Agricultural Science·Soil · NSSCO 2.6
Soil fertility, nutrients & the nitrogen cycle
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Why does one farmer's maize stand tall and deep green while the neighbour's is short and yellow, on the very same day, under the same sun? The answer is hidden in the soil. In this lesson we meet the six nutrients plants need, learn to read the hunger signs in a leaf, follow nitrogen as it cycles from the air into the soil and back again, and see how compost, legumes and careful feeding keep a Namibian farm fertile for years.
What you'll learn in this lesson
By the end you should be able to (NSSCO Agricultural Science 2.6):
- Describe the major functions of the plant nutrients nitrogen, phosphorus, potassium, calcium, magnesium and sulfur
- Describe the symptoms of nutrient deficiency in nitrogen, phosphorus and potassium
- State one organic and one inorganic source of nitrogen, phosphorus and potassium
- Identify and explain factors affecting soil pH such as rainfall, irrigation, application of fertilisers or manure, removal of crop residue, bacterial/microbial actions and parent materials
- Describe the nitrogen cycle: decomposition by microorganisms, nitrogen fixation in the roots, absorption of nitrogen compounds and their conversion to proteins, and the return of nitrogen to the soil or atmosphere (names of individual bacteria not required)
- Explain the negative effects of salt on plant growth
- Describe how to make compost from garden refuse and other available organic substances
- Explain the effects of overuse of fertilisers
- Explain the significance of legumes in maintaining soil fertility
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