تاثیر سامانه‌های خاک‌ورزی حفاظتی بر توزیع اندازه منافذ و ویژگی‌های هیدرولیکی خاک در شرایط شور و در تناوب کشت جو-گلرنگ

شوری آب و خاک یکی از چالش‌های عمده کشاورزی در ایران و جهان بوده و اصلاح خاک‌های شور نیازمند مصرف آب زیادی است. بنابراین با توجه به محدودیت منابع آب، بازنگری در روش‌های اصلاح این خاک‌ها ضروری است. در این پژوهش تاثیر سه نوع سامانه خاک‌ورزی (مرسوم، کم‌خاک‌ورزی و بی‌خاک‌ورزی) بر ویژگی‌های فیزیکی یک خاک‌ شور در ایستگاه تحقیقاتی کشاورزی کبوترآباد در جنوب شرقی شهر اصفهان طی چهار سال بررسی شد. این ویژگی‌ها شامل توزیع اندازه منافذ، گنجایش مزرعه‌ای (θfc)، نقطه پژمردگی دائم (θpwp)، آب قابل استفاده (awc)، و منحنی مشخصه رطوبتی (wrc) خاک بود. مدیریت‌ها نیز شامل حذف بقایای گیاهی در خاک‌ورزی مرسوم و حفظ بقایا در سامانه‌های کم‌خاک‌ورزی و بی‌خاک‌ورزی بودند. خاک مکان اجرای این آزمایش دارای بافت لوم رسی سیلتی بود. برای تجزیه آماری از طرح کرت‌های خردشده در زمان در قالب طرح پایه کاملاً تصادفی استفاده شد. نتایج نشان داد که مقدار منافذ درشت (macro-p) در تیمارهای کم‌خاک‌ورزی، بی‌خاک‌ورزی و خاک‌ورزی مرسوم به‌ترتیب برابر 0/032، 0/029 و cm-3cm-3و0/022 بود. همچنین تیمار کم‌خاک‌ورزی بیش‌ترین مقدار منافذ متوسط (meso-p) را دارا بود و مقادیر θfc در تیمارهای کم‌خاک‌ورزی و بی‌خاک‌ورزی (به‌ترتیب 0/250 و cm³ cm⁻³و0/247) به‌طور معنی‌داری بیش‌تر از خاک‌ورزی مرسوم (cm³ cm⁻³و0/238) بود. مقادیر awc100 در بین تیمارها تفاوت معنی‌دار نداشت. در سال‌های سوم و چهارم، تفاوت‌های واضح‌تری بین منحنی‌های wrc، به‌ویژه در مکش‌های ماتریک کم، مشاهده شد. تیمارهای خاک‌ورزی حفاظتی باعث افزایش فراوانی منافذ درشت و متوسط و بهبود شاخص‌های هیدرولیکی خاک شدند. نتایج نشان داد که خاک‌ورزی حفاظتی می‌تواند به‌عنوان جایگزینی مناسب برای خاک‌ورزی مرسوم در شرایط خشک و شور، بهبود شرایط خاک و بهره‌وری منابع آب را فراهم کند.

the impact of conservation tillage systems on soil pore size distribution and hydraulic properties under saline conditions and barley-safflower rotation

