Nazmi, L., Asadi, H., Manukyan, R. and Naderi, H. 2012. Influence of tillage displaced soil on the productivity and yield components of barley in northwest Iran. Can. J. Soil Sci. 92: 665–672. In hilly landforms subject to long-term cultivation, erosion has denuded the upper slope positions of topsoil, and accumulated topsoil in the lower slope positions. Slope gradient and position effects aggregation processes, which in turn impact soil productivity. A field experiment was conducted to assess the tillage-induced soil displacement and its effects on the soil properties and barley (Hordeum vulgare var. Sahand) biomass production for three different landscapes. The study was conducted on a hill slope seeded with barley (1.4–10.1° slope) located in the Mollaahmad watershed of the Ardabil province in northwestern Iran. For this purpose, soil samples were collected from four slope positions in a grassland as well as an agricultural field (dryland). A field experiment was conducted to evaluate the effects of slope gradient and position on barley growth and soil quality. Soil generally had lower organic carbon, available phosphorus, calcium carbonate equivalent, soil water content and mean weight diameter of soil aggregates in the farmland than the grassland, and in the upper slope positions than in the lower slopes. Significantly higher barley growth indices were associated with lower slope positions. Agronomic productivity of the soil was lowest for landscapes with the highest slope gradient. The relationships between tillage erosion and yield components were found to be significant. Spike weight and slope position had the largest contribution for the explanatory capacity of canonical variables (tillage erosion and yield components) estimated when compared with other parameters (slope gradient, dry matter, spike number, grain yield and 1000-grain weight). The findings in this study can be used as a tool to assist farmers, soil and water conservationists, and other policymakers in decision making regarding the use of lands.
Complications of Amniocentesis in Northwest IRAN