Poster for CIAT 2009 Knowledge Sharing Week

1. Integrated Soil Fertility Management in cassava-legume systems
Pieter Pypers (TSBF-CIAT), Jean-Marie Sanginga (CIAT), Kasereka Bishikwabo (CIAT),
Sylvain Mapatano (DIOBASS), Adrien Chifizi (DIOBASS), Masamba Walungululu (UCB),
Wivine Munyahali (UCB), Janvier Bashagaluke (UCB), Willy Tatahangy (INERA),
Nkonko Mbikayi (INERA) and Bernard Vanlauwe (TSBF-CIAT).
System productivity
Productivity and net revenue in cassava-legume systems can be maximized using Integrated Soil Fertility Management (ISFM).
ISFM combines (i) improved germplasm, (ii) mineral fertilizer application, (iii) organic matter management and (iv) adapted agronomy.
This was demonstrated in on-farm trials with farmer groups in Sud-Kivu, Democratic Republic of Congo.
legume grain yield cassava tuber yield cassava stem yield net revenue
3000 30 20 6000
cassava tuber yield (t ha-1)
cassava stem yield (t ha -1)
bean grain yield (kg ha-1)
net benefits (US$ ha-1)
B/C = 6.7
B/C = 6.6
15
2000 20 4000
B/C = 6.8
B/C = 6.3
10
B/C = 4.8
1000 10 2000
5
0 0 0 0
fertilizer application - - - NPK NPK - - - NPK NPK - - - NPK NPK - - - NPK NPK
integration of - - 2nd - 2nd - - 2nd - 2nd - - 2nd - 2nd - - 2nd - 2nd
a 2nd legume legume legume legume legume legume legume legume legume
cassava spacing 1x1 2x0.5 2x0.5 2x0.5 2x0.5 1x1 2x0.5 2x0.5 2x0.5 2x0.5 1x1 2x0.5 2x0.5 2x0.5 2x0.5 1x1 2x0.5 2x0.5 2x0.5 2x0.5
Notes: Cassava spaced at 1m x 1m was intercropped with 2 legume lines between the cassava lines, and does not allow intercropping of a 2nd
legume. Cassava spaced at 2m (between rows) x 0.5m (within row) was intercropped with 4 legume lines between the cassava lines
in the 1st season (equal crop density as in the 1m x 1m system), and allows integration of another legume in the 2nd season (2 lines intercropped between the cassava lines).
In treatments with integration of a 2nd legume, a bush bean was grown in the 1st season, followed by a climbing bean in the 2nd season (5 months after cassava planting); the legume yield presented is the sum for the 1st and 2nd legume.
All treatments received a basal manure application of 2.5 t ha -1. Fertilizer was applied at 2 bags of NPK (17:17:17) ha -1 at planting (equally distributed to the cassava and the legume, and applied in the planting holes/lines).
In the treatment with fertilizer application and integration of a 2nd legume, additional fertilizer (1 bag ha-1) was applied at planting of the 2nd legume.
Improved germplasm Mineral fertilizer application
 Viral diseases are a major constraint for cassava  Cassava is often considered as a crop with low nutrient
production, particularly cassava mosaic disease demands that can be grown in poor or degraded soils.
(CMD). Cassava brown streak virus disease (CBSD) is
 Cassava exports high amounts of nutrients, particularly N
threatening cassava production in eastern and
(up to 70 kg N ha-1, mostly through aboveground biomass)
southern Africa.
and K (up to 160 kg K ha-1, mainly through the tubers).
 Disease-resistant cassava germplasm is essential to
 Cassava is highly responsive to fertilizer application.
increase productivity and stimulate investment in the
Observed tuber yield responses to fertilizer (2-3 bags of NPK
cropping system.
17:17:17 ha-1) varied between 30 and 160 %.
 Use of germplasm tolerant to abiotic stresses can aid
 Legumes are most responsive to P-containing fertilizers.
overcoming specific crop constraints, and stimulate
Cassava affected by mosaic disease Control (no inputs) P application enhances nodulation and N fixation.
investment in nutrient inputs. In legumes, tolerance to
Observed grain yield responses in beans varied between
drought, soil acidity and low soil P are important traits.
20 and 150%.
 Improved germplasm should be responsive to nutrient
 Appropriate fertilizer management (banding P-fertilizer in
application and have a high yield potential, to
the legume line, split application of N and K to the cassava)
maximize returns to investment in mineral fertilizer
and timely planting and weeding are essential to maximize
or organic inputs.
fertilizer use efficiency.
 Cassava and legumes are compatible in terms of
 Compound NPK-fertilizer is suitable because it matches the
water and nutrient demands. Choosing cassava
nutrient requirements of both crops.
varieties with a tall, slow-closing canopy can allow
integrating legumes during two consecutive seasons.  Activities are on-going to formulate site-specific fertilizer
recommendations, based on local soil conditions and crop
CMD-resistant cassava NPK applied at 2 bags ha-1
requirements.
Organic matter management Adapted agronomy (crop spacing)
2000
 Soil organic matter enhances nutrient cycling Civu (rich in organic matter, responsive)
 Cassava is commonly planted at a
and availability, performs important biological Kalongo (poor in organic matter, often degraded)
spacing of 1m x 1m (10,000 plants ha-1).
functions and improves soil physical conditions.
bean grain yield (kg ha )
-1
1500  Spacing the cassava at 2m between rows
 Organic matter application is often crucial to and 0.5m within the row allows
generate yield increases. Degraded soils with intercropping with legumes during two
low organic matter content are commonly 1000 consecutive seasons. Adapted agronomy
unresponsive to mineral fertilizer, but can be can increase legume production by 40%,
rehabilitated by adding organic inputs. Recent without affecting cassava production.
findings suggest that such unresponsive soils 500
 Crop rotation is important to reduce pest
can be identified using local soil classification
and disease pressure. The cassava 1st legume: groundnut (2 months after planting cassava)
knowledge. In Sud-Kivu, farmers distinguish red
0 intercropping system is sufficiently versatile
soils (Kalongo) and black soils (Civu).
control NPK manure manure to accommodate different legumes
+NPK
 Organic matter can be produced in situ, using (beans, soybean or groundnut).
promiscuous dual-purpose soybean or
 Combining improved germplasm, fertilizer
climbing beans.
application, organic matter management
 N fixation by legumes may increase above- and adapted agronomy can double net
ground biomass yield in cassava, which is revenue of the system.
important for food (leafs) and planting material
 This system has been positively evaluated
(stem cuttings).
by farmer groups. Farmers are currently
 Interactions between organic matter and using the system for multiplication of
mineral fertilizer remain poorly understood in planting material, and experimenting in a
cassava-based systems. large number of adaptation trials.
Dual purpose soybean 2nd legume: climbing bean (6 months after planting cassava)
Contact: p.pypers@cgiar.org www.cialca.org