Interactive Effects of Irrigation Water Salinity and Soil Fertility on Salinity and Sodicity Build-up in Soil and Yield and Cation Composition of Palmarosa (Cymbopogon martinii) and Lemongrass (Cymbopogon flexuosus)

Interactive effects of irrigation water salinity [0.8 (control), 5.2, 10.4, 14.5 and 18.8 dS m⁻¹) and soil fertility (a recommended and an increased fertility level) on the salinity and sodicity build-up in soils and yield and cation composition of palmarosa (Cymbopogon martinii) and lemongrass (Cymbopogon flexuosus) were studied. The experiment was conducted in the open bottomed reinforced concrete cemented cylindrical barrels embedded in the field and filled with sandy loam soils. The sustained use of saline water increased the pH, EC_e and SAR_e of irrigated soils. The lower value of EC_e and SAR_e and higher value of soil pH in the root zone of irrigated soils was recorded at the end of monsoon season than at the ouset of monsoons. The herb and oil yield of palmarosa significantly decreased at high salinity (EC_iw 18.8 dS m⁻¹) while that of lemongrass consistently decreased with increase in salinity. Increasing soil fertility increased the herb and oil yield of palmarosa but had no effect on lemongrass. The concentration of Na in shoot tissue of palmarosa and lemongrass increased with increase in salinity. Palmarosa had lower concentration of Na and higher capacity to maintain their K and Ca concentrations in the shoot tissues at high salinity than lemongrass. A high accumulation of Na and low concentration of K and Ca in shoot tissues was in accordance with the drastic herb yield reduction in lemongrass under increased salinity stress.