Water Management in Horticultural Crops

Root characteristics

• Root systems in the field are seldom uniform with depth. Root penetration is seriously affected by a hard pan or compacted layer in the soil profile. In a shallow soil, roots may be confined to a thin layer of soil irrespective of their usual pattern. Similarly, high water table limits normal root growth. Crops with extensive and dense roots can utilize soil moisture more effectively and lower residual soil moisture than crops with sparse and shallow roots.
• Rooting depth of annual field crops on deep well drained soils range from 0.30 to 2.0 m. In general, the root zone depth of crops on clayey soils is reduced by 2.5 to 35 per cent and on sandy soils increased by 2.5 to 35 per cent.
Table 2.Rooting depths (m) of annual crops on deep well drained soils
Shallow		Medium		Deep
Onion	0.3 - 0.5	Chillies	0.6 – 0.9	Maize	1.0 – 1.6
Cabbage	0.4 - 0.5	Peas	0.6 – 1.0	Soybean	1.0 – 1.5
Cauliflower	0.3 - 0.5	Tomato	0.7 – 1.5
Potatoes	0.4 – 0.6


• The soil depth from which the crop extracts most of the water needed to meet its evapo-transpiration requirements is known as effective root zone depth(table 2.). It is also called as design moisture extraction depth, the soil depth used to determine irrigation water requirements for design. It is the soil depth in which optimum available soil moisture level must be maintained for high productivity of crops. If two or more crops with different rooting characteristics are to be grown together, the design depth should be that of the crop having the shallower root system.