Exam References

Question 1

Point 1 (Paragraph 1)

Answer 1

(Abd-Alla, et al., 2023) and (Menegat, et al., 2022) -

-highly dependent on synthetic N to facilitate global population growth
-110 million tonnes to agricultural soil in 2020-2021
-increase 50% from 2012 levels by 2050

Question 2

Point 2

Answer 2

(Blumenthal, et al., 2008)

-N fertilisers used in high volumes as most limiting factor in crop production
-Influencing yeild and nutritional properties of the crop

Question 3

Point 3

Answer 3

(Belete & Yadete, 2023)

-N synthetic fertilisers compromise agro sustainability
-Facilitate short rotation monocultures causing soil degradation, acidification, and erosion
-Risks future crop failure
-60% of fertilisers leach into environment

Question 4

Point 4

Answer 4

(Abd-Alla, et al., 2023)

-465 teragrams C02 reasled from fertiliser manufactroing annually, not transport or field application
-using the Haber-Bosch

Question 5

Graph (after first paragraph)

(Between points 4 and 5)

Answer 5

(Menegat, et al., 2022)

Figure 1 - Global rate of nitrogen fertiliser applied per unit of cropland (kgN/ha)

X - 1964 - 2018 (year)
Y - Fertilisation Rate (0 - 65) (KgN/ha)

Practice graph draw up

Question 6

Point 5 (Paragraph 2)

Answer 6

(Mylona, et al., 1995)

-N fixing symbiosis, rhizobia bacteria invade a legume plant species root system whereby it is released into cytoplasm and surrounded by plant-derived peribacteroid membrane.
-Forms nodules on roots, matures to synthesise atmospheric N into ammonia in exchange for carbohydrates as an energy source

Question 7

Point 6 (Paragraph 3)

Answer 7

(Johnston & Poulton, 2018) and (DEFRA, 2020)

-Agro benefits of biologically fixed N widely known
-Mixed farming legume-rich arable ley rotations commonplace in UK until 1960-70’s (1)
-Disappeared as become increasingly uneconomical (2)

Question 8

Point 7

Answer 8

(Coolegde, et al., 2022)

-Temporal leys alleviate soil degradation and build soil fertility and structure
-Naturally reduces crop pests, pathogens and weeds
-Economic diversification provides notorious livestock pasture, livestock recycle nutrients back into the soil

Question 9

Point 8

Answer 9

(Pan, et al., 2022)

-Decrease dependence on expensive N fertilisers
-Reducing fertilisers reduces denitrification and therefore N turnover in soil
-reduce the approx 2.5 to 5.8 terragrams of nitrous oxide its application releases atmospherically annually

Question 10

Point 9

Answer 10

Austen, et al., 2022

-Decades degraded arable soil
-Three year grass-clover ley cycle improved soil quality
-Direct drilled wheat after herbicide treatment, yield between 92 - 106% UK average in 2018 producing 7.7 t ha-1 whilst only using 25% conventional fertiliser amount (~35 kgN/ha-1)
-At least double the wheat yield produced by ploughing and min tillage with no prior ley rotation
-Figure 2

Question 11

Point 10

Answer 11

(Nkonya, et al., 2016)

-Outlines negative effects continual monoculture cropping has on soil productivity
-Whilst proving soil health and fertility can be regenerated in a relatively short period, slows soil erosion
-Reducing the estimated 66 billion USD global cost of associated soil-degrading agricultural practices

Question 12

Figure 2 (between points 10 and 11)

Answer 12

(Austen, et al., 2022)

Figure 2. Total wheat grain yield in 2018 (t ha-1, corrected to 15% moisture) (ploughed = 3.9 t ha-1, min tillage = 3.4 ha-1 and ley/direct drilled = 7.8 t ha-1)

X = upto 8 Total grain yield (t ha-1, corrected to 15% moisture)

Y = Ploughed, min tillage, ley/direct drilled (Tillage treatment)

Question 13

Point 11 (Paragraph 4)

Answer 13

(Adamczewska-Sowinska & Sowinski, 2020)

-Monoculture to polycultures (grow both N fixing species (mainly legume) and non-N fixing species simultaneously)
-Increase biologically fixed ammonia increases N availability to non-legume crops
-Reduces N fertilisers dependance

Question 14

Point 12

Answer 14

(Adhikari, et al., 2021)

-Rice paddies planting Azolla
-Symbiotic relationship with cyanobacteria Anabaena azollae

Question 15

Point 13

Answer 15

(Kimani, et al., 2020)

-Increase biological source of N, decrease expensive N fertiliser
dependence
-Significantly reducing N2O emissions aprrox between 79-84% per grain yield

Question 16

Point 14

Answer 16

(Fukagawa & Ziska, 2019)

-Important as rice a staple food for more than half the worlds population

Question 17

Point 15 (Paragraph 6)

Answer 17

(Elevitch, et al., 2018)

-Leguminous agroforestry trees usually support both arbuscular mycorrhiza and nodulating N-fixing bacteria
-Alley cropping
-Reduced soil degradation and erosion
-Increasing nutrient build-up and use efficiency
-Carbon Sequestration
-Increase biodiversity

Question 18

Point 16

Answer 18

Rosenstock, et al., 2014

-Gliricida sepium (legume tree species) with maize (Zea mays) central Africa
-42% greater yield compared to non-fertilised fields
-Similar yield magnitudes to field receiving 92 kg mineral N fertiliser per hectare
-More annually stable yields (over 13 year period)

Question 19

Point 17

Answer 19

(Bracken, 2019)

-Polycultures more sustainable
-Lower fertiliser requirement
-More efficient use of limiting nitrogen
-Greater pest resistance
-Increase soil stability
-Certain scenarios retaining similar primary crop yields

Question 20

Conclusion

Answer 20

-Utilising biological N-fixing plant
-Sustainable agriculture delivering food more efficiently with less inputs and waste including the use of N fertiliser
-Management implemented correctly, reduce N limitation, minimal or no N fertilisers
-Reduced expenditure
-Improves soil fertility and structure
-Greater food security with more stable and resistant yields to inevitable climatic changes
-Mitigates against climate change as production and application of fertilsers releases largeramounts of C02 and N2O