BIO3082 Lecture Notes - Lecture 13: Food Security, Peak Phosphorus, Grain Growth
Lecture 13 – Food Security 4: Food security in a changing world
• 60% people in world live on three grasses: rice, maize and wheat
• Increase of crop activity in 1960s to feed the populations
Three Main Drivers of Green Revolution
• Dwarf varieties of crops plants e.g. wheat, rice (1)
o More productive
▪ Invest more into reproduction
o More efficient
▪ Everything transferred to grain
▪ Harvest index concept
• Grain/biomass of whole plant
• Only so much water and nutrients – increase
productivity by having it in grain
o Grain growth and nitrogen contents of grains
▪ Nitrogen content increases → grain protein increases
• Flagleaf nitrogen concentration plateus → transfers it to
grain after photosynthesis
▪ Factors affecting grain size
• Water availability
• Photosynthesis
• Nutrients
• Number of cells
• Fertilizers: N, P, K (2)
o Increases in west and Asia
o Need to increase quality of fertilisers in African countries to increase
production
o Yield is driven by increase in fertiliser use
o Big nine macronutrients
▪ Carbon, oxygen, hydrogen
▪ Nitrogen, potassium, calcium, magnesium, phosphorus and
sulphur
o Importance of nitrogen
▪ Nearly all terrestrial systems are nitrogen limited
▪ Atmsophere is 70% N2
▪ Plants cannot access atmospheric nitrogen
• Use mostly ammonium (NH2) and nitrate (NO3)
• Can use urea and some organic compounds
▪ Farmers use animal manure to add nitrogen
▪ Invention of Haber-Bosch process – fertilisers could be made
from air
o Limits of use of fertilizers
▪ Nitrogen is a pollutant
▪ High costs
▪ Haber-Bosch process very energy intensive → CO2 emissions
o Resources are not in unlimited supply
▪ Peak phosphorus
▪ Have to add nitrogen and phosphate for plants to grow
▪ Phosphates are limited
find more resources at oneclass.com
find more resources at oneclass.com
