No abstract

Soil moisture is important for crop cultivation and its adequacy to meet crop-water requirements is determined by the degree of soil management practised and the quantity of water applied to the soil. This study investigates soil moisture dynamics on three plots: Bare (clean, weeds removed), Weedy (kept weedy), and Mulched (cleared of weeds and fully covered with grass mulch) during rainy and dry periods at the Teaching and Research Farm at the University of Cape Coast, in the coastal savanna zone of Ghana. Soil moisture dynamics under different levels of soil compaction were also studied. A Massey Ferguson tractor (MF265) was used to compact the soil at various levels by making 0, 1, 5, 9 and 13 passes. During both the rainy and the dry periods, moisture retention in the soil under bare, weedy and mulched plots increased with depth. During the rainy period, the mean soil moisture retention was in the order: Mulched > Weedy > Bare at both 0-20 cm and 20-40 cm depths. Within a 7-day period, soil moisture measurements from a day after heavy rainfall (intensity > 7 mm h -1 ) gave mean moisture losses of 2.7, 4.1 and 3.9% for the Bare, Weedy and Mulched plots, respectively. During the dry period, however, the mean soil moisture retention was of the order: Mulched > Bare > Weedy at both 0-20 cm and 20-40 cm depths. Mean moisture loss during a 7-day dry period was 4.5, 2.9 and 3.4% for the Bare, Weedy and Mulched plots, respectively. Under different levels of soil compaction, the mean moisture retention in the soil increased from 8.3% at 0 pass to 17.8% at 13 passes within the 0-20 cm depth, whilst it decreased from 13.3 to 5.9% from 0 to 13 passes, respectively, within the 20-40 cm depth. It was realized that at less than two passes, the mean soil moisture retention within the 0-20 cm depth was less than the mean moisture retention within the 20-40 cm depth, but the converse happened for more than two passes. The study showed that mulching the soil surface helped to retain enough soil moisture during both the rainy and the dry seasons. Also, soil with high sand content required some sort of soil compaction in order to retain enough moisture at the crop rooting zone. l'humidité du sol de la profondeur 0-20 cm est inférieure à celle de la profondeur 20-40 cm, mais que le contraire est apparu pour plus de deux passages. L'étude montre que l'application du mulch sur la surface du sol aide à retenir suffisamment d'humidité du sol pendant les deux saisons, pluvieuse et sèche. De plus, le sol à forte teneur en sable nécessite une certaine compaction pour retenir suffisamment d'humidité dans la zone racinaire.

Proper agricultural land management strategies improve soil structural properties, thereby reducing soil loss by water erosion. This study was conducted to estimate soil losses from plots of different agricultural land management using the Water Erosion Prediction Project (WEPP) (95.7) model. The study took place in a semiarid region in Kenya. The mean annual rainfall was 694 mm. The WEPP (95.7) model was initially used to estimate total sediment loading from the catchment into a reservoir. The estimate was about 2871 t corresponding to an average sedimentation rate of 1063 t km"" year"', which was about 76% of the measured total sediment inflow into the reservoir. Soil losses were estimated within 10 plots on the catchment of different sizes and slopes with the following treatments: conventional tillage (hand hoeing) with maize and soybean intercropping (HOCOBE); conservation tillage (disc plough) with maize and soybean intercropping (COBEAN); conservation tillage with only maize cultivation (CNTCORN); and conservation tillage with only soybean cultivation (CNTBEAN). The soil loss reduction of COBEAN, CNTCORN and CNTBEAN relative to HOCOBE ranged between 27-47%, 16-29% and 12-25%, respectively, depending on the size and slope of the plot. In general, conservation tillage reduced soil loss relative to conventional tillage. However, with conservation tillage, the single cropping system resulted in greater soil loss than the intercropping system. In the case of single cropping with conservation tillage, the soil loss reduction for maize ranged between 4 and 9%, relative to soybean. Overall, the study showed that there would be a significant reduction of soil losses from plots if conservation tillage with an intercropping system (maize and soybean) were to be adopted on agricultural lands in semiarid regions.Key words agricultural land; semiarid regions; soil loss; tillage; water erosion; WEPP (95.7) model Estimation des pertes de sol au sein de placettes, sous l'effet de différents modes de gestion agricole Résumé De bonnes stratégies de gestion agricole améliorent la structure du sol et de ce fait permettent de réduire la perte de sol par érosion hydrique. Cette étude a été conduite dans le but d'estimer les pertes de sol subies par des placettes présentant différents modes de gestion agricole, en utilisant le modèle WEPP (Water Erosion Prediction Project-Projet de Prédiction de l'Erosion Hydrique) (95.7). L'étude a été menée dans une région semi-aride du Kenya. La pluviométrie moyenne y est de 964 mm par an. Le modèle WEPP (95.7) a été initialement utilisé pour estimer le transfert total de sédiments du bassin versant vers un réservoir. L'estimation s'est élevée à o environ 2871 t, ce qui correspond à un transfert annuel moyen de 1063 km" an"

The impacts of small-scale mining on the vegetal cover as well the livelihoods of communities in mined areas in developing countries such as Ghana are far-reaching. This study assessed the impacts of small-scale mining on flora of conservation and economic significance through quantification of species richness, and species diversity. Mined and unmined sites were chosen in the Dunkwa East Municipality of Ghana. Five belt transects each (200m × 200m) were constructed in both sites. Each belt transect was divided into 100 quadrats (20m × 20m) and plant species in each of the quadrat were identified in the field and or the herbarium of the School of Biological Sciences, University of Cape Coast. One hundred and fifty seven species distributed in 140 genera and 54 families were identified in the mined area whilst the 209 species identified in the unmined area were in 185 genera and 73 families. Plant families Euphorbiaceae, Rubiaceae and Asteraceae were more diverse whilst Asteraceae, Poaceae and Euphorbiaceae were dominant in the unmined area. In the mined area, however, Poaceae, Euphorbiaceae and Asteraceae were more diverse. Pteridium aquilinum, Tridax procumbens and Waltheria indica in the unmined area and Chromolaena odorata, Sporobolus pyramidalis and Euphorbia hirta in the mined area were the dominant species. Small-scale miming activities have caused reduction in species diversity, richness and economic and commercial values in the area. Higher disturbance of the flora has resulted in more secondary species in the mined area. Restoration is required in the study area.

No abstract