AGROSTATISTICAL ANALYSIS OF RAINFALL DATA FOR THE HUMID AND SUB HUMID STATIONS OF NIGERIA

Abstract

Agroclimatological information provides the basic tool for proper and profitable agricultural planning. The study was aimed at carrying out detailed analysis of rainfall data of iong term duration in humid and subhumid stations in Nigeria using Onne and Ibadan meteorological data. Data were analysed to obtain general rainfall characteristics such as precipitation index, distribution and variability of the two stations. The shortcoming of these methods led to the development of further analysis of the rainfall data to obtain daily soil water budget the falling rate soil water budget based on some reasonable assumption and this was used to calculate daily water supply budget which was further analysed to obtain the runs of consecutive days with wet soil thus enabling determination of time of sowing and harvesting. The rainfall data was modelled using the first order Markov chain to determine the dependence of wet and dry days. The probability of a dry day following a dry day for Ibadan varies between 0.44- 0.98 and 0.64- 0.99 for Onne. The study indicate that for the purpose of agricultural planning in these zones, there is the need to take into account the weather condition of at least two previous days in order to predict the occurrence of wet or dry spell during the growing season. Significant reduction of about 20. days was recorded in the length of the growing season over the period under study for both sites. Also a significant decline in rainfall total .was observed particularly in Onne. The result obtained would be useful for agricultural planning and mapping on regional scale. It is equally adaptable to growing season determination