KEYWORDS Nitrogen Pulling effect N leaching Diffusion Distribution patterns

ABSTRACT Nitrogen (N) plays an important role in the production of maize. In the absence of N in soils plants shows stunted growth and yellowish leaves and result into reduced crop yield. The study was conducted during two irrigation seasons of 2012 at Nkango Irrigation Scheme, Malawi in a Randomised Complete Block Design (RCBD). The factors were water and nitrogen and both were at four levels. The study inferred that movement, direction and distribution patterns of nitrogen concentration is influenced by evaporation of water from the soil surfaces, pulling effects by plant roots, deep percolation through gravitational force, and ability of plant roots to create environment that is conducive to diffusion of nitrogen. To minimize losses of nitrogen through leaching and ensure that nitrogen is deposited within active root zone, plant should not receive water after physiological maturity

Temporal and spatial variations in hydro-climatic extremes in the Lake Victoria basin

A study was carried out to investigate variability in long term hydro-climatic extremes in the Lake Victoria basin, East Africa. The study aimed at determining whether the long term historical changes in frequency and magnitude of hydro-climatic extremes are statistically significant, to give more light on the differentiation of climate variability from climate change. Long term extremes for 22 rainfall and 10 river flow gauge stations were examined. The hydro-climatic extremes were aggregated at levels from daily, decadal, to monthly scales defined for two wet seasons in the area, the long rainy season extending from March to May (MAM) and the short rainy season extending from October to December OND), and time slices of 10 years using a sliding window approach. An empirical statistical technique based on Quantile Perturbation Method (QPM) was used. Quantile perturbations that represent empirical changes for precipitation and river flow extremes were derived. Significant decreasing trends in precipitation were observed in the 1930s, 1970s and 1980s, while significant increasing trends were common in the 1960s, late 1980s, and 1990s to the most recent years (2000–2006). In general, significant trends were dominant in the OND compared to MAM season for precipitation and river flow extremes. Results indicated further that there are differences in geographic location of significant trends in the hydro-climatic variables investigated implying that impacts are not spatially coherent. Areas with significant trends appeared to be concentrated in the North to North eastern parts compared to those in the southern parts of the basin.status: publishe