Management of salinity stress in tomato (Solanum lycopersicum L.) through zinc nutrition

Soil salinity is an essential threat to the productivity and quality of vegetable crops. Tomatoes are the major vegetable, and their response to salinity and salinity management strategies has been widely studied. However, the studies evaluating alleviation strategies at the field level are meagre. A field experiment was conducted to research zinc nutrition's effect on salinity stress alleviation in two tomato cultivars. The experiment consisted of two cultivars (PKM 1 and Sivam) and four levels of zinc application as ZnSO4(0, 25, 50 and 75 kg ha-1) with three replications. The growth, yield, physiological and biochemical parameters were recorded during harvest. Results showed that among the cultivars, Sivam recorded the higher plant height (87.9 cm), number of branches (11.2), dry-matter production (139.6 g plant-1), number of fruits (85.1) and fruit yield (83.2 t ha-1). Growth trends and yield attributes were observed under salinity stress with increasing zinc application levels. The highest fruit yield was recorded in Sivam and PKM 1 with ZnSO4application at the rate of 75 kg ha-1. Applying ZnSO4 at the rate of 75 kg ha-1 recorded higher fruit yields of 33.7 and 92.8 t ha-1in cultivars PKM 1 and Sivam, respectively. The percent increase in yield in cultivar PKM 1 and Sivam over control was 27.1 and 27.8, respectively. Nutrient availability and uptake increased with ZnSO4 application and was the highest at 75 kg ha-1. Physiological parameters viz. leaf area, specific leaf area, total chlorophyll content, membrane stability index, and chlorophyll stability index were improved with ZnSO4 application. Proline content was not affected by the ZnSO4 application. The activity of catalase and superoxide dismutase was increased by applying ZnSO4. The correlation of ZnSO4application with the growth, yield, physiological and biochemical parameters shows that zinc sulphate application positively affects all the factors affected by soil salinity. Hence, applying ZnSO4 at the rate of 75 kg ha-1can be compulsorily recommended for tomato growers of the region to overcome zinc deficiency and boost the fruityield under saline conditions.