Citation
Zawawi, Norziana Zin
(2007)
Sustainable Grain Maize Production In A Gliricidia Alley Cropping System.
Masters thesis, Universiti Putra Malaysia.
Abstract
Crop production under Ultisols in the humid tropics is usually limited by N
deficiency and acid soil infertility problems. Effectiveness of legume residues as
a nitrogen source is generally known to improve crop productivity by enhancing
the availability of soil N where chemical fertilizer use often leads to deterioration
in environmental quality. The aim of the study was to evaluate Gliricidia sepium
residues (leaves and roots) as a potential source of N for a sustainable grain
maize production in an alley cropping system in the tropics. In order to identify
the determinants of the N dynamics of the Gliricidia sepium residues (leaves and
roots), a laboratory incubation experiment was carried out with an Ultisols
amended with Gliricidia sepium leaves, roots and their mixtures for 50 days.
Quality of Gliricidia sepium residues was in order of leaves > mixtures > roots.
The nitrogen and carbon mineralization also followed the same sequence
(P<0.05) and this observation suggests that the potential of Gliricidia sepium
residues to increase soil inorganic N depends on their quality. Results obtained showed that the Gliricidia sepium residues treatment was able to mitigate the soil
acidity. The addition of Gliricidia sepium residues also increased major soil
nutrient availability such as N, P, K, Ca and Mg. An experiment was carried out
in semi-field conditions to compare the 15N labeling technique for estimating
maize crop N uptake from Gliricidia sepium leaves and roots using direct 15N
labeling and 15N dilution method. Results indicate that N contributed by
Gliricidia sepium leaves to maize measured by direct 15N labeled and 15N
dilution method were not significantly different (P>0.05). The percentage of
nitrogen derived (%Ndfr) from the Gliricidia sepium 15N labeled leaves (direct
labeling) was 26.9% and 41.9% from unlabeled leaves (15N dilution) in maize
stover. Meanwhile, in maize cob, the %Ndfr from Gliricidia sepium leaves was
24.3% using 15N direct labeling and 46.4% using 15N dilution method. A field
study was conducted using the 15N dilution method on N contribution from
Gliricidia sepium leaves either integrated with or without additional urea
fertilizer, or, with or without the presence of hedgerows. There was no
significant difference (P>0.05) in maize yield upon application of Gliricidia
sepium leaf mulch with urea fertilizer (LM+FERT) compared to Gliricidia
sepium leaf mulch only (LM), suggesting that without additional amount of urea,
in situ Gliricidia sepium leaf pruning is equally effective in maize production.
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