[Parameters: Topic='AGRICULTURE', Term='SOILS', Variable_Level_1='NITROGEN', Detailed_Variable='NITRATE']
Nitrogen Fertilizer Trials In Nigeria, SOMNET Long Term Soil Organic Matter DatabaseEntry ID: OAU.Nigeria
Abstract: This experiment was started at a tropical location in 1971 on a site that was
originally undisturbed rainforest. The site was secondary forest
before the experiment began, and has been under its present use since
the initiation of the project. the soil is an Oxic Tropodolf, sandy
The experiment consists of the following land use and treatments:
Continuous cultivation with different crops ... each season. Treatments
are (rates of split applications are 23 and 46, 46 and 92, 92 and 184,
and 138 kg/ha): 1) Continuous application of 3 sources of N
fertilizer, 2) Ammonium sulphate (4 levels), 3) Urea (4 levels), 4)
Calcium ammonium nitrate (4 levels), 5) Control plot (no N
The measurements made (Data available), methodology, and frequency are
a) Vegetation measurements made and frequency
Yield: Yearly or 2 times per year
Total above-ground dry matter: Yearly or 2 times per year
Also root length at 2 weeks and height of crop at 2, 4, 6, 8, and
10 weeks after planting - for each crop
b) Soil sampling
Time zero soil measurements taken. Soil samples to depth 15cm were
taken before treatments applied. Samples no kept.
Measurements taken were: soil texture, organic matter (%), field
moisture capacity, soil pH, available P, total N, and exchangeable K,
Ca and Mg.
Details of soil sampling method: Surface samples (0-15cm) were
collected with sampling tube from each treatment plot. 25 core samples
were taken from each plot. These were bulked in a bucket after which
subsamples were taken for analysis. Auger soil samples were also taken
up to a depth of 120 cm in all the treatment plots for some specific
analyses. Soil is separated into layers.
Details of measuring depths and soil layers: Depths: 15-30,
30-60, 60-90 and 90-120 cm depth. Samples were not taken at any given
frequencies, only for specific parameter determination.
c) Soil measurements made and frequency
Total carbon: As Organic matter content in 1971, 1975, 1981, 1985
Method of measuring total carbon: Organic matter content of soil
determined by chromic acid digestion method (Allison, 1965). Total C
can be estimated with an appropriate multiplication factor.
Total nitrogen: Once at time zero (1971)
Method of measuring total nitrogen: Kjeldahl method as described by
Nitrate nitrogen: Once.
Method of measuring nitrate nitrogen: Soil nitrate-nitrogen
Other measurements: Exchange acidity and exchangeable aluminium
were determined from both surface and subsoil samples. Samples were
separated into layers to a depth of 120cm. Available P and
exchangeable K were determined.
This information was compiled for the GCTE-SOMNET Database, Pete
Smith, Pete Falloon, David Powlson, and Jo Smith. Soil Science
Department, IACR-Rothamsted, UK.
Start Date: 1971-01-01
AGRICULTURE > AGRICULTURAL CHEMICALS > FERTILIZERS
AGRICULTURE > AGRICULTURAL PLANT SCIENCE > CROP/PLANT YIELDS
AGRICULTURE > SOILS > CALCIUM
AGRICULTURE > SOILS > CARBON > TOTAL CARBON
AGRICULTURE > SOILS > MAGNESIUM
AGRICULTURE > SOILS > NITROGEN > NITRATE
AGRICULTURE > SOILS > NITROGEN > TOTAL NITROGEN
AGRICULTURE > SOILS > ORGANIC MATTER
AGRICULTURE > SOILS > PHOSPHORUS > AVAILABLE PHOSPHORUS
AGRICULTURE > SOILS > POTASSIUM > EXCHANGEABLE POTASSIUM
AGRICULTURE > SOILS > SOIL CHEMISTRY > EXCHANGEABLE ALUMINUM
AGRICULTURE > SOILS > SOIL MOISTURE/WATER CONTENT
AGRICULTURE > SOILS > SOIL PH
AGRICULTURE > SOILS > SOIL TEXTURE
BIOSPHERE > VEGETATION > BIOMASS
LAND SURFACE > SOILS > CALCIUM
LAND SURFACE > SOILS > MAGNESIUM
LAND SURFACE > SOILS > NITROGEN > NITRATE
LAND SURFACE > SOILS > ORGANIC MATTER
LAND SURFACE > SOILS > PHOSPHORUS > AVAILABLE PHOSPHORUS
LAND SURFACE > SOILS > POTASSIUM > EXCHANGEABLE POTASSIUM
LAND SURFACE > SOILS > SOIL CHEMISTRY > EXCHANGEABLE ALUMINIUM
LAND SURFACE > SOILS > SOIL MOISTURE/WATER CONTENT
LAND SURFACE > SOILS > SOIL PH
LAND SURFACE > SOILS > SOIL TEXTURE
Quality a) Details of the plots
Width of smallest plot is 68.9 m
Length of smallest plot is 91.5 m
Slope: 0.5-2.0% . Shape: Uniform
Details of direction of cultivation: Parallel to long axis of plots.
Width of Discard Strip around plot: 2 rows from the edge (planting
distance varies for different crops).
... Details of homogeneity of the plots: No information on homogeneity or
variability available. The plot area is reasonably flat with a
slope range of 0 to 2%. The vegetation at time zero was uniform as was
site history. No site characterization at time-zero. Site
homogeneity is based on uniform topography and some soil
b) Details of replication, randomization and controls
There are at least 5 replicates in the experiment.
The experiment has a restricted randomized plot design. RCBD
(Randomized Complete Block Design). The treatments were
randomized completely within each replicate. The total plot area was
broken into five replicates.
There is one control plot in each block/replicate. The control
plot has not received any N-fertilizer treatment since the beginning
of the study. Yield measurements were taken from the control plots
after the guard rows had been excluded.
Access Constraints none
Use Constraints Link to the following location to view data use policy of SOMNET members:
Data Set Progress
Role: TECHNICAL CONTACT
Department of Soil Science, Obafemi Awoldwo University,
Province or State: ILE-IFE
Role: DIF AUTHOR
Phone: (301) 614-6898
Email: Tyler.B.Stevens at nasa.gov
NASA Goddard Space Flight Center Global Change Master Directory
Province or State: MD
Postal Code: 20771
Obi, A.O. (1976) Relative effects of different N-fertilizers on soil pH
and crop yield in a Western Nigerian soil. Nig. Agric. J. 13: 1.
Obi, A.O. (1989) Long-term effects of continuous cultivation of a
tropical ultisol in Sothwestern Nigeria. Expl. Agric. 25: 207.
Obi, A.O., Adeptu, J.A. & Uponi, J.I. (1987) Crop tolerance of soil
acidity resulting from long-term continuous application of nitrogen
fertilizers. Ife J. Agric. 9: 1-2.
Creation and Review Dates
DIF Creation Date: 2000-01-11
Last DIF Revision Date: 2003-09-12