مجله پژوهش آب در کشاورزی
سال بیست و نهم شماره 2 (تابستان 1394)

In order to investigate the effect of irrigation and straw mulch on yield and yield components of bean، a split-plots experiment with randomized complete block design in three replications was conducted in Astaneh Ashrafiyeh city during 2012. In this study، irrigation management treatments including no irrigation، irrigation frequencies of 6، 12، and18 days، and different amounts of straw mulch as 0، 1، 2، and 3 cm thickness were examined. The results of the analysis of variance revealed that irrigation management and different levels of mulch had significant effects on seed yield. But، their interaction was not significant on seed yield. The trend of variations indicated that the highest seed yield with 2431. 3 kg ha-1 was associated with irrigation frequency of 6 days. [n response to the main effects of mulch levels، the highest average seed yield (1585. 6 and 1518. 4 kg ha-1) was obtained in the 2 and 1 cm treatments، respectively. Also، using straw mulch in irrigation conditions prevented severe seed loss in comparison with no mulch condition. The highest water use efficiency was in irrigation frequency of 18 days with an average of 0. 58 kg m-3. Water use efficiency at straw mulch levels of 1 and 2 cm was observed as 0. 63 and 0. 6 kg m-3، respectively.

To study the effects of industrial effluents on accumulation of heavy metals in soil and cultivated canola، the farms irrigated with the wastewater of Amol Industrial City were selected and samples of wastewater، irrigation water، soil، roots، stems، leaves، and grains of canola were collected. Then، the amount of chromium، cadmium، nickel and lead in samples of soil، water and canola organs were determined. The data were analyzed based on statistical factorial analysis in complete randomized block design. Mixing of industrial wastewater with irrigation water increased concentrations of chromium، cadmium، nickel and lead in irrigation water. pH of irrigation water decreased under the effect of industrial wastewater، although EC increased. Industrial wastewater also increased the accumulation of heavy metals in soil. Accumulation of available chromium was affected by wastewater in locations 1، 2، and 3، increasing to 0. 11، 0. 14 and 0. 13 mg/kg، respectively. Accumulation of elements in the surface layer (0-20 cm) of soil was more than the subsurface (20-40 cm). Amounts of total and available cadmium in surface layer of soil in the control site were 1. 07 and 0. 1 mg/kg، which was affected by wastewater، with the greatest increase in the third location reaching 1. 48 and 0. 16 mg/kg. Also، nickel and lead increased by wastewater. Accumulation of Cr، Cd، Ni، and Pb in rapeseed organs increased by wastewater application. Accumulation of Cr in leaves and shoot of canola in the second location increased by، respectively، 57. 45% [S1] and 2. 62 times compared to the control. Transfer factor of metals from soil to shoot was more than the other organs. Accumulation of chromium and nickel in canola leaves exceeded the permissible level. Risk Index of the investigated elements in canola grain increased by irrigation with industrial wastewater. Accumulation of cadmium in canola grain reached dangerous levels.

Deficit irrigation، as a limiting factor for growth، will affect physiological characteristics of plants. In order to investigate the effects of deficit irrigation on yield، chlorophyll fluorescence، dry weight of stems and leaves، and leaf area index of sunflower، this study was performed at the research farm of Agriculture and Natural Resources University of، Sari، Iran، in 2013. The experimental treatments were arranged as randomized complete block design with three replications. The irrigation regimes consisted of full irrigation (FI)، regulated deficit (DI75، DI55)، and partial root-zone drying irrigation (PRD75، PRD55). The results indicated that the effect of irrigation treatments on yield، photosynthetic efficiency، maximum fluorescence (Fm)، minimum fluorescence (Fo)، leaf area index، shoot dry weight، leaf dry weight، and head dry weight was significant. Comparison showed that water stress significantly decreased grain yield، photosynthetic efficiency index and maximum fluorescence (Fm)، whereas the minimum fluorescence (Fo) was increased. The maximum seed yield (5148 kg ha-1) was attained in full irrigation treatment and had no difference with PRD75 treatment. The maximum leaf area index at the end of the growing season was 4. 3 and recorded in FI and had no difference with PRD75، DI75 and PRD55. Overall، treatment PRD75 is recommended since it reduced water consumption by 16. 8 percent relative to FI treatment and had no significant difference with full irrigation treatments (FI) in terms of seed yield، quantum yield، and other growth parameters.

