نشریه بوم شناسی کشاورزی
سال دوازدهم شماره 4 (زمستان 1399)

Crop models can integrate the complex interactions of soil properties, climatic conditions, crop management practices, and crop genetic characteristics. One of the main aspects of crop simulation models is the possibility to use them across various environmental and management conditions, provided that they have been evaluated under a wide range of growing conditions. The Decision Support System for Agrotechnology Transfer (DSSAT) modeling platform is leading crop modeling system that is widely applied in various environments. Testing crop models under various temperature environments are essential to apply models to climate impact studies. The objective of this study was the testing and evaluation of DSSAT-Nwheat model across a wide range of climate conditions in Iran.

Nwheat model, which recently integrated into DSSAT, was evaluated for four wheat cultivars using observations from field experiments included a wide range of climate and management. Cultivars were Shahriyar, Pishtaz, Tajan, and Chamran cultivated in cold, temperate, humid and tropical regions in Iran, respectively. The locations represent four different wheat mega-environments, a concept used by wheat breeders for testing cultivars. The management information used at each site was obtained from the Seed and Plant Improvement Institute. Daily weather data, management events, and soil characteristics imported to DSSAT. The performance of the DSSAT-Nwheat during the calibration and evaluation was assessed using different statistics, Root Mean Square Error (RMSE), Normalized Root Mean Square Error (nRMSE), Willmott’s index (d), and coefficient of determination (R2) of a 1:1 regression line. A sensitivity analysis was conducted using 30 years of observed weather data from Tabriz, Mashhad, Gorgan, and Ahwaz. For the sensitivity analysis scenarios, the temperaturewas increased by 3, 6, and 9°C, and atmospheric CO2 concentration levels were set at 360, 540, and 720 ppm.

Evaluation results showed that DSSAT-Nwheat model simulated planting to anthesis and planting to maturity accurately with RMSE values less than four days, nRMSE less than 3%, and d index close to one. Also, evaluation of grain yield showed that RMSE varied from 568 kg ha-1 for Tajan cultivar up to 933 kg ha-1 for Chamran cultivar. In general, nRMSE and d index for grain yield were less than 20% and higher than 0.8, respectively, which showed good calibration accuracy. In DSSAT-Nwheat model, the specific heat stress function explains heat stress effects during grain filling on grain yield in cultivars. Chamran cultivar is somewhat resistant to end season heat stress, so the DSSAT-Nwheat model underestimated in the warm regions. Because the cultivars differ regarding resistance to the end season heat stress, crop models need to consider cultivar-specific tolerance to heat stress to better simulate temperature effects on wheat cropping systems. The response of the model to the increase in temperature was different in regions and levels of CO2 concentrations. Elevated atmospheric CO2 concentrations lessened some of the adverse effects of high temperature. Therefore, the sensitivity analysis of DSSAT-Nwheat model to temperature variations and elevated atmospheric CO2 concentrations showed that the model could be used in studies of climate change impacts on wheat production. This model can be employed to explore the integrated effects of temperature, atmospheric CO2concentrations, water, nutrients, and agronomic management practices in a range of wheat growing environments.

The results of this study showed that the DSSAT-Nwheat model had reliably good performance under a wide range of management and environmental conditions. This calibrated model can now be used for assessing impacts of various agronomic management strategies and decisions in wheat cropping systems under current and anticipated climate change. But more importantly is the calibration method and using a large number of climatological data to calibrate.

Introduction:

Water and plant density have a complex interaction. Determination of optimum density is an effective strategy to improve the efficiency of available resources usage and to increase the yield per unit area. Despite extensive research on the effects of different levels of irrigation and plant density for different crops, including corn, information on the optimization of these resources, using response-surface methodology (RSM) is scarce. Therefore, the objective of this study was to determine the optimal level of irrigation and plant density in corn production based on central composite design (CCD).

