Land leveling and changes in soil properties in paddy fields of Guilan province, Iran.

摘要

The aim of this study was to evaluate the impacts of land leveling on some of soil properties. Land leveling as an effective strategy for paddy land management is one of the most important programs run by the Ministry of Jihad-Agriculture in Guilan province, northern part of Iran. Precise land leveling improves irrigation application, fertilization efficiency, and uniform soil moisture for germination. Also, it increases yields and cultivable lands and reduces delivery losses. Running land-leveling projects, however, leads to such disadvantages as severe soil alteration and consequently disruptions to the soil physical, chemical, and biological properties. Based on statistical analysis, on the one hand land, leveling led to significant increases (P<0.01) in bulk density, clay percentage, and EC, and on the other hand, it resulted in significant decreases (P<0.01) in the soil organic matter, silt percentage, NPK, pH, soil respiration, bacterial community, and microbial biomass carbon. Microscopic images of buried slides indicated that there was a reduction in the soil microorganism communities and diversities as well. With regard to the management of paddy fields, despite beneficial impacts of land leveling, the results indicate that due to malperformance of the project, which is a consequence of the use of inappropriate machinery and/or nonremoval of surface soil and its re-diffusion, most of soil-desirable properties are reduced and are not revitalized even after 4 years.