BIO 162- ch. 36.2 A Dynamic mixture of living and nonliving components

texture

the proportions of gravel, sand, silt, and clay

why is soil texture important

it affects the ability of roots to penetrate and obtain water and nutrients, as well as to anchor and support the plant body

affects the soil’s ability to hold water and make it available to plants

texture and water content dictate the oxygen available for cellular respiration

ways that farmers can reduce soil loss

planting rows of trees as windbreaks

using techniques that minimize the amount of plowing and tilling needed to control weeds

planting crops in strips that follow the contour of hillsides

anions in soil

usually dissolved in soil water because they interact with water molecules via hydrogen bonding (minue phosphate ions); are readily available to plants for absorption but are also easily washed out of soil by rain

leaching

the loss of nutrients via the movement of water through soil

cations in soil

dissolve in soil water but are not as immediately available as anions

cations interact with

organic matter that is rich in negatively charged organic acids; and the surfaces of clay particles that are in rich mineral anions

cation exchange

occurs when protons or other soluble cations bind to negative charges on soil particles and cause bound cations to be released from the soil

they become available for uptake by nearby plant roots