Evaluating the SSM Model Efficiency in Simulating the Wheat Growth under Water Stress Conditions

IntroductionWheat (Triticum aestivum L.) has become very important as a valuable strategic product with high energy level. The importance of investigating environmental stresses and their role in predicting and evaluating the growth and crops yield is essential. A wide range of plant response to stress is extended to morphological, physiological and biochemical responses. Considering the rapid advancement in computer model development, plant growth models have emerged as a valuable tool to predict changes in production yield. These growth simulation models effectively incorporate the intricate influences of various factors, such as climate, soil characteristics, and management practices on crop yield. By doing so, they offer a cost-effective and time-efficient alternative to traditional field research methods. Material and MethodsThis research was conducted in the research farm of Varamin province, which has a silty loam soil texture. The latitude and longitude of the region are 35º 32ʹ N and 51º 64ʹ E, respectively. Its height above sea level is 21 meters. According to Demarten classification, Varamin has a temperate humid climate. The long-term mean temperature of Varamin is 11.18 ° C and the total long-term rainfall is 780 mm. In this study, in order to simulate irrigated wheat cv. Mehregan growth under drought stress, an experimental based on completely randomized blocks (CRBD) including: non-stress as control (NS), water stress at booting stage (WSB), water stress at flowering stage (WSF), water stress at milking stage (WSM) and water stress at doughing stage (WSD) with three replications during growth season 2019-2020 was carried out in Varamin, Iran. Crop growth simulation was done using SSM-wheat model. This model simulates growth and yield on a daily basis as a function of weather conditions, soil characteristics and crop management (cultivar, planting date, plant density, irrigation regime). Results and DiscussionBased on the results, the simulation of the phenological stages of irrigated wheat cv. Mehregan under water stress condition using SSM-wheat model showed that there was no difference between observed and simulated values. Summary, the values of day to termination of seed growth (TSG) were observed under non- stress, stress in the booting stage, flowering, milking and doughing of the grains, 222, 219, 219, 221, 221 days, respectively andsimulation values with 224, 221, 220, 221, respectively. However, with their simulation values, there were slight differences with 224, 221, 220, 221, respectively. Acceptable values of RMSE (11.7 g.m-2) and CV (3.5) indexes showed the high ability of the SSM model in simulating the grain yield of irrigated wheat cv. Mehregan under water stress conditions. Grain yield values were observed in non-stress conditions of 5783, water stress in booting, flowering, milking and doughing of the grain stages in 5423, 5160, 5006 and 5100 kg. h-1, respectively. While the simulated values were 5630, 5220, 4920, 4680 and 4880 kg. h-1, respectively. Based on the findings, observed and simulated values of leaf area index (LAI) were observed under water stress condition in the booting, flowering, milking and doughing of the grain stages (4.3 and 4.47), (4.33) and 4.46), (4.4 and 4.57) and (4.4 and 4.58) cm-2, respectively. Evaluation of the 1000-grain weight of irrigated wheat cv. Mehregan under the water stress showed that the SSM model was highly accurate. RMSE (4.6 g.m-2) and CV (1.8) values indicate the ability of the SSM model to simulate the 1000-grain weight of irrigated wheat cv. Mehregan. Also, the simulated values of the harvest index were 34.7 % in non-stress conditions, which decreased by 6 % compared to the observed value. Harvest index values were observed under water stress conditions in the in the booting, flowering, milking and doughing of the grain stages in 30.2, 29.3, 29.9 and 29.5 %, respectively. Compared to its observed values, it was reduced by 3, 3.5, 5, and 5.5 %, respectively. ConclusionBased on the findings, the slight difference between the observed and simulated values demonstrates the SSM model's capability to accurately capture water stress impacts on the phenological stages, grain yield, and yield components of irrigated wheat cv. Mehregan during critical growth stages, including booting, flowering, milking, and doughing. The results indicate that the SSM model is effective in simulating wheat growth under water stress conditions, showcasing its potential as a valuable tool for modeling irrigated wheat growth. The model's ability to account for water stress and its effects on various growth parameters makes it a reliable and efficient tool for predicting crop performance in water-limited environments

