The correct answer is D. All of the above.
- Gravity water is water that is held in the soil by gravity. It is the water that is found in the largest pores in the soil and is the most easily available to plants. However, it can also be the most easily lost to runoff or evaporation.
- Hygroscopic water is water that is held to soil particles by molecular attraction. It is the water that is found in the smallest pores in the soil and is the least available to plants. However, it is also the most resistant to loss to runoff or evaporation.
- Capillary water is water that is held in the soil by surface tension. It is the water that is found in the intermediate pores in the soil and is the most available to plants after gravity water. It is also less easily lost to runoff or evaporation than gravity water.
All three types of water are important for plant growth. Gravity water is the most available to plants, but it is also the most easily lost. Hygroscopic water is the least available to plants, but it is also the most resistant to loss. Capillary water is the most available to plants after gravity water, and it is also less easily lost than gravity water.
The amount of each type of water in the soil depends on the soil type, the amount of rainfall, and the type of plant. Sandy soils have large pores and hold less water than clay soils. Soils with a lot of organic matter hold more water than soils with little organic matter. Rainfall adds water to the soil, and plants take up water from the soil. The type of plant also affects the amount of water it takes up. Plants with deep roots can take up water from deeper in the soil than plants with shallow roots.
The amount of water in the soil is important for plant growth. Plants need water to photosynthesize, to transport nutrients, and to cool themselves. If there is not enough water in the soil, plants will wilt and die. If there is too much water in the soil, plants may rot.