Explanation

(a)Characteristics of Clay: 
- Particle size less than 0.002mm/ very fine particles/ smooth texture. 
-Very small pore spaces. 
-Numerous pore spaces.  
- High water holding capacity. 
- Hard when dry. 
- Poor drainage. 
-Very easy to mould into shape/High plasticity. 
- It swells when wet and cakes when dry. 
- Absorbs and releases heat slowly. 
- Sticky when wet. 
- Poor aeration. 
-High nutrient level/High Cation Exchange Capacity. 
-Colloidal in nature. 
-High capillarity. 

(b) Effects of drought on plant growth and development: 
-Delay in flowering/reduction in flowers/flower abortion. 
-Poor crop establishment. 
-It leads to a reduction in leaf area. 
-There is a reduction in cell size and inter-cellular volume. 
-Several physiological processes may decrease due to the dehydration of protoplasm. 
-Water stress produces important changes in carbohydrate and nitrogen metabolism of plants. 
-There is a decrease in the production of green matter. 
-There is a reduction in photosynthesis. 
-It impairs desired quality, that is, appearance, fibre content, firmness, etc. 
-There is reduction in yield. 
-Wilting. 
-Possible death of plants/crop failure. 
- Lower resistance/prone to diseases. 
-Difficulty in pegging especially in groundnut. 

(c) Symptoms of phosphorus deficiency in crops: 
-Purple and brownish colouration of leaves, from tip backwards. 
-Stunted growth. 
-Poor root development. 
-Immature fruit drop. 
-Lodging in cereal crops. 

(d)  Ways in which soil reaction and soil temperature are important in crop production 
(i) Soil Reaction: 
-It affects the activities of soil micro-organisms. 
-It affects the availability of certain soil nutrients. 
-It affects the solubility of certain elements which may be toxic to crops at higher concentration. 
-It determines the type of crops to grow. 
(ii) Soil Temperature: 
-The decomposition of soil organic matter is also affected. Influences rate of seed germination. 
-Influences the rate of photosynthesis. 
-Affects distribution of crops.
 - Affects maturity and ripening of crops. 
-Influences the rate of evapo-transpiration. 
- Influences root development. 
- It affects the population of soil microbes. 
-Low temperature causes a decrease in metabolic activities and reduction in enzymatic reactions. 
-High temperature will also affect the activities of micro-organisms. 
- It affects the level of soil moisture, absorption of water and nutrients by roots. 

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