seminar 2: Daniell Flashcards
what is the pessimistic and optimistic prediction by 2050 for the rise in human pop size?
10bn
plateau at 8bn
are the cereal production and human pop size lines parallel and what does this mean?
no
per person on the planet there is less food
- higher demand for increased yield
the Haber-Bosch process has been industrialised within the last century
- what is it?
- what % of the worlds energy is spent making ammonia from this process
- artificial N fixation process and the main industrial procedure for ammonia production today, splits 3 stable N bonds to form reactive N
- 2%
per unit of food production what is happening to use of N, particularly as fertiliser?
using more and more reactive N
what did steffen et al estimate and what were 3 things discovered?
safe operating space for a range of systems
- direct agricultural involvement
- N cycle beyond its limit so high risk
- P cycle beyond its limit and may run out
what does it mean we cant continue to do because the N cycle is beyond its limit?
cant put as much reactive N into atmosphere mainly from fertiliser as it causes eutrophication and GHG emission
according to 2016 UK estimates what % is due to agriculture and why is this an underestimate?
10%
does not include fertiliser production
in terms of GHG emissions from agriculture how does nitrous oxide compare to CO2?
- what is the main source for each of the gases?
N2O 3 times more potent than CO2
- CO2: fuel for agriculture
- methane: ruminants
- N20 from fertilised field and leakage from N cycle
when looking at the C footprint for malt production what % GHG emissions is from
- fuel
- N20 from soil
- N fertilsier
- 17%
- 35%
- 48%
from an EPA give 3 points on the nitric and adipic acid production industrial process for reducing emissions
- major source N20
- all processes involved have costs
- if all processes in play can save 79% GHG emissions
from an EPA give 4 points on the non rice croplands for reducing emissions
- no costs to reducing emissions such as if tillage of fields
- less fertiliser, less GHG emission
- sometimes increased fertiliser can reduce emissions
- if all processes in play can save only 10%
what does increasing N do to grain yield and why only until a point?
increases
saturation occurs
where is the EU on the yield response curve?
not adding N we need for optimum yield but are adding max fertiliser can for economic yield
- cost if reduce N
where is China on the yield response curve?
further along than EU as adding lots of fertilizer as is cheap but means poor N use efficiency and lots of GHG emissions and leaching damage
- gain if reduce N
where is Brazil on the yield response curve?
adding low levels of N
- if add more N can cut GHG emissions
in the N cycle is there competition?
yes for compounds in the system such as ammonia which is competed for by plants, microbes and nitrifiers
what are the stages of denitrification?
NO3 -> NO2 -> NO -> N20 -> N2
why is N fixation highly regulated?
very expensive so not fixed unless needed to such as in N limiting systems, for example legumes do this
what is soil made up of?
bacteria and aggregates surrounded by water film
small pores are often low in water, what will bacteria here do?
be denitrifying to maintain respiration using nitrogen oxides and nitrates as a different electron receptor to O2
in the soil and plant system why is there competition for nitrate?
plant uses it for assimilation
bacteria and fungi use it to maintain respiration
in the plant microbe interaction what does the plant do? (4)
- physically alters soil environment
- chemically alters by releasing nutrients and C
- releases signalling compounds that initiate plant microbe symbiosis
- produce antimicrobial compounds that interfere with quorum sensing and inhibit microbial activity
what are some issues that may arise from plant microbe interactions? (4)
- plant growth limited by nutrient availability and ammonia is used by microbes
- roots often outcompeted for N by microbes
- microbial transformations of N limit availability of N
- nitrifying bacteria convert ammonia to nitrate leading to loss of N
in a fertilised system what is there a flush of after it rains?
nitrous oxide
