تغييرات شوري اعماق خاك در اثر آبياري با آب شور

Deep salinity changes due to irrigation with saline water

اﯾﻦ ﺗﺤﻘﯿﻖ ﺑﻪ ﻣﻨﻈﻮر ﺑﺮرﺳﯽ ﺗﺎﺛﯿﺮ ﺷﻮري آب آﺑﯿﺎري ﺑﺮ ﮐﯿﻔﯿﺖ ﺧﺎك در ﺳﻄﺢ و اﻋﻤﺎق اﻧﺠﺎم ﮔﺮﻓﺖ. در اﯾﻦ ﺗﺤﻘﯿﻖ از ﻧﺴﺒﺖﻫﺎي ﻣﺨﺘﻠﻒ ﺳﻨﮓ ﻧﻤﮏ ﻃﺒﯿﻌﯽ و آب ﭼﺎه ﺑﺎ دﺑﯽ 35ﻟﯿﺘﺮ در ﺛﺎﻧﯿﻪ )در ﻣﺨﺘﺼﺎت ً39/5 º59 27َ و ًº36 27َ 39/2( ﺑﻪ ﻣﻨﻈﻮر اﯾﺠﺎد ﺷﻮريﻫﺎي ﻣﺘﻔﺎوت در ﺷﺮاﯾﻂ ﮐﺸﺖ ﮐﻠﺰا اﺳﺘﻔﺎده ﺷﺪ. در ﺷﺮاﯾﻂ ﻣﺎﻧﺪﮔﺎر ، در ﯾﮏ ﻏﻠﻈﺖ ﻣﺸﺨﺺ از آب آﺑﯿﺎري، ﺗﻮزﯾﻊ ﻣﺘﻔﺎوت در ﺟﺬب آب ﺳﺒﺐ ﺗﻮزﯾﻊ ﻣﺘﻔﺎوت ﺷﻮري در ﺧﺎك ﻣﯽﺷﻮد. ﺑﺮ اﯾﻦ اﺳﺎس ، از ﻣﻌﺎدﻻت ﺗﺎﺑﻊ ﺟﺬب آب ﻧﻤﺎﯾﯽ، ذوزﻧﻘﻪاي و اﻟﮕﻮي ﺟﺬب ﺟﻬﺖ ﺑﺮرﺳﯽ ﺗﻐﯿﯿﺮات ﺷﻮري اﺳﺘﻔﺎده ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﺑﺎ اﻓﺰاﯾﺶ زﻣﺎن ﺑﻌﺪ از ﮐﺎﺷﺖ و اﻋﻤﺎل ﺗﯿﻤﺎرﻫﺎي ﻣﺨﺘﻠﻒ آﺑﯿﺎري، ﻣﻘﺪار ﺷﻮري ﻋﺼﺎره اﺷﺒﺎع ﺧﺎك در اﻋﻤﺎق ﻣﺨﺘﻠﻒ ﺧﺎك اﻓﺰاﯾﺶ ﻣﯽﯾﺎﺑﺪ. در 3ﺗﺎرﯾﺦ اوﻟﯿﻪ ﻣﻘﺪار ﺗﻔﺎوت در ECﻋﺼﺎره اﺷﺒﺎع ﺧﺎك ﺧﯿﻠﯽ زﯾﺎد ﻧﯿﺴﺖ و در ﺗﺎرﯾﺦ 4و 5ﻧﻤﻮﻧﻪ ﺑﺮداري )ﯾﻌﻨﯽ 102 و 118 روز ﺑﻌﺪ از ﮐﺸﺖ ﮐﻠﺰا( ﻣﻘﺪار ﺗﻔﺎوتﻫﺎ ﺑﯿﺸﺘﺮ ﻣﯽﺷﻮد. دﻟﯿﻞ ﺗﻔﺎوت ﮐﻢ در ﺗﺎرﯾﺦﻫﺎي 71 ،56 و 87 روز ﺑﻌﺪ از ﮐﺸﺖ ﮐﻠﺰا، وﺟﻮد ﺑﺎرش در اﯾﻦ ﻣﺪت ﻣﯽﺑﺎﺷﺪ. در 71روز ﺑﻌﺪ از ﮐﺸﺖ ﮐﻠﺰا ﻣﻘﺪار ECﻋﺼﺎره اﺷﺒﺎع در اﻏﻠﺐ ﺗﯿﻤﺎرﻫﺎ ﮐﺎﻫﺶ داﺷﺖ و از روﻧﺪ اﻓﺰاﯾﺸﯽ ﭘﯿﺮوي ﻧﻤﯽ ﮐﺮد ﮐﻪ دﻟﯿﻞ آن وﻗﻮع ﺑﺎرش در ﺑﺎزه اول اﻟﯽ 15ﺧﺮداد ﺑﻮد؛ ﮐﻪ ﺑﺎﻋﺚ آبﺷﻮﯾﯽ اﻣﻼح ﺷﺪه و ECﻋﺼﺎره اﺷﺒﺎع ﺧﺎك ﮐﺎﻫﺶ ﯾﺎﻓﺘﻪ اﺳﺖ. اﻟﺒﺘﻪ ﺑﺎﯾﺪ اﺷﺎره داﺷﺖ ﮐﻪ در ﺗﯿﻤﺎر I4ﭼﻨﯿﻦ روﻧﺪي ﻣﺸﺎﻫﺪه ﻧﻤﯽﮔﺮدد. زﯾﺮا ﮐﻢآﺑﯿﺎري ﺷﺪﯾﺪ در اﯾﻦ ﺗﯿﻤﺎر ﺑﺎﻋﺚ ﺗﺠﻤﻊ اﻣﻼح در ﺳﻄﺢ ﺧﺎك ﺷﺪه اﺳﺖ ﮐﻪ ﺑﺎرشﻫﺎ ﺗﻨﻬﺎ ﺳﻄﺢ ﺧﺎك را آبﺷﻮﯾﯽ ﻧﻤﻮده و اﻣﻼح را ﺑﻪ اﻋﻤﺎق ﭘﺎﯾﯿﻦﺗﺮ ﻣﻨﺘﻘﻞ ﮐﺮده اﺳﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻣﺪل ذوزﻧﻘﻪاي ﻗﺎدر ﺑﻪ ﭘﯿﺶﺑﯿﻨﯽ ﺷﻮري ﻋﺼﺎره اﺷﺒﺎع ﺧﺎك ﻧﻤﯽﺑﺎﺷﺪ. اﯾﻦ روش ﺷﻮري ﻋﺼﺎره اﺷﺒﺎع ﺧﺎك را ﺑﺴﯿﺎر ﺑﯿﺸﺘﺮ از واﻗﻌﯿﺖ ﺑﺮآورد ﻣﯽﮐﻨﺪ و ﻧﺘﺎﯾﺞ آن ﺗﻨﻬﺎ در ﺷﻮري 0/5دﺳﯽ زﯾﻤﻨﺲ ﺑﺮ ﻣﺘﺮ ﺗﺎﺣﺪودي ﻗﺎﺑﻞ ﻗﺒﻮل اﺳﺖ. در ﻣﻘﺎﺑﻞ، ﻧﺘﺎﯾﺞ دو ﻣﺪل دﯾﮕﺮ ﯾﻌﻨﯽ ﻣﺪل ﻧﻤﺎﯾﯽ و ﻣﺪل ﺗﺎﺑﻊ ﺟﺬب، ﻧﺘﺎﯾﺞ ﻣﻨﺎﺳﺐ ﺗﺮي را اراﺋﻪ دادﻧﺪ. ﻣﺪل ﻧﻤﺎﯾﯽ در اﯾﻦ ﺳﻪ ﺳﻄﺢ آﺑﯿﺎري داراي دﻗﺖ ﻗﺎﺑﻞ ﻗﺒﻮلﺗﺮي ﻧﺴﺒﺖ ﺑﻪ ﻣﺪل ﺗﺎﺑﻊ ﺟﺬب ﺑﻮد.

