(a) Explain the term 'conjunctive use of water'. Suggest the management practices to improve poor quality irrigation water with…

Conjunctive Use and Salinity Management

Conjunctive use of water refers to the planned, coordinated exploitation of surface and groundwater reservoirs to optimize water supply, mitigate seasonal deficits, and prevent hydrologic imbalances like waterlogging and salinization. Irrigation water quality deteriorates due to high Electrical Conductivity (EC, causing osmotic stress and physiological drought), high Sodium Adsorption Ratio (SAR, causing soil dispersion and crusting), and elevated Residual Sodium Carbonate (RSC, precipitating calcium and raising pH).

Managing such poor-quality water relies on systematic dilution and amelioration:

• Blending saline groundwater with canal water reduces total EC and SAR before application, whereas cyclic use deploys good-quality canal water during sensitive germination stages and poorer water during later vegetative phases.
• Leaching requirement (LR) must be satisfied through calculated over-irrigation to flush salts below the root zone, complemented by organic mulching to arrest capillary rise and evaporative salt deposition.
• Amelioration of high RSC/sodic water requires gypsum application to substitute exchangeable sodium with calcium, combined with organic amendments (FYM, pressmud) to improve soil aggregation.
• High-frequency drip irrigation maintains high matric potential, diluting soil solution salts, while subsurface drainage and cultivating salt-tolerant cultivars (e.g., KRL-210 wheat, CSR mustard developed by ICAR-CSSRI) ensure sustained crop productivity.

Waterlogging: Causes and Mitigation

Waterlogging occurs when the groundwater table rises into the crop root zone, saturating soil pores, driving out oxygen, and inducing root asphyxiation and denitrification. Natural causes include heavy precipitation, riverine backwater flooding, poor natural gradients, and subsurface impermeable clay or kankar pans. Anthropogenic causes include extensive seepage from unlined canals (as observed in the Indira Gandhi Canal command), over-irrigation, obstruction of natural drainage pathways by infrastructure, and lack of field drainage.

Mitigation strategies combine preventive and curative measures:

• Preventive strategies focus on canal lining to eliminate seepage, adopting precision micro-irrigation to avert deep percolation, and scheduling irrigation based on soil-moisture deficits.
• Curative strategies involve surface drains to evacuate storm runoff and horizontal subsurface drainage (perforated corrugated PVC tile drains) to de-saturate root zones and evacuate saline effluent.
• Vertical drainage through operational tubewells dynamically lowers the water table while yielding water for conjunctive use.
• Bio-drainage utilizes deep-rooted, high-transpiration vegetation (e.g., Eucalyptus tereticornis, Casuarina) along canal banks to bio-pump shallow groundwater.

Farm Planning: Necessity and Limitations

Farm planning is an advance operational blueprint that systematically allocates scarce farm resources (land, labour, capital, and water) across enterprises. It is necessary to optimize input-use efficiency, minimize climatic and market risks through enterprise diversification, ensure sustainable land intensification, and align cropping patterns with agro-ecological capacity and local water availability.

However, farm planning in India is constrained by:

• Structural constraints, primarily severe land fragmentation and shrinking operational holdings (averaging ~1.08 ha), which restrict scale economies.
• Resource and capital limitations that impede investment in modern micro-irrigation and tile drainage infrastructure.
• Environmental and market uncertainties, including erratic monsoon patterns and farm-gate price volatility, which disrupt predetermined enterprise plans.
• Inadequate access to reliable, real-time agro-meteorological forecasts and customized farm-level extension advisory.

Integrating farm-level planning with regional conjunctive water use and drainage management provides the necessary operational pathway for climate-resilient agriculture in degraded canal commands.