abstractsoil and water salinity is one of the major agricultural challenges in iran and worldwide, and reclaiming saline soils requires substantial water consumption. therefore, re-evaluating reclamation methods in the light of water resource limitations is essential. this study examined the effects of three tillage systems (conventional tillage, reduced tillage, and no-tillage) on the physical properties of a saline soil in isfahan over four years. the studied soil properties included pore size distribution, field capacity (θfc), permanent wilting point (θpwp), available water content (awc), and water retention curve (wrc). the management practices included residue removal in conventional tillage and residue retention in reduced tillage and no-tillage systems. the results showed that the macroporosity (macro-p) values in the reduced tillage, no-tillage, and conventional tillage treatments were 0.032, 0.029, and 0.022 cm³ cm⁻³, respectively. the reduced tillage treatment also had the highest mesoporosity (meso-p) and the θfc values in reduced tillage and no-tillage (0.250 and 0.247 cm³ cm⁻³, respectively) were significantly higher than in the conventional tillage (0.238 cm³ cm⁻³). the awc100 values were similar across the treatments, but the highest value was for the no-tillage treatment (0.210 cm³ cm⁻³). in the third and fourth years, more distinct differences were observed in the wrcs, particularly at low matric suctions. conservation tillage treatments increased the macropores and mesopores and improved the soil hydraulic indices. the results indicate that conservation tillage can serve as a suitable alternative to conventional tillage in the dry and saline conditions, improving soil conditions and water resource efficiency.background and objective: one of the major agricultural challenges in iran and the world is soil and water salinity. reclamation of saline soils requires significant amounts of water, making it essential to reconsider reclamation methods in the light of water resource limitations. conservation tillage can improve soil physical quality and enhance water retention (steponavičienė et al., 2024). researchers have reported an increase in macropores in no-tillage systems and an increase in micropores in conventional tillage systems (bhattacharyya et al., 2006). considering the salinity of soils and the arid and semi-arid climate in iran, preserving plant residues and using conservation tillage methods could help prevent related problems. this study examines the effects of three types of tillage systems on the physical properties a saline soil in isfahan.methods: this research was conducted over four years at the kabutarabad agricultural research station to examine the effects of three tillage systems (conventional tillage, reduced tillage, and no-tillage) on soil physical properties, including pore size distribution, field capacity (θfc), permanent wilting point (θpwp), available water content (awc), and water retention curve (wrc). in the conventional tillage, the soil was fully plowed and all crop residues were removed. in the reduced tillage, a chisel plow was used, and in the no-tillage, direct seeding was performed with minimal traffic and standing residues of the previous crop (about 5 tons per hectare) were retained. the cropping pattern followed a rotation of barley in the first and third years, and safflower in the second and fourth years. soil pores were classified into three major groups: macropores (macro-p), mesopores (meso-p), and micropores (micro-p), based on the wrc data. the study was conducted using a split-plot design in a completely randomized block design with three replications.results: the macro-p values in the reduced tillage, no-tillage, and conventional tillage treatments were 0.032, 0.029, and 0.022 cm³ cm⁻³, respectively, attributed to the increased soil organic matter in the reduced tillage and no-tillage treatments. the reduced tillage also had the highest meso-p (0.141 cm³ cm⁻³), with a significant increase, especially in the fourth year. over time, tillage systems had a greater impact on coarse and medium pores. the θfc values in reduced tillage and no-tillage (0.250 and 0.247 cm³ cm⁻³, respectively) were significantly higher than in the conventional tillage (0.238 cm³ cm⁻³). the presence of organic matter in the reduced tillage and no-tillage treatments led to a significant increase in θfc compared to conventional tillage. there was no significant difference between the θpwp values among the reduced tillage and no-tillage treatments, but they were higher than those in the conventional tillage. the awc100 values were similar across the treatments, but the highest value was for the no-tillage (0.210 cm³ cm⁻³). in the first and second years, there was little difference in the wrcs among the treatments. however, in the third and fourth years, more distinct differences were observed, particularly at low matric suctions. in these years, the no-tillage and reduced tillage had higher soil water retention at low matric suctions compared to the conventional tillage. conventional tillage had lower saturated water content compared to the reduced tillage and no-tillage treatments. over time, especially from the third year onward, saturated water content increased, which is attributed to the accumulation of soil organic matter and increased porosity.conclusions: this study investigated the impact of different tillage systems on soil physical and hydraulic properties over four years. the results showed that conservation tillage systems increased the macroporosity and mesoporosity, and improved soil hydraulic indices such as saturation water content, field capacity, permanent wilting point, and available water content. other benefits of these systems include the improvement of saline conditions through increased soil organic matter and reduced evaporation. additionally, conservation tillage, by preserving plant cover and minimizing soil disturbance, helps reduce moisture loss and enhance water use efficiency. these findings suggest that conservation tillage can serve as a suitable alternative to conventional tillage in dry and saline conditions, improving soil conditions and water resource efficiency.references:1- steponavičienė, v., žiūraitis, g., rudinskienė, a., jackevičienė, k., bogužas, v., 2024. long-term effects of different tillage systems and their impact on soil properties and crop yields. agronomy 14(4), 870. https://doi.org/10.3390/agronomy14040870.2- bhattacharyya, r., prakash, v., kundu, s., gupta, h., 2006. effect of tillage and crop rotations on pore size distribution and soil hydraulic conductivity in sandy clay loam soil of the indian himalayas. soil tillage res. 86(2), 129–140. https://doi.org/10.1016/j.still.2005.02.018.