The Effects of Length of Fallow & Cultivation Periods on the Fertility and Productivity of Lixisols in the Dizi Catchment, Illubabor Region
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Date
1991-12
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Addis Ababa University
Abstract
The purpose of this study was: (1) to assess the effect of
fallow perioda on the fertility of soils, (2) to evaluate
the compounded effecta of fallow periodS and cropping years
on the fertility and productivity of 80ila. Experiments
were conducted on tallow-sites and on-tarU plota (previously
fallowed fj,elds) to attain the above objectives. oata on
soil and crop oharacteristics were collected using field and
laboratory procedure.. The collected data were analyzed
using descriptive statistics and statistical methods such aa
correlation, analysis of variance and regression.
The results of the experiment. on-fallow sites and on-farm
plota indicat.e improvements in 80118 of the physical and
chemical properties of the 80ils with increase in fallow
periods/years. The rates of regeneration were sore
pronounced in the earlier fallow periods and decline in
time. However, the rates of restoration of organic'matter
and some other evaluated nutrients on the on-farm plots were
higher than those on-tallow s1 tes. Por example, orqanic
matter, total n.itroqen, calcium rates of restoration in the
on-farm plots were higher than the on-fallow sites by 8.5
percent, 4.3 percent , 1.6 me/l00g respectively.
The findinqs in the on-farm plots, reveal the combined
effect8 of fallow periods and cropping years on the
fertility and productivity of the soils. Por example, the
amount of increase in organic matter was predicted at 16
percent when the fallow period increased from the first to
the second year, whereas it increased by only 0.5 percent
between 19 and 20 years of fallow. On the contrary, organic
matter decreased by 12 peroent between the first and seoond
years of cropping and the rate of its degradation declined
to 2.5 percent between 10 and 11 years.
The increase in maize yield on the average was estimated to
be 28 percent with every doubling in fallow period (e.g. 1,
2, 4, 8, 16 '0' years). On annual besis this increase was
declining in time. For instance, the estimated maize yield
increase was as high as 28 percent between the first and
second year of fallow, but this increase dropped to 4.8
percent between 10 and 11 years of fallow. On the other
hand, maize yield decreased with cultivation years. Por
instance, the decline in maize yield varied between 20
percent between the first and second year of cropping and
3.7 percent when the cropping year was 10 to 11 years.
From the above, it is realized that the recurrence of
cropping- fallow cycles (particularly if each cycle lasts
short duration) result in soils with low fertility and
productivity status. This emphasizes the very high risk of
soil degradation with increasing population density and
attendant intensity of CUltivation. The thesis at hand
suggests some possible measures Which must be taken to
ameliorate this problems.
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Keywords
Effects of Length of Fallow, Productivity of Lixisols