INFLUENCE OF STUBBLE MANAGEMENT, TILLAGE AND PRECURSOR CROP ON SOIL PHYSICO-CHEMICAL PROPERTIES IN SOUTHEASTERN ETHIOPIA

摘要

Soil physical and chemical properties critically affect the growth and development of crops. A multi-factor trial was conducted from 1992-94 at the Kulumsa research station in southeastern Ethiopia in two parallel sets (i.e., under mechanized and ox-plow tillage systems). The trial examined the effects of stubble management, tillage practice and cropping sequence on soil physical and chemical properties. At the time of sowing wheat in 1994, soil sampling was carried out to determine soil chemical andmoisture contents; during tillering stage of the wheat crop, soil penetrometer resistance (PR) was measured. The results showed that organic matter (OM) was consistently increased by partial or complete retention of straw and reduced by stubble burningin both sets of the trial. Minimum tillage combined with partial retention of straw increased soil OM the most. A faba bean precursor crop (in 1992) increased soil NO_3 and NH_4 levels measured in 1994. Soil NH_4 in the mechanized trial was negatively affected by stubble burning. Soil PR increased with depth in both trials, and was affected by the interaction of tillage practice and depth: the increment of PR with depth was greater under conventional than under minimum or zero tillage. An increment of soil PR, especially in the rooting zone of the wheat crop, may hinder rooting and ultimately affect crop performance. Soil moisture contents were lower under stubble burning treatments, under minimum tillage systems, and as sampling depth increased.