**8. Implications and effects of climate change on the characteristics of effective rainfall in agriculture**

Most agricultural activities such as land clearing, planting, and harvesting time need to be informed about the start and end dates of rainfall, rainfall amount, and the length of the growing season [1, 31, 32].

Understanding the variation of precipitation and its trend and the characteristics of the growing season is critical for planning and designing appropriate

#### *Climate Change and Its Consequences in Agriculture DOI: http://dx.doi.org/10.5772/intechopen.101444*

adaptation strategies at the basin level [33]. Increasing or decreasing rainfall and changes in rainfall distribution will affect water balance and will change the frequency of droughts and floods [34]. Research shows that precipitation and temperature changes are not uniform in all parts of the world and there are temporal and spatial fluctuations in different regions of the world) [35].

The amount of annual precipitation and it's seasonal distribution, as well as changes in the beginning and end date of precipitation in many regions of the world, have changed following the trend of rising temperatures on the planet. Many types of research have been conducted by researchers globally to understand the characteristics of precipitation, indicating that precipitation changes in some places increased and in some others have decreased, including [36–41] can be noted.

Dryland farming is defined as the production of crops without irrigation in semi-arid regions of the world, where annual rainfall is between 250 and 500 mm. The success rate of dryland farming in these regions depends on annual rainfall, appropriate distribution of precipitation during the growing period, start and end date of precipitation. If the date of rainfall delays in autumn, germination of crops, especially cereals, is delayed and this causes other growing stages to begin and end with delay. Under these conditions, the thermal needs of the plant are not provided in the autumn; Therefore, the plant, especially wheat, faces unfavorable conditions in the winter; and eventually, it may be destroyed due to freezing temperatures.

Van de Giessen et al. [42] believe that in West Africa, south of the coast, the start of the precipitation season has shifted forward. Rao et al. [43] believe that this evidence cannot always represent climate change. Other researches in this region did not illustrate a significant trend [44]. Future changes in the tropical rotation pattern may cause seasonal changes and lead to increased uncertainty at the start of the precipitation season [45].