Drought stress is one of the main problems regarding agricultural productions throughout the world، especially in arid and semi-arid regions like Iran. Manyresearchers studies various effects of drough stress on root and shoot parts of crop. But، there is not more information about root growth of tomato. In this study، the effect of drought stress on root growth، yield and yield components of tomato was investigated under greenhouse conditions. The experimental design was a randomized block design with four irrigation treatments comprising 100%، 80%، 60% and 40% of water requirement in three replications. Fruit weight، diameter and quantity، dry weight of shoot part، root volume، wet weight of root، dry weight of root and root length were measured at the end of growing season. Generally، drought stress had significant effect (p<0. 01) on yield، yield components and root attributes of tomato. Themaximum fruit weight (602. 53 g)، fruit quantity (9. 33)، diameter (4. 86 cm)، dry weight of shoot part (127. 64 g)، root volume (0. 38 L)، wet weight of root (268. 97 g)، dry weight of root (24. 25 g)، root length (239386 cm) and root area (33860 cm2) was corresponded to 100% water requirement treatment. In general، the results showed. The root volumehadmaximum correlated with yield and yield components of tomato.

The water crisis and the increase in population necessitate improvement of efficiency of water use. Application of new methods of irrigation and irrigation management is a way to optimize the use of available water resources. In order to study effect of different deficit irrigation managements of potato in furrow and tape drip irrigation methods on water use productivity and yield of potato، an experiment was performed at Chahar Mahal va Bakhtiari Research Farm of Agricultural and Natural Resources Research Center in 2013. The experiment was based on randomized complete blocks with split-split plot design with three replications. The furrow and tape drip irrigation methods were allocated to the main plots، while the two potato cultivars were in the sub-plots and four deficit irrigation managements including FI (100%)، RDI80 (80%)، RDI65 (65%) of available water depletion (AWD)، and partial root-zone drying (PRD) during full growth period were in the secondary sub-plots. Analysis of variance showed that there were significant (P≤0. 01) differences between deficit irrigation managements for tubers yield، tubers percentage of dry matter، number of tuber per plant and water productivity. Drip irrigation in comparison with furrow irrigation resulted in reduction of irrigation water amount (40%)، increase in yield (10%)، agronomic water productivity (43%)، and economical water productivity (40%). The highest economical water productivity (73240 Rials/m3) belonged to partial root-zone drying (PRD). Due to the limitation of water resources، the best suggestion for optimizing water use is using tape irrigation and deficit irrigation management through partial root-zone drying (PRD) for producing potato.

Various tillage systems have different degrading and or beneficial effects on soil structure and aggregates of top layers and، thus، affect infiltration characteristic especially the infiltration rate and the slope of infiltration equation. The objective of this study was to evaluate the effect of tillage method and depth on infiltration، penetration resistance، plant available water، and crop yield in Tabriz plain in a clayey textured soil. In this study، four treatments including A1 (chisel plowing at 20 cm depth)، A2 (moldboard plowing at 20 cm depth)، A3 (moldboard plowing at 30 cm depth) and A4 (no tillage) were compared in three replications using a randomized complete block design. Results indicated that there was significant difference between treatments in infiltration rate at different time increments (1، 2، 5، 10، 30، 60، 120 and 180 min). Based on the slope of infiltration equations، the infiltration rate in A1 decreased more rapidly than the other treatments. Initial infiltration rate in A3 (482. 8 mm hr-1) was higher than the other treatments، but differences between the other treatments were not significant. This difference may be attributed to tillage depth. Infiltration rate in A3 was higher than the other treatments but its preference in comparison with A4 (no tillage) just extended until 60 min and then declined rapidly. This result shows that the layer below the tillage depth controls infiltration rate after about 1. 5 hr. In all the four measured layers (0-10، 10-20، 20-30 and 30-40 cm)، A3 and A4 had the minimum and maximum penetration resistance، respectively. Effect of tillage treatments on plant available water and crop yield was not significant.

Reference crop evapotranspiration (ETref) is measured directly (lysimeter method) or estimated indirectly (mathematical models). In this study، daily evapotranspiration (ET) was calculated by some mathematical models for alfalfa and was compared with ET data gathered daily from a drainage lysimeter during six months. To evaluate and select the best model، ET data values were compared using statistical criteria including R2، NRMSE، MAE، MBE، and d. Results showed that the best models in the daily timeframe were: Hargreaves-Samani (HS)، Jensen-Haise (JH) and Turc. For the HS model، values of NRMSE and d were 0. 126 and 0. 930، and MAE was 0. 477 (mm. d-1)، respectively. The best models for monthly time-frame were HS، American Society of Civil Engineering-Penman-Monteith (ASCE-PM)، and Turc. Generally، HS model had the highest R2 values of 0. 985، 0. 998 and 0. 998 for daily and monthly periods، respectively، and ASCE-PM had the lowest MBE compared to lysimeter data. To estimate total ET during the alfalfa growth period in the Shahrekord plain، results showed that، models have over-estimated، except Turc and Priestley – Taylor models. ASCE-PM had the nearest ET (1161. 7 mm) to lysimeter data (1157. 6 mm). In the national document of irrigation، the alfalfa irrigation water requirement was reported at 649 mm (in the corresponding period)، which is much less than the value measured.

