Irrigation
Ramin Fazloula; Hedyeh Pouryazdankhah
Abstract
IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility ...
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IntroductionMazandaran province is one of the most important rice and citrus-producing areas in Iran, where most of the citrus orchards and agricultural fields are irrigated with groundwater. On the other hand, irrigation water pH is one of the basic qualitative factors that determine the solubility and biological availability of chemical components in the soil such as nutrients and heavy metals, and it can affect agricultural production.Materials and MethodsThe coastal strip of Mazandaran Province toward the southwest of the Caspian Sea is situated in the north of Iran with an area of 8,252 km2 between 35.77 to 36.99 N latitudes and 50.36 to 57.13 E longitudes. In this study, the temporal and spatial variations of groundwater salinity were studied in the coastal strip using data from 300 wells, collected by Mazandaran Regional Water Company. Data included mean pH for each 6-month period of 9 consecutive years, from 2012 until the end of 2020. pH maps and maps of the risk probability area for rice and citrus growth were obtained by using Ordinary Kriging (OK) and Indicator Kriging (IK) in ArcGIS 10.7.1 software, respectively. Classifications were selected according to the properties pH range for the growth of citrus (5.8, 8) and the optimum pH for rice (6.8) in OK method. The indicator amount of pH was considered equal to 6.8 in IK method. Thereby, areas belonging to different pH classes were outlined and places with the risk probability for growing the rice and citrus were identified.Results and DiscussionThe 11 different models for semivariograms were drawn, and the best one was chosen according to the lowest nugget-to-sill ratio, and thus Stable and Exponential were obtained as the highest frequency for first and second half-years. The indices of cross validation for each selected semivariogram were estimated within acceptable ranges. In Ik method, the pH of studying area was classified into 4 ranges of <5.8, 5.8–6.8, 6.8–8.0, >8, and the percentage area of each classification derived from the ArcGIS software, the average area of each classification during the studying period was calculated zero, 0.6, 83.5 and 15.9 percent, respectively. It showed that most part of the study area located in the range of 6.8-8. It means most rice fields and citrus orchards were irrigated by the groundwater with the pH close to neutral. The obtained maps in the OK method indicated that the pH of the groundwater was not acidic in any points and alkaline conditions were observed in the western and eastern parts of the province. Therefore, The IK method was used to further investigate and determine the vulnerable areas. The probability of pH risk in rice and citrus growth was classified into 4 ranges (0-20%, 20-40%, 40-60% and 60-100%), and the average percentage area of each classification along the period was estimated 94.9, 4.8, 0.3 and zero percent, respectively. Using the IK method, higher probability of groundwater pH reducing the yield in citrus orchards and rice fields was found in eastern parts of Mazandaran province, which was about 5% of total studying area. Also, the results of the study in these 9 consecutive years did not show any decreasing or increasing trend in pH changes and consequently the area under each classification.ConclusionGenerally, the results indicated that the pH of groundwater for irrigating the citrus orchards and rice fields was appropriate in the most parts of the province and merely in the eastern part of the province, low water alkalinity may make a risk probability for rice and citrus growth in both western and eastern parts of the province. Due to the fact that alkaline water causes soil alkalinity and consequently reduces the solubility of phosphorus and some other plant nutrients in soil, it is suggested to supply the optimum required fertilization amounts of the nutrients in soil. However, the amount of fertilization should be on the basis of field research results. It is also proposed to study the condition of rice and citrus growth and the irrigated water in more details through the farms of western parts of the province. Due to the fact that most citrus orchards in this province are irrigated under the pressurized irrigation systems and using groundwater for irrigation, it is suggested that the Langelier Saturation Index (LSI) be examined in future research.
Fatemeh Fattahi-Naghani; Mahdi Ghobadinia; abdolrahman mohammadkhani; Mohamad reza Nori Emamzadeie
Abstract
Introduction: Change and decrease in atmospheric precipitation in recent years as well as increase in population and further demand for agriculture in the arid and semi-arid regions (such as Naghan) has led to a significant decrease in surface and groundwater resources. Therefore, achieving optimal utilization ...
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Introduction: Change and decrease in atmospheric precipitation in recent years as well as increase in population and further demand for agriculture in the arid and semi-arid regions (such as Naghan) has led to a significant decrease in surface and groundwater resources. Therefore, achieving optimal utilization of water in agriculture, new irrigation systems has been considered to gain the most crop yield with less amount of water consumption. Also cultivated area can be expanded by these systems, containing lands with irregular topography, due to the high water distribution uniformity. Besides developing irrigation system, irrigation management is an important tool for increasing crop productivity. Researchers have shown that applying deficit irrigation (DI) under drip system, has led to improve the quality of grape yield, decrease water consumption and increase water efficiency. The aim of this study is to investigate the effect of irrigation system and water stress on water consumption, yield and physiological indices of grapes.