 An experiment was conducted by using response-surface methodology with the central composite design and two replications on corn at the Research Farm of Ferdowsi University of Mashhad, during the 2015 growing season. The experimental treatments were the highest and lowest levels of irrigation volume (6000 and 14000 m-3.ha-1) and plant density (5 and 9 plants.m-2). Grain yield (GY), biological yield (BY) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Consumption rate of irrigation and density were optimized based on three scenarios: economic, environmental and eco-environmental. Grain yield of corn and WUE were considered as the main factors to determine the optimum level of treatments under the economical and environmental scenarios, respectively. In the eco-environmental scenario, the main factor was WUE and grain yield.

The results indicated that at low level of irrigation (6000 m3.ha-1) plant density and grain yield correlated with others as quadratic so that by increasing the density from 5 to 7 plants.m-2,grain yield first increased and then decreased with enhancing density to 9 plants.m-2.It seems that at low levels of irrigation, reduction and enhancement of plant density, respectively, as a result of increasing evaporation from soil surface and increasing competition in resource uptake (light and water) has reduced grain yield. Grain yield at high levels of irrigation showed a relatively linear relationship with incrementing plant density, and the highest grain yield with 1324.9 g.m-2was obtained from treatment of 14000 m3.ha-1 of water and density of 9 plants.m-2. Nevertheless, the results of model fitting showed that the highest grain yield with 1318.4 g.m-2 was attained from the density of 7 plants.m-2 and 14000 m3.ha-1 of water. Therefore, it seems that with the simultaneous enhancement in plant density and irrigation, vegetative growth due to lack of light has increased, as a result of grain yield than optimum densities (7 plants.m-2) has shown a decrease.The regression model could significantly indicate that impact of independent variables on the grain yield, biological yield and water use efficiency (dependent variable). In economic scenario with considering 8 plants.m-2 and irrigation of 14000 m3.ha-1 the maximum of economical yield with 1345.8 g.m-2 was achieved in which biological yield and water use efficiency were 4534.7 gr.m-2 and 0.98 kg.m-3 of water, respectively. In environmental scenario also the choice of the density of 7 plants.m-2 and irrigation of 7939 m3.ha-1 the highest water use efficiency (1.21 kg.m-3) was attained in which grain yield that was 988.6 g.m-2. Based on eco-environmental scenario with choice of the density of 7.5 plants.m-2 and irrigation of 10848.5 m3.ha-1 the maximum grain yield and water use efficiency was obtained in 1240.7 g.m-2 and 1.16 kg.m-3 of water, respectively.

Due to lack of water resources and environmental problems caused by the excessive use of water, applying appropriate management practices such as proper planting density to optimize these resources is essential. The best way to achieve the highest economic yield and water use efficiency and, to reach sustainable agriculture is the choice of eco-environmental scenario in which by application of the density of 7.5 plants.m-2 and irrigation level of 10848.5 m3.ha-1 the maximum grain yield and water use efficiency with 1240.7 g.m-2 and 1.16 kg.m-3 of water was obtained, respectively.

Rice (Oryza sativa L.) as the second most important crop globally and provides 80% calorie and 5% protein requirement of people is Southeast Asia. After wheat, the rice is main food of the Iranian people. This plant is cultivated in 15 provinces of the country on an area of about 600,000 hectares. Up to 1961 rice production in Iran was able to answer the internal rice requirement but at present due to population increase and economic enhancement compared to previous decades, production is less than requirement amount so there are so much importing rice the moment. Water is most limiting factor for rice production in Iran. Among other crops, rice with consumption of 80% of Southeast Asia use the highest share of water. About 70% of share of 25% global regular water is consumed by agriculture and 25-30% of has been in use for rice production. Rice is a large water consumer and its yield quite depends on climate and thus deficit water as a consequence of it. The main tendency of the Iranian people is, to consume quality rice cultivars such as Hashemi, Sadri, Ali Kazemi, Sadri Domsiah. They have a long slender grain and a head rice recovery (HRR) of 60 to 63 percent, an intermediate amylose content (AC), aroma and elongation qualities. However water is the main limitation of rice cultivation in Iran and management of water supply, distribution and consumption along with proper yield, has a major role in the continuation of rice production in Iran. So selection of cultivars compatible with intermittent irrigation management and at the same time, relatively good quality and higher yield, increases Physical productivity of water and farmers incomes. 

