نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشیار بخش علوم خاک، دانشکده کشاورزی و منابع طبیعی داراب، دانشگاه شیراز
2 گروه علوم خاک و آب، دانشکده کشاورزی و منابع طبیعی داراب، دانشگاه شیراز، شیراز، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The exchange of mineral interlayer potassium (K) with soluble cations in the soil can release this form of K and supply a portion of the potassium required by plants in K-depleted soils. In the present study, the ability of 0.01M CaCl2, NaCl, and a mixture of CaCl2 and NaCl to extract non-exchangeable K from four soils with distinct characteristics over twelve 15-minute extraction periods, and the changes in soil’s capacity to re-fix K were investigated. The studied soils contained a high amount of smectite in the clay fraction with smaller amounts of chlorite, illite, and palygorskite minerals also present. Overall, NaCl extracted more K than CaCl₂ in all soils, with increases of up to 24, 64, 68, and 83% for soils 1, 2, 3, and 4, respectively. The highest amount of K was extracted from soil 3 (Ustorthents), while the lowest was from soil 4 (Torriorthents). Although, there was no significant difference between CaCl2 and NaCl in terms of K extraction in the initial three extraction stages, NaCl extracted a greater amount of K from all soils in the subsequent nine stages with increases ranging from 47 to 149%. This enhanced extraction may be attributed to the effect of Na on the clay dispersion, which increases the contact of the solution with the exchange sites and preventing the re-fixation of K by smectites. The capacity to fix K in soil 1 (Haploxerets) was significantly higher than in the other soils, while soils subjected to NaCl extraction exhibited a reduced ability to fix K.
کلیدواژهها [English]
EXTENDED ABSTRACT
The soils of arid and semi-arid regions of Iran contain a large amount of potassium (K) in available forms. However, some plants cultivated in these soils have recently exhibited symptoms of K deficiency. The exchange of mineral interlayer potassium (K) with soluble cations in the soil can release this form of K and supply a portion of the potassium required by plants in K-depleted soils. The ability of different cations to exchange potassium varied across different soils. Although, sufficient information exists regarding the effect of calcium on the release of non-exchangeable K, the influence of Na in the soil solution on the K release process has been less extensively studied.
In the present study, the ability of three different salt solutions including 0.01 M CaCl2, NaCl, and a mixture of CaCl2 and NaCl to extract non-exchangeable K from four soils with distinct characteristics over twelve 15-minute extraction periods, as well as the changes in soil’s capacity to re-fix K were investigated.
The results indicated that the studied soils contained a high amount of smectite in the clay fraction with smaller amounts of chlorite, illite, and palygorskite minerals also present. The amounts of clay and lime in the studied soils ranged 9-51 and 3-56%, respectively. The total K content also varied, ranging from 0.58 to 0.92%, with approximately 7.1-18.8% of K present in the non-exchangeable form. Overall, in all soils, NaCl extracted more K than CaCl2 (up to 24, 64, 68 and 83% for soils 1, 2, 3 and 4, respectively). Conversely, there was no significant difference in K extraction between CaCl2 and the mixture of CaCl2 and NaCl over a 180-minute period. The highest amount of K was extracted from soil 3 (Ustorthents), while the lowest was from soil 4 (Torriorthents) as 111 and 274 mg kg-1, respectively. On average, CaCl2, HCl and CaCl2+NaCl extracted 155, 246 and 168 mg kg-1 of K from the four soils. Although, there was no significant difference between CaCl2 and NaCl in terms of K extraction in the initial three extraction stages (rapid stage), NaCl extracted a greater amount of K from all soils in the subsequent nine stages (gradual stage) with increases ranging from 47 to 149%. This enhanced extraction may be attributed to the effect of Na on the clay dispersion, which increases the contact of the solution with the exchange sites, as well as the role of Na in preventing the re-fixation of K by K-fixing minerals, particularly smectites. The extracted soils fixed 77-433 mg kg-1 of added K. The capacity to fix K in soil 1 (Haploxerets) was significantly higher than in the other soils, and this may be due to the dominance of clay and smectite as the main mineral responsible for K fixation in arid soils. Soils subjected to NaCl extraction exhibited a reduced ability to fix K, possibly due to the role of Na in preventing the collapse of smectite and the subsequent fixation of K.
In general, it can be concluded that in the soils of arid regions, an appropriate concentration of Na in the soil solution or irrigation water can release non-exchangeable soil K into soluble forms that are available for plant uptake or leaching. This factor should be taken into account when managing K fertility in these soils.
Conceptualization, Mahdi Najafi-Ghiri; methodology, Hamid Reza Boostani; software, Mahdi Najafi-Ghiri; validation, Mahdi Najafi-Ghiri and Hamid Reza Boostani; formal analysis, Mahdi Najafi-Ghiri; investigation, Mahdi Najafi-Ghiri, Hamid Reza Boostani, Nazanin Soleimani and Younes Ghazeri; resources, Mahdi Najafi-Ghiri; data curation, Mahdi Najafi-Ghiri and Hamid Reza Boostani; writing—original draft preparation, Mahdi Najafi-Ghiri; writing—review and editing, Mahdi Najafi-Ghiri and Hamid Reza Boostani; visualization, Mahdi Najafi-Ghiri; supervision, Mahdi Najafi-Ghiri; project administration, Mahdi Najafi-Ghiri; funding acquisition, Mahdi Najafi-Ghiri and Hamid Reza Boostani. All authors have read and agreed to the published version of the manuscript.”
Data is available on request from the authors.
This work was supported by Shiraz University.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The authors declare no conflict of interest.
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