Final answer:
To improve soil drainage and water retention, add organic material such as compost or peat moss, which enhances soil structure, porosity, and nutrient content while maintaining moisture levels suitable for plant growth.
Step-by-step explanation:
To improve both drainage and water holding capacity in soil, you can add organic material such as compost or peat moss. The organic substances help create better structure in the soil, which increases soil porosity and allows excess water to drain away more efficiently, while at the same time, enhancing the soil's ability to retain moisture. The balance of sand and clay content in loams creates an ideal texture for agricultural purposes as it can drain excess water yet retain a good amount of moisture.
Adding organic material can also increase the content of nutrients in the soil, and provide energy for soil microorganisms that play a crucial role in maintaining soil health. Soil structure is vital as it involves the ratio of solids, water, and air, which influences oxygen levels and water availability to plants. To address an existing soil structure that's either too sandy or too clay-rich, adjustments can be made by adding the appropriate materials to achieve better texture and functionality.