اثر اختلاط سه نوع ماده آلی با خاک بر حداکثر چگالی ویژه ظاهری خشک و گنجایش رطوبت بحرانی خاک در طول فشردگی

The effects of three kinds of organic matter on the physical characteristics of two soil series (Coarse Loamy, Mesic, Typic, Xerofluvents and Fine Mixed, Calcixerollic, Xerochrepts) were studied along with the measurement of maximum dry bulk density (MDBD) and the corresponding critical moisture content (CMC). Soil samples were taken from a depth of 0-20 cm and the percentage of organic matter and soil texture were determined. Three kinds of organic matters (peat, farmyard manure and filter press apple) were mixed with the soils at four levels (0, 4, 8 and 12% by mass), and were compacted using 10, 20 and 30 proctor hammer blows. The compaction tests on soils were carried out at different moisture contents. The present experiment, using factorial design, was randomly conducted in three replications. The results of this study showed that while the mean MDBD declined significantly (P<0.01) from 1.53 to 1.28 gr.cm-3, the mean CMC increased from 23.32 to 33.28% as the organic matter increased from 0.12%. In all the experiments, CMC decreased with increasing compaction efforts, so that the effect of mixed organic matter and soil in terms of MDBD reduction and CMC increase was decreasing in the order, peat, farmyard manure and filter press apple. The clay loam soil showed lower values of MDBD but higher values of CMC as compared to the sandy loam. The significant interaction effect observed between incorporation of organic matter and soil compaction were meaningful. Finally an equation as to the relationship between MDBD and CMC was proposed for the purpose of mixing the three organic materials with soil.