Aaron Tening

Fixation of potassium in some soils of the sub‐humid zone of Nigeria

Abstract Studies of potassium (K) fixation in the soil were conducted by evaluating the effect of applied K on the extractability of K with time. A series of five K‐sorption treatment solutions, 0.11, 0.22, 0.45, 0.90, and 1.80 cmol/kg were prepared and applied as potassium chloride (KCl) to three sets of soils. The first set of soil samples was extracted with one normal ammonium acetate (1N NH4OAc) extractant for K after one day of incubation. The second and third sets were extracted with the same extractant after seven and 42 days of incubation, respectively. The amount of K fixed was determined. Correlation between applied K and K fixed was carried out. The mean proportion of K fixed ranged from 0 in soils from Kurmin Biri to 55% in soils from Funafuna upon addition of 0.11 cmol K/kg. While fixation increased with increase in the concentration of added K, there was no linear relationship between the proportion of K fixed and the amount added at higher incubation periods. Potassium recovered also increa...

Investigating the Management of Geological Hazards and Risks in the Mt Cameroon Area Using Focus Group Discussions

The scientific evaluation of hazards and risks remains a primary concern in poorly known volcanic regions. The use of such information to develop an effective risk management structure and risk reduction actions however also poses important challenges. We here present the results of a series of focus group discussions (FGDs) organised with city councillors from three municipalities around Mt Cameroon volcano, Cameroon. The Mt Cameroon area is a volcanically and tectonically active region regularly affected in the historical past by lava flows, landslides and earthquake swarms, and has a potential for crater lake outgassing. The lower flanks of the volcano are densely populated and the site of intense economic development. The FGDs were aimed at the elicitation of (1) the knowledge and perception of geological hazards, (2) the state of preparedness and the implementation of mitigation and prevention actions by the municipalities, (3) the evaluation of the effectiveness of the structure of communication channels established to respond to emergency situations, and (4) the recovery from an emergency. In all three municipalities stakeholders had good knowledge of the risks, except for processes never experienced in the region. They generally grasped the causes of landslides or floods but were less familiar with volcano-tectonic processes. Stakeholders identified the lack of strategic planning to monitor hazards and mitigate their impacts as a major weakness, requesting additional education and scientific support. Response to natural hazards is mostly based on informal communication channels and is supported by a high level of trust between local scientists, decision makers and the population. Actions are taken to raise awareness and implement basic mitigation and prevention actions, based on the willingness of local political leaders. The strong centralisation of the risk management process at the national level and the lack of political and financial means at the local level are major limitations in the implementation of an effective risk management strategy adapted to local risk conditions. Our case study highlights the need for earth and social scientists to actively work together with national and local authorities to translate the findings of scientific hazard and risk assessment into improved risk management practices.

Potassium status of some selected soils under different land‐use systems in the subhumid zone of Nigeria

Abstract Twenty surface soils (0 to 15 cm), selected to represent a wide range of available potassium (K) status and three different land‐use systems (fodder bank, continuously fertilized cropped land and fallow land) across the subhumid zone of Nigeria, were used for the investigation. Laboratory and greenhouse studies were carried out to assess their K status. Available, non‐exchangeable, and total K were determined. The supplying power of the soils was assessed by exhaustive cropping in the greenhouse using Stylosanthes hamata cv. Verano as the indicator plant. While 75% of fodder banks sampled had available K less than 0.20 cmol/kg, only 50% and 13% of continuously fertilized cropped and fallow lands, respectively, had available K less than 0.20 cmol/kg. Potassium weathering coefficient was highest at the lowest exchangeable K and highest [calcium (Ca) + magnesium (Mg)]/K ratio. Total K ranged from 2.30 to 47.06 cmol/kg, with available K forming 1.47% of the total K. The amount of non‐exchangeable K r...

Critical potassium deficiency levels for a grass/ legume pasture grown on soils of the subhumid zone of Nigeria

Abstract A greenhouse experiment was conducted to determine the critical deficiency levels of potassium (K) in the subhumid zone soils for predicting response of a mixture of Andropogon gayanus and Stylosanthes hamata cv. Verano to K application. Twenty coarse textured soils, having loamy sand to sandy loam textures and with exchangeable K contents ranging from 0.08 to 0.97 cmol/kg, were used. Two rates of K applied were 0 and 80 mg K/kg. Application of K on soils testing less than 0.18 cmol/kg significantly increased the dry matter yields of both Andropogon and stylo tops. Soil K was significantly related to relative yields of Sole Andropogon (r = 0.60∗∗), sole stylo (r = 0.78∗∗∗), and Andropogon/stylo mixture (r = 0.77∗∗∗). There was a high correlation between the K concentration in plant tissue and the relative yields of sole Andropogon (r = 0.68∗∗), sole stylo (r = 0.67∗∗), Andropogon in mixture (r = 0.65∗∗), and stylo in mixture (r = 0.64∗∗). The graphical model of Gate and Nelson indicated the criti...

Potassium requirements of a grass/legume pasture established on selected soils of the subhumid zone of Nigeria

Abstract The fast depletion of available potassium (K) in soils of the subhumid zone (SHZ) of Nigeria has become a problem for the formulation of fertilizer recommendations, especially in the grass/legume mixtures of the fodder bank system. Five different K fertilizer recommendation models viz. Control, Conventional Rate, Fractional Recovery, Mitscherlich Baule Units, and Nutrient Supplementation Index were employed to determine the amount of K required to satisfy the needs of an Andropogon/stylo mixture. Andropogon gayanus (grass) and Stylosanthes hamata cv. Verano (legume) seeds were sown in June 1991. Cutting started two months after planting and continued at monthly intervals during the rainy season and bimonthly in the dry season till mid dry season when there is usually feed crisis. The Andropogon/stylo mixture grown on soils of the SHZ will require no K fertilization when the soil test value is more than 0.20 cmol/kg. The soils require an application of 52 kg K2O/ha when the soil test value is less...