This experiment was conducted as split-plot based on complete block design with three replications in Rice Research Center in 2014 and 2015. The employed treatments consisted of five irrigation levels (permanent flood, and rotational by 5, 8, 10 and every 15 days) and four cultivars (Khazar, Gilane, Hashemi, and 8431) as main and sub-factors, respectively. After transplanting, for the first 15 days no irrigation was applied till fully established of plants. At raining situations, water level was determined before rainfall to prevent more water than was already determined as treatment. Main ground was two times ploughed.  Transplanting was done on 15 April using transplants with 20-25 cm length and have 4 to 5 leaves. Before transferring the transplants, the transplanted ground was irrigated for easier pull out of transplants and no damage imposed to roots. Trains including leaf and stem dry weight, leaf area index (LAI), crop growth rate (CGR), net assimilation rate (NAR), leaf area ratio (LAR), relative growth rate (RGR) and specific leaf area (SLA) were measured at booting stage.

Study results showed that the interaction of irrigation and cultivar was significant (p < /em>≤0.01) for leaf and stem dry weight, LDW, TDW, and NAR.  In addition, LAI, LWR were also significant (p < /em>≤0.01) for irrigation treatment. Daily irrigation resulted in highest yield and at no stress condition (daily irrigation) the cultivar 8431 and Hashemi showed the highest and lowest growth respectively. Under 5 and 8 days interval irrigation the cultivar 8431 showed that highest tolerance to water stress while Hashemi was the weakest ne. Under intensive stress (irrigation levels of 10 and 15 days) Khazar showed the highest tolerance but Gilane showed the least tolerance. Therefore, knowledge of various cultivars response is quite vital for any management to achieve the highest yield at water-limited conditions.

This study showed that permanent flood water is the ideal condition for rice to produce the highest yield. As time interval of irrigation increased rice plants yield decreased. Under optimum condition, Hashemi showed the poorest cultivar while 8431 cultivar showed superior across all cultivars. Similar results obtained at irrigation intervals of 5 and 8 days.

Potato (Solanum tuberosum L.) accounts for the largest share in production of food products after wheat, rice and corn, which plays an important role in the nutrition and food basket of the world. Currently, the issue of food security and supplying is very important in different parts of the world and thus prediction of its demand that is increasing. Also, growing population will intensify this issue too. A key strategy to overcome the nutritional challenge of the growing population of the world is eliminating the gap between the current achievement in farms and the yield which can be achieved by using the best cultivars compatible with the environment and the best water, soil and plant management methods.

In this study, potential yield of potato was estimated using the SSM-iCrop2. then the production and yield gap of potato were investigated with two methods of Global Yield Gap Atlas (GYGA) and Arc GIS software by interpolation method for Golestan province. For this aim, the information of potato cultivation management in the province level and the daily data of 23 synoptic weather station as well as their soil data were used. Meanwhile, potential yield gap analysis protocol (GYGA protocol) was used to identify the main weather stations named reference weather stations (RWSs) and climates where potato is planted in Golestan province. Potential yield of potato was estimated within the area covered by each RWS, and then scaled up to the province level. In order to implement the interpolation method in ArcGIS software, initially, potential yield of 23 stations in the Golestan province was estimated. Afterwards, the potential and actual yield in the whole province was estimated using Kriging and IDW methods, respectively.

