Water is the life of plant and must be supplied in proper quantity. Most of the soils receive water through the rain also water is added by the way of irrigation from well, tank or canal etc. Too much water may suffocate the plant roots and to little may not be able to sustain the plants. Excess water is (a) harmful to crops and soils, (b) wastage costly input

Normally about 80 p.c.roots of a crop are in the first foot of the soil and the remaining go deeper. With deep rooted crop like cotton, orchard trees their roots deep down and utilize moisture at greater depths. At the field capacity stage, the crop draws water easily from the soil and grows rapidly. The growth progressively decreases as the soil moisture approaches wilting point. It may cause moisture stress, which may encourage root growth. Normally the crop should not be allowed to extract more than 50 p.c. available water otherwise the plants beginning to wilt and their growth is checked. High moisture level develops tenderness in plants. Following harmful effects cause due to excess water-

1. The field will get water logged and the crop cannot get sufficient water and air, as good aeration and warmth in the root zone are essential for proper plant growth.

2. Bacteria that change organic matter into plant foods cannot get necessary air and warm temperature in the soil.

3. Desirable chemical reactions cannot take place and nutrient availability is not easily to the plants.

4. Proper root development and absorption of nutrients is not accelerated.

5. Seed germination is affected due to poor aeration and warm temperature.

6. Plants affected by diseases and pest attack.

Excess water cause water logging conditions, soil may be ill drained and causes following harmful effects.

1. In low lying areas excess water if cannot be carried away as surface runoff causes water logged condition which affects aeration and soil temperature.

2. The fine texture soils due to poor permeability the water cannot move downward fast enough and accumulates on the surface, obstructing aeration. In sandy soil if heavy irrigation is given the water will rapidly percolate down and will be wasted.

3. The water table may be high and the additional water accumulates and chokes the air spaces and saturates the surface and sub-soil.

4. Many toxic salts affecting water absorption by roots and causes damage to crops.

5. Agricultural operation viz. inter cultivation cannot be carried out properly.

6. Weeds, which compete for nutrients, space and light, grow rapidly and interfere, crop growth and cultural operations.

7. Due to excess water structure of soil get affected.

2. Wastage Costly Input

i) Fertilizers loss- Due to excess water, leaching losses of fertilizer namely urea,occur and unavailable to the plants. Also availability of other nutrients affected.

ii) Poor germination- Due to poor aeration and warmth in the soil, seed germination is badly affected and ultimately there is a poor stand of crop.

iii) Effect on irrigation layout- Excess water cause damage to irrigation layouts namely sara, basin, and furrow, which cause flowing of water and required labour to correct the layout.

iv) Effect on cultural operation- Excess water interfere with inter cultivation, field requires frequent weeding as excess water accelerates weed growth. Due to wetting of land harrowing, earthing-up etc.get affected and farm implements turn to wear –tear.

v) Additional cost of labour and plant protection- Due to frequent weeding and damage cause to layout it requires more labour for weeding and correction of irrigation layout. As plants/crop affected due to diseases and attack of pests it add cost of control measure of these diseases and pests.

Thus excess water causes harmful effects on soil and plant and other input it is necessary to apply proper drainage methods and reclamation.

Ag.
Technologies
(Water Mgmt.)