Comparison of corn-based cropping systems for smallholder farmers in Nigeria
Akim Omokanye, Frank Kelleher and Alison McInnes
University of Western Sydney, Hawkesbury, NSW, Australia
ABSTRACT
Land-use intensification in Sub-Saharan Africa to meet increasing human food
and animal feed demands has led to overexploitation of land resources. Rising
prices of fertilizers, however, are forcing smallholders to reduce inputs of
inorganic N for cereal production.
In Nigeria, cereals and legumes are important components of most cropping
systems where ruminants are fed crop residues. The integration of small amounts
of inorganic N fertilizer, along with N from legumes, has the potential to
overcome N depletion in these intensive land use systems. In this study, field
experiments were conducted at a mid latitude (33o S) site in Australia to evaluate
the effect of legumes on maize yields in cropping systems typical of sub-humid
rainfall zones in Nigeria. Five cropping systems (CS) have been studied over two
years, comprising: i) corn – field pea – corn (CS1), ii) corn – intercropped
barley/lucerne – intercropped corn/lucerne (CS2), iii) intercropped corn/cowpea –
field pea – intercropped corn/cowpea (CS3), corn – barley – corn (CS4) and corn
– fallow – corn (CS5). In CS1, field pea was incorporated into the soil at mid
flowering, prior to subsequent corn planting, while for CS3 it was grown to
maturity for grain. Sub-plots within all corn (Zea mays L.) crops were fertilized
with 0, 60 or 120 kg N ha-1.
Productivity of the initial corn crop was similar for all cropping systems. For the
second corn crop (following the legume/barley/fallow treatments), mean grain,
stover and whole-plant yields were highest in CS1 and lowest in CS2 (P<0.05).
Corn yields in all CS increased significantly (P<0.05) with N fertilizer application
rates. Corn grain and whole-plant N uptake differed significantly (P<0.05)
between CS for second year corn, ranging from 82 to 121 kg N ha-1 and 127 to
198 kg N ha-1 respectively. Application of 60 and 120 kg N ha-1 increased mean
total N uptake by 36 and 65% respectively relative to the 0 kg N ha-1 control. N
recovery, as a percent of applied inorganic N fertilizer, was highest in CS4 (57%)
and lowest in CS2 (34%). Cropping options for the multiple crop/livestock
requirements and the implications of this research for Nigerian smallholders are
briefly discussed.
INTRODUCTION
Small-scale or family farms of less than 5 ha remain the basic food crop
production unit in Nigeria, accounting for over 90 percent of agricultural
production. Farm sustainability is threatened by rising real prices of purchased
inputs, forcing smallholder corn (Zea mays L) producers to use less inorganic N
fertilizer. The traditional approach to soil fertility maintenance (where land is not
limiting) has involved fallowing. However, increasing human (FAO, 1995) and
livestock populations (Winrock, 1992) have reduced the number of years farmers
can leave land in fallow, resulting in negative nutrient balances exacerbated by
lower use of external inputs (Rhodes et al., 1996). The importance of the
smallholder sector to the total economy and food supply of Nigeria led the
International Institute of Tropical Agriculture and International Livestock
Research Institute, in collaboration with farmers and Nigerian agricultural
research institutes, to identify appropriate technologies to sustainably increase
productivity. They include crop rotation systems, cover crops in rotation with
food crops, crop-livestock integration with dual-purpose legumes such as cowpea
and groundnut, and multistrata systems that combine annual and perennial crops.
The integration of small amounts of inorganic N fertilizer, along with N from
legumes in these cropping systems, has potential to overcome N depletion in
intensive land use systems. This paper reports research on corn-based cropping
systems using both grain and herbaceous legumes with limited applied N
fertilizer. The research was conducted at a mid-latitude (33oS) site in Australia,
using cropping systems typical of Southwest and Northcentral Nigeria.
MATERIALS AND METHOD
Experiments were conducted at Richmond, near Sydney, NSW, between
November 2000 and February 2002. In the first cropping cycle, corn was grown
between November 2000 and February 2001, then followed by a legume (field
pea), a cereal (barley), or a short fallow in the winter season. The second cropping
cycle began with corn planted in November 2001. In this paper, only the response
of the second corn crop is reported and discussed. Soil properties prior to
commencement of the study are shown in Table 1. Total precipitation (rainfall
plus supplementary irrigation) for the growing season (November 2001 –
February, 2002) was 737mm.
Table 1. General soil properties of the experimental site.
