تاثیر سامانه‌های خاک‌ورزی حفاظتی بر برخی ویژگی‌های فیزیکی خاک لوم رسی سیلتی در شرایط شور

مساحت زیاد خاک‌های شور در ایران و کاهش کیفیت این خاک‌ها ایجاب می‌کند که کارایی سامانه‌های کشاورزی حفاظتی در این‌گونه زمین‌ها نیز مورد بررسی قرار گیرند. این پژوهش با هدف بررسی تغییرات ویژگی‌های فیزیکی خاک در سه نوع مدیریت متفاوت خاک‌ورزی و بقایای گیاهی شامل: 1) خروج بقایا از مزرعه و خاک‌ورزی مرسوم، 2) حفظ بقایا و کم‌خاک‌ورزی، و 3) حفظ بقایا و بی‌خاک‌ورزی در تناوب جو و گلرنگ و در یک خاک‌ شور و شوری آب آبیاری 5/35 دسی‌زیمنس بر متر به مدت چهار سال انجام شد. در پایان هر کشت نمونه‌های خاک از لایه‌های 10-0، 20-10 و 30-20 سانتی‌متر تهیه شده و ویژگی‌های فیزیکی خاک شامل چگالی ظاهری و تخلخل، و پایداری خاکدانه‌ها با شاخص‌های میانگین وزنی قطر (mwd) و میانگین هندسی قطر (gmd) تعیین شد. پس از هر دوره تناوب کشت، نفوذ آب به خاک اندازه‌گیری شده و با برازش مدل کوستیاکوف اصلاح‌شده پارامترهای مربوطه تعیین شد. نتایج تجزیه واریانس داده‌ها در چهار سال آزمایش نشان داد که تفاوت اغلب ویژگی‌های خاک در پایان آزمایش در اثر اعمال تیمارهای خاک‌ورزی نسبت به شاهد معنی‌دار شد. به‌طوری‌که بیش‌ترین مقادیر mwd و gmd (به‌ترتیب 2/53 و 1/90 میلی‌متر)، تخلخل (51/2 درصد) و شدت نفوذ نهایی (31 سانتی‌متر بر ساعت) در تیمار بی‌خاک‌ورزی و کم‌ترین مقادیر mwd و gmd به‌ترتیب 2/02 و 1/29 میلی‌متر)، تخلخل (47/8 درصد) و شدت نفوذ نهایی (3/5 سانتی‌متر بر ساعت) در تیمار خاک‌ورزی مرسوم مشاهده شد. در کل نتایج این پژوهش نشان داد اجرای تیمارهای خاک‏ورزی حفاظتی باعث افزایش ماده آلی و بهبود پایداری خاکدانه‌ها، افزایش تخلخل و نفوذ آب به خاک شد.

the impact of conservational tillage systems on some physical properties of silty clay loam saline soil

the large area of saline soils in iran and decreasing in quality of these soils require that the effectiveness of conservation tillage systems in such lands be investigated. this project aims to determine changes in soil physical properties in three different types of tillage system and plant residue management, including: 1) conventional tillage system and removal of crop residues from soil surface, 2) reduced tillage system and preservation of crop residues, and 3) no tillage system and preservation of crop residues in rotation of barley and safflower in a saline soil with irrigation water salinity of 5.35 ds/m for four years. some soil physical properties such as bulk density and porosity, and aggregate stability indices of mean weight diameter (mwd) and geometric mean diameter (gmd) were measured in soil samples prepared from the layers of 010, 1020 and 2030 cm. after each crop rotation period, water infiltration into the soil was measured and the modified kostiakov model was fitted to obtain the optimized parameters. the results of variance analysis of the data in the four years of the experiment showed that the difference in most of the soil properties at the end of the experiment was significant due to the tillage treatments compared to the control. the highest mwd and gmd (2.53 and 1.90 mm, respectively), porosity (51.2%) and final infiltration rate (31 cm/h) were observed in the no-tillage system. while the lowest mwd and gmd (2.02 and 1.29 mm, respectively), porosity (47.8%) and final infiltration rate (3.5 cm/h) were recorded in the conventional tillage system. overall, our findings showed that the increment in the soil organic matter due to the implementation of conservational tillage treatments improved the stability of soil aggregates and increased soil porosity and water infiltration into the soil. background and objective: presence of sodium in the salt-affected soils causes the dispersion and disintegration of clay particles, which leads to the destruction of the soil structure and, as a result, poor aeration of the root growth environment and the reduction of root penetration and water storage in the soil. the binding of clay particles and maintaining the soil structure strongly depend on the soil salinity and sodicity, the soil organic matter content, the rate of wetting and the type of soil clays (2). tillage practices could reduce the soil bulk density in the plow layer, which gradually returns to its initial level upon consolidation due to natural processes. these changes depend on the type of soil and tillage tools (3). hajabbasi et al. (4) studied the effects of different tillage methods on the mwd in kabutarabad, isfahan. in no-tillage treatment, the mwd was 20% higher than in other treatments. water infiltration and microporosity in two soil types (i.e., silty loam and sandy loam) were significantly lower in the conventional tillage than in no-tillage, while no significant difference was observed for the macroporosity (1). methods: the current research was carried out at kabutarabad agricultural research station, located in the southeast of isfahan city, in fixed plots of the conservation agriculture experimental site for four years in split plots design. the main plots included three different types of tillage system and crop residue management, including: 1) conventional tillage and removal of residues from the field, 2) reduced tillage and preservation of residues, and 3) no tillage and preservation of residues. soil layers of 010, 1020 and 2030 cm were considered as sub-plots. at the time of harvesting of each crop, soil samples were prepared from the three layers and physical properties were measured in the laboratory. after harvesting, the water infiltration into the soil was measured by the double rings method.