CH14 Soil Resources - EVR 1001

soil

uppermost layer of Earth's crust that supports plants, animals, and microorganisms

state factors that form soil

-weathering of parent material
-time
-climate
-organisms
-topography

soil composition

-mineral particles (45%)
-organic material (5%)
-water (25%)
-air (25%)

soil horizons

the horizontal layers into which many soils are organized, from the surface to the underlying parent material

soil organisms

millions of microorganisms in 1 tsp of fertile agricultural soil

services of soil organisms

-decaying and cycling organic material
-castings
-breaking down toxic materials
-cleansing water
-soil aeration
-mycorrhizae

nutrient cycling

nutrients are cycled between plants, organisms, and soil

soil texture properties

-sandy soils have good drainage
-clay is small and has high surface area

clay and nutrient-holding capacity

outer surfaces of clay have negative charge and attract positively-charged nutrients

soil acidity

-affects solubility of certain plant nutrients
-optimum soil pH is 6-7
-acid precipitation alters soil and causes forest decline

soil taxonomy

soil classification method places soils into 12 orders

spodosols

-form under coniferous forests
-too acidic for farmland

alfisols

-temperate deciduous forests
-high precipitation
-fertile soil

mollisols

-temperate, semiarid grassland
-fertile soil
-used to grow most grains
-deep rooting grasses

aridisols

-arid regions
-low precipitation

oxisols

-tropical and subtropical areas
-high precipitation
-little organic material

soil environmental problems

-soil erosion causes loss in soil fertility

soil erosion

-increases movement of sediment among ecosystems
-water pollution

nutrient mineral depletion

harvesting crops disrupts natural nutrient cycling

soil salinization

-gradual accumulation of salt in the soil
-arid and semi-arid areas

desertification

degradation of once-fertile land into nonproductive desert

desertification causes

-overgrazing
-erosion
-forest removal
-overcultivation

zai holes

the man who stopped the desert

conservation tillage

residues from previous year's crops are left in place to prevent soil erosion

crop rotation

rotating use of different fields from crop to crop each year, to avoid exhausting the soil

contour plowing

plowing matching natural contour of land

strip cropping

alternate strips of different crops along natural contours

terracing

creating terraces on steep slopes to prevent erosion

cover cropping

crop planted primarily to protect soil from erosion after the harvest of one crop and before the next crop is planted

organic fertilizers

-chemically complex, slow-acting, long-lasting
-animal manure
-crop residue
-bone meal
-compost

soil reclamation (restoration)

1. stabilize land to prevent further erosion
2. restoring soil to former fertility

agroforestry

land use practices in which trees and crops are planted together to improve soil fertility in degraded soils