Soil
depth
0-15 cm
15-30 cm
pH
(CaCl2)
5.05
5.05
Organic C
(%)
0.4
0.4
Kjeldahl N
(%)
0.084
0.081
C:N
4.7
4.9
P
(mg/kg)
16
17
Sand
(%)
84
84
Silt
(%)
4
4
Clay
(%)
12
12
The experiment was a split-plot design replicated three times. Main plots
comprised five cereal – legume CS (Figure 1).
2000
N
D
J F
major wet season
CS1:
CS2:
CS3:
CS4:
CS5:
M
|
2001
A M
J
J A S
minor wet…|
dry season
corn------------------║
field pea ---------------▐
corn------------------║ lucerne-----barley--- ---------- ---║
corn/cowpea inter- ║----║cp
field pea--------------- ║
corn------------------║
barley--- -------------- ║
corn------------------║
short fallow period
║ harvest
║cp
cowpea harvest
O
N
|
2002
D J
F
major wet season
M
corn- -------------------║
corn------------- -------║
corn/cowpea ------ ---║
corn ----------- -------║
corn ------------ ------║
▐ field pea green manure incorporation
Figure 1. Layout of experiment with sole corn or corn-cowpea intercrop following
(i) legumes grown for green manure (CS1), forage (CS2) or grain (CS3), (ii)
another cereal (barley) (CS4) and (iii) fallow land (CS5). Rainfall seasons in
Nigeria are shown in relation to the production calendar at the research site.
In CS1, field pea was incorporated into the soil at mid flowering, while in CS3 it
was grown to maturity and harvested for grain. In CS2, lucerne was planted in
February 2001. The lucerne was mown, removed and subsampled for hay and
silage determination just prior to planting the second corn crop. Prior to corn
planting, all plots except CS2 were rotary harrowed, and 20 kg P ha-1 (as single
superphosphate) and 18 kg K ha-1 (as KCl) were broadcast on all CS. Sub-plots
within all corn plots were fertilized with 0, 60 or 120 kg N ha -1 as Nitram
(NH4NO3, 34% N), 50% 14 DAS (days after sowing) and 50% 42 DAS. The N
fertilizer was drilled along the rows. The main-plots were 18.5m x 9.1m and subplots 5.5m x 9.1m. Corn (Pioneer 3153) was planted with a cone seeder at 60,000
plants ha-1 on November 16, 2001. CS2 was direct drilled with zero-tillage. Subplots comprised eight rows with 75cm row spacing. Stomp 330E (330g L-1 a.i.
Pendimethalin) was applied pre-emergence by boom spray at 4.5 L ha-1 to all plots
except CS2. In CS3, inoculated cowpea seed (cv. Red Caloona) was planted by
hand, 28 DAS of corn, in hills 30 cm apart along the corn interrows. Hills were
thinned to 1 plant hill-1 10 days after emergence, giving a cowpea population of
53,200 plants ha-1. After corn harvest, Fusillade, (212g L-1 a.i. Fluazifop-p butyl)
was sprayed post-emergence between cowpea rows to control grass weeds. At
maturity, corn was cut at ground level from 4 m lengths of the 4 central rows in
each plot, separated into ears and stalk and weighed fresh. Fresh stalk subsamples were chopped, weighed, dried at 700C for 48 h then weighed again for
determination of stover dry matter (DM) yield. All harvested ears from each subplot were dried, weighed and shelled for determination of corn grain yield.
Subsamples of grain and stover plus husks were ground to pass through a 0.75
mm mesh and analyzed for N, P, K and Ca. Nitrogen was determined by
nitric/hydrochloric acid digestion followed by Complete Combustion Gas
Chromatography. Phosphorus, K and Ca were determined by acid digestion and
Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP – AES). N
fertilizer replacement values (NFRV) were estimated by generating an N response
curve for a non-legume monoculture. The yield (or N uptake) of a non-legume
crop with no applied N, following a legume, was then compared to that estimated
from the response curve. The amount of N fertilizer required to produce a similar
yield in monoculture is considered the NFRV of the legume. For NFRV to be
valid, yield of the crop following the legume should be significantly higher than
that of the non-legume control. N uptake was determined as the product of N
concentration and dry matter yield. Percentage recovery of fertilizer N applied
(RFN; %) was estimated as the ratio of (N uptake at N60 or 120 – N uptake at N0) to
applied N at N60 or 120. Nitrogen utilization efficiency (NutE) (kg kg-1) was
estimated as the ratio of grain yield to total plant N uptake. Analysis of variance
(ANOVA) using Proc GLM (SAS, 1997) was used to determine treatment effects
on all parameters. Where ANOVA indicated significant treatment or interaction
effects, treatment means were compared by LSD test at P≤0.05.
