A Study of Soil Erosion at Ha-Makuya. July 2012 Kwena, Nelly, Mulweli, Dinice & Tracey (mentor)
Introduction Erosion = natural process that shapes the landscape. Human activities (deforestation, over-grazing) can accelerate soil erosion and affect plants, animals and people. Soil stores nutrients and water - without soil plants cant grow. Soil also stores carbon, which if released, would contribute to global warming.
Soil is important for: – Growing crops to feed people – Supporting vegetation for animals to graze. – Providing habitats for biodiversity. – When soil washes away it silts up rivers and dams - negatively affecting water quality. Introduction
Aim To investigate whether the soil at Ha-Makuya is eroded and how to prevent further erosion from occurring. Hypothesis Soil erosion is visible at Ha-Makuya because of overgrazing and poor farming practices.
Methods General observations for vegetation type and cover, and livestock
Methods 3 tests were carried out: 1.Soil structure – stability of soil when placed in water 2.Leaf litter – organic matter in the soil 3.Infiltration rate – how fast soils absorb water
ObservationEroded SiteNon-eroded Site Vegetation Poor grass cover Few small shrubs Good grass cover Few shrubs and trees Livestock Heavily used by cattle Cattle paths present (walk to river) Seldom used by cattle (only in winter) No cattle paths Soil Structure Soil block broke up very quickly (few seconds) Soil block took long time to break up (several minutes) Table 1. Comparison of vegetation, livestock & soil structure at the eroded and non-eroded sites. Results
Figure 1. Average soil organic matter measured at the two sites. Results
Figure 2. Soil Infiltration rate measured at the two sites. Results Eroded - slow Non-eroded = fast
Discussion The eroded site had poor soil structure, very little vegetation and high animal disturbance. Grazing removes vegetation, meaning that there is less leaf litter available to accumulate on the soil surface when plants drop their leaves. Less leaf litter means that there is less organic matter in the soil. This makes the soil structure poor (as shown by the soil structure test) because organic matter holds the soil together.
Less organic matter in the soil slows infiltration (as seen from the infiltration test). This mean that during rain, more water runs off the surface, carrying soil with it. This leads to erosion and the silting up of rivers and dams. Less organic matter in the soil means that nutrients are not being replaced through decomposition. Breaking the nutrient plant cycle is bad for future plant growth which affects grazing and growing crops. Discussion
Conclusion Our hypothesis is accepted because soil erosion was found, probably because of over-grazing by animals. Poor soil structure and erosion at Ha-Makuya are caused by removing too many plants from the environment. Over-grazing by animals negatively effects the soil, making it more difficult to grow crops or feed livestock in the area. The people around Ha-Makuya need to be educated on good farming practices to prevent further erosion and poor soil quality.
Even though our project was about soil, we also needed to think about livestock, plants and even rivers! The 2 other groups of learners on the camp studied these parts of the environment by asking different scientific questions. Can the vegetation at Tshulu camp support livestock? What is the water quality of the Mutale River, using invertebrates as bio-indicators. My Final Thoughts
The 3 projects overlapped. Ive learned that the different parts of an ecosystem are all connected. Being a scientist is not just about collecting data. Ive learned that scientists must ask relevant questions that benefit people and the environment. The data we collected made me change my views. Ive learned to appreciate biodiversity, its function and how humans can influence it. Biodiversity and ecosystems cannot be replaced. I've learned that our environment provides all of the resources and processes that humans rely on. These are called Ecosystem Services. My Final Thoughts
Thanks Mr. Joe Sibya – for organising the camps The Science Team (Sharon, Rob, Thabo & Dave) Tracey – Soil project mentor Madzhulu Tshulu camp staff & helpers Audience – for listening