Evaluation of Wastewater Effects on Soil Chemical Characteristics, Microelements Concentration, Heavy Metals Accumulation and Mize Yield (Single Cross 704)

IntroductionIncreased agricultural activities, the occurrence of successive droughts, and limited freshwater resources, along with increasing population, have made a priority for the importance of protecting water resources in programs of developed and developing countries. Due to the climatic conditions in Iran, which has a wide range of arid and semi-arid characteristics, facing the challenge of water resources crisis, is inevitable. Therefore, the use of wastewater is very important.Materials and MethodsThis research was conducted in the research farm of Sari University of Agricultural Sciences and Natural Resources (SANRU), which has a silty clay soil texture. The latitude and longitude of the region are 36º 40ʹ N and 53º 04ʹ E, respectively. Its height above sea level is 21 meters. According to Demarten classification, Sari city has a temperate humid climate. The long-term average temperature of Sari is 11.18 °C and the total long-term rainfall is 780 mm. In order to evaluate the wastewater effects on soil chemical characteristics, microelements concentrations, heavy metals accumulation and Maize yield (Single Cross 704), an experiment was carried out as factorial based on a completely randomized design with treatments included; Water source factor (wastewater (A1), well water (A2)), Irrigation (subsurface method (I1) and (drip method (I2)) with three replication in 2018-2019 under lycimetric conditions, at the Sari Agriculture and Natural Resources University (SANRU), Iran.Results and DiscussionAccording to this study results, the effect of type of irrigation source on soil electrical conductivity, soil microelements and heavy metals accumulation of the soil was significantly different (P ≤ 0.01). The highest soil electrical conductivity with a value of 1.8 dS.m-1 was observed in the conditions of using treated wastewater. The highest amount of total nitrogen, phosphorus and potassium were related to the source of treated wastewater with values of 0.086, 24.2 and 222.2 mg.kg-1, respectively. The results showed that the accumulation of soil Pb (0.07) and Cd (0.014 mg.kg-1) in irrigation with treated wastewater increased compare to the well water source by 0.05 and 0.010 mg.kg-1, respectively. Also, the effect of irrigation method and the interaction effect of source and method irrigation on soil chemical characteristics, microelements concentration and heavy metals accumulation were not significant. The use of wastewater by increasing soil stability improves soil physical condition, increases soil fertility, increases photosynthetic products, increases the efficiency of plant photosynthetic system and ultimately improves plant growth. The use of subsurface irrigation resulted in a 67% increase in grain yield and 28% increase in biomass productivity compared to the drip method. Adequate nutrients during the reproductive growth stage of the plant play an important role in grain growth. Therefore, it can be said that the nutrients in the wastewater have increased the grain yield compared to using the well water source. Because the wastewater contains nutrients and micronutrients such as; nitrogen, phosphorus, potassium, calcium, zinc and iron were relative to the well water source and increased maize grain yield. The results showed that the use of effluent compared to well water, caused the absorption of more heavy metals lead and cadmium in the grain, leaf and stem of maize. Due to the use of wastewater water source, the amount of Pb uptake among different parts of the maize, with values of 27.2, 22.5 and 20.5 mg / g, respectively, related to the grain, leaf and stem. However, the uptake of Cd in the grains, leaves and stems was 2.32, 1.35 and 2.01 mg / g, respectively. According to the results, the high concentration of heavy metals Pb and Cd due to the use of wastewater in the grain sector directly threatens human health. Also, the concentration of heavy metals Pb and Cd in the leaf and stem parts of corn, by endangering the health of livestock and poultry, indirectly affects human health.ConclusionThe results showed that irrigation with treated wastewater due to its richness in nutrients and microelements, improves soil fertility and creates favorable conditions by increasing soil organic matter and mineral for plant growth. Also, according to the permissible threshold values of the concentration of heavy metals Pb and Cd in plants, the accumulation of heavy metals Pb and Cd in the grain, stem and leaf of single cross 704 corn, will not be a problem for consumers. Optimal use of wastewater can increase soil fertility and the ability of plants to absorb nutrients from the soil and ultimately increase plant yield