چكيده فارسي :
در زمان انجام عمليات كاشت، داشت و برداشت در مزرعه، خاك زراعي تحت تاثير نيروهاي مختلف قرار گرفته و ويژگي هاي آن دچار تغييرات مي گردد. هدف از اين پژوهش بررسي اثر فشردگي خاك روي ويژگي هاي فيزيكي و هيدروليكي آن مي باشد. بدين منظور پس از انتخاب چهار تيمار (تيمار شاهد)، ، و (تيمارهايي كه تراكتور به ترتيب 1، 3 و 5 بار از روي آنها عبور كرده است) از خاك هر تيمار بعد از اعمال نيروي مورد نظر، نمونه برداري شد و ويژگي هاي آن ها در آزمايشگاه اندازه گيري گرديد. ميزان نفوذ آب در خاك در هر تيمار اندازه گيري و يك نقطه رطوبت – مكش نيز برداشت گرديد. براي تعيين هدايت هيدروليكي اشباع و غير اشباع و پارامترهاي نگهداشت آب خاك از كد Hydrus 3D و از روش حل معكوس استفاده شد. چگالي ظاهري در تيمارهاي ، و نسبت به تيمار شاهد به ترتيب 41/17، 87/26 و 65/35 درصد افزايش، ميزان تخلخل كل به ترتيب 55/16، 36/25 و 04/33 درصد و هدايت هيدروليكي اشباع به ترتيب 09/38، 05/59 و 43/61 درصد كاهش نشان داد اما چگالي حقيقي تقريبا ثابت ماند. با فشردگي خاك در اثر اعمال نيرو از سطح آن پارامترهاي ، ، و (به ترتيب رطوبت باقيمانده و اشباع، هدايت هيدروليكي اشباع و پارامتر تجربي مدل ون گنوختن) كاهش و پارامترهاي و (به ترتيب پارامتر عكس مكش ورود هوا و پيوستگي منافذ) روند افزايشي داشتند. اثر اعمال نيرو روي پارامتر معني دار نبوده ولي روي پارامترهاي ، ، ، و معني دار بود.
چكيده لاتين :
Many forces applied to soil surface during cultivation season cause soil compaction, which affects many soil physical and hydraulic parameters. Under field condition, different forces affect the soil and cause changes in its characteristics. The aim of this study was to determine the effect of soil compaction on soil physical and hydraulic properties. Four treatments including T0 (no tractor pass), T1 (one pass), T2 (three passes) and T3 (five passes), were selected. Treatments were irrigated regularly as local farmers’ schedule. After three months, soil samples were taken for determination of some soil properties such as particle and bulk density, shape of cumulative infiltration curve, soil moisture retention curve, and saturated and unsaturated hydraulic conductivity. Water infiltration rate was measured in each treatment using a double ring infiltrometer. Residual water content at a given water pressure head was obtained in laboratory. Inverse solution was used to estimate soil water retention and unsaturated hydraulic conductivity functions parameters by Hydrus 3D code. Results indicated that by increase in the number of tractor passes over the soil surface, bulk density of T1, T2 and T3 treatments increased by, respectively, 17.41%, 26.87% and 35.65% compared to T0. Total porosity of T1, T2 and T3 treatments decreased 16.55%, 25.36%, and 33.04 % and saturated hydraulic conductivity of the same treatments also decreased 38.09%, 59.05%, and 61.43 % compared to T0, respectively. Particle density was constant. Residual moisture , saturated , saturated ,and van Genuchten increased, while and decreased due to increase of soil compaction. Soil compaction effect on , , , and parameters was significant, but the effect was insignificant on parameter. Significant probability of these five parameters is different.
