مجله پژوهش آب در کشاورزی
سال سی و دوم شماره 4 (زمستان 1397)

Management of soil and water resources and sustainable development of agriculture by increasing rice yield and water productivity has high importance. Consolidation of paddy fields is one of the solutions for this purpose. In this regard, this research aimed to investigate role of consolidation projects in paddy fields on water productivity. The research was done in Astaneh Ashrafiyeh, in Guilan Province, on paddy fields in 3 situations (upland, middle land, and lowland) and 2 farm types (traditional and consolidated), with 5 replications, during 2015 and 2016 . The data on rice yield and different water productivities were analyzed based on double split plot with Tuckey mean analysis method. The results showed that average yield of traditional and consolidated fields were 3958 and 3901 kg ha-1, respectively, without any significant difference. In traditional fields, the gross productivity based on evapotranspiration alone and evapotranspiration plus percolation was, respectively, 3% and 3 % more than those in the consolidated fields. However, net productivity based on evapotranspiration alone, evapotranspiration plus percolation, and water use in consolidated fields was, respectively, 50%, 51%, and 54% more than in traditional fields. Therefore, planning and implementing consolidation projects on paddy fields can increase water productivity.

]

The problem of soil salinity exists in the paddy field areas in Iran, especially in the Caspian Sea coastal areas, due to its proximity to the sea and low altitude with saline and shallow water table. Besides, considering that rice is one of the most important strategic crops for economy of Iran and the people in this area, this research was necessary in order to investigate the possibility of production of rice in the presence of shallow and saline groundwater table. This research was performed as a physical model (insulated metallic lysimeter) in the Meteorological Research Center of College of Agriculture and Natural Resources, University of Tehran, in 2017. The complete randomized design included two treatments with shallow water table: FSG and SSG, with fresh (control) and saline water, respectively. The salinity of irrigation water was 0.94 dS/m for both treatments. Moreover, for SSG treatment, the EC of shallow groundwater was 20 dS/m at 40 cm soil depth and was regulated as an artificial recharge. The results of salinity profile in SSG treatment showed that there was almost no mixing of fresh and saline water in interstitial zone (under the hard pan from 30 cm to 40 cm of soil surface). In this manner, there was insignificant effect of salinity in the root zone, because of existing of permanent water layer in rice field and downward water flow, which makes an obstacle for upward flow for saline water. This problem did not affect the rice yield, which didn’t decrease. The results of data analysis confirm this and show that shallow groundwater salinity has no significant effect on the parameters like leaf area index (LAI), root length (RL), plant length (PL), membrane stability index (MSI), chlorophyll (SPAD), relative water content (RWC) and the biomass (BIO). The difference between the performance of the control and the salinity treatments was about 1 to 12 percent, while the grain and biological yield in SSG treatment compared with FSG treatment decreased 3.2% and 4.5 percent, respectively. Therefore, considering the significant leaching of soil after cultivation, the negligible loss of yield and upward movement of saline water in the soil, production of rice and other plants in such areas seems possible. Also, with the help of efficient and effective use of lands with shallow saline groundwater, we can decrease the pressure on conventional soil and water resources.

To study the effect of different drip irrigation regimes and superabsorbent materials on the fruit quantity and quality characteristics of Zahedi date palms, a field experiment was carried out in split plot arrangement using randomized complete block design with three replications. Deficit irrigation treatments with three levels including 100%, 75%, and 50 percent crop water requirement based on the Ntional Water Document were in the main plots and superabsorbent treatments with three levels including without superabsorbent (control), use of Aquazorb superabsorbent (300 g per date palm), and use of Zeolit superabsorbent (4 kg per date palm) were in the sub plots. The results of analysis of variance showed that the effect of deficit irrigation on fruit weight, fruit length, water productivity, and potassium, and the effect of superabsorbent materials on fruit length, potassiom and total sugar was significant at 1% level. Also, intraction effects of deficit irrigation and superabsorbent materials on fruit weight and potassium content (at p<1%) and on the fruit length (at p< 5%) was significant. Use of superabsorbent materials in condition of irrigation with 100% crop water requirement did not have a positive effect on the quantity and quality characteristics of date fruit. But, under irrigation with 75% and 50% crop water requirement, superabsorbents significantly improved some quality characteristics of the fruit. Water productivity with 75% crop water requirement increased by 29.4% as compared with the 100% treatment, and use of Aquazorb and Zeolit superabsorbents increased water productivity (14.5% and 17.7 percent, respectively) as compared with the control. In general, irrigation with 75% crop water requirement (with consumption of 8052 m3 ha-1) and use of Zeolit superabsorbent for date palms (Zahedi cultivar) is suggested for Ghasreshirin area.

