate or combined applications of Si and K). Solely Si application improved okra (DM) and N-nutrition (TN and NUE) under both saline (Salt+) and non-saline conditions (Salt-). This improvement was more pronounced in the former than the latter. However, Si+ did not have significant effect on DM and fresh weights of pods as compared with the control (Si-). Solely applied K fertilizer increased the growth, N uptake and ultimately pod yields. Moreover, the combined use of Si and K could significantly enhance total DM(TDM), TN, amounts of N derived from fertilizer (Ndff), soil (Ndfs) and %NUE in the entire okra plants as well as pod yield. In conclusion, solely applied K or in combination with Si could be considered as an effective agricultural practice to reduce salt stress in okra plants and increase the growth and ultimately pod yields.