Precolonial agricultural terracing in Bokoni, South Africa : Typology and an exploratory excavation

Earlier work on the terraced settlements of the Bokoni area (16th to 19th century, Mpumalanga province, South Africa) focussed on the homesteads, their contents, layout and chronology. This paper suggests a terminology and typology of agrarian structures in Bokoni in order to improve comparative approaches in Africa and beyond. The typology and an excavation of the terracing have made possible preliminary conclusions relevant for the further analysis of the terracing and stone-walling in Bokoni. The terracing developed incrementally, whereby cultivation, stone-clearing and terracing were intermixed processes. This is supported both by the organic content in a section of a terrace and by a phytolith analysis. The phytolith analysis furthermore indicated that maize was cultivated on the terraces, but this should be seen as a pilot study only, and presence of maize in Bokoni must be tested with other archaeobotanical methods.

Site works, Hill House, Chapel Hill, Brisbane

Terracing of site in preparation for construction.

Excavation, Hill House, Chapel Hill, Brisbane

Terracing of site in preparation for construction.

Assessment of Efficiency and Adequacy of Retention Terraces

Due to losses caused by water erosion, the development of techniques that increase the efficiency of soil conservation practices is fundamental. Terracing of agricultural lands is an important conservation practice. Bearing in mind that improperly built terraces may negatively affect the landscape, the purpose of this work was to evaluate the efficiency as well as the adequacy of retention terraces. Assessments were performed in four terraces implanted in different states, all located in the mideastern region of the state of Minas Gerais. The water storage efficiency of the terraces was determined by comparing the effective with the required storage capacity, as established in the project. Proposals were also made for the adequacy of the assessed terraces, based on the correction of the characteristics that jeopardized storage efficiency. The storage efficiency of three of the four assessed terraces was below the required levels (0.5-13 %). The main properties influencing storage capacity were: uniformity of ridge crest height, terrace end closure, and the cross section finishing. In two of the three low-efficiency terraces, the correction of these characteristics proved sufficient to raise the storage efficiency to nearly 100 %.

Phosphorous and nitrogen changes in compost-amended schist soils in vineyards in the D.O. Priorat wine-producing area (NE Spain)

The impact, on nitrogen and phosphorous dynamics, of applying compost at different rates was investigated in soils developed on schist in new terraced vineyards (NTV) and in undisturbed areas (NC). Repacked soil columns amended with 0 (control), 50 t ha –1 (T1) and 100 t ha–1 (T2) of compost were studied under laboratory conditions simulating both situations. The columns were maintained for 1 year, during which time a total of 300 mm of simulated rainfall was applied in ten 30 mm applications. Soil organic matter (OM), nitrogen and phosphorous contents were analysed at the end of the study period and leachates were analysed after each simulated rainfall event. Significant differences in nitrate leaching were observed between the control and the treated soils and these differences were greater in the NC (control = 1.368 g, T1 = 1.526 g and T2 = 1.686 g) than in the NTV soils (control = 0.61 g, T1 = = 1.068 g and T2 = 1.283 g). The relative effect was greater in the NTV soils (T1/control = 1.11 vs. 1.75 and T2/control = 1.23 vs. 2.1 for NC and NTV, respectively). The nitrate concentration in the leached water reached up to 400 mg L–1, which implied a risk of groundwater pollution. Phosphorous losses through leaching were very low with concentrations of < 0.15 mg L–1, without any significant differences between treatments. The phosphorous concentrations in the surface horizon increased by 50.8% in T1 and by 66.8% in T2 in the NC soils, compared with increases of 20.3% and 38%, respectively, in the NTV soils. Due to the high infiltration capacity of the study soils, leaching effects must be considered in order to prevent groundwater pollution.

Meio ambiente e agricultura na microbacia hidrográfica do Córrego Palmitalzinho - Regente Feijó/São Paulo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Planejamento agroambiental de uma microbacia hidrográfica utilizando um sistema de informações geográficas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Impactos ambiental e socioeconômico do uso e ocupação dos solos da microbacia Jardim Novo Horizonte, em Ilha Solteira, SP

Pós-graduação em Agronomia - FEIS

EC38-118 Soil and Moisture Conservation in Nebraska

When the white men first explored Nebraska, they found little erosion taking place. They found the hills, particularly in eastern Nebraska, covered with a dense growth of grass, underlain with a thick mat of decaying debris. The valleys were even more densely covered with the water-loving grasses and sedges. The soil underneath the prairie was black and spongy, the result of centuries of accumulating humus. The valleys bordering the streams were boggy and abounded with springs. Clear water flowed constantly in the streams. The upland draws in the more favorable parts of the state were heavily covered with the big bluestem and slough grass. Springs occurred in many of these. Soil erosion in Nebraska has not progressed to as great an extent as in states to the east and to the south. This is because of the comparatively lower rainfall in Nebraska, because the land has been farmed for fewer years in this state, and because some Nebraska soils are comparatively less erosive. This extension circular covers factors which influence erosion, erosion control practices, and storage of soil moisture.

