Dryland Farming and Rainfed Agriculture

Dryland agriculture refers to cultivation of crops entirely under rainfed conditions without supplemental irrigation. Based on annual precipitation and moisture availability indices, the Government of India and ICAR classify dryland agriculture into three distinct categories:

• Dry Farming: Practiced in areas where annual rainfall is less than 750 mm. Crops often experience severe moisture stress throughout the growing season. No irrigation is available, and moisture conservation practices are mandatory.
• Dryland Farming: Practiced in regions receiving rainfall between 750 mm and 1150 mm. Precipitation is higher than the evapo-transpiration demand during a part of the crop growth period. Short-to-medium duration crops are cultivated with appropriate rainwater harvesting and soil moisture conservation.
• Rainfed Farming: Practiced in areas receiving more than 1150 mm of annual rainfall. Crop production is seldom constrained by soil moisture stress, but excess water removal or drainage management is often critical during heavy monsoon downpours.

Efficient moisture conservation is the cornerstone of successful dryland crop production. Both in-situ and ex-situ techniques are deployed to maximize effective infiltration and minimize surface runoff and evaporation losses.

• Tillage Operations: Summer ploughing immediately after the harvest of the preceding crop opens up hard soils, enhances infiltration, and destroys deep-rooted weed species and insect pupae. Minimum tillage is practiced to preserve soil structure.
• Mulching: Application of organic residues (straw, crop stubbles, husk) or synthetic plastic films on the soil surface significantly reduces soil evaporation, moderates soil temperature, and suppresses weed emergence.
• Contour Bunding and Terracing: Executed across the slope to break the length of the slope, reduce runoff velocity, and promote deep percolation of rainwater into the root zone.
• Antitranspirants: Chemical sprays like reflective types (Kaolin at 3-5%), film-forming types (Hexadecanol, Silicone oils), growth retardants (Cycocel / CCC), and stomatal closing types (Phenyl Mercuric Acetate - PMA) are applied to reduce transpiration losses during prolonged dry spells.

Crop plants growing in dryland regions must possess specific physiological and morphological traits to survive and yield under moisture-deficient environments.

• Drought Avoidance (Escape): Short-duration varieties complete their life cycle before the onset of severe seasonal drought (e.g., pearl millet Pennisetum glaucum and early-maturing pulses like green gram Vigna radiata).
• Drought Tolerance with High Turgor: Plants maintain cell turgor pressure through osmotic adjustment (accumulation of proline, soluble sugars, and potassium ions) enabling continued metabolic functions under low water potentials.
• Drought Resistance (Dehydration Tolerance): Morphological adaptations include thick cuticles, sunken stomata, reduced leaf area, hairy pubescence, and deep root systems capable of exploring moisture from deeper soil strata.

Aberrant weather conditions such as delayed onset of monsoon, early withdrawal, prolonged dry spells, or mid-season droughts require dynamic agronomic interventions.

• Delayed Onset of Monsoon: Shift from long-duration crops to short-duration, drought-tolerant crops or millets (e.g., replacing maize with pearl millet or finger millet). Adjust plant population by widening row spacing or increasing seed rate for higher tillering.
• Mid-season Drought: Implement interculture operations (hoeing and weeding) to create a soil mulch and break capillary pores, spray antitranspirants, or thin out alternate crop rows to conserve moisture for remaining plants.
• Life-saving Irrigation: If farm ponds or harvested rainwater is available, apply light irrigation at critical moisture-sensitive stages such as flowering and grain filling.

A watershed is a geohydrological unit draining to a common point. Watershed management integrates soil and water conservation with crop production, afforestation, pasture development, and livestock management.

• Water Harvesting Structures: Construction of farm ponds, percolation tanks, check dams, and gully plugs to trap runoff water for supplemental irrigation during dry spells.
• Ridge to Valley Approach: Conservation works begin at the ridge of the catchment and proceed systematically downwards to the valley outlet to regulate water velocity and prevent soil erosion.
• Socio-Economic Integration: Community participation, participatory rural appraisal (PRA), and equitable distribution of harvested water ensure long-term sustainability of dryland farming systems.