Abstract

Reliable information on the starting and ending of growing season as well as its length will greatly assist in appropriate planning for rainfed agriculture farming practices. The objective of this study is to determine the start, end and length of growing season, based on dependable rainfall during wet (20%), normal (50%) and dry (80%) years, which were retrieved from historical rainfall records analysis of seven stations in Gedarif state for the period 1985 to 2014. The seven studied stations were categorized into two groups according to the total seasonal rainfall. During wet years, Group I had about 900 mm/year and Group II about 700-790 mm/year. In normal years, Group I had about 660-700 mm/year and Group II had 515-570 mm/year. During dry years, Group I had 490-550 mm/year and Group II had 350-425 mm/year. The results showed consistent trend of starting dates of the growing seasons; regardless of the high seasonal variability and variation in amount and distribution of rainfall among the stations and seasons. Similar results were obtained using the MODIS Enhanced Vegetation Index (EVI) for three different years representing different probability levels (2013, dry; 2000, Normal; 2007, wet). Groups I and II in normal and wet years had 70 to 90% of the total annual rainfall during the growing season. In dry years, Group I had 70 to 80% of the total rainfall during the growing season, while Group II had only 50 to 65%. The two groups have indicated different seasonal characteristics (start of growth season, end of growth season and length of growth season) in the dry, normal and wet years. Length of the growth season increases with early start of the season and in wetter years.

Key words: Season start, season end, sowing date, dry season, normal season, wet season.