Presented by Thomas Kätterer, Professor at the Swedish University of Agricultural Sciences (SLU), during GIZ's session, "Biochar and Its Practical Application to Restore Degraded Lands", at GLF Africa 2021.

1. Biochar and its practical application to restore degraded lands –
Experiences from field experiments in Kenya
Thomas Kätterer, Swedish University of Agricultural Sciences (SLU)
Co‐authors:
Kristina Röing de Nowina; Center for International Forestry Research (CIFOR)
Dries Roobroeck, International Institute of Tropical Agriculture (IITA)
Geoffrey Kimutai, International Institute of Tropical Agriculture (IITA)
Bernard Vanlauwe, International Institute of Tropical Agriculture (IITA)
Olof Andrén, Oandren, Uppsala
Erik Karltun; Swedish University of Agricultural Sciences (SLU)
Gert Nyberg; Swedish University of Agricultural Sciences (SLU)
Cecilia Sundberg, KTH Royal Institute of Technology, Stockholm

2. Biochar (BC) and soil fertility – 3 regions in Kenya
Main questions
• How do crop yields respond to different doses of BC?
• How persistent are yield responses over time?
• How do different feedstocks affect yield responses?
Experiments
• Long‐term trials since 2006
• Short‐term trials, 3‐4 seasons
• Participatory trials on 150 farms

3. Long‐term trials, since 2006
• Maize/soybean rotation
• BC rate 100 Mg ha‐1
• BC from Acacia
• 3 sites
• 20 seasons

4. Yield responses to biochar and mineral fertilizer, 10 years, 20 seasons
• Average yield responses to biochar
were 1.2 and 0.4 Mg ha‐1 in maize
and soybeans, respectively.
• Average yield responses to mineral
fertilizer were 1.6 and 0.6 Mg ha‐1 in
maize and soybeans, respectively
• Yield increases due to fertilization
and biochar application were
additive
• Yield responses were persistent over
time
Kätterer et al., 2019 Field Crops Res. 235, 18‐26
UC: Unfertlized
FC: Fertilized

5. 0
2
4
6
8
Grain yield (Mg ha
‐1
)
Embu
0
2
4
6
8
Grain yield (Mg ha
‐1
)
Kwale
0
2
4
6
8
0 1 5 10 0 1 5 10
Grain yield (Mg ha
‐1
)
Siaya
LR2015 SR2015 LR2016 LR2017
Unfertilized Fertilized
(Kätterer et al., in prep)
• 9 sites in 3 regions
• Maize monoculture
• Randomized block design
• BC produced at one site
with the same kiln
• Different BC feedstocks
• BC rates 1, 5, 10 Mg ha‐1
• DAP (18‐46‐0) 60 kg N ha‐1
• 1.5 years, 2‐3 seasons
Control
1 Mg ha‐1 BC
5 Mg ha‐1 BC
10 Mg ha‐1 BC
No fertilizer Fertilized
On‐farm trials – yield response at 4 BD rates per site and season
0
1
2
3
4
5
6
7
0 5 10
Grain yield (Mg ha
‐1
)
Biochar rate (Mg ha‐1)
Unfertilized
Fertilized
Across sites and seasons
• 4 tons more maize with 10 tons
of BC
• Response was consistent across
sites and feedstocks (coconut
shell, maize stover, coffee
husks)

6. (Karltun et al., in prep)
Participatory trials on 150 farms – maize yield increase vs. biochar dose
• Three regions – 50 farmer/region
• Maize and sukuma wiki (separate)
• Paired design – with/without biochar
but same management
• BC produced by farmers in their
stoves
• BC rates varied
• BC feedstocks varied
• Fertilization/manure varied
• 2 years, 2‐3 seasons

7. Conclusions
• BC effect on yield was persistent over 20 season
• BC effect was rather independent on feedstock type
• Already small doses of BC (1 ton ha‐1) doubled yields
• 10 tons biochar plus NP fertilizer increased yields almost 10 times
• Effects of BC and fertilizer were additive
• Mechanisms must be investigated further
• Soil application of locally produced biochar is a promising concept for increasing
food security on smallholder farms in Kenya

8. Thanks for your attention!
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