Salinity is one of the most widespread global environmental threats to agricultural production, especially in arid and semi-arid regions. This study was conducted to investigate the effect of irrigation water salinity on soil quality at the surface and depths. Therefore, in this study, different ratios of natural salt rock and well water with a flow rate of 35 liters per second (in the coordinates of 39.5 39 39.59 and 360.23.29) were used to create different salinities. The results showed that with increasing time after planting and applying different irrigation treatments, the salinity of soil saturated extract increases at different soil depths. As it is known, in the first 3 dates, the amount of difference in EC of soil saturated extract is not very large and in the 4th and 5th sampling dates (ie 102 and 118 days after rapeseed cultivation) the amount of differences increases. Of course, it should be noted that such a trend is not observed in I4 treatment. Because severe lack of irrigation in this treatment has caused the accumulation of salts in the soil surface that rainfall has only leached the soil surface and transported the salts to lower depths. As it is known, increasing the time and applying dehydration and salinity treatments increase the osmotic and matrix potential at different soil depths, so applying different amounts of leaching according to a proper schedule is very important and necessary. The results showed that the trapezoidal model is not able to predict the salinity of soil saturated extract. This method estimates the salinity of the soil saturated extract much higher than the reality and its results are only somewhat acceptable at salinity of 0.5 dS / m. In contrast, the results of the other two models, namely the exponential model and the absorption function model, have provided more appropriate results. The exponential model in these three irrigation levels has a more acceptable accuracy than the absorption function model