نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم خاک، دانشکده کشاورزی، دانشگاه آزاد اسلامی، اهواز، ایران
2 گروه مهندسی محیط زیست، واحد تهران شمال، دانشگاه آزاد اسلامی، تهران، ایران
3 گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه آزاد اسلامی، اهواز، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The purpose of this study is to compare of subsurface drip irrigation (SDI) and surface irrigation on the soil phosphorus fractionation in sugarcane cultivation in Hakim Farabi Company in Khuzestan province. For this purpose, soil sampling was carried out in two separate fields with SDI and surface irrigation systems at 30, 90, 150 and 210 days after planting and at two depths (0-15 and 15-30 cm). Average sugarcane growth, as an indicator of root activity and biomass production, in SDI was about 54% higher than the surface irrigation method. In both irrigation methods, all phosphorus fractions were decreased over time up to 210 days after planting. In SDI, Ca8-P (11 mg/kg decrease) and Ca10-P (10.7 mg/kg decrease) and a lesser extent Fe-P (8 mg/kg decrease) showed the greatest decrease respectively, which indicate greater use of phosphorus from these components by sugarcane, while the order of decrease in furrow irrigation was Fe-P (8.7 mg/kg decrease), O-P (7.7 mg/kg decrease), and Ca10-P (7 mg/kg decrease). The Ca8-P fraction, as a chemical fraction of phosphorus in calcareous soils that plays a major role in providing plant available phosphorus and converting to Ca2-P. In SDI, The Ca8-P fraction decreased from concentration of 100.3 mg/kg to 89.3 mg/kg over time (from T1 to T4), while in the furrow irrigation method this phosphorus fraction was changed from 105 to 102 mg/kg. The average relative proportions of various phosphorus fractions were ordered as Ca10-P (48.7%) > Ca8-P (37.2%) > Fe-P (6.7%) > O-P (4.2%) > Al-P (2.6%) > Ca2-P (0.5%). Therefore, the type of irrigation method is effective in the distribution and amount of phosphorus fractions in the soil, because it affects plant root activity and microorganism activity. This resulted that SDI had a greater reduction in phosphorus fractions compared to surface irrigation.
کلیدواژهها [English]
Subsurface drip irrigation (SDI) involves the application of small amounts of water directly to the plant's root zone. In SDI, sufficient amounts of water and nutrients (based on required by the plant) are placed in the root zone. Indirect effects of SDI on plant nutrition include: 1) improving the moisture content in the root zone and consequently soil ventilation, 2) effect on the concentration of nutrients in the soil solution and the distance of diffusion to the root surface, and 3) changes in the availability of nutrients due to improved activity of microorganisms. Due to the differences in the amount of water used in various irrigation methods, distinct chemical phosphorus fractions various in the soil can be expected. Due to the lack of studies on the effects of SDI and surface irrigation methods on various phosphorus fractions in sugarcane cultivation, this study was conducted to investigate phosphorus fractions in the soil in the two mentioned irrigation methods.
For soil sampling during the plant growth period and subsequent analyses, a furrow was randomly selected from odd-numbered irrigation sections (1, 3, 5, 7, and 9) in the SDI field. Four stations were established along each furrow at predetermined intervals for soil sampling. A similar sampling strategy was employed in the control (furrow irrigation) field. Sampling was done at 30 (T1), 90 (T2), 150 (T3) and 210 (T4) days after planting. In order to phosphorus fractionation, soil samples were combined and subsamples were selected in triplicate. Soil samples were collected at horizontal distances of 20 cm from the drip irrigation pipes and at vertical depths of 0–15 cm, 15–30 cm.
In order to compare the two irrigation methods, germination and weekly growth were measured. The procedure of sequential extraction was performed according to Jiang and Gu (1989) who separated six phosphorus fractions: (1) dicalcium phosphate (Ca2-P); (2) Octacalcium phosphate (Ca8-P); (3) Al-phosphate (Al-P); (4) phosphorus associated with free iron oxide (Fe-P); (5) phosphorus occluded in crystalline Fe oxides (O-P); and (6) apatite (Ca10-P).
Average sugarcane growth, as an indicator of root activity and biomass production, in SDI was about 54% higher than the surface irrigation method. The sugarcane height measured at the end of experiment was 65.3 and 49.2 cm in SDI and surface irrigation methods, respectively. In both irrigation methods, all phosphorus fractions were decreased over time up to 210 days after planting. More difference of octacalcium phosphate fraction between two irrigation methods with plant growth could be an indicator of greater uptake of phosphorus by sugarcane from this fraction. In SDI, Ca8-P (11 mg/kg decrease) and Ca10-P (10.7 mg/kg decrease) and a lesser extent Fe-P (8 mg/kg decrease) showed the greatest decrease respectively, which indicate greater use of phosphorus from these components by sugarcane, while the order of decrease in furrow irrigation was Fe-P (8.7 mg/kg decrease), O-P (7.7 mg/kg decrease), and Ca10-P (7 mg/kg decrease). The average relative proportions of various phosphorus fractions were ordered as Ca10-P (48.7%) > Ca8-P (37.2%) > Fe-P (6.7%) > O-P (4.2%) > Al-P (2.6%) > Ca2-P (0.5%). In both irrigation methods, the labile and readily absorbable fraction of dicalcium phosphate (Ca2-P) constitutes less than one percent of total phosphorus fractions, while the highest percentage of abundance is related to Ca10-P, followed by octacalcium phosphate (Ca8-P). Although the irrigation method was effective in the amounts of some chemical fractions, it did not different in the percentage of these fractions, especially in the stable chemical forms of calcium phosphate. The main reason is the very high amounts of calcium phosphates in calcareous soils in arid and semi-arid region.
The irrigation method is effective in the distribution and amount of phosphorus fractions in the soil, because it affects plant root activity and microorganism activity. This resulted that SDI had a greater reduction in phosphorus fractions compared to surface irrigation.
Author contributions
J.S: designed and carried out the experimental work, collected and analyzed the data, conceptualization, writing – original draft, writing – review and editing. A.A and K.M: contributed to the design and interpretation of the results, writing – review and editing, revised the final version of the manuscript. T.B: reviewed the various versions of the article manuscript. M.A.L: contributed to the design experiment, Supervision. All authors have contributed to this scientific work to its publication.
Not applicable.
The authors avoided data fabrication, falsification, plagiarism, and misconduct. This article does not contain any studies with human participants or animals.
The author declares no conflict of interest.
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