تغييرات كيفيت خاك‌هايي با رژيم‌هاي رطوبتي مختلف در اثر زراعت: با تاكيد بر كيفيت فيزيكي خاك

Changes in quality of soils with different moisture regimes as affected by cultivation: with an emphasis on soil physical quality

ﻋﻤﻠﯿﺎت ﮐﺸﺎورزي ﻣﯽﺗﻮاﻧﺪ ﭘﯿﺎﻣﺪﻫﺎﯾﯽ زﯾﺎن ﺑﺎر ﺑﺮ ﮐﯿﻔﯿﺖ ﺧﺎكﻫﺎ داﺷﺘﻪ ﺑﺎﺷﺪ. آﮔﺎﻫﯽ از ﺗﻐﯿﯿﺮات زﻣﺎﻧﯽ ﮐﯿﻔﯿﺖ ﺧﺎك در اراﺿﯽ ﮐﺸﺎورزي ﺑﺮاي ﻣﺪﯾﺮﯾﺖ ﺑﻬﯿﻨﻪ زﻣﯿﻦﻫﺎ و رﺳﯿﺪن ﺑﻪ ﺑﯿﺸﯿﻨﻪ ﺑﻬﺮهوري اﻗﺘﺼﺎدي ﺿﺮوري اﺳﺖ. در اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺮﺧﯽ وﯾﮋﮔﯽﻫﺎي ﻓﯿﺰﯾﮑﯽ ﭼﻬﺎر ﺧﺎك زراﻋﯽ ﺑﺎ ﺧﺎكﻫﺎي ﺷﺎﻫﺪ ﻏﯿﺮزراﻋﯽ ﻫﻤﺠﻮار آنﻫﺎ ﻣﻘﺎﯾﺴﻪ ﮔﺮدﯾﺪ. در ﻫﺮ ﻣﻨﻄﻘﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ، ﭼﻬﺎر ﻧﻤﻮﻧﻪ ﺧﺎك )ﺷﺎﻣﻞ دو ﻧﻤﻮﻧﻪ ﺧﺎك زراﻋﯽ و دو ﻧﻤﻮﻧﻪ ﺧﺎك ﻏﯿﺮزراﻋﯽ ﻣﺠﺎور آن( اﻧﺘﺨﺎب ﮔﺮدﯾﺪ. ﺣﺴﺎﺳﯿﺖ ﺑﻪ ﺗﺸﮑﯿﻞ ﺳﻠﻪ، ﻣﻨﺤﻨﯽ رﻃﻮﺑﺘﯽ ﺧﺎك، ﺗﻮزﯾﻊ اﻧﺪازه ذرات و ﻣﻨﺎﻓﺬ ﺧﺎك، ﻣﻘﺎوﻣﺖ ﻣﮑﺎﻧﯿﮑﯽ، ﻣﻘﺪار رﻃﻮﺑﺖ در دﺳﺘﺮس و ﻣﻘﺪار ﺗﺨﻠﺨﻞ ﺗﻬﻮﯾﻪاي، ﻇﺮﻓﯿﺖ زراﻋﯽ ﻧﺴﺒﯽ، ﮔﻨﺠﺎﯾﺶ آب اﻧﺘﮕﺮاﻟﯽ اﻧﺪازهﮔﯿﺮي ﺷﺪﻧﺪ. ﺑﻪ ﻃﻮر ﮐﻠﯽ در اراﺿﯽ ﺗﺤﺖ ﮐﺸﺖ، ﻣﻘﺪار ﻣﻮاد آﻟﯽ ﺧﺎك )1/81 در ﺑﺮاﺑﺮ 2/70 درﺻﺪ(، ﭘﺎﯾﺪاري ﺳﺎﺧﺘﻤﺎن ﺧﺎﮐﺪاﻧﻪﻫﺎ )5/2 در ﺑﺮاﺑﺮ 7/4(، ﻣﻨﺎﻓﺬ رﯾﺰ )0/28 در ﺑﺮاﺑﺮ 0/39(، رﻃﻮﺑﺖ ﻇﺮﻓﯿﺖ زراﻋﯽ )0/27 در ﺑﺮاﺑﺮ 0/34( و ﻧﻘﻄﻪ ﭘﮋﻣﺮدﮔﯽ داﯾﻢ )0/15 در ﺑﺮاﺑﺮ 0/20( و آب ﻗﺎﺑﻞ دﺳﺘﺮس ﮔﯿﺎﻫﺎن )0/11 در ﺑﺮاﺑﺮ 0/15( ﻧﺴﺒﺖ ﺑﻪ اراﺿﯽ ﻏﯿﺮزراﻋﯽ ﮐﺎﻫﺶ ﯾﺎﻓﺖ )0/05≤ P(. ﺑﺎاﯾﻦ ﺣﺎل، ﻓﺮاواﻧﯽ ﻣﻨﺎﻓﺬ درﺷﺖ )0/39 در ﺑﺮاﺑﺮ 0/23( و ﺣﺴﺎﺳﯿﺖ ﺑﻪ ﺗﺸﮑﯿﻞ ﺳﻠﻪ )0/70 در ﺑﺮاﺑﺮ 0/57( در اراﺿﯽ ﺗﺤﺖ ﮐﺸﺖ اﻓﺰاﯾﺶ ﻧﺸﺎن داد )0/05≤ P(. ﻣﯽﺗﻮان ﻧﺘﯿﺠﻪ ﮔﺮﻓﺖ ﮐﻪ ﻋﻤﻠﯿﺎت ﮐﺸﺖ و ﮐﺎر، ﻣﻮﺟﺐ ﮐﺎﻫﺶ ﮐﯿﻔﯿﺖ و ﻓﺮوﺳﺎﯾﯽ ﺧﺎك ﻣﯽﮔﺮدد و ﺿﺮوري اﺳﺖ ﺑﺎ ﻣﺪﯾﺮﯾﺖ ﻣﻨﺎﺳﺐ از ﺗﺎﺛﯿﺮات ﻧﺎﻣﻄﻠﻮب آن ﺟﻠﻮﮔﯿﺮي ﺷﻮد.

Agricultural practices may decline the quality of soils. Knowing the temporal changes of soil quality in the agriculture lands is crucial for optimal management of lands and to achieve the maximum economic efficiency. In this study, some physical characteristics of four cultivated soil were compared with neighboring non-cultivated soils as control treatments. A given site, four soil samples (including two soil samples from cultivated lands and the two soil samples from adjacent non-cultivated lands) were collected. Soil structural stability, soil moisture retention curves, particle size distribution and porosity of soil, mechanical strength, plant available water and aeration, relative field capacity, integral water capacity was measured. Generally, in the cultivated lands, soil organic matter content (1.81 vs. 2.70 %), soil structural stability (5.2 vs. 7.4), microporosity (0.28 vs. 0.39), field capacity (0.27 vs. 0.34) and permanent wilting point (0.15 vs. 0.20) water contents and plant available water content (0.11 vs. 0.15) were decreased (P ≤ 0.05) in comparison with the uncultivated lands. However, the macroporosity (0.39 vs. 0.23) and soil sensitivity to crusting (0.70 vs. 0.57) were increased (P ≤ 0.05) compared to the uncultivated lands. It could be concluded that agricultural practices decline the soil quality and there is a need to take measures to avoid their negative impacts through proper management.