The application of Rainfall-Potential evapotranspiration (P-PE) model to yam (Dioscorea rotundata) Production was carried out in an on-farm yam trial during the 2006-2007 and 2007-2008 cropping seasons in Abeokuta, South western Nigeria. The experiment was a 3 x 2 factorial arrangement of three varieties of yam (Efuru, Ise-osi and Oniyere), two planting dates (early and late). The resulting 6 treatments were replicated three times with 14 mounds in each plot, in randomized complete block design. The general model for selecting the planting date of each yam cultivar in the two experimental years was 0.1PE

PE, the physiological parameters and hydrothermal agro-climatic indices measured during the different phenological stages of yam grown were analyzed with respect to the various treatments. The result showed that model T 1 defined as Σ(P-0.1PE) ≤ 10mm appeared as the best model that significantly (P < 0.05) influenced emergence rate, phenological growth and tuber yield. The implications of the study for appropriate schedule of farm operations vis à-vis agronomic practices for yam cultivation have been noted.

Estimation and forecast of groundwater recharge and capacities of aquifers are essential issues in water resource investigation. In the current research, groundwater recharge and the recharge coefficient were determined through a case study using empirical methods applicable to the tropical zones. The related climatological data between January 1983 and December 2014 were collected from Ogun-Oshun River Basin Development Authority (OORBDA), Ogun State, Nigeria. Using empirical formulae. The results showed that groundwater recharge was 194.7 mm per year, evapotranspiration was 1296.2 mm per year, and the recharge coefficient was 20.2% for the study area. The result also showed that about 11% of rainfall infiltrated the aquifer, 73% was lost to evapotranspiration, and 16% ended up as run-off. Correlation between climatic parameters and groundwater recharge showed the highest correlation between recharge and rainfall. Temperature, humidity, solar radiation and evapotranspiraton were obtained at the 0.01 significance level; the results of linear regressions proved that precipitation has a significant effect (with R 2 = 0.983) on estimated recharge.

This study assessed rainfall extremes for agricultural overview in Nigeria using trend analysis and probability of exceedance expressed as normal for an average at 50% exceedance, wet for greater than average 20% exceedance and dry for lower than average 80% exceedance. The annual rainfall trend indicated variability in the six geopolitical regions with North-East having the lowest range and South-South area with highest. The average monthly rainfall exceedance showed that all part of the Nigeria experienced rainfall more than 100 mm at all levels of probability. The rainfall exceedance time series indicated extremes as well as critical values of 20% and 80% exceedance conditions at many stations during the study period. The critical values of exceedances in dry occurrences are in short-time scales in Northern region while, wet exceedances occurrences for long time scales in South-East, South-West, North-Central and North-West. The study revealed periods of extreme rainfall of significant magnitude susceptible to crop failure in the different regions if reliable cropping management plans is not put in place.

Growth parameters namely number of leaves, leaf area per plant and plant height were recorded in a field experiment in the late rainy season of 2016 to study the crop growth-weather relationship of four maize cultivars namely TZPB-SR-W, DMR-LSR-Y, ART/98/SW6 and BR/9928. The experimental plots were arranged in a Randomize Complete Block Design replicated three times. The crop growth parameters (number of leaves, plant height and leaf area) and selected agrometeorological indices namely rainfall, maximum and minimum temperature, relative humidity and sunshine hour were subjected to correlation analysis. The study confirmed that number of leaves for the cultivars used for this research was the most sensitive parameter to rainfall, minimum temperature and relative humidity fluctuations whereas it was least sensitive to maximum temperature and sunshine hour. Cultivars plant height and leaf area demonstrated highest sensitivity to maximum temperature and sunshine hour, respectively in the study area. The correlations coefficients (r) obtained in the experiment revealed that rainfall, minimum and maximum temperature and sunshine hour were positively correlated with crop growth parameters, but relative humidity was negatively correlated with all selected growth parameters. It was recommended that number of leaves be used as the most critical factor in determining maize cultivars sensitivity to weather vagaries in the study area.

An on-farm yam experiment was conducted to confirm the agro-climatic potential of Abeokuta, South-western Nigeria for three white yam varieties (Dioscorea rotundata). Three varieties of yam (Efuru, Ise-osi and Oniyere) was selected and related to crop growth and yield. The experiment was laid out in randomized complete block design in three replicate. The result showed that all yam varieties evaluated were suitable for planting in the area. However, Efuru and Ise-osi synchronized perfectly with the pattern of Actual Water Availability and produced good vegetative growth with Leaf Area Index LAI, of 1.08 and 0.91 thereby leading to high tuber yield of 12 tonnes ha -1 and 11.64 tonnes ha -1 , respectively. Oniyere had LAI of 0.44 resulting in a lower tuber yield of 11.53 tonnes ha -1 .