Effect of alkali and canal waters in cyclic and blended mode on potato (Solanum tuberosum)-sunflower (Helianthus annuus)-sesbania (Sesbania sesban) cropping sequence

Response of potato (Solanum tuberosum L.)-sunflower (Helianthus annuus L.)-sesbania [Sesbania sesban (L.) Merr.] cropping sequence to conjunctive use of good quality canal water [EC_CW 1.1 dS/m, residual sodium carbonate (RSC) nil, sodium adsorption ratio (SAR) 1.7] and alkali water (EC_AW 3.8 dS/m, RSC 15.5 me/L, SAR 11.8) was evaluated for 6 years (2007–2008 to 2012–2013) on a well-drained sandy-loam soil [ECe 2.3 dS/m, pH 8.1, exchangeable sodium percentage (ESP) 5.5]. Increase in soil pH (8.9–9.1), salinity (3.4–4.7 dS/m) and sodicity (ESP 24.1–39.5) as a consequence of irrigation with alkali water affected the growth and yields of all the crops. When averaged for 6 years, the relative yields ranged between 48 and 78% for potato and 55 and 73% for sunflower in case of cyclic use of alkali water compared to canal water. However, the relative yields ranged 58 to 83% for potato and from 52 to 78% for sunflower when alkali water was used in blended mode. Considerable deterioration in the quality of potato in terms of grade, size and keeping quality, and reduction in oil content of sunflower was observed. The change in soil properties in different modes of water application was in accordance with the proportions of alkali water applied. The analysis on use of canal and alkali waters in similar proportion further indicated that cyclic application of canal water during the initial stages would minimize the adverse effects of alkali water.