ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY AND ENVIRONMENT

14-23

Authors: K Ogedengbe, A O OkeK Ogedengbe, A O Oke

Small earth dams are important structures in the management of water resources for food security in developing nations. The construction of such dams at cheap rates depend on the availability of suitable earth material within the site location. The suitability of a given soil for use in earth dam construction is dictated by its geotechnical properties. The geotechnical properties of soils from three locations along the Ogun River in Iseyin, Nigeria, a predominantly farming community have been evaluated for their suitability as earth dam material. Although, the liquid limit (LL) determined for the samples are in the impermeable core zone, the samples from shoku (LOC3) has the lowest LL making it most suitable soil in terms of LL. the Soil from Ogunremi (LOC1) had the highest percentage large grains while the sample from Ajambata (LOC2) had the lowest. Soils from the 3 locations fall within the permeable shell zone which implies that without further enhancement, the soils will allow seepage when used for earth dam construction. The consolidation properties showed decrease in the coefficient of compressibility and coefficient of consolidation with increase in pressure in the locations. Coefficient of consolidation was peaked at 100-200 kN/m2 for LOC2, was least at 100-200 kN/m2 for LOC1 and decreased linearly with increase in pressure for LOC3. Samples from LOC2 and LOC3 exhibited better coefficient of consolidation than samples from LOC1 as the pressure increased within the 100-200 kN/m2 range. This is indicative of a relatively cohesive soil of medium shear strength. The investigation shows that the soil from all the location would need some form of improvement to make them adequately suitable as earth materials for dam construction. Further studies, would be carried out to address these needs.

34-43

Authors: J A Otun, J K Adewumi

This study analyzed the sequences of dry and wet spells occurrence using the 1918-2004 rainfall data from the Sudano-Sahelian region in Nigeria (SSRN). It evaluates and uses the distribution and probabilities of the intra-season dry spell to describe how effective crop planning can be achieved in the midst of prevailing dry spells in SSRN. The approach adopted also involves the use of some other empirical computations to determine the risk level and percentage frequencies of dry spells for successive days after sowing (DAS) a crop. The results of the probabilities of maximum dry-spell length exceeding 7 to 15 days over the next 30-days helped to assess if the break of a dry spell due to rain has a significant impact on the subsequent spell length. The maximum dry spell length at five probability levels (risk levels) for different DAS and rainfall thresholds as well as the computation of the probable length of growing season provides estimates of appropriate time of sowing, type of crop to grow, and the cropping pattern to be adapted in the midst of the prevailing dry spell conditions in SSRN.

59-66

Authors: S A Iya, H U Kabri, B Aliyu, A Umaru

The design and construction of a manual precision rice planter was undertaken with the aim of achieving precise planting on the farm. The machine was designed, constructed and tested on the University farm in Yola-Nigeria, using locally available materials. The machine consists of roller-metering device that rotates and receives constant flow of seeds from a bottomless hopper, a furrow opener and covering device. There is a front land wheel from which the seed-metering device is directly driven through chain and sprockets. The frame is made of hollow pipe on which the entire assembly is mounted. The machine performance evaluation was carried out using paddy rice BG 302 variety. The actual field capacity of the machine was found to be 0.067ha/h with field efficiency of 77.9%, and application rate of 21.62 kg/ha. The planter has a mean planting depth of 3.2cm, hill distance of 15.12 cm and 6 seeds per hill. It was concluded that efficient and precision planting could be better achieved with this kind of machine than with rice seed broadcasters

78-89

Authors: E A Okunade

An engineering classification map and isopleths are produced for the subgrade soils of Jigawa and Kano States of Nigeria. Usage is made of historical and existing results of soil and materials investigations in the area, with a view to harnessing these resources and reducing the efforts, time and money to be expended in carrying out preliminary investigations in connection with future planning, design, location and construction of road projects in the area.