Materials and Methods: The study field was located in Naghan, Chaharmahal & Bakhtiari Province, Iran. Experiences were done during summer 2016, in a completely randomized block design, with four replications in a grapevine garden The treatments included: CTRL, Furrow irrigation as common method in the area (control), surface irrigation with 100% water requirement (SI100), surface irrigation with 60% water requirement(SI60), drip irrigation with 100% water requirement(DI100) and drip irrigation with 60% water requirement (DI100).At the beginning of the experiences, 20 vine trees were selected with average of 60 years old. The field was divided into blocks, and the treatments were applied, randomly. Then the blocks were set up for the surface and drip irrigation. As the next step, required water was collected in a reservoir to obtain constant and reliable amount of water. In the control treatment, irrigation schedule of the gardeners (custom of the region) were considered in which irrigation event was at the beginning of the season. Also, drip and surface irrigation treatments were according to the soil water deficit. At the end of the experiment, water use efficiency, product performance, RWC, number of cubes per cluster, the weight of the cube in the cluster, cluster length, the number of main branches of the cluster and also qualitative properties such as soluble solids (Brix), total acid and pH of grape juice were measured.
Results and Discussion: According to the results of qualitative traits, the amount of applied water significantly affected the grapes pH in the level of 5%. The lowest grapes pH was due to the control treatment and the highest to the surface irrigation 60%. Also, measuring total soluble solids (TSS) in grape indicated significant difference in 1% level which revealed that deficit and drip irrigation increased sugar in grapes and therefore quality of the crop. The results of quantitative traits showed the number of cubes in treatments had a significant difference at a probability level of 1%. Number of cubes in surface irrigation treatment 100% (SI100) had the highest value, while the quality of the crop was lower. The treatments differed significantly in weight of 100 cubes and the drip irrigation treatment 100% (DI100) did not have a significant difference with control treatment, while deficit irrigation resulted in reducing the crop weight. Relative water content of leaves (RWC) had the highest amount in the control treatment, while low water stress reduced this index. Wet and dry yields were highest in the control treatments (CTRL); while, the lowest amount was due to the low irrigation treatments of DI60 and SI60 with 19% and 34% reduction, respectively for the wet and dry yield. Drip irrigation with 100% water requirement (DI00) was not significantly different from the control treatment in most of the quality parameters, cluster and yield characteristics but had less water consumption and higher water use efficiency.
Conclusions: Regarding the conditions of the region and the reduction of water resources, an accurate and efficient plan for irrigation is needed. So, the common method of irrigating in the region was assessed, as well as new methods of applying drip system and deficit irrigation. The results of this study indicate that drip irrigation system with 100% water requirement has no significant difference with the conventional irrigation method in the region, on quality and quantity of the gape yield. However, applying the drip system reduced the water consumption by 40%, and increased efficiency. Hence, drip irrigation system is suggested to be replaced by the traditional system.
Mohammad Reza Rigi; Mohsen Farahbakhsh
Abstract
Introduction: The environment is contaminated through intensive or inappropriate use of herbicides. Quantifying the fate of applied herbicides in the soil is essential for minimizing their mobility in the soil and environmental pollution. The adsorption behavior of the soil-applied herbicides is one ...
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Introduction: The environment is contaminated through intensive or inappropriate use of herbicides. Quantifying the fate of applied herbicides in the soil is essential for minimizing their mobility in the soil and environmental pollution. The adsorption behavior of the soil-applied herbicides is one of the most important factors governing its environmental impacts such as degradation, transition and leaching. To date, No studiy has been conducted to investigate the effects of DOM on the sorption of metribuzin by soils. The objective of this study was to investigate the impacts of DOM on metribuzin sorption by two defferent soils.
