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Introduction to Soil Structure and Health

Like any living entity, plants require nutrients to live, grow, and reproduce. Those who live off the land know the importance of keeping soils healthy for crops to grow to their full potential. In figuring out how to do this, you must first understand how the condition of your soils affect the crops you produce.

Acidic soils of the Tropics

Acidic soils are soils with a pH lower than 7. For most plants, having a pH between 6 and 7.5 is ideal (see table 1 for more exact numbers), but soils can become dangerous when their pH drops beneath 4.5. As the pH drops, aluminum becomes more soluble, toxifying the soil and harming the plants. Bacteria activity and nitrogen fixation (the process in which atmospheric nitrogen is ’fixed’ into an organic form that is useable for plants) also decreases if the soils become too acidic.

Testing and Replenishing Your Soils

Neil Rowe Miller, Agriculture and Livelihoods Technical Advisor, Eastern Africa

Soil infertility is a key constraint to crop production for small farmers. Soils throughout Sub-Saharan Africa are degraded and deficient in nutrients and organic matter. As a result, there is a growing demand for soil testing services from farmers and NGO staff who want guidance on which inputs are best, and how much they should apply to restore soil health and fertility.

Lands that are most at-risk for degra dation or desertification are those with fragile ecosystems or in places with higher populations. Poor farming practices that don’t concentrate on replenishing the soils after taking from them are also a major issue leading to decreased land quality. Unprotected soils are vulnerable to compaction and erosion as well as sun exposure which can kill off valuable microbial populations.