نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم و مهندسی خاک، دانشکده مهندسی و فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج، ایران
2 گروه بیابان‌زدایی، دانشکده کویرشناسی، دانشگاه سمنان، سمنان، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
In this study, our aim is to investigate the effect of salinity stress of NaCl+CaCl2 and CaCl2 ionic compositions in maize (Zea Mays L.) root mass. Two parallel greenhouse experiments were conducted in pots in a randomized complete design with 4 replicates. The different salinity levels (0, 61, 126, 252 and 336 kPa) were similarly applied in both ionic compositions. The osmotic potential in pots was kept constant after the treatment initiation. The maize root response was investigated using osmotic potential, ion concentration and electrical conductivity salinity parameters and then were evaluated by linear Maas-Hoffman and non-linear van Genuchten-Hoffman models. The imposed salinity stress significantly affected root mass in both NaCl+CaCl2 and CaCl2 ionic compositions. The results of this study revealed that osmotic potential is a more appropriate parameter than ion concentration and electrical conductivity for maize root response to salinity stress. Based on osmotic potential, the salinity threshold values of NaCl+CaCl2 and CaCl2 ionic compositions were obtained 0 kPa and 2.49 kPa, respectively which implies effect of ion type on sensivity of maize root mass to salinity stress. The estimated root mass values using reduction functions indicated that exponential model of van Genuchten-Hoffman in both NaCl+CaCl2 (nRMSE=4.71) and CaCl2 (nRMSE=5.69) ionic compositions had more accuracy than linear model of Maas-Hoffman. In addition, modeling efficiency of exponential model (EF=0.991) was larger than linear model (EF=0.98).
کلیدواژه‌ها [English]
Low precipitation and high evapotranspiration due to the increasing of weather temperature cause drought stress and soil salinization. In order to fill the gap between demand and supply of freshwater, use of marginal waters including urban wastewater, drainage water and saline water is necessary in arid and semi-arid areas. Plant yield is primarily in relation with physiological response to abiotic stresses. Salt stress affect maize yield in two ways including osmotic stress generated by saline solution around roots and ionic effect (ion toxicity) resulting from excessive ion absorption. Plant response to salinity stress depends on the ionic compositions in soil solution, accumulation of ions in plant tissue and climate conditions. The reports by different studies indicate that nonlinear models could provide higher performances than linear models. The main objectives of this research were: (1) investigating maize root mass response to salt stress using different salt compositions (2) evaluating salinity water uptake reduction functions using maize root tissue.
Two parallel experiments were performed in a greenhouse with maize. The average air temperature and relative humidity of greenhouse were 30±10 oC and 30±20 %, respectively. The soil material was collected from the layer of 0-30 cm depth from agricultural field in Abyek area situated in Qazvin province. The soil material was passed through a 4 mm sieve for cultivation and part of the soil samples were passed through a 2-mm sieve for determination of soil physical and chemical properties. The maize (Zea mays, L., var. SC704), was cultivated in pots. Soil texture was determined with the Hydrometer method. The pH and EC were measured in the saturated soil extract. The saline water separately were produced by NaCl+CaCl2 and CaCl2 salt compositions in tap water. Five salinity treatment with osmotic potentials 0, -61, -126, -252 and -336 were provided for each salt composition. As the salinity treatments started, the matric potential in the salinity experiment was kept at −10 kPa, using the hanging water column technique. From the moment that salt water replaced the tap water in the pots, the quantity of drainage water was recorded daily for each pot and the root water uptake was calculated.
Salinity of irrigation water significantly affected maize root mass in both NaCl+CaCl2 and CaCl2 salt compositions. Salinity stress differently decreased root mass in both salt compositions due to ion type effect. In both NaCl+CaCl2 and CaCl2 salt compositions, S3 and S4 salinity treatments showed insignificant difference, while S2 salinity treatment showed significant difference with S0, S3 and S4 salinity treatments. However, NaCl+CaCl2 and CaCl2 salt compositions showed significant and insignificant difference between S1 and S2 salinity treatments, respectively. This different is related to beneficial effect of Ca2+ ion in CaCl2 salt composition in mild salinity level (S2). Comparing linear regression models in NaCl+CaCl2 and CaCl2 salt compositions showed that response of root mass to osmotic potential is more relevant than ion concentration and electrical conductivity. On the other hand, evaluating response of root mass to salinity indicated that nonlinear van Genuchten-Hoffman model had lower nRMSE and higher EF than linear Maas-Hoffman model.
The results indicated that maize root mass influenced by ion type in different salt compositions under similar osmotic potential. Investigation of different salinity parameters showed that osmotic potential is more appropriate parameter relative to ion concentration and electrical conductivity for utilizing in simulation models and irrigation planning in saline condition. In addition, evaluating reduction functions indicated that estimation efficiency of exponential model on measured data was higher than linear model.
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
Data available on request from the authors.
The authors would like to thank all participants of the present study.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
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