Quality Assessment of Tubewell Water for Irrigation and Impact on Soil and Crops in Central Punjab, Pakistan

Abstract

Aims: The study was conducted to assess the quality of tubewell (TW) waters for irrigation and their effects on soils and crops. Place and Duration of Study: Canal Command Area (CCA) of Chichawatni and Sahiwal tehsils of district Sahiwal, Punjab, Pakistan during 2012 and 2013. Methodology: A total of 529 TW water samples were collected from nine distributaries of Lower Bari Doab Canal (LBDC); four on right side (RD); five on left side (LD).Twenty composite soil samples were collected at plough layer depth (0 to 15 cm) from the selected farmer fields irrigated with TW and canal water (CW). Soils were analysed for pHs, ECe, and water samples were analysed for EC, cations (Ca2++ Mg2+, Na+) and anions (CO32-, HCO3-) and then RSC and SAR were computed. Total dissolved salts (TDS) of TW waters were used to estimate the amount of salts added into soil with the irrigation. The salts addition into soil under different crops was also calculated using the consumptive use by crops. The yield data of crops were recorded from 20 farmer’s fields irrigated with CW and TW waters to evaluate the effects of water quality on the yields. Results: Data based on EC, RSC and SAR values showed that 71% TW waters were saline and >20% samples were sodic in nature. The quality of TW water in RD was comparatively better than in LD due to its location between LBDC and Ravi River. The farmers used poor quality TW waters (TDS from 218 to 3309 mg L-1) that added 0.66 to 10.05 t ha-1 salts into soil with 0.30 m irrigation water. Similarly, 15.75, 27.80, 33.36, 44.48 and 55.99 t ha-1 TDS were deposited in soil by wheat, cotton, potato, spring maize and rice, respectively, irrigated with TW water of TDS 3309 mg L-1. The yields of crops reduced from 3 to 15% where usually TW water was used compared to CW irrigated fields. Conclusion: Results showed that quality of 71% TW waters was not suitable for irrigation purpose due to higher concentration of soluble salts. The concentrations of chemical constituents in water from the LBDC aquifer system vary both depth and location wise. The application of TW irrigation having different salinities added substantial amount of soluble salts into soil that affected the soil quality. Resultantly, the yields of different crops reduced from 3 to 15%. Presently the farmers are using brackish TW water with CW but the continuous use of poor quality irrigation water would have serious consequences for sustainability of soil and crop productivity in the area.