CGS NS 202 Study Guide - Final Guide: Primary Production, Tillage, Crop Residue
16 May 2018
School
Department
Course
Professor
o Gross production: assimilation of energy by autotrophs
o Net primary production (NPP): energy remaining after respiration, used to generate biomass
• Net primary production of ecosystems
o High net primary productivity: ecosystems whose plants rapidly convert solar energy to biomass (S.A, Africa)
• Population Growth = Urbanization and Sprawl
• Meat consumers: America, australia
• Degradation of Land Resources
o Overgrazing
▪ Most significant contributor to soil degradation
▪ Rangelands occupy 40% of Earth’s land surface
▪ Rangelands occupy four times as much area as croplands, primarily in regions unsuitable for crops
▪ Land degradation most pronounced in Australia (80%) and Africa (49%); also evident in the Middle
East, northern india, central asia, mongolia, northern and western china
• Degradation of Land Resources
o How to Avoid Soil Erosion
▪ Conservation tillage-- leaves 30% of more of soil surface covered with previous year’s crop residue
▪ Mulch-till- entire field is tilled before planting, with crop residue partially incorporated into soil
▪ Strip-till- fields are tilled only in narrow raised rows to be planted; remainder is left with residue
▪ No-till: crops are planted in undisturbed residue of the former crop on field without tilling
o Terraces, conservation tillage, and filter strips help reduce erosion rates while maintaining or even increasing
crop yields.
o Improper mechanical tillage
o
o Repeatedly growing crops without fallow periods
o Poor water management of irrigated fields
▪ Water logging
▪ Salinization -- salts naturally present in soil dissolve in rising water table and accumulate at surface,
positioned plant roots
▪ Salinization causes potentially irremediable damage
o Deforestations
o Forests cover approx 30% of world's land area
o Clearing land for agricultural causes greatest loss
o Gathering of fuelwood also causes significant loss
o Commercial lumbering decimates tropical hardwoods
o Cattle ranching has destroyed more tropical forest than any other activity-70% of forested land in panama and
costa rica is now pasture land
• 10 countries with largest annual net forest loss:
o Brazil, sudan, mexico, argentina, etc.
• Net forest Gain
o China, us, spain, india
• Solutions?
o Produce and consume less meat
o Rotate crops; don't plan monocultures
o Artificially select domesticated crop species for better yield
▪ Modern tech. Does this via genetic engineering which is faster than selection of offspring
▪ GMOS
• Climate Change and the Human Impact on the Environment
o Geological Time Scale
▪ The sun will increase solar output
▪ Natural heating of earth will occur
▪ Eventually earth will be too hot to support life
▪ Smaller changes in the sun's activity may affect climate
• Sun spots
• The Little Ice Age
o Cooling of climate between 1150 and 1460
o Very cold climate between 1560 and 1850
o Agriculture
▪ Growing seasons changed 15-20%
find more resources at oneclass.com
find more resources at oneclass.com