Materials and Methods: In this research, DOM (0, 10, 20, 40, 80 and 160 mg of OC/L) adsorption in two different soil samples was assayed under laboratory conditions at constant temperature. The effect of pH and DOM concentrations (0, 10, 40 and 160 mg/L) on metribuzin (1.5, 2, 3, 4, 5 and 6 mg/kg) adsorption was also studied. Soil samples were selected and collected from surface layers (0–20 cm). The soil samples were air-dried and passed through a 2-mm sieve. The DOM sorption in both soils was performed by adding 10 ml DOM solution with a series of initial concentrations in each 15 ml glass tube containing 1.00 g soil. All the DOM solutions contained 0.01 mol/L CaCl2 and 0.01 mol/L thymol, and the pH of the solutions were adjusted to 9.0 (about the pH of the initial extracted DOM solution) with 0.1 mol/L HCl or 0.1 mol/L Ca(OH)2. The tubes were shaken at 140 rpm for 24 h at 22°C. After centrifugation at 4,500 rpm for 15 min, the DOM concentrations in solutions (presented as OC) were measured using a total organic carbon analyzer. Sorbed organic carbon was calculated from the difference between the OC content of the DOM solution, which was initially added, and that found in equilibrium solution with the soil, of which the amount of native DOM released from the air-dried soil samples was subtracted. DOM solutions (10 ml) with different concentrations were added to the soils in 15 ml glass tubes with PTFE lined screw caps. The solid-to-solution ratios were adjusted to attain 20–80 percentage of the initially added metribuzin adsorption by the soils. All the DOM solutions contained 0.01 mol/L CaCl2 to maintain a constant ionic strength and 0.01 mol/L thymol to inhibit potential microbial activities, and the pH values of the solutions were adjusted to 9.0 with 0.1 mol/L HCl or 0.1 mol/L Ca(OH)2. Metribuzin was mixed at high concentration in acetonitrile before being added to the DOM solutions. Acetonitrile concentrations were always less than 0.1 percentage of the total solution volume to avoid the cosolvent effect. The tubes were shaken at 140 rpm for 24 h at 25°C. Preliminary studies showed that sorption equilibrium was approached within this time period. After mixing, the tubes were centrifuged at 4,500 rpm for 15 min, and 1.0 ml of the supernatant was removed into a sampling vial for analysis. All sorption samples were conducted in triplicate. The sorption experiments were conducted at different pH values in the absence of DOM by addition of HCl and Ca(OH)2 as required to solutions containing 0.01 mol/L CaCl2 and 0.01 mol/L thymol. The investigated pH values ranged from 4 to 9.5. The initially added concentration of metribuzin was 5 mg/L. After shaking and centrifugation, the pH values of the supernatants were measured using a pH meter. The samples were analyzed by gas chromatography equipped with a mass (6890N, Agilent, USA). Metribuzin sorption was calculated from the difference between the total amount of metribuzin initially added to the solution and the amount remained in the solution at equilibrium.
Results and Discussion: Dissolved organic matter (DOM) was adsorbed on the soils and the experimental data was better fitted to the Freundlich isotherm (R>0.999). The KF parameter amount of DOM sorbed on the soils were 3.82 and 0.95 L/kg for the soils of 1 and 2, respectively which suggested that the soils have low affinity to metribuzin . In the presence of DOM, the sorption behaviors of metribuzin by the soils were different. The effects of DOM on metribuzin sorption were dependent on the characteristics of soils and the concentrations of present DOM. Metribuzin sorption by soil 1 and soil 2 was inhibited in the presence of DOM. Metribuzin sorption was quantified by comparing the apparent distribution coefficient of metribuzin in the presence of DOM (Kd*) and the absence of DOM (Kd). The sorption was promoted when the ratio of Kd*/Kd was more than 1, and was inhibited when the ratio of Kd*/Kd was less than 1. The aqueous solubility, sorption, and bioavailability of metribuzin are pH dependent. The effects of pH on the metribuzin sorption by soils showed when pH increased from 4 to 9, metribuzin sorbtion by soils was decreased. When the pH was higher than 6.0, it was clear that the amount of sorbed metribuzin decreased as the solution pH increased in each soil in the absence of DOM. Metribuzin was present in both molecular and ionic forms owing to the ionization in the pH range examined in the study. As the solution pH increases, the protonic form decreases. Therefore, the sorption of metribuzin protonic form and the negatively charged surface of soils become more pronounced and the amount of metribuzin partitioned to soil decreases. In addition, an increasing pH may enhance the release of native organic matter from the soils into the solution that results in the decrease of metribuzin sorption. At the same pH, the amount of metribuzin sorbed by soil 2 was lower than soil 1 which was probably owing to the different organic matter content of the soils.
Conclusions: The effects of DOM on metribuzin sorption were dependent on the characteristics of soils and the concentrations of present DOM. In general, metribuzin sorption by the soils was inhibited in the presence of DOM. Metribuzin sorption by the soils also decreased with increasing the solution pH in the absence and present of DOM. The results of the study will be useful for the better understanding of the behavior of metribuzin in soils and its ecological risks.
