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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Addis Ababa University


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.



Effects of Length of Fallow, Productivity of Lixisols