Remember that drought is a very serious agricultural problem. Drought has been defined as the deficit that results when the soil moisture is insufficient to meet the demands of potential evapotranspiration.
Droughts are of three types: (i) permanent droughts associated with dry climates; (ii) seasonal droughts where there are well-defined periods of dry weather; and (iii) droughts because of precipitation variability.
In any case drought is the result of insufficient rainfall. Average rainfall is not a true indicator of drought. What is more important is the seasonal distribution of rainfall, its dependability, intensity, and the form of precipitation.
Moreover, drought is determined on the basis of the water need of a specific crop growing under a particular combination of environmental conditions. If the minimum need of water is not met for such conditions, the crops do not develop properly.
There are certain factors which help in the occurrence of droughts. Decreasing relative humidity, windy weather and higher temperatures are the causative factors of drought. The rate of evaporation being high, the soil moisture is lost rapidly.
Crops grown in such soils as have high moisture holding capacity are able to tolerate a dry period lasting for a short period of time, and in such cases the damage to the crop is negligible.
Different types of crops have different moisture requirements. In fact, the non-availability of the minimum amount of moisture need of a particular crop is the true indication of drought.
In order to combat the drought hazard, various measures have been suggested. They are irrigation, artificial rainfall, dry farming, crop rotation and the cultivation of such crops as require minimum amount of soil moisture.