EC38-118 Soil and Moisture Conservation in Nebraska

When the white men first explored Nebraska, they found little erosion taking place. They found the hills, particularly in eastern Nebraska, covered with a dense growth of grass, underlain with a thick mat of decaying debris. The valleys were even more densely covered with the water-loving grasses and sedges. The soil underneath and prairie was black and soggy, the result of centuries of accumulating humus. The valleys bordernig the streams were boggy and abounded with springs. Clear water flowed constantly in the streams. The upland draws in the more favorable parts of the state were heavily covered with the big bluesteam and slough grass. Springs occurred in many of these. Soil erosion in Nebraska has not progressed to as great an extent as in states to the east and to the south. This is because of the comparatively lower rainfall in Nebraska, because the land has been farmed for fewer years in this state, and because some Nebraska soils are comparatively less erosive. This extension circular covers the factors which influence erosion, erosion control practices and storage of soil moisture.

Geographic information system-based decision support for soil conservation planning in Tajikistan

Soil erosion on sloping agricultural land poses a serious problem for the environment, as well as for production. In areas with highly erodible soils, such as those in loess zones, application of soil and water conservation measures is crucial to sustain agricultural yields and to prevent or reduce land degradation. The present study, carried out in Faizabad, Tajikistan, was designed to evaluate the potential of local conservation measures on cropland using a spatial modelling approach to provide decision-making support for the planning of spatially explicit sustainable land use. A sampling design to support comparative analysis between well-conserved units and other field units was established in order to estimate factors that determine water erosion, according to the Revised Universal Soil Loss Equation (RUSLE). Such factor-based approaches allow ready application using a geographic information system (GIS) and facilitate straightforward scenario modelling in areas with limited data resources. The study showed first that assessment of erosion and conservation in an area with inhomogeneous vegetation cover requires the integration of plot-based cover. Plot-based vegetation cover can be effectively derived from high-resolution satellite imagery, providing a useful basis for plot-wise conservation planning. Furthermore, thorough field assessments showed that 25.7% of current total cropland is covered by conservation measures (terracing, agroforestry and perennial herbaceous fodder). Assessment of the effectiveness of these local measures, combined with the RUSLE calculations, revealed that current average soil loss could be reduced through low-cost measures such as contouring (by 11%), fodder plants (by 16%), and drainage ditches (by 53%). More expensive measures such as terracing and agroforestry can reduce erosion by as much as 63% (for agroforestry) and 93% (for agroforestry combined with terracing). Indeed, scenario runs for different levels of tolerable erosion rates showed that more cost-intensive and technologically advanced measures would lead to greater reduction of soil loss. However, given economic conditions in Tajikistan, it seems advisable to support the spread of low-cost and labourextensive measures.

Carbon sequestration in Himalaya's alpine meadows: Mitigating cropping encroachment on pastures in Northern Pakistan

Rangelands store about 30% of the world’s carbon and support over 120 million pastoralists globally. Adjusting the management of remote alpine pastures bears a substantial climate change mitigation potential that can provide livelihood support for marginalized pastoralists through carbon payment. Landless pastoralists in Northern Pakistan seek higher income by cropping potatoes and peas over alpine pastures. However, tilling steep slopes without terracing exposes soil to erosion. Moreover, yields decline rapidly requiring increasing fertilizer inputs. Under these conditions, carbon payment could be a feasible option to compensate pastoralists for renouncing hazardous cropping while favoring pastoral activities. The study quantifies and compares C on cropped and grazed land. The hypothesis was that cropping on alpine pastures reduces former carbon storage. The study area located in the Naran valley of the Pakistani Himalayas receives an annual average of 819 mm of rain and 764 mm of snow. Average temperatures remain below 0°C from November to March while frost may occur all year round. A total of 72 soil core samples were collected discriminating land use (cropping, pasture), aspect (North, South), elevation (low 3000, middle 3100, and high 3200 m a.s.l.), and soil depth (shallow 0-10, deep 10-30 cm). Thirty six biomass samples were collected over the same independent variables (except for soil depth) using a 10x10x20 cm steal box inserted in the ground for each sample. Aboveground biomass and coarse roots were separated from the soil aggregate and oven-dried. Soil organic carbon (SOC) and biomass carbon (BC) were estimated through a potassium dichromate oxidation treatment. The samples were collected during the second week of October 2010 at the end of the grazing and cropping season and before the first snowfall. The data was statistically analyzed by means of a one-way analysis of variance. Results show that all variables taken separately have a significant effect on mean SOC [%]: crop/pasture 1.33/1.6, North/South 1.61/1.32, low/middle/high 1.09/1.62/1.68, shallow/deep 1.4/1.53. However, for BC, only land use has a significant effect with more than twice the amount of carbon in pastures [g m-2]: crop/pasture 127/318. These preliminary findings suggest that preventing the conversion of pastures into cropping fields in the Naran valley avoids an average loss of 12.2 t C ha-1 or 44.8 t CO2eq ha-1 representing a foreseeable compensation of 672 € ha-1 for the Naran landless pastoralists who would renounce cropping. The ongoing study shall provide a complete picture for carbon payment integrating key aspects such as the rate of cropping encroachment over pastures per year, the methane leakage from the system due to livestock enteric fermentation, the expected cropping income vs. livestock income and the transaction costs of implementing the mitigation project, certifying it, and verifying carbon credits. A net present value over an infinite time horizon for the mitigation scenario shall be estimated on an iterative simulation to consider weather and price uncertainties. The study will also provide an estimate of the minimum price of carbon at which pastoralists would consider engaging in the mitigation activity.