Application of Spatial Modeling to the Study of Soil Fertility Pattern
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Date
2008-09
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Addis Abeba university
Abstract
Spatial statistical analysis was undertaken to study the variability of potato
yield data due to soil fertility pattern. Seed potato yield were measured from
field uniformity trial conducted at Hollota and Kulumsa agricultural research
centers in year 2001 on an area of 0.15 hectare at each site. The harvested
area was divided in to basic units of 1.2x1.5 m and a total of 1658 and 931
plots were considered from Hollota and Kulumsa respectively. The basic
units were combined in different plot sizes to acquire the required plot
dimension.
In this study, the Monte Carlo test for completely spatial randomness is
applied and the result shows no complete spatial randomness detected in the
series of potato yield data for both sites.
Thus, to set a model adjusted for spatial pattern, Moran’s index and Geary’s
coefficient were applied to test for global and local spatial autocorrelation
respectively. The result shows posit ive spatial autocorrelation detected
among potato yield data using Rook’s weighted neighboring plot relations.
The result also shows, increasing plot size will not generally make the
observed spatial autocorrelation insignificant.
An autoregressive model, that is adjusted for presence of spatial
autocorrelation in simulated plot size of 12m2 is fitted for row and column
effect for each site. The result shows significant positive association
between neighboring plots row effect and the adjusted potato yield. In
addition, the result from comparison of model adjusted for presence of spatial
autocorrelation and conventional OLS based analysis of variance shows the
autocorrelation parameter accounts significant percent of variation among
potato yield in both sites
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Modeling to the Study