About This Project

Agricultural soils in The Gambia, West Africa, are highly acidic, which greatly reduces plant growth and ultimately crop yield. The common method of increasing agricultural pH- limestone- is not widely available in The Gambia. However, oyster shells, which have the same property to increase soil pH are widely available, but not currently used. This study looks to investigate the rate of application of oyster shells needed to raise pH to optimal levels for the staple crop groundnut (peanut)

Ask the Scientists

What is the context of this research?

Agricultural soils in The Gambia are highly acidic (pH <5); caused by years of intensive soil utilization, weatherization, and a low rate of soil organic matter inputs. These acidic soils reduce the availability of nutrients to plants, and cause "unresponsive" soils to inputs- resulting in low yields; the average yields of groundnuts, the Gambia's staple crop, are 200%+ lower than their potential. Regardless of improved inputs (the current approach), if the soil pH issue persists, yields increases will be limited. This project aims to address the underlying soil pH issue by utilizing oyster shells, a locally plentiful material, shown to raise soil pH and also improve other soil quality characteristics. This is expected to increase yields and to improve long-term soil health.

What is the significance of this project?

The use of oyster shell-meal (grounded) as a means to improve soil health has already been shown to have the potential to increase groundnut yields by 100% in Nigerian research farm soils. In addition, studies conducted in West African soils have shown oyster shells greatly improve soil pH in soils, increase organic matter, water holding capacity of the soil and increase soil calcium levels. However, the rate of the optimal application needed for groundnut has not been investigated. Meanwhile, there is a high level of interest to find a market for byproducts of the oyster industry, which currently are commonly disposed of without a use. If an effective application rate is found, it can be the basis for a circular economy between oyster harvesters and farmers.

What are the goals of the project?

This project is in partnership with a local oyster non-profit and soil management-focused non-profit. The goals of the project are to determine an optimal rate of oyster shell-meal application to mitigate soil acidity issues to maximize groundnut yields; this will be achieved through a randomized split-plot design on-farm study assessing 4 different rates of oyster shell application across 3 different regions in the Gambia. Additionally, the project will assess the economic feasibility of using oyster shells as agricultural input; and transfer findings to local private industry, non-profits and governmental programs.