Page 44 - soil-plant-water relationship and water requirement

SOIL-PLANT-WATER RELATIONSHIP AND WATER REQUIREMENT

Recommended MAD values by soil texture for deep rooted crops are:

1. Fine texture (clayey) soils 40%
2. Medium texture (loamy) soils 50%
3. Coarse texture (sandy) soils 60%

4.4 ROOTING DEPTH AND MOISTURE EXTRACTION PATTERNS

The soil is a storehouse for plant nutrients, a biological activity environment, a plant
anchoring, and a water reservoir for plant growth.

The amount of water a soil can store for plant use is determined by its physical
properties. It also determines the frequency of watering and the capacity of the
irrigation system required to enable sustained crop growth and development.

Genetic factors determine the type of root system a plant develops. Some plants grow
deep tap roots, while others develop a large number of shallow lateral roots.

The depth of the soil reservoir that maintains water available to that plant is affected
by the rooting qualities of the plant as well as soil parameters such as compaction layers
and water management.

The distribution of the plant roots determines its moisture extraction pattern.
Figure 4.4-1 shows typical root distribution for several field and vegetable crops.

Figure 4.4-1 Typical water extraction pattern in uniform soil profile

Annual crop rooting depths vary by growth stage and should be considered when
determining the amount of water to be refilled each irrigation. Because all plants have
shallow roots at the beginning of their lives, just light and frequent irrigation is required.

For most plants, the concentration of moisture-absorbing roots is highest at the upper
part of the root zone (usually in the top quarter). The zone with the highest root

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