Compared to clay soils, sandy soils contain much more soil and air, drain well, and warm quickly. They also dry out quickly, which necessitates frequent watering that washes out valuable nutrients. The stressful condition varies according to the particular plant and its needs. There are systemic insecticides, fungicides, and weed killers. T taproot - a main root that grows straight down.
Dandelions have taproots, so do oak trees.
Taproots can go very deep if there is a lack of surface water. The object is to give the plant a more open structure. In growing plants from seed, thinning out means removing excess seedlings so those remaining are spaced far enough apart to develop well. Temperature and humidity affect transpiration rate. U unsaturated zone - portion of the soil profile which contains both air and water.