JWSS - Journal of Water and Soil Science

Integrated simulation of water resources systems is an efficient tool to evaluate and adopt various options in macro-policies and decision-making procedures that are in line with the sustainable development of drainage basins. One of the drainage basin management policies is to enhance the efficiency of agricultural land use. Considering the complicated function of the drainage basin elements and their interaction with each other due to water discharge fluctuations caused by various factors such as climate change, the evaluation of these policies is of great importance. Given the low irrigation efficiency in Iran, the present study was aimed to evaluate the effects of management scenarios (including long-term irrigation efficiency increased up to 20% with 5% intervals) and discharge fluctuation scenarios (including 5% and 10% decrease in the average basin inflows) on the reliability and vulnerability of water resources system in Dez Basin. The integrated scenarios were simulated in the WEAP model. The scenarios were separately simulated for the Dez irrigation network and all farmlands across Dez Basin. According to the results, reliability was decreased by 5.69 and 18.89% in the scenarios with 5% and 10% decrease in the average basin inflows, respectively. Furthermore, the irrigation efficiency of 20% in the scenario considering the current inflows ended up with the reliability of 73.58%. Moreover, in the scenario involving 5% decrease in the average basin inflows, the reliability was increased by 3.8% with an increasing efficiency of 20%; with 3.8% and 5.7%, there was an increasing efficiency of 15% and 20% in all farmlands, respectively. In the scenario consisting of 10% decrease in average basin inflows, the reliability was increased by 1.91%, 3.8%, and 5.7% with the increasing efficiency of 10%, 15%, and 20%; on the other hand, with, these were 3.8% 9.46%, and 13.2% with increasing efficiency in all farmlands, respectively. In all scenarios, the vulnerability was found to fluctuate between 25% and 31%, which was systematically analyzed.

Today, one of the biggest challenges facing the world is the lack of water, especially in the agricultural sector. In this research, we investigated the effects of irrigation method and deficit irrigation with the urban refined effluent on biomass, grain yield, yield components and water use efficiency in single grain crosses 704 maize. This research was carried out in a randomized complete block design with two irrigation systems (furrow irrigation (F) and drip irrigation (T)) and three levels of deficit irrigation treatments of 100 (D₁), 75 (D₂) and 55 (D₃) percent of water requirements in three replications, in 2017, at the collage of Abourihan Research field, University of Tehran, in Pakdasht County. The results showed that the highest yield of biomass was 2.426 Kg m^-2 for full drip irrigation treatments; also, there was no significant difference between D₁ and D₂ treatments. The highest grain yield was 1.240 kg m^-2 for the complete drip irrigation treatment. The highest biomass water use efficiency was obtained for the treatment of 75% drip irrigation, which was equal to 5.3 kg per cubic meter of water. Therefore, a drip irrigation system with 75% water requirement is optimal and could be recommended.

In order to study and evaluate the drought stress indices in surface irrigation by furrow method on grain yield, the yield components and water use efficiency, an experiment was conducted at Behbahan Agricultural Research Station in 2014-16. The experiment was conducted as a split plot in a randomized complete block design with 4 replications. Irrigation at two levels (irrigation after 100 and 200 mm evaporation from Class A pan, respectively) was evaluated as the main factor and corn cultivar was considered at 6 levels as the sub-factor. Comparison of the  mean water use efficiency in irrigation and cultivar interactions showed 100 mm evaporation from Class A pan and cultivars V4 (PH1), V5 (PH3) and V2 (SC Mobin) were ranked the first and foremost, respectively, with the  yields of 1.353, 1.299 and 1.296 kg of corn per kg of water consumed, respectively. The mean water consumed in 2014 of the experiment in 100 and 200 mm evaporation from Class A pan was 521.2 and 462.4 mm, respectively. Pearson correlation coefficient results  also showed that with increasing the  yield components, such as the  number of grains per row and number of rows, the  1000-grain weight was  increased due to  the highly significant correlation coefficient of 1000-grain weight with grain yield (r = 0.8776).  Consequently, grain yield was also increased. The highest values of SSI, STI, MP, TOL, GMP HM and YI indices were calculated in V4 (PH1). The higher values of the above indices in cultivar V4 (PH1) than other cultivars caused this treatment to be introduced as the superior one. The decreasing trend of corn yield, which was caused by water deficit stress, increased SSI, STI, MP, TOL, GMP and YI indices, while it decreased corn yield, leading to incremental changes in the YSI indices.