Salinity tolerance threshold of fruit crops is obtained based on the reduction in yield under saline conditions compared to non-saline conditions. In order to determine salinity tolerance threshold and yield reduction per unit increase in soil salinity in selected almond genotypes, a factorial experiment was carried out. The study was based on completely randomized design (CRD), with two factors: (1) genotypes in 11 types (Tuono, Nonpareil, Mamaei, Shokoufeh, Sahand, Shahrood12, A200,1-25, 1-16 and 13-40 budded on GF677 rootstock, and GF677 rootstock (without budding as control), and (2) salinity of irrigation water at five levels (0.5, 2.5, 4.9, 7.3 and 9.8 dSm-1). At the end of experiment, salinity tolerance threshold and yield reduction slope were calculated based on dry weight (biomass).The results showed that the type and combination of rootstock and scion affect the salinity tolerance threshold and yield reduction slope. The lowest salinity tolerance threshold was observed in 1-16 (2.22 dS/m), Mamaei (2.28 dS/m), and Sahand (2.39 dS/m) genotypes, respectively. On the contrary, the highest salinity tolerance threshold was observed in Shokoufeh (5.80 dS/m), Shahrood12 (4.84 ds/m) and 1-25 (4.80 ds/m).The highest yield reduction slope was observed in 13-40 (8.05%), A200 (7.86%), and Nonpareil (7.55%) genotypes, respectively. In contrast, the lowest yield reduction slope was observed in Shahrood 12 (5.60%). Overall, the results showed the level of salinity that reduced the yield by 50% in Shahrood 12, Shokoufeh, and 1-25, were 5.05, 4.43 and 3.55 dS/m greater than GF677 rootstock (without budding), respectively. EC50 in Shahrood 12, Shokoufeh, 1-25 and GF677 was observed in salinity intensity of 13.23, 12.59, 11.71 and 8.16 dS/m. It should be noted that in previous studies, 100% decrease in yield was reported by salinity level of 7 dS/m, while in Shahrood 12 and Shokoufeh cultivars budded on GF677 rootstock, we observed only 12% and 9% yield reduction by salinity of 7 dS/m. Therefore, we suggest that Shahrood 12 and Shokoufeh cultivars budded on GF677 rootstock could be cultivated in areas with moderate salinity.

To prepare the National Water Document of the country, a 25-year statistical period of 1970-1995 has been used to calculate daily potential evapotranspiration. Due to the climate changes that have taken place in recent years, updating this national valuable work is necessary. Since so far there has been no study on determining the changes in irrigation requirement of plants of cropping pattern in Kermanshah plain in the current climate conditions compared to the values presented in NETWAT software, this subject was investigated. In this study, to calculate crops water requirement, the meteorological data of 2006-2007 to 2015-2016 were used. In order to estimate the net irrigation requirement for cropping pattern in Kermanshah plain, ET0 calculator software was used to calculate evapotranspiration of reference crop. Then, the evapotranspiration values of the cropping pattern, the effective rainfall and, eventually, the amount of net irrigation requirement of the crops were calculated. The comparison between the values obtained in this research with available values in NETWAT software indicate that, for most plants, the obtained values in this study are on average 1.2 times the amounts presented in the NETWAT software. This ratio is about 2 for wheat and barley and about 1 for clover, cantaloupe, pea, and almond. The results of lysimeteric researches in the study area confirms the correctness of the performed calculations in this study.

