Soil Moisture Relationships

Water (soil moisture) is the most common limiting factor for better yields in groundnut production. Groundnut crop need 600 to 700 mm of water over the season for a high-yielding crop. This can come from either rain, irrigation or stored soil moisture.
However it is not the total amount of moisture that the crop receives that is most important. Timing of rainfall or irrigation can have a dramatic effect on both crop yield and quality.
There are three important periods for maintaining adequate moisture:

• At planting to encourage germination
• From 50 to 100 days after planting as the pegs enter the soil and the pod begins to develop. Water is most critical at this time.
• Pod filling until maturity of pods.

The water absorbed by the groundnut during the first month after sowing is relatively small. Hence the very early growth phase after seedling emergence is not highly sensitive to moisture stress. The period of 6-8 weeks after sowing when the flowering is vigorous is very sensitive to moisture stress. At the peak of flowering, the root system is less efficient and the demand for water is high. So, this period is most sensitive to any moisture deficiency in the soil. It will be difficult for pegs to penetrate the soil if there is any prolonged dry spell during this stage of the crop.
Soil moisture deficit during the vegetative phase generally delays flowering and maturity, reducing the crop growth and yield. Moisture stress during flowering causes flower drop, and also impairs pollination. The early phase of pod setting is especially sensitive to any soil moisture deficit and this reflects on decreased pod weight. Very often rain fed groundnut crop experiences soil moisture stress when rains fail during the monsoon season. Practices like contour cultivation in a sloping field, soil mulching, intercultivation, and good weed control help in soil moisture conservation to face failure of rains during the crop growth. Spraying of 2% urea at the times of soil moisture stress experienced by crop also helps to overcome moisture stress.