Changes in soil infiltration cause changes in irrigation efficiencies; therefore, estimating it in calculating irrigation efficiencies provides a more accurate estimate of irrigation performance indicators. In a study conducted on ARC2-7 farm in Amirkabir agro-industry in the 2010-2011 crop year, during four irrigations; two furrows were selected in terms of uniform infiltration and variable infiltration with a length of 140 and a width of 1.83 m. In the furrow assuming uniform infiltration two flume type II, at the beginning and end of it, were installed and the cumulative infiltration was determined by the volume balance method. The furrow with variable conditions was divided into four sections by installing five flumes. By examining the spatial variations of the mean cumulative infiltration, its value decreased from the first to the fourth section for the first irrigation by 15% and for the subsequent irrigations by 13%. Temporal changes of cumulative infiltration decreased by 27 and 30% for the first and second sections and by 26% for the third and fourth sections. An 11% increase in the average weight of the aggregate diameter and a 7% decrease in bulk density indicate physical changes in the soil. Surface runoff losses increased from 8 to 18.77% in the furrow assuming uniform infiltration and from 10.91 to 19.77% in the furrow with variable infiltration, and application efficiency decreased by 6%.

To investigate and evaluate the effects of different levels of drip irrigation on grain yield and yield components, oil yield, seed oil percentage, and seed water use efficiency, an experiment was performed at Behbahan Agricultural Research Station during two crop years 2018-19 and 2019-20. The experiment was conducted in split plots based on a randomized complete block design with 3 replications. The amount of water in tape drip irrigation was compared at four levels of 40, 60, 80, and 100% water requirement in main plots and two sesame cultivars Local of Behbahan and Shevin in subplots from the beginning of flowering. Comparison of mean interaction effects of irrigation levels and cultivars showed that the treatment of 100% water requirement in the Behbahan local cultivar with the yield of 1218.0 kg/ha was ranked first and foremost. Water consumption in the highest treatment (100% water requirement and Behbahan local cultivar) was calculated to be 5389.4 m³/ha. Treatments of 100% and 80% of water requirement in superior cultivar (local Behbahan) with water use efficiency of 0.226 and 0.210 kg/m³ had no significant difference, respectively, and were in the first place. Pearson correlation coefficient calculated for the measured traits showed that the highest correlation of water volume was calculated (r = 0.9271) with the weight of one thousand seeds. Significant correlations of water volume with grain yield and yield components indicated that sesame was susceptible to drought stress and attention to optimal water management in sesame cultivation. Therefore, decreasing the volume of water consumed and consequently drought stress in sesame reduced yield and yield components.

Due to the climatic conditions of Iran, increasing water scarcity, and the effect of drought stress on the efficiency of irrigation water consumption and chemical fertilizers application, an experiment was conducted to investigate the effect of irrigation intervals (6, 9, and 12-day intervals), different levels of nitrogen fertilizer (200, 300, and 400 kg urea per hectare) and cultivation methods (on-ridge or heeling up and in-furrow) on yield and productivity of sugarcane as a factorial design based on randomized complete block design in 3 replications at Hakim Farabi Agro-Industry Company in Khuzestan province. The results showed that the maximum (106.73 tons/ha) and minimum (59.10 tons/ha) sugarcane yields were observed in 9-day and 12-day irrigation intervals, respectively. Also, the highest sugarcane yield (99.89 tons per hectare) was obtained in the treatment of 400 kg urea per hectare and the in-furrow planting method resulted in a higher yield compared to the on-ridge planting method. The highest water productivity in sugarcane stem yield and sugar production with 3.55 and 0.34 kg per cubic meter of applied water, respectively, was obtained in a 9-day irrigation interval. A significant increase in water use efficiency in sugarcane stem yield was observed in 400 kg urea/ha compared to the other two fertilizer levels. However, there was no significant difference in water productivity of sugar yield between different fertilizer treatments. The results showed that 6 and 9-day irrigation intervals in most of the studied traits were not significantly different. Therefore, using a 9-day irrigation interval is suggested in the studied area when the sugarcane cultivation area is high and the amount of available water is limited. In-furrow planting method can also be effective in reducing water consumption. Therefore, deficit irrigation and proper nitrogen fertilizer consumption can be very effective in sugarcane cultivation.