In this research, the effect of vemicompost on yield and yield components of tomato and okra was investigated under irrigation with contaminated water. The experiment included two treatments using vermicompost and control with three replications; and it was conducted at the Campus of Agriculture and Natural Resources of Razi University. Vermicompost was applied at 25 ton per hectare in two stages: 10 t/ha at the crop cultivation period, and 15 t/ha one month after cultivating. The effect of vermicompost growth indexes including plant height, stem diameter, fruit diameter and weight, chlorophyll index, stem and leaf dry matter percentage and yield were investigated. The comparison of the average yield of tomato and okra showed that only fruit weight of tomatoes was statistically significantly different, and there was no statistically significant difference between the two treatments in other characteristics. In tomatoes treated with vermicompost, plant height, stem diameter, chlorophyll index, stem and leaves dry matter percentage were increased by 2.3%, 0.3%, 7.3%, 5.6% and 9.1 percent and fruit diameter, fruit weight and yield were decreased 25.5%, 42.6% and 73.2 percent, respectively compared with the control. Also, in okra under application of vermicompost, plant height, stem diameter, fruit diameter, fruit weight, chlorophyll index and yield were increased by 10.3%, 1.2%, 10.4%, 13.3%, 3% and 35.7%, while stem and leaves dry matter percentages were increased by 5.5% and 11.7%, respectively, compared with the control. Considering the significant reduction in tomato fruit weight and reduction of its fruit diameter and yield, as well as reduction of stem and leaves dry matter in okra, and in light of the high risk of using contaminated water and possible contamination of the fruit and reduction of its quality and health, the use of vermicompost for these crops under irrigation with contaminated water is not recommended. In general, the use of contaminated water is unacceptable for human and animal foods.

Using proper irrigation management leads to optimum utilization of water, soil, and fertilizer and production of high yield and quality products. In order to investigate the effect of irrigation intervals and surface and subsurface drip irrigation systems on growth indicators of Rosmarinus officinalis L., a field experiment was carried out during 2015 growing seasons at an experimental farm in Kerman city. The treatments were laid out in split plot using a Randomized Complete Block Design with three replications. The treatments comprised three irrigation levels (I 1 =25, I 2 =40 and I 3 =55 mm evaporation from class A pan) in the main plots, and two drip irrigation systems (surface and subsurface) in the sub plots. The results showed that I 2 in comparison with I1treatment led to 44 mm water saving. However, dry weight, height of plants, number of shoots per plant and leaf area index decreased by 12.9%, 12.6%, 13.6% and 5.3 percent, respectively, while water use efficiency increased 3.6 percent. Also, results showed that water use efficiency, dry weight, height of plants, number of shoots per plant, and leaf area index increased by, respectively, 15.1%, 18.3%, 9.7%, 12.5% and 15 percent in subsurface drip irrigation compared to surface method. Therefore, for Rosmarinus officinalis L. cultivation in Kerman area, application of I 2 in subsurface drip irrigation system is the best way to increase the water use efficiency for the drought years.

Multidimensional nature of water flow, plant uptake, and high frequency of water application increase the complexity in modeling soil moisture dynamics from trickle irrigation. By determining soil hydraulic properties, parameters of root distribution model for pistachio trees in the field, evapotranspiration and inflow flux, soil moisture distribution was modeled using HYDRUS-2D model for surface (DI) and sub-surface drip irrigation (SDI) systems. Also, soil moisture content in the following days after irrigation was measured at different lateral and vertical distances from the tree by using Moisture Meter Profile Probe. Leaf stomatal conductance was used to test the model and parameterize water-stress response function. The h50 for pistachio tree, which represents the pressure head at which the water extraction rate is reduced by 50%, was calculated 4935 cm. HYDRUS outputs were compared with measured data in corresponding locations, and values ofME, RMSE, E and R2 statistics were obtained -0.002, 0.02, 0.7, 0.741 for DI and 0.006, 0.021, 0.761, and 0.794 for SDI respectively. The calculated transpiration by HYDRUS showed high correlation with stomatal conductance, especially in SDI. Based on plant measurements and HYDRUS results, root water uptake in SDI was significantly more than DI. Therefore, using SDI systems, by decreasing evaporation, saves more water and increases irrigation efficiency. The calculated root water uptake and measured stomatal conductance for the pistachio trees revealed that soil moisture perfectly supports plants until four days after irrigation. Thus, by decreasing irrigation interval in the field, maximum potential of drip irrigation systems can be achieved.

