MINERALIZATION OF NEEM SEED CAKE AND EFFECT ON GROWTH AND NUTRITION OF SORGHUM IN A NORTHERN GUINEA SAVANNA ALFISOL
MINERALIZATION OF NEEM SEED CAKE AND EFFECT ON GROWTH AND NUTRITION OF SORGHUM IN A NORTHERN GUINEA SAVANNA ALFISOL
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Date
2013-02
Authors
MOHAMMED, Kehinde Olayemi
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Abstract
Four neem seed cake levels 0, 1, 2 and 4 ton (t) ha-1 along with varying rates of inorganic
fertilizer recommendation (0, ¼, ½ and full) for sorghum were evaluated in the laboratory,
greenhouse and in the field for their mineralization and/or decomposition potentials, impact on
soil fertility, productivity and nutrition of sorghum in the Northern Guinea Savanna of Nigeria
in a factorial completely randomized design with three replications. Results showed that NSC
contained 265.35 g kg-1 OC, 45.95 g kg-1 N, 2.75 g kg-1 P, and 12.35 g kg-1 K mean
concentration in both years indicating its potential in improving soil fertility and plant growth.
Treatments did not significantly (P ≤ 0.05) increase sorghum growth and dry matter yield
(DMY) in the greenhouse. The quarter recommended rate (RR) recorded a higher increase in
DMY and plant height while combinations of 2 t ha-1 NSC + ¼ RR and 4 t ha-1 + FRR gave
non-significant increase in stem girth and number of leaves respectively. Treatments showed
significant (P ≤ 0.05) difference in only P concentrations in sorghum tissue. The 4 t ha-1 of NSC
significantly increased P and K concentrations while combined application of 4t ha-1 + FRR
recorded the highest N concentration. As regards the effects of treatments on soil properties after
cropping, sole NSC and CF treatments resulted in soil pH reduction, implying that application of
these materials can lead to soil acidification. Significant (P ≤ 0.05) increases were observed in
the effect of treatments on exchangeable acidity, nitrogen, potassium and calcium. Soil
microbial biomass carbon correlated with soil total organic carbon (TOC) (r = 1), and was
generally positively related to the soil organic matter which implied the ability of the organic
material to form stable aggregates. Laboratory incubation study showed an initial rapid
cumulative N mineralization rate in the first twenty-one (21) days followed by slower release
with time. At 98 days, cumulative N mineralization represented 50 % of total N applied as neem
seed cake. N mineralization pattern showed that ammonium-N fraction in the soil far exceeded
nitrate-N fraction, accounting for 91.5% of the N mineralized from the NSC. The simple rate
constant (h=k) gave a better fit to mineral-N released than the Gompertz function in the
laboratory study. However, in the field, cumulative N mineralization with time showed an initial
rapid rate in the first six (6) weeks after incubation followed by slower release in 2009 and 2010.
N mineralization pattern showed that ammonium-N fraction in the soil slightly exceeded the
nitrate-N fraction in 2009, accounting for about 52% of N mineralized from neem seed cake
while in 2010 N mineralization pattern showed that nitrate-N fraction in the soil far exceeded
the ammonium-N fraction, accounting for 64% of the N mineralized from NSC. Generally,
highest concentration of ammonium was observed during the first twenty-eight (28) days of
incubation. The best fit for net N mineralization in the field was displayed with the Gompertz
function. Weight loss of NSC was rapid within the first twenty-eight (28) days with about 70%
lost in 2009. Significant (P < 0.05) decrease in dry mass was observed for seven sampling
periods in 2010; dry mass loss was rapid during the first fourteen (14) days of decomposition
relative to later periods. However, NPK level did not affect dry mass loss of NSC significantly
(P < 0.05). Decomposition best fit was described by the asymptotic negative exponential model.
In the field trial, significant treatment effects were observed on sorghum growth parameters.
Leaf number, dry matter yield and plant height increased with simple combined application of
the amendments. Effects of the various treatments (regression) on yield was significant, a
reflection of the contribution of treatments to soil nutrient status. Combined application of 1 t ha-
1 + FRR had highest sorghum grain yield. Yield parameters were better enhanced in NSC
amended plots in 2009 and 2010 (P < 0.01). There was no significant effect of treatments on P
and K concentrations in sorghum tissues in 2009. The effect of treatments on soil properties
after cropping, sole CF and NSC treatments resulted in soil pH reduction, implying increase in
acidity. Significant (P ≤ 0.05) increases were observed in the effect of treatments on organic
carbon and exchangeable potassium in 2009 and 2010 with sole NSC application while in 2010
significant effect was observed for exchangeable potassium, calcium and exchangeable acidity
in sole NPK plots. Non significant treatment effect was observed for tannin content in both years
while significant (P ≤ 0.05) response was obtained for effect of chemical fertilizer in 2009 for
crude protein. The present study revealed that NSC has high residue quality and can be used as a
nutrient source. Its integration with CF was shown to be an important management strategy for
improving fertility and productivity of the savanna soils
Description
A DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU
BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF
DOCTOR OF PHILOSOPHY OF AHMADU BELLO UNIVERSITY, ZARIA.
DEPARTMENT OF SOIL SCIENCE
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA.
FEBRUARY, 2013
Keywords
MINERALIZATION,, NEEM SEED CAKE,, EFFECT,, GROWTH,, NUTRITION,, SORGHUM