E. Farahani, M.r. Mosaddeghi, A.a. Mahboubi,
Volume 16, Issue 61 (10-2012)
Abstract
Hardsetting phenomenon is an indicator of poor soil physical quality. Hardsetting soils are soils with high rate of mechanical strength increase upon drying and are hardened and/or compacted when dry out. It is difficult to till such soils. Hardsetting soils have additional limitations such as poor aeration at wet conditions, low infiltrability and high runoff and erosion. Most of Iran soils have low organic matter content and it is expected that hardsetting phenomenon occurs in some of these soils. This study was conducted to investigate the hardsetting phenomenon on 9 soil series collected from Hamadan province. Three types of mechanical strength consisting tensile strength (ITS), unconfined compressive strength (UCS), and penetration resistance (PR) were measured on the repacked soil samples prepared in the lab. The ITS, UCS and PR tests were done on the soil cores which had been prepared at bulk density (BD) equal to 90% of critical BD for root growth (0.9BDcritical). The effects of intrinsic properties on the hardsetting phenomenon were studied, too. Based on the suggested definition in “International Symposium on Sealing, Crusting and Hardsetting Soils” to International :::union::: of Soil Science, in which a hardsetting soil has air-dry tensile strength ≥ 90 kPa, one soil (medium-textured) out of the studied soils showed the hardsetting phenomenon at 0.9BDcritical. It might be concluded that medium-textured soils are more susceptible to hardsetting. For all of the studied soils, the ITS increased with the increase in clay content. The increasing impacts of clay and carbonate contents were also observed for the UCS and PR, respectively. Calcium carbonate could act as a cementing agent in between the soil particles and brings about the soil susceptibility to hardsetting. Moreover, the decreasing trend of all soil mechanical strengths was observed with water content increase. Slope (b) of the exponential model (fitted to the soil mechanical strength characteristic curve), as an index of hardsetting, had positive correlation with the sand content and negative correlation with the silt content. Overall, texture and calcium carbonate content are major and effective properties in terms of hardsetting phenomenon in Hamadan soils.
A. Heidari, A. Hemmat, S.m Rezvani,
Volume 18, Issue 67 (6-2014)
Abstract
efficiency was investigated during a 2-year period (2009-2010) in a silty clay loam soil in Tajarak Research Station
(Kaboudarahang Township), Hamedan. The experimental design was a strip-plot within a randomized complete blocks
design. The horizontal band, the irrigation water rate after flowering, included full and deficit irrigation (100% and 75%
potato water requirement) and the vertical band, kind of inter-planting row tillage including 1- subsoiling to 30-35 cm
soil depth, 2- chiseling to 20-25 cm soil depth, 3- sweeping to 5 cm soil depth and 4- no-till. During the growing
season, soil mechanical resistance (cone index) in two stages and water infiltration into the soil were measured. At the
end of the growth season (harvesting time), potato yield quantity and quality were measured. Result showed that the
effect of inter-row tillage on soil mechanical resistance was significant. Subsoiling and chiseling had lower soil
mechanical resistance and higher water permeability between treatments, respectively. The effect of inter-row tillage on
potato yield was significant so subsoiling and chiseling had a higher potato yield between treatments, respectively. The
effect of irrigation water rate on potato yield was not significant. The effect of inter-row tillage on water use efficiency
wasn’t significant.