The present study aimed to investigate the factors affecting the use of wastewater in agriculture sector. The study was conducted by a descriptive-surveying method through field survey of farmers' perspectives in Khorramabad Township and review of documented data. The validity of research tool (questionnaire) was obtained using viewpoints of experts, and for reliability of questionnaires, a pilot test was conducted. The Cronbach’s Alpha coefficient of higher than 0.76 showed that research tool was reliable. The studied population was farmers in Khorramabad Township who used treated wastewater to irrigate their farmlands. Sample size was determined using the Cochran formula (n=199). Questionnaires were distributed randomly among the respondents. For data analysis, we used the descriptive statistics indexes such as mean, mode, standard deviation, and stepwise multiple linear regression. The results showed that the informatics channels for farmers did not have a satisfactory performance. Among the economic factors, the price of wastewater, among the social factors, the acceptance of applying wastewater in agriculture, and among the environmental factors, drought and water shortage had the higher priority compared with other items. Regression results showed that the level of knowledge about nutritive values of wastewater and safety of agricultural products and recommendations of experts in the farm were the strongest explanatory variables in willingness of farmers for using wastewater in agriculture. These variables explained 44 percent of dependent variable changes. Based on the results of the research, specialized workshops by experts are recommended to increase farmers' awareness and knowledge about the use of wastewater in agriculture.

The effects of salinity and boron content of irrigation water on growth and micronutrient concentrations of purslane plant were studied. The growing population of the world and increasing demand for food has led to the unavoidable utilization of saline soils for crop production. Purslane is an annual herbaceous plant that grows well in saline soils. Boron (B) is an essential element for plants and may exist in toxic concentrations in saline soils, but the plants require it in small amount. To evaluate the effects of salinity and B levels of irrigation water on the yield and micronutrient concentrations of purslane plant, a factorial experiment with a completely randomized design in three replications and 35 treatments was conducted in greenhouse condition. The irrigation water had the salinity levels of 0.5, 2.5, 5.0, 10.0, 15.0, 20.0 and 25.0 dS/m and boron contents were 0, 0.5, 0, 1, 2, and 4 mg/liter. The results showed that the highest dry weight for aerial parts (1.29 gr) and root (0.24 gr) and the highest plant height (31.16 cm) and concentration of copper (29.1 mg. kg-1) in aerial parts were measured for the treatments irrigated by water with the salinity level of 0.5 dS/m and boron level of 0 mg/L. The highest concentration of iron (93.65 mg. kg-1) in aerial parts was measured for the plants irrigated by water with the salinity level of 10 dS/m and boron concentration of 0.5 mg/L. The highest concentration of zinc (64.26 mg. kg-1) in aerial parts was measured for the treatments irrigated by water with the salinity level of 2.5 dS/m and boron level of 2 mg/L. The highest concentration of manganese (98.26 mg. kg-1) in aerial parts was obtained from the treatments irrigated by water with the salinity level of 0.5 dS/m and boron level of 2 mg/L. In general, the results of this study indicate that for obtaining high yields of purslane plant, the salinity level of irrigation water should not be higher than 2.5 dS/m and the boron level should be less than 0.5 mg/L.

Due to the important role of irrigation water chemical composition in the yield of crops and its effects on the soil structure, it has been taken into consideration by the agricultural sector planners. In this regard, the sour and burning taste of water in some agricultural wells around the HamehKasi village in Hamedan province has caused concerns about their water composition and possible detrimental effects on soil stucture and plant growth. Therefore, the present study was conducted to evaluate the water quality and the trend of changes in its composition. In this study, 6 gaseous water-wells were identified and their salinity was measured 15 times in three years (5 times each year), and the trend of their electrical conductivity changes was evaluated by SPSS software. Also, from each well, one sample was taken in order to determine the electrical conductivity, cations and anions content, and their chemical indices were calculated and evaluated by means of different criteria and diagrams. The results showed that calcium and bicarbonate ions have the highest concentrations in these waters, and the water of the mentioned wells was considered as unconventional and was Ca-Mg-HCO3 type. The water salinity of these wells was high (from 2.96 to 6.07 dS/m), and had very high salinity and sodicity (C4S4) after correction of the sodium adsorption ratio. Due to high salinity of water, fine-textured soil and lack of sufficient water for leaching, it is expected that the soil will be salinized in the root zone by irrigation, and as a result, the yield of plants and especially perennial plants would decrease. However, the statistical analysis of the electric conductivity changes of gaseous water-wells in HamehKasi area indicated that the salinity of their water decreased significantly over time. Consequently, the quality of water in the HamehKasi area in terms of irrigation improved over time.