RESULTS AND DISCUSSION
Corn DM yields varied significantly between cropping systems for the second
corn crop following winter legumes, barley or fallow. When pooled across
fertilizer rates, mean yields were highest with CS1 and lowest with CS2. Grain
yield varied from 5.2 to 8.0 t ha-1 and stover from 5.3 to 9.5 t ha-1 (Figure 2).
Grain yield increased by 12, 19 and 4 % for CS1, CS3 and CS5 respectively, and
20.0
stover
grain
18.0
16.0
DM yield (t/ha)
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
CS1 CS2 CS3 CS4 CS5
0
CS1 CS2 CS3 CS4 CS5
60
N f ertiliser rates (kg/ha)
CS1 CS2 CS3 CS4 CS5
120
Figure 2. The influence of cropping systems and N fertilizer rates on corn grain
and stover DM yields (t ha-1) from the second year corn cropping season.
decreased by 27 and 1 % for CS2 and CS4 respectively, compared to mean grain
yield of the first year corn crop. In CS2, early corn seedling growth was slow due
to adverse effects of the lucerne intercrop. Corn growth in CS2 recovered after
supplementary irrigation, but the early competition was reflected in lower final
harvested yields. Nitrogen fertilizer application significantly increased grain
(P=0.0003) and stover (P=0.0001) DM yields. Increasing N application from 60
to 120 kg had no effect on grain and stover yields. No significant CS x N rate
interaction effects were recorded on grain and stover DM yields.
Mineral contents (Figure 3) were highest in CS2, the lowest yielding CS, and this
was attributed to a yield dilution effect under finite mineral supply conditions.
Cropping systems incorporating a legume (CS1, CS2 and CS3) showed
consistently higher Ca levels than the non-legume alternatives (data not shown).
While differences in most other mineral determinations were significant, no
consistent trend with yield was evident. Lower N and P contents in the higher
yielding CS were attributed to yield dilution. Even with the inclusion of legumes
in the CS, stover quality (for livestock feed) in terms of N and Ca content was
1.00
stover
grain
N content (%)
0.80
0.60
0.40
0.20
0.00
1.00
P content (%)
0.80
0.60
0.40
0.20
0.00
CS1 CS2 CS3 CS4 CS5
0
CS1 CS2 CS3 CS4 CS5
60
N fertiliser rates (kg/ha)
CS1 CS2 CS3 CS4 CS5
120
Figure 3. The influence of cropping system and N fertilizer rate on N and P
content (%) of second-year corn grain and stover.
well below the critical levels of 1.8% N and 3.5% Ca for young beef cattle
(Minson et al., 1976). Similarly, with the exception of CS2, P concentrations were
below the critical level of 0.12% (Little,1980). This stresses the need for protein
and other mineral supplementation by small-scale farmers feeding corn straw to
their livestock. Mean corn grain and stover N uptake differed significantly
between CS and N rates, but no CS x N rate interaction was recorded. N uptake
varied from 82-121 kg N ha-1 (grain) and 48-77 kg N ha-1 (stover) (Figure 4),
which is consistent with yield dilution effects. Corn grain N uptake in CS4 (corn –
barley – corn) was lower than in CS5, reflecting N removal by barley and greater
N availability after the CS5 fallow, indicating greater N depletion in the CS4
cereal - cereal monoculture. Nitrogen fertilizer application, up to 120 kg ha-1, also
significantly increased corn N uptake.
300.0
st over
grain
N uptake (kg/ha)
250.0
200.0
150.0
100.0
50.0
0.0
CS1 CS2 CS3 CS4 CS5
0
CS1 CS2 CS3 CS4 CS5
60
N fert iliser rat es (kg/ha)
CS1 CS2 CS3 CS4 CS5
120
Figure 4. The influence of cropping systems and N fertilizer rates on corn grain
and stover N uptake (kg ha-1) from the second-year corn cropping season.
NutE was significantly affected by both CS and N rate, with no CS x N rate
interaction. NutE was lower for CS2 and CS1 than the other systems (Figure 5).
