مجله پژوهش آب در کشاورزی
سال سی و هفتم شماره 4 (زمستان 1402)

Optimal use and management of water resources is very important. Also, choosing the appropriate irrigation method plays a vital role in saving water consumption in the agricultural sector. Therefore, in the current research, the effect of the irrigation method on the simulation of sugar beet yield was investigated using the AquaCrop model. In this study, the effect of two methods of drip irrigation (tape) and surface irrigation (furrow) and three levels of irrigation water (50%, 75%, and 100% of the plant's water requirement) on the yield of sugar beet plants was investigated in Sarayan-Ayask region, Iran. A factorial experiment was conducted based on a completely randomized design with 4 replications in 2021-22. The results showed that irrigation method had a significant effect on leaf diameter, leaf length, leaf weight, tuber diameter, and tuber length and weight of sugar beet tuber. Also, according to the results, drip irrigation had greater effect than furrow irrigation on the studied traits. Then, the grain and biomass yield was simulated using the AquaCrop model and the simulated values were calibrated and verified using observational data. Calibration was done using two replications of 100% and 50% stress levels, and validation was done using the replication of 75% stress level. The NRMSE, RMSE, RD and R2 coefficients of the model calibration values showed that the simulated and validated values were close to each other and these values were more precise in drip irrigation than in furrow irrigation. Validation values of two irrigation methods also showed the ability of model in simulating grain yield and biomass.

Iran is located in the dry belt of the earth and its rainfall is one third of the global average. Therefore, proper management of water resources is necessary, especially in the agricultural sector. For this purpose, in 2022, a research was conducted with the aim of investigating the effect of several soil amendments in Khorram Abad region, in the research farm of Lorestan University. The experiment was factorial with a randomized complete block design in three replications. Treatments were irrigation water at 4 levels of I1=100%, I2=80%, I3=60%, and I4=40% of the water requirement and different soil moisture amendments including vermicompost (C) 6 t/ha, biochar (B) 1.5 t/ha, superabsorbent (S) 63 kg/ha, and organic mulch (M) 7.5 t/ha and the control treatment (I). Results showed that the highest productivity, biological yield, and plant height were related to I1-C treatment, which were 126.71 t/ha, 46.27 t/ha and 2.35 meters, respectively. The highest water productivity and biological productivity at the probability level of 5% was I2-C, which was calculated as 16.79 kg of fresh fodder/m3 of irrigation water and 5.9 kg of dry matter/m3 water. In general, vermicompost and biochar also increased the fresh and biological yield, height, and water productivity of corn. The use of mulch in 100% and 80% treatments had better effect, but with the increase in water stress (i.e. I3 and I4), effect of mulch decreased (5.3% and 1% relative to the control). Superabsorbent in I100, I80, I60 treatments showed lower effect (9.3%,7.2%, 3% less fresh weight than the control, respectively). However, with increasing stress, I4 had better results (7.6% higher fresh yield than the control). Therefore, in Khorram Abad region, the amount of 6 t/ha of vermicompost and 80% of the water requirement applied by drip tape irrigation for fodder corn is recommended to increase the production rate while saving 20% of water consumption.

In most arid and semi-arid areas, water limitations are one of the main reasons for the reduced plant growth and yield under irrigation and dry land (rainfed) conditions. The aim of this study was to compare the morphophysiological responses of rapeseed cultivars to supplementary irrigation and dryland conditions. For this purpose, an experiment was carried out as a split plot in the form of a randomized complete block design with three replications during 2017-2018 in the Gachsaran Agricultural Research Station. Irrigation treatments were at four levels (no irrigation=I0, supplementary irrigation at flowering stage=I1, supplementary irrigation at grain filling stage=I2, and supplementary irrigation at flowering stage+ grain filling=I3) in the main plot, and cultivars Hayola 401, R. J. S, and Shirali as factorial in the sub-plots. The results showed that supplementary irrigation increased plant height, number of sub-branches per plant, 1000- grain weight, grain yield, and oil percentage compared to rainfed conditions. With supplementary irrigation, the weight of 1000 grains increased by 32% compared to rainfed. Grain yield increased from 755 in rainfed conditions to 2350 kg.ha-1 with two supplementary irrigations. With two supplementary irrigations, the oil content increased by 11.8% compared to the rainfed conditions. In all irrigation treatments, grain yield and oil content of Hayola 401 were higher than R. J. S and Shirali cultivars. In general, supplementary irrigation improved morphophysiological traits, yield, and percentage of grain oil. In rainfed rapeseed cultivation, with supplemental irrigations at flowering and grain filling, water productivity increased from 0.21 to 0.53 kg m-3 grain yield from 755 to 2350 kg ha-1 and oil percentage from 35.4 to 36.9.

