http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/en/ Presentation by Tim Crews (The Land Institute) describing soil-related challenges for crop production and research on the benefits of perennials vs. annuals to enhance soil characteristics. The presentation was delivered in occasion of the “Putting Perennial crops to work in practice” workshop in Bamako, Mali (1-5 September 2015).

1. Land and Soil Issues in Africa:
Disturbance, succession and the promise
of ecological intensification
Tim Crews
The Land Institute
Bamako, Mali, September 4, 2015

2. Limitations to Productivity
-erosion by wind and water
-profound nutrient limitation
N, P and other elements
-phosphorus fixation on Fe and
Al oxides
-difficulty improving soil organic
matter status
-soil acidity
-low effective rainfall
(loss through runoff and
leaching)

3. Limitations to Productivity
-erosion by wind and water
-profound nutrient limitation
N, P and other elements
-phosphorus fixation on Fe and
Al oxides
-difficulty improving soil organic
matter status
-soil acidity
-low effective rainfall
(loss through runoff and
leaching)

5. Limitations to Productivity
-erosion by wind and water
-profound nutrient limitation
N, P and other elements
-phosphorus fixation on Fe and
Al oxides
-difficulty improving soil organic
matter status
-soil acidity
-low effective rainfall
(loss through runoff and
leaching)

7. Ecosystem Services
Regulating
• Biological pest control
• Pollination
• Nutrient mineralization
(Bommarco et al. 2013)
Driver: Biodiversity

8. Ecosystem Services
Regulating
• Biological pest control
• Pollination
• Nutrient mineralization
Supporting
• Soil formation and erosion
prevention
• Nutrient retention
• Build soil organic matter
--Soil structure (root
penetration, gas exchange,
water infiltration)
--Carbon storage and ghg
gas regulation
• Water infiltration, storage
and purification(Bommarco et al. 2013)
Driver: ?Driver: Biodiversity

10. frequencymagnitude
extent

11. Frequency + Magnitude + Extent

12. Global median changes in soil depth per year
in millimeters
Native
Ecosystem
No-till
Agriculture
Plowed
Agriculture
MontgomeryPNAS2007
+0.004 -0.065-1.520

13. Schlesinger1986
Loss of soil carbon to the atmosphere with plow conversion of
perennial plant communities to annual agriculture.

14. Temperate Grasslands Annual Grains
2.5 m
BNPP: 52, 67% (24-87%)
Annual turnover: 47-58%
Saugier et al. 2001,
Lauenroth and Gill 2003
BNPP: 15%
Annual turnover: 100%
Goudriaan et al. 2001
J. Richardson/J. Glover
Belowground Allocation (% of NPP)

15. Our food-producing
ecosystem is set back to--and
held--in a very early stage of
secondary succession
Implications?

16. nitrate leaching
gases (N2,N2O)
30-60% of the nitrogen
fertilizer applied to grain fields
is not taken up by the crop runof
f

17. “Discontinuous, insufficient or no fertiliser application over a certain
period of time may lead to severe soil degradation through nutrient
depletion and loss of organic matter. ….The two states, responsive
and non-responsive soils do not necessarily represent a continuum.
Reversibility may be lost when a certain threshold of soil degradation
is surpassed. The magnitude of the distance between these two
alternate states is known as hysteresis.”
Tittonell & Giller 2013
Retro-succession
From secondary towards primary succession
Soils to parent material

18. Tittonell & Giller 2013

19. Tittonell & Giller 2013

20. Improve sustaining and regulating
ecosystem services
Water holding capacity
Aggregate structure
Belowground food web
Nutrient availability
J. Richardson/J. Glover

21. Soilprotection
Carbonandnutrientretention
Functionsofsoilmicrobiome
Wateruptakeefficiency +
-
S U C C E S S I O N

22. C entering from photosynthesis kg / m2 / yr
0.25 0.18
C in soil organic matter kg / m2
5.6 21.6
Desert Tundra

23. R
o
o
t
s
b
u
i
l
d
S
O
M
2011-Nature

24. Estimates of annual C sequestration from
grassland restoration and cellulosic
biofuel studies
Restored grasslands: 332 kg C ha-1 y-1 (31-13000)
Post & Kwon 2000
Miscanthus biomass 160-820 kg C ha-1 y-1
Mishra et al. 2013
J. Richardson/J. Glover

25. In the conversion of CRP land into cropland, one tillage
event resulted in the loss of ~8 years of carbon sequestration
being lost compared to no-till (herbicide) conversion

26. Glover et al. 2010
Relative abundance of nematode trophic groups from Culman et al. 2010
Perennial Hay MeadowAnnual Wheat

27. Annual sorghum in a very low fertility trial at ICRISAT, Mali

28. Pigeon pea in a very low fertility trial at ICRISAT, Mali
Using N to go after P?

30. ~45 km north of London, 704mm precip yr-1, 120m elevation
Broadbalk Continuous
Wheat since 1844
Park Grass Hayed
Perennial Meadow
Since 1856
Rothamsted Research

31. 0
2
4
6
8
10
12
14
16
18
0-23 24-46 47-69 70-92
µgPgdw-1soil
Soil depth (cm)
Broadbalk Without Fertilization (nil)
Annual Wheat
0
20
40
60
80
100
120
140
0-10 11-23 24-46 47-69 70-92
Soil depth (cm)
µgPgdw-1soil
Park Grass Without Fertilization (nil)
Perennial Hay
Comparison of resin-available Pi and microbial biomass Po with depth
= resin-available Pi
= microbial biomass Po
Crews & Brookes 2013

32. 0
10
20
30
40
50
60
Active Po
Low Pi
Active cycling Po vs. as proportions of total P
%Pheldinfractions
Perennial
Annual
Perennial
Annual
No P Fertilizer + P Fertilizer

33. Photo: D. Larson

34. Udawattaetal.2008

35. macro-pores created by
large perennial roots
improve infiltration
Greater soil organic matter
contents improves water
storage
Deep roots expands crop
water uptake potential in
time and space

36. J. Richardson/J. Glover
Translocation of nutrients into
roots, rhizomes and crowns
Nutrient retention by deep roots
SOIL ORGANIC MATTER
• More N & P cycling in and out of
soil organic pools
• Shift in soil microbiome can favor
more efficient mycorrhizae and
N mineralizing microfauna
• Phosphorus stays available in
organic forms rather than
becoming fixed to Fe or Al oxides