Nutrient uptake dynamics and dilution for cassava

1. OYSCGA
Study area, fertilizer treatments, yield assessment and data analysis
On-farm experiments were conducted at six locations in Nigeria across the major cassava growing agro-
ecologies of Western Africa (Tropical Rainforest – Cross River (Ogoja and Ikom), Forest Transition
Savanna – Edo (Ekpoma), and Guinea Savanna – Benue (Otukpo) during two seasons (2016-2017 and 2017-
2018).
RESULTS
www.iita.org I www.cgiar.org
Nutrient uptake dynamics and dilution for cassava
J.G. Adielea,d,*, A.G.T. Schuta, K.S. Ezuib, P. Pypersc, A. Olojeded, A.O. Anod, C.E. Egesid, K.E. Gillera
aPlant Production Systems Group, Wageningen University, P.O. Box 430, 6700 AK, Wageningen, The Netherlands
bAfrican Plant Nutrition Institute, ICIPE Campus, Duduville – Kasarani, Thika Road, Nairobi Kenya
cInternational Institute of Tropical Agriculture, ICIPE Campus, P.O. Box 30772-00100, Nairobi Kenya
dNational Root Crops Research Institute, Umudike, KM 8 Ikot Ekpene Road, P.M.B 7006, Umuahia Abia State, Nigeria
Intermediate harvest @ 4 and 8 months after planting (MAP). Final harvest 2016 and 2017 were @ 14 and
12 MAP. Weights of each harvested plant part (leaf, stem, and the storage root) were recorded per plot.
Sub-samples were collected and oven dried at 60°C until constant weight. Dried subsamples from leaves
with petioles, stems, and storage roots were analysed for total N, P and K concentration. R software (R
Core, 2019), version 3.5 with the lme4, lmerTest, and Predictmeans packages was used for statistical
analysis.
Findings
• The average uptake of N, P and K by
the whole plant at 4 MAP, across all
treatments, years and locations were
67, 61 and 52 %, respectively.
• The relative nutrient uptake and
allocation to plant parts overtime for
fertilized and unfertilized plants were
similar.
• Whole plant nutrient concentration
decreased with increasing biomass. On
average, the variation in the nutrient
dilution accounted by DM
accumulation was about 65% for all
nutrients.
Table 1. Nutrient application rates per treatment, (f) represents full rate of the optimized nutrient.
Treatment Nitrogen (N) Phosphorus (P) Potassium (K)
(kg ha-1)
1. Control 0 0 0
2. N150P40K180 150 40 180
3. NfPfK180 300 100 180
4. NfPfKf 300 100 300
Figure 1. Cassava cumulative plant nutrient uptake for N panels a,b,c, P in
panels d,e,f and K in panels g,h,i and total biomass in panels j,k,l. Symbols
indicate average values for harvests at 4, 8 and final harvests across the two
years. The arrows indicate the percentages of N, P and K uptake and biomass
production at 4 MAP compared to final harvest. NOTF = N150P40K180,
NfPfK2 = NfPfK180
Dynamics of whole plant nutrient uptake
Table 2. Critical dilution coefficients of N, P and K for different N, P and K levels, including nutrient limiting (Control) and
non-nutrient limiting (NfPfKf) conditions
N Dilution
curve
P Dilution
curve
K Dilution
curve
Treatment NC =
a(DM)-b
R2 NP = a(DM)-b R2 NK = a(DM)-b R2 Range DM
t ha-1
Control 32(DM)-0.55 0.53 3.1(DM)-0.48 0.45 19(DM)-0.6 0.57 5 - 60
N150P40K180 107(DM)-0.82 0.84 9(DM)-0.73 0.77 47(DM)-0.67 0.74 5 - 60
NfPfK180 90(DM)-0.67 0.67 8(DM)-0.6 0.72 40(DM)-0.58 0.80 5 - 60
NfPfKf 82(DM)-0.61 0.73 7.4(DM)-0.54 0.57 43(DM)-0.54 0.71 5 - 60
Nutrient dilution at different nutrient application rates
INTRODUCTION
The increasing demand for cassava in West Africa offers farmers the opportunity to
intensify production, earn higher incomes and boost their food supply. Therefore, the use
of inorganic fertilizers to improve productivity is inevitable in the future. Typically, the
assimilates are mostly partitioned to the shoot during canopy establishment and
partitioning to storage organs strongly increases from about 4 months after planting
(MAP). Understanding the nutrient uptake and dilution pattern during the growth cycle
can help to know the temporal nutritional demands of cassava and modify management
practices that will prevent nutrient deficiency as well as excess.
Objectives were to:
(1) understand the nutrient uptake of cassava as affected by fertilizer application;
(2) quantify the proportions of N, P and K in plant-parts and
(3) establish nutrient dilution curves and nutrition indices for cassava.
Nutrient dilution curve for maximum growth rate
Proportions and concentrations of N, P and K in
leaves, stems and roots
Figure 3. Proportions of N, P and K in leaves, stems and storage
roots at different growth stages, from approximately 4 months
after planting to full harvest (FH) across location and years.
Figure 4a, b and c. N, P and K dilution curves for plant nutrient concentrations as
function of total plant biomass per treatment, location and year. Each observation
represents an average of three replications for each treatment. The black dotted lines are
the upper and lower ‘envelop curves’ – Cmax and Cmin and the green line represents the
N, P and K dilution curves for treatments that are non-nutrient limited.
Figure 2. Differences between treatments in average N, P and K
concentrations (g kg-1) across locations and years in leaves, stems and
storage roots at different growth stages.
Nutrient concentration in leaves, stems and storage roots