The Food Crisis Flashcards
What are some key events in the agri-revolution?
Domestication of livestock and crops, labour availability, landscape modification, rotations, efficient tools, policy incentives, mechanisation, crop breeding and artificial inputs (pesticides and fertilisers)
What is soil degradation?
A reduction in the ability of soil to produce crops or support livestock
What are some of the causes of degradation?
Grazing and harvesting, removal or biomass, tillage and erosion
What are some solutions for soil degradation?
Contour strip cropping, vegetation, hedgerows, mulch, terracing
How much does agriculture contribute to GHG?
25%
Which GHG is emitted the most from agriculture?
N2O, poor soil management causes 1.8billion tonnes
What is nitrification?
Aerobic conversion of ammonium into nitrite then nitrate ion (which can be taken up by the plants)
What is denitrification?
The anaerobic conversion of nitrates into nitrogen gas by bacteria, which is then released into the atmosphere. Has high energy yields for efficient metabolism.
How is some N2O released during dentification?
Nitrate reduced to nitrite, nitrite reduced to N2O (nitric oxide) (only few bacteria have the gene to do this) majority of N2O reduced to N2, water synthesised throughout
What are the environmental controls for denitrification?
Temperature, soil moisture, soil redox, substrate availability and pH
What are mycorrhizas?
A mutualistic association between plant roots and soil fungi (exchange nutrients for sugar)
What are some ectomycorrhizal host plants?
Predominantly woody perennial plants including boreal and north temperate forests and dipterocarps in SE Asia
What is mycelium?
The collective name for a network of hyphae (fine filaments produced by fungi)
What evidence is there that plants can take up organic form of nitrogen directly?
Synthesise a C-13 and N-15 version of glycine and inject in soil. Glycine taken up directly as C-13:n-15 ratio remains the same in the tree as what was injected- no messing with the molecules seen
What is ammonification?
Conversion of organic N to ammonium (usually from dead waste)
What plant family does nitrogen fixation?
Fabaceae family, they also form mycorrhizal and rhizobia, but these are separate
What is nitrogen fixation?
The reduction of N2 from the atmosphere to ammonia and hydrogen gas by bacteria living symbiotically in the root nodules of plants. It is catalysed by the nitrogenase enzyme.