Accurate estimation of evapotranspiration plays an important role in quantification of the water balance at regional scale for better planning and managing water resources. Evapotranspiration can be obtained from either estimation of potential ET using data of meteorological stations or، directly، from field measurements. ET is subject to rapid changes in time and space، attributable to the wide spatial variability of precipitation، hydraulic characteristics of soils، and vegetation types and densities. Therefore، it is nearly impossible to determine its spatial and temporal distributions over large areas only from lysimeter and precise measuring instruments. Thus، researchers have used remote sensing data to estimate areal actual ET. In this study، actual evapotranspiration variations of Neyshabour plain was investigated by algorithm of energy balance of the earth since 2000 to 2013 by using MODIS images and meteorological data. Also، the determined evapotranspiration was compared and evaluated with Penman-Monteith and Hargreaves-Samani models. Low amount of coefficients of the error between Penman-Monteith model and SEBAL algorithm showed the accuracy of SEBAL model in the estimation of evapotranspiration and its parameters. The results derived from comparison of evapotranspiration and NDVI vegetation index indicated a good correlation between vegetation and evapotranspiration (R2=0. 908). Also، the variations of NDVI index، land surface temperature، and evapotranspiration in the studied fields showed that evapotranspiration increased by lower land surface temperature and higher densities of vegetation.

Evapotranspiration is one of the important components of hydrological cycle whose accurate estimate is needed for design and management of irrigation systems، simulation of crops products، and programming water resources management. In this research، to predict monthly reference evapotranspiration، ANFIS and GP models were employed and 38 years (1973-2010) of data were collected from six synoptic weather stations located in the northwest of Iran. At first، monthly reference evapotranspiration was estimated by FAO-Penman-Montieth method for the selected stations and was considered as the output of GP and ANFIS models. Then، a regression equation between effective meteorological parameters and evapotranspiration was fitted and different input patterns for the models were determined. Relative humidity as the less effective parameter was deleted from input of the models. Also، in this study، to investigate effect of “memory” on prediction of evapotranspiration، one، two، three and four months lags were used as the input of the models. Results showed that both models estimated monthly evapotranspiration with high accuracy، but ANFIS model was better than GP model.

Recently، use of synthetic materials has increased in irrigation and drainage projects due to their environmental advantages. Also، use of geotextile and PLM has been considered in drainage projects instead of granular envelopes. This study was conducted to evaluate the efficiency of geocomposite envelope-drain to reduce water-table levels. To simulate natural conditions of a drained land in the laboratory، a soil and sand tank was used that simulated part of a drainage trench in addition to adjusting the height of water table. Three envelope-drains with different geotextile envelope and drainage pipes with granular and PLM (PP450 type) envelopes were tested. In this study، the perimeter of drainage pipe and envelope-drains was equal. The results of this study showed that the performance of envelope-drain in draining excess soil water and lowering water table was similar to the drainage pipe with granular envelope. Under hydraulic head of 110 cm، in the center of the drain، drop in the water surface profile of geocomposite envelope-drain was 14. 3% lower than the drainage pipe with granular envelope. By increasing the horizontal distance to the drains، drop in the water table profile of geocomposite envelope-drain was 9. 8% lower than the drainage pipe with granular envelope.

In on-farm development projects، implementation of subsurface drainage system is one of the most important issues. Considering the high costs of preparing mineral envelope for subsurface drain pipes، continued execution of such projects، especially in Khuzestan province، has faced some difficulties. To overcome such a problem، use of synthetic envelopes or، where soil characteristics allow، subsurface drainage without using envelope may also be an option. Thus، in this research، in an experimental field of 20 ha under wheat in Shadegan region (Khuzestan province)، the performance of subsurface drainage without using envelope was compared with the conventional drainage by mineral envelope. Each experimental unit had five subsurface drain pipes (laterals) spaced at 50 m and installed at depth of 1. 7m، with a length of 220 m. To study water table condition، some piezometers were installed perpendicular to the middle laterals of each unit. Also، the rates of drains discharge and drainage water quality of the middle laterals in each unit were measured in manholes constructed on them. The maximum salinity of drainage water from drains with mineral envelope (replicates 1 and 2) and drains without envelope were 36. 9، 52. 1، and 47 dS/m، respectively، and the minimum salinities were 25. 7، 23. 6 and 12. 6 dS/m. The maximum drain discharge in the first replication of mineral envelope was 0. 59 lit/sec، and for the second one was 0. 28 lit/sec and in the drains with no envelope was 0. 23 lit/sec. Investigation of Salt Exit Index (SEI) of soil showed that salt leaching continued during the wheat growing season. Results of drains discharge showed the acceptable operation of drains without envelope and proper performance of drains with mineral envelope during the growing season. No sediment discharge was observed in any treatment.