Water scarcity is the biggest problem in Hamadan Province. In the meantime, agricultural sector is more vulnerable than other economic sectors due to its high share of water consumption. Policymakers are interested in adopting appropriate policies and tools to manage crisis and tackle water scarcity problems. This study aimed to determine the economic value of water in the agricultural sector of the province and the potential for revenue generation of this resource in the production of irrigated crops. Selected products for the study included wheat, barley, alfalfa, potato, sugar beet, corn, grain fodder, watermelon, garlic, cucumber, tomato, grape, and walnut products. Data was obtained through questionnaires and interviews with farmers for the 2018-19 crop year and for estimating economic value of water using Cobb-Douglas production form. The results showed that the economic value of water in different crops was greater than the water supply costs. The economic value of water for the mentioned products was equal to 2043, 3775, 6023, 3506, 2136, 1956, 1778, 4902, 36750, 16337 and 4929, 15840 and 20064 Rials/m3 and, on average, 9232 Rials/m3 of water, respectively. These figures are compared to the cost of extracting water from underground sources the most expensive source is 496 Rials/m3, which shows a big gap between these numbers; therefore, it is possible to price water at the same rate as the above figures. This provides incentives towards more efficient water use in this economic sector.

Water stress occurs as a result of the imbalance between soil water in the root zone and plant water use, which necessitates determining the water stress index of the plant. Surface soil moisture is directly related to plant water content. Availability of satellite data has led to temporal and spatial resolution of field data and offers new opportunities for monitoring crop conditions. In this research, accurate and continuous monitoring of soil moisture content, as a representative of soil moisture stress, was done with field measurements of soil moisture, and comparison with multispectral data of Landsat 9 and Sentinel 2 satellite images. The relationship between plant indices, as an independent variable, and soil surface moisture, as a dependent variable, was studied using linear multivariate regression and M5 tree regression methods. Considering the non-linearity of the relationship between soil moisture and spectral reflectance, linear multivariate regression did not show satisfactory results with coefficient of determination (R2) of 0.46 and 0.34 for Landsat 9 and Sentinel 2 satellites, respectively, as well as the root mean square error (RMSE) equal to 0.043 and 0.052. However, M5 tree regression showed more acceptable results, such that by establishing 16 and 20 regression relationships for Landsat 9 and Sentinel 2 satellites, the soil moisture was estimated withR2 of 0.70 and 0.67 and RMSE of 0.033 and 0.038, respectively. The results showed that the estimation of soil moisture with methods based on machine learning, such as the M5 model, increases the accuracy of calculations. In the M5 decision tree regression, a high number of variables does not necessarily lead to an increase in the accuracy of soil moisture estimation, and a relationship with the highest accuracy was found in the low number of variables. Therefore, the relationship obtained at the field level can be used to evaluate soil water stress and determine irrigation time in agricultural lands on a large scale, without measuring soil data.

Agricultural sector is the largest consumer of fresh water worldwide. Therefore, finding a suitable alternative for the use of fresh water in agriculture can be a key solution to future water crisis issues. Application of saline water by using appropriate methods can be an option for irrigating salt-tolerant plants. One of these methods may be magnetizing irrigation water. In the present study, to investigate the effect of magnetized water on the fresh and dry weight, as well as the essential oil of the medicinal plant Maryam Goli (Salvia L.), a pot experiment was conducted in an open space using a factorial design and completely randomized layout with four replications. The experimental treatments included salinity of irrigation water prepared from different concentrations of Caspian Sea water (30%, 50%, 70%, and 100% mixing with well water) and a control treatment (well water), in both magnetic and non-magnetic conditions. Due to rainfall during the growth season, at the end of the experiment, the saturation extract salinity (EC) of the soil corresponding to the control treatment and the 30%, 50%, 70%, and 100% water mixtures were 3.15 (I0), 3.65 (I1), 4.55 (I2), 4.75 (I3), and 5.06 (I4) dS/m, respectively. The results showed that, in the I4 treatment, both the dry and fresh weights of the plant decreased by 40% and 25%, respectively. However, regarding the effect of magnetized water, the results indicated that in saline treatments with soil EC less than 3.65 dS/m (I0 and I1), use of magnetized water prevented a significant decrease in the weight of Maryam Goli plant shoots. Furthermore, the research results demonstrated non-significant changes in the essential oil of Maryam Goli plant due to irrigation with different salinities as well as magnetic water. Based on the results, it is recommended that irrigation management of Maryam Goli plants using magnetized saline water be carried out in such a way that the saturation extract salinity of the soil does not exceed 3.65 dS/m during the growing season.

Biochar as a porous material is rich in biological carbon in a stable form. Its structure is capable to store water and nutrients. Therefore, it is used for retention of such materials, especially in sandy soils. Biochar can improve water productivity in the agricultural sector in drought stress condition to achieve food security in the world. In order to study the effect of deficit irrigation and biochar on yield of coriander in a coarse-grained soil under water stress, this research was conducted using a factorial manner and a completely randomized design in the research greenhouse of Urmia University. The experimental treatments included three levels of irrigation: 100%, 75%, and 50% of the plant water requirement, and three levels of biochar application: 0, 2.5%, and 5% of the weight of each pot, which totally included 27 treatments. Irrigation was applied on the basis of plant requirement and soil water content below field capacity and the applied water was measured during the growing season. For each pot, quantitative parameters including weights of dry and wet plant, stem, leaf, and root were accurately measured. The results showed that the effects of irrigation levels and biochar on some measured parameters were significant at the probability level of 1% and 5%. The results demonstrate that by applying deficit irrigation, the measured quantitative parameters and plant yield decreased. The highest value of the parameters was obtained from the treatment of 100% water requirement and use of biochar up to the level of 2.5% of the soil. Therefore, applying suitable amount of the biochar as soil amendment improves coriander plant's growth and yield.