Minor Seanonal Rainfall Variability over Southern Ghana

Rainfall variability has resulted in extreme events like devastating floods and droughts which is the main cause of human vulnerability to precipitation in West Africa. Attempts have been made by previous studies to understand rainfall variability over Ghana but these have mostly focused on the major rainy season of April-July, leaving a gap in our understanding of the variability in the September-November season which is a very important aspect of the Ghanaian climate system. The current study seeks to close this knowledge gap by employing statistical tools to quantify variabilities in rainfall amounts, rain days, and extreme precipitation indices in the minor rainfall season over Ghana. We find extremely high variability in rainfall with a Coefficient of variation (CV) between 25.3% and 70.8%, and moderate to high variability in rain days (CV=14.0% - 48.8%). Rainfall amount was found to be higher over the middle sector (262.7 mm – 400.2 mm) but lowest over the east coast (125.2 mm – 181.8 mm). Analysis of the second rainfall season using the Mankandell Test presents a non-significant trend of rainfall amount and extreme indices (R10, R20, R99p, and R99p) for many places in southern Ghana. Rainfall Anomaly Indices show that the middle sector recorded above normal precipitation which is the opposite for areas in the transition zone. The result of this work provides a good understanding of rainfall in the minor rainfall season and may be used for planning purposes.

Investigation of 18 physiologically dormant Australian native species: germination response, environmental correlations and the implications for conservation

For physiologically dormant (PD) species in fire-prone environments, dormancy can be both complex due to the interaction between fire and seasonal cues, and extremely deep due to long intervals between recruitment events. Due to this complexity, there are knowledge gaps particularly surrounding the dormancy depth and cues of long-lived perennial PD species. This can be problematic for both in situ and ex situ species management. We used germination experiments that tested seasonal temperature, smoke, dark and heat for 18 PD shrub species distributed across temperate fire-prone Australia and assessed how germination was correlated with environmental factors associated with their home environments. We found extremely high levels of dormancy, with only eight species germinating above 10% and three species producing no germination at all. Seven of these eight species had quite specific seasonal temperature requirements and/or very strong responses to smoke cues. The maximum germination for each species was positively correlated with the mean temperature of the source population but negatively correlated with rainfall seasonality and driest months. The strong dependence on a smoke cue for some of the study species, along with examples from other studies, provides evidence that an obligate smoke response could be a fire-adapted germination cue. Germination response correlated with rainfall season of the source populations is a pattern which has often been assumed but little comparative data across sites with different rainfall seasonality exists. Further investigation of a broader range of species from different rainfall season environments would help to elucidate this knowledge gap.

Trend and Variability Analysis of Rainfall and Extreme Temperatures in Burundi

This study investigated the variability and trend of rainfall and extreme temperatures over three eastern and northeastern regions of Burundi during the period 1980-2015. Data used were collected from seven stations belonging to the geographical institute of Burundi. Annual and seasonal variability are assessed using standardized anomaly, coefficient of variance and precipitation concentration index. In addition, non parametric statistic tests Mann Kendall and Sen’s slope estimator are used to detect trends in rainfall, maximum and minimum temperatures. The results reveal a high monthly and inter-annual variability of rainfall whereas the temperature does not show high fluctuation at monthly scale. The northern region presents the lowest amount of rainfall for the first rainfall season (October-January) when drought is frequently observed. No significant rainfall trend detected over all regions at seasonal and annual scales whereas significant increasing trend was observed for both maximum and minimum temperatures over all regions. The spatial distribution of rainfall and extreme temperatures displays also a wide variation across the region depending on topography of the study area.

Evaluation of Sesame Yield and Yield Component under Different NPSZnB Fertilizer Rates in Western Tigray, Ethiopia

Sesame is one of the most popular oil crops in the Western Tigray Ethiopia. Blended fertilizers containing N, P, S, Zn and B have been recommended to ameliorate site specific nutrient deficiencies in different districts of Tigray. Field experiment was conducted during rainfall season of 2018 and 2019 to study the effect of NPSZnB fertilizer on sesame (Sesamum indicum L.) in vertisols of Western Tigray at the Humera station, Banat and Kebabo Kafta Humera and Tsegede Wereda’s. The treatments consisted of six levels of NPSZnB 0, 50, 100, 150, 200 and 250 kg ha-1 and one blanket recommendation NP was applied. Data were recorded on sesame yield and yield components. The results revealed that addition of graded rate of NPSZnB significantly increased yield and yield attributes over the control. Analysis of variances showed that grain yield, number of capsule per plant, number of seeds per capsule and number of branching per plant was significant differences at (P< 0.001). Grain yield increases from 421 kg ha-1 to 630.1 kg ha-1 as NPSZnB increases from 0 (control) to 150 kg ha-1 and 421 kg ha-1 to 626.2 kg ha-1 as NP increases from 0 (control) to 41 N kg and 46 P205 kg ha-1 respectively. But NPSZnB was not significant with blanket recommendation of NP (41 kg N and 46 kg P205 ha-1), this indicates that either the blend or blanket NP can be used but not one to replace the other.