Increased planting densities of cassava and maize, and the application of nitrogen, phosphorus, and potassium fertilizer increased the productivity of cassava-maize intercrops in southern Nigeria. Both maize cob yield and cassava root yield followed the same trend of being higher at high planting densities and with fertilizer application. A maize fertilizer regime targeting nitrogen, phosphorus, and potassium performed better than a cassava-targeting regime for maize yields, while the cassava regime performed better under very low soil fertility conditions. The height of maize from previous crops can be used as a proxy for soil fertility and predicting the response of maize to fertilizer - responses were higher when maize height was

1. Developing Recommendations for Improved
Cassava-maize Intercropping in Southern Nigeria
OYSCGA
Introduction
Cassava-maize intercropping is commonly practiced in southern Nigeria. Maize provides
food and income early in the season (~ 3 months) before the cassava harvest (~ 9 - 15
months later). However, both crops produce low yields (cassava < 10 tha-1 and maize < 1
t ha-1) in farmers’ fields, while attainable cassava yields are > 48 t ha-1 and maize yields
are > 5 t ha-1.
Materials and Methods
Sixty-two (in 2016) and seventy (in 2017) non-replicated trials were established in
farmers’ fields in five states within two agro-ecologies (Humid forest and Derived
Savanna) in Nigeria. Farmers could choose between 2 early maturing (90 to 95 days)
maize varieties (yellow or white grains) and 2 erect cassava varieties (TME 419 or TMS
98/0851). In 2016, we tested cassava and maize at low planting densities (10,000 and
20,000 plants ha -1, respectively) against high densities of both crops (12,500 and
40,000 plants ha-1), and 2 fertilizer regimes: FM with 90:20:37 and FC with 75:20:90
kg ha-1 of N:P:K. In 2017, cassava was always planted at high density and maize tested
at low and high planting densities in the 2 fertilizer regimes; FC was modified to
90:20:90 kg ha-1 of N:P:K. Fertilizer was applied in FM as basal N:P:K 15:15:15, plus
two equal splits of urea at 3 & 5 weeks after planting (WAP); in FC application was as
basal TSP plus three splits of urea and MoP at 4, 11 & 17 WAP.
Objectives
• To determine the effect of increased maize planting densities on maize cob and
cassava root yield.
• To determine the effects of 2 fertilizer regimes (targeting maize = FM or targeting
cassava = FC) on maize cob and cassava root yields.
• To derive a proxy for soil fertility assessment as a basis for fertilizer recommendations.
Maize:
the number of marketable cobs was higher at high than at low planting density in both
years with and without fertilizer application (Fig. 1). The FM fertilizer regime performed
better than the FC regime.
Cassava:
root yield followed a similar trend as marketable cob numbers in both years (Fig. 1).
However, there was a slight (< 5 %) decline at high maize density compared to low
density in 2017.
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Using maize height as predictor to response to NPK fertilizer appears
possible. When maize height in control treatments was ≤ 142 cm at maturity, response to
NPK was higher and always positive, producing on average 0.4 large cobs m-2 (Fig. 3),
than when maize plants were taller than 142 cm.
Fig.1: Effect of (maize and cassava) planting densities and NPK on marketable cobs (a,c) and tuberous root (b,d) yields in cassava-
maize intercropping system. LC: low density cassava (10000); HM: high density cassava (12500); nil: 0:0:0 NPK; FM: 90:20:37 NPK;
FC: 75:20:90 NPK. All planting densities are in hectare.
(a) (c)
(b)
(d)
Year 2016 Year 2017
Results - average treatment responses
Conclusion
Increasing planting densities of cassava and maize, and N:P:K application increased the
productivity of cassava-maize intercrops. The height of maize from previous cropping can
be used as a proxy for soil fertility and thus the expected response of maize to fertilizer
application.
Results – fertilizer response across sites
Fig. 2: Relationships between number of marketable cobs (a,b) and tuberous root (c,d) yields with
and without (control) NPK application. Negative value implies a negative effect of fertilizer
application.
(a)
(d)
(b)
(c)
Fertilizer regime
FM
FC
Results – a proxy for soil fertility
Fig. 3: Conditional inference tree for the expected effect of fertilizer on the number of large cobs m-2 (y-axis)
explaining response to N:P:K fertilizer across sites using maize height as a predictor.
Charles Chigemezu1,3, Christine Kreye2 Magdalena Necpolova1, Pieter Pypers2, Adeyemi Olojede3, Mutiu Busari4, Mark
Tokula3, Florence Olowokere4, Shola Ejalonibu3, Ademola Adebiyi2 Meklit Tariku2, Stefan Hauser2, Johan Six1
1 Swiss Federal Institute of Technology, ETH-Zurich, Switzerland; 2 International Institute of Tropical Agriculture (IITA), Nigeria and Kenya; 3National Root Crops Research Institute (NRCRI), Nigeria;
4Federal University of Agriculture Abeokuta (FUNAAB), Nigeria
Maize and Cassava:
In both years, both
crops followed the same
trend: fertilizer response
declined and became
negative as the soil
fertility of the site
increased as indicated
by cob and cassava
yield in the control
treatment. The maize
fertilizer regime tends to
be superior across all
sites for the maize crop.
For cassava, there
appears to be shift
when control yields
were very low, the
cassava fertilizer regime
outperformed the maize
regime.