CS1 produced the highest corn yield, but its NutE appeared to be inversely related
to grain yield. This is supported by the fact that even at N0, corn grain yield from
CS1 was higher than that in all other CS. This demonstrates the advantage of field
pea incorporation as green manure on subsequent corn yield, compared to the
other CS winter options investigated, particularly at low external N input.
Average values of NutE decreased significantly with increasing N input from 49
at N0 to 45 (N60) and 42 (N120) kg kg-1. This was lower after legume (CS1, CS2
and CS3) than non-legume crops. RFN was unaffected by CS, N rate and CS x N
rate interaction. Similar observations have been reported by Delogu et al. (1998)
and López.-Bellido and López-Bellido (2001).
NutE
70
% Recovery of applied N
60
kg/kg or %
50
40
30
20
0
60
CS4
CS5
CS3
CS2
CS1
CS5
CS4
CS3
CS2
CS1
CS5
CS4
CS3
CS2
0
CS1
10
120
N f ertiliser rates (kg/ha)
Figure 5. The influence of cropping systems and N fertilizer rates on corn Nu tE
(kg kg-1) and percent RFN from the second year corn cropping season.
The NFRV of legumes for subsequent corn are shown in Table 2. On DM yield
and N uptake bases, the NFRV of CS1 was mostly higher than CS3. NFRV was
lower for grain than for stover and whole plant, in terms of both DM yield and N
uptake. The high value, on an N uptake basis, for stover in CS3 remains
unexplained. However, it may result from greater N availability from the cowpea
intercrop. NFRV of CS2 could not be determined on a DM yield basis because of
low yield. The higher NFRV from CS1 indicates that field pea green manure
incorporation could contribute to soil N maintenance and improve corn
production, when used as a winter season alternative to fallow between corn
crops. This would be a far better approach to crop land management than the
traditional system of simply leaving land to fallow, where land is not limiting.
Table 2. Estimated N fertilizer replacement values (NFRV, kg N ha-1) of legumes
in corn production from the second corn cropping season.
Cropping system
CS1
CS2
CS3
*
Not determined
Dry matter basis
Grain Stover whole-plant
N uptake basis
Grain Stover whole-plant
24
ND*
15
34
4
16
54
ND
23
39
ND
19
37
13
56
38
8
30
CONCLUSION
These results indicate that yield and quality of corn grain and stover in
smallholder corn-based cropping systems in Southwest and Northcentral Nigeria
could be significantly improved if fallow was replaced by a legume green manure
crop in the winter season. This would compensate for lower inorganic N inputs.
Financial analysis of the cropping systems investigated will be based on Nigerian
costs and prices.
REFERENCES
Delogu, G., Cattivelli, L., Pechioni, N., De Falcis, D., Maggiore, T., Stanca, A.M.
(1998). Uptake and agronomy efficiency of nitrogen in winter barley and winter
wheat. Eur. J. Agron. 9: 11-20.
Little, D.A. (1980). Observations on the phosphorus requirement of cattle for
growth. Research in Veterinary Science, 28, 258-260.
López-Bellido, R.J. and López-Bellido, L. (2001). Efficiency of nitrogen in wheat
under Mediterranean conditions: effect of tillage, crop rotation and N fertilization.
Field Crops Research, 71: 31-46.
Minson, D.J., Stobbs, T.H., Hegarty, M.P and Playne, M.J. (1976). Measuring the
nutritive value of pasture plants. In: Shaw, N.H. and Bryan, W.W. (eds) Chapter 13,
Bulletin 51. (Commonwealth Bureau for Pasture Field Crops: Hurley, England).
Rhodes, E., Bationo, A., Smaling, E.M.A. and Visker, C. (1996). Nutrient stocks and
flows in West African soils. Pp. 22-32 in Restoring and Maintaining the Productivity
of West African Soils: Key to Sustainable Development, ed by A.U. Mokwunye, A.
de Jager, and E.M.A. Smaling. IFDC Miscellaneous Fertilizer Studies No. 14.
SAS Institute. (1997). SAS/STAT Users Guide, Release 6.12. SAS Inst., Cary, NC.
Corresponding Author Contact Information:
Akim Omokanye, University of Western Sydney, College of Science, Technology &
Environment, Centre for Horticulture and Plant Sciences, Building J4, Hawkesbury
Campus, LOCKED BAG 1797, PENRITH SOUTH DC NSW 1797, AUSTRALIA,
Phone: 61 2 4570 1135, Fax: 61 24570 1684, A.Omokanye@uws.edu.au, Poster,
Small farm diversification and competitiveness