Humans and Agriculture PDF

Humans and Agriculture - About 14,000 years ago, we converted from a foraging lifestyle to a farming lifestyle artifically selecting best - Wheat has been grown for about 10,000 years yield of wheat - These wheat cultivars went...

Humans and Agriculture - About 14,000 years ago, we converted from a foraging lifestyle to a farming lifestyle artifically selecting best - Wheat has been grown for about 10,000 years yield of wheat - These wheat cultivars went through artificial selection - Selected for traits that are beneficial for cultivation - Resources were supplied, water, nutrition (fertilizers,1940) and space between plants - Plant breeding-→ Green revolution (yield increased to sustain the demand from growing population) - - Disadvantage of growing the same crop for 10,000 years (monoculture) - Genetic engineering and high-tech agriculture 10 billion current population > 8 2 billion. ??? How to produce enough ? by 2050 ? how plants grow & reproduce will help us survive understanding - Genetic Modification (GM) native to be inserted to a ↳ foreign gene HOMEOSTASIS genome Environment/metabolism pH solutes water temperature pressure Metabolism (life!) maintain the Internal environment to Homeostasis : Regulating state a relatively stable for changes process compensating/adjusting - it is a dynamic external environment. in the internal and - How do plants maintain their balance? - Uptake of water and nutrients from soil - What is available in soil and where does it come from? - What nutrients are essential for plant growth? How do we know? - How do plants transport water and nutrients to other parts - How do plants transport sugar? Mechanisms - How do plants exchange gases through the stomata? we cannot even make our own Methionine (start codon)  Essential Elements for Plants ▪ Essential element: 17 essential elements for plants needed for optimal growth of plants - Components of nucleic acids (N, P), amino acids (N, S) Function as enzyme cofactors (Ca2+) Role in photosynthesis (Mg2+, Fe2+, Fe3+) or regulation of osmotic potential (K+) ▪ Macronutrients essential in large quantities not essential elements C,H, O, from air and water, not considered minerals(account for 96 % of dry mass) - N, P, K, S, Ca, Mg are mineral nutrients, available to plants through the soil as dissolved ions in water need to be in their IONIC form - ▪ Micronutrients essential in trace quantities Cu2+, Cl-, Ni2+ ↳ trace amount , but essential Nitrogen Limitations ▪ Nitrogen (N) Abundant element in air, most limiting to plant (78 %) Triple bond requires specific enzyme Nitrogen cycle provides soil nitrogen Nitrogen Cycling ▪ Nitrogen fixation incorporates atmospheric N2 into plant-available compounds NH4+ Nitrogen-fixing bacteria ▪ Bacterial ammonification breaks decaying organic N compounds into NH4+ Plants take up NH4+, but prefer NO3- ▪ Bacterial nitrification oxidizes NH4+ to NO3- ▪ Plants convert NO3- to NH4+ to assimilate N into organic compounds  Atmospheric nitrogen (N2) Decaying organic matter Fertilizers Nitrogen-fixing NO3– converted to bacteria convert N2 to ammonia NH4, which is moved (NH3) which via xylem to the Ammonifying shoot system dissolves to form ammonium N - bacteria Ammoni- Nitrifying bacteria (NH4+) Fixation fication Ammonium Nitrification Nitrate (NO 3–) (NH4+) Copyright © 2013 by Nelson Education Ltd. Fig. 40.8, p. 1007  ↓ Nitrogen fertilizer = ↓ Neo = ↓ Global warming (ntrous oxide) Organics ladding legumes) ( more potent than CO2 in trapping heat N2 NH3 NH4+ NO3- Legume (pea) Root nodules: Symbiotic NO3- association with nitrogen fixing bacteria. NH4+ Organics C O  of so tall (due to use - lodging problems = plants grew more nitrogen fortizers) 3 Yielded of ble so unstable became yet plants increased height.  Nitrogen Depletion from soil - Harvesting of crops removes all the nutrients from soil - Early agriculture- shifting of lands for agriculture - Allowed to land to replenish lost nitrogen through free- living bacteria or symbiotic association with roots - Increase in population led to continuous use of lands - Depleted all nitrogen- an essential element How to Improve Nitrate content in soil? - Crop rotation with legumes helps but not sufficient - Use of nitrate fertilizer tremendously increased yield during green revolution (1940 -1970) Caddition of legumes) - Plants grew taller and posed lodging problems - Led to developing dwarf breeds of both rice and wheat (reducing a hormone required for stem elongation) How to deal with tall, lodging prone plants? - Plants grew way taller and posed lodging problems - Researcher bred cereals (crossing with other cultivated varieties) - Led to developing dwarf breeds of both rice and wheat (reducing a hormone required for stem elongation) - This allowed the dwarf crop to produce more yield with fertilizers and had no lodging problems  Excess?? Fertilizers end up in the water system - Only 10% of nitrogen added to crop-lands ends up in the biomass, rest of them are lost as surface runoffs and end up in rivers/lakes/oceans - This causes algal blooms (eutrophication) which eventually sink to the bottom where bacteria feed on them leading to depletion of oxygen - Leads to catastrophic consequences to animal life on the sea or lake floors. - It is a huge trade-off, we benefit tremendously by applying Nitrogen fertilizers but end hurting the ecosystem due to the run-off Eutrophication: Enrichment of an ecosystem with chemical nutrients such as compounds containing nitrogen and phosphorous https://iboess.wikispaces.com/5.4+Eutrophication Soil ▪ Living skin of the earth ▪ Contains soil-mineral particles, compounds, ions, decomposing organics, water, air, organisms sand is larger Soil particles are various in sizes, ex, sand (2-0.02mm), silt (0.02-0.002mm), and clay particles (