Due to water scarcity, it is impossible to utilize all irrigated cropland in arid and semi-arid areas. Therefore, dense cultivation with a drip irrigation system that delivers water directly to the plant's root zone is an appropriate choice to enhance water productivity. The objectives of the present study were to compare wheat yield and water productivity under two different water distribution patterns in the drip-tape irrigation system and surface irrigation in full irrigation and deficit irrigation levels. The experimental treatments consist of two irrigation systems (drip-tape (DT), and surface irrigation (SU)), and three different irrigation levels (a full irrigation level (W1), two deficit irrigation levels, the irrigation interval twice, and the same irrigation depth of W1 level (W2), applied half of the irrigation depth of W1 level at the same time (W3)). The SU was implemented in place with 100% efficiency to avoid runoff. The yield in full irrigation level in DT was 5338.4 kg/ha and in SU was 5772.8 kg/ha. Applying deficit irrigation in two irrigation systems has different effects due to various water distribution patterns. In the DT, the most yield reduction was in W2, and in SU was in W3. The highest water productivity in DT was observed in W3 with a 1.44 kg/m3 value. The highest water productivity in SU was observed in W2 with a 1.46 kg/m3 value. For each irrigation system, some type of deficit irrigation management is optimal.

To monitor and compare the changes of salts in the soil profile around the roots of the corn plant, the plant yield, and the productivity of corn water, an Experimental was conducted in a completely randomized block of three repetitions in two crop years 2017-2018 and 2018-2019 at Ahvaz Agricultural Research Station. Experimental treatments included two subsurface drip irrigation systems with a working depth of 30 cm from the soil surface and tape irrigation and two irrigation intervals of 2 and 4 days. The results of monitoring soil solutes obtained from sampling depths (0-25, 25-50, and 75-50 cm) showed that soil salinity in the second year in both systems as a result of improving the quality of irrigation water from 3.61 dS/m to 2.01 dS/m, it was reduced by two times. The results of soil salinity monitoring showed the highest ratio of salinity reduction with a 2-day irrigation interval in both irrigation systems. The most leaching was done at the irrigation depth of 25-50 cm in the subsurface drip irrigation system and at the depth of 0-25 cm in the tape system. The highest yield of corn dry fodder was 9.13 and 7.13 tons per hectare, respectively, and the best water efficiency based on dry corn fodder at the rate of 13.74 kg/m was obtained in the strip drip irrigation system (tape) with a two-day irrigation interval and in the second crop year. Also, the results of the soil salinity measurement showed that the implementation and exploitation of the drip irrigation system can be the basis for improving the quality of the soil as the most important non-renewable resource of agriculture.

Due to the lack of water resources and excessive evaporation in the country, it is necessary to have a detailed irrigation program and a suitable management method. The present research was conducted to investigate the effect of superabsorbent and mulch in Khorramabad in July 2022 in a factorial combination with a completely randomized design in three replications. The first experimental factor was irrigation water treatment in 4 levels including irrigation that provided 100% water requirement (I100), 80% of crop water requirement (I80), 60% of crop water requirement (I60), and 40% of crop water requirement (I40). The second factor included different corrective materials including plant mulch (M), superabsorbent (S), and control treatment (I). The results showed the maximum amount of wet and dry yield and crop height was related to I100-M treatment, i.e. 100 percent water requirement and compost corrective material, which were 89.52 tons per hectare, 29.42 tons per hectare, and 2.27 meters. The maximum wet and biological productivity for I40-S was calculated as 14.24 kg of wet matter per cubic meter of water and 4.75 kg of dry matter per cubic meter of water. The lowest wet and dry yields were related to I40-M, which decreased the yield of the control treatment by 6.5 percent and 0.9 percent. The lowest productivity was related to the I100-S treatment, which was calculated as 3.13 kilograms per cubic meter of water for biological productivity and 9.14 kilograms per cubic meter of water for wet weight productivity. In general, mulch had a better performance in the treatments where the water stress was low, but when the water stress increased, the performance of the mulch treatments decreased. In the superabsorbent matter, the treatments with complete irrigation or with less stress, yield decreased, but the treatments with increased stress showed better results than most of the corrective materials and the control treatment.