According to the Agricultural Jihad Report, the actual yield of Golestan province (a ten-year average) was reported as 22 t.ha-1, while the actual yield calculated based on the interpolation method was estimated equal to 22 t.ha-1. However, the actual yield calculated using the global yield gap atlas (GYGA) method was estimated as 20 t.ha-1. Heigh yield of potato in the province was reported by farmers up to 55 tons, which was considered as potential in the province to be compared with GYGA and interpolation methods, so that in the GYGA method, 52 t.ha-1 and in the interpolation method, finding was 42 t.ha-1. yield gap and relative yield in the GYGA method (33 t.ha-1 and 38 percent), and interpolation (20 t.ha-1 and 52 percent) were obtained. Also, in GYGA method, the values ​​were estimated using only two stations, but in the interpolation method the province's yield was estimated using 23 stations and daily meteorological data. The GYGA protocol is a bottom-up approach used by Hochman et al. (2016) to assess the variation of national yield from climatic zoning to analyze similar agro-cluster groups. So far, several studies have been done using this protocol. Gobbett et al. (2017) showed that wheat lands in Australia are located in six key climatic regions. They selected 22 reference stations in this area and calculated the limited water potential yield using the APSIM model (for the years of 1996 to 2010).

The results showed that both Global yield gap Atlas (GYGA) and interpolation method had accurate estimation of actual and potential production and yield, but those values obtained using statistics and 23 weather stations in the interpolation method, and using just 2 weather station (Hashemabad and Gorgan stations) in the Global Atlas method. As previously mentioned, the GYGA method is designed to estimate the yield gap at the national level, which can calculate the potential yield, production, and yield gap in a wide range even with the least amount of information. One of the advantages of GYGA protocol is that the results obtained at any point in the world are comparable to other areas and cultivations of that particular product. Based on the comparison made in this study, it was concluded that the Global yield gap Atlas method should be used to estimate the yield of the country.

There is an increasing interest to produce medicinal plants as the demand for these natural products is also increasing in the world. Since the middle of the twentieth century, after identifying the negative side effects of chemical drugs, medicinal plants have been replaced by chemical drugs in many cases.  Due to the climatic diversity, Iran has a high potential for the production of medicinal plants, however, only a very small portion of the world’s market for medicinal plants is allocated to Iran. Considering the possibility of negative effects of chemicals on the quantity and quality of medicinal plants, it is necessary to use ecological principles. On the other hand, it seems that the cultivation of medicinal plants along with other crops would reduce weed and pest population due to the allelopathic properties of these plants. Cultivation of medicinal and aromatic plants has several advantages like higher net returns per area unit, low incidence of pests and diseases, improvement of degraded and marginal soils, longer shelf life of final products and foreign exchange earning potential. Black seed (Nigella sativa L.) is a widely used medicinal plant throughout the world which belongs to Ranunculaceae family. This experiment was carried out to evaluate physiological growth indices, yield and yield components of black seed affected by nitrogen rate and plant density under Mashhad climate conditions.

This experiment was conducted at the Agricultural Research Station of the Ferdowsi University of Mashhad, located in 10 km south-east of Mashhad (59° 36ˊ East, 36° 15ˊ N, 985 meters above sea level) during the 2016-2017 growing season. The experiment was conducted as factorial layout based on a randomized complete block design with two factors and four replications. Treatments were four plant densities (60, 120, 180 and 240 plants.m-2) and four nitrogen rates (0, 50, 100 and 150 kg N per ha as urea). Studied traits were leaf area index (LAI), dry matter accumulation (DM), crop growth rate (CGR), relative growth rate (RGR), plant height, yield components (such as number of branches per plant, number of follicles per plant, number of seeds per follicle and 1000-seed weigh), seed yield, straw yield and biological yield. SAS software was used to analyze the data and the comparison of means was done using Duncan multiple range test at 5% probability level. Charts were also drawn using Excel software.

The results indicated that the plant density and nitrogen rates affects leaf area index (LAI), dry matter accumulation (DM), crop growth rate (CGR), relative growth rate (RGR), plant height, yield components (such as number of branches per plant, number of follicles per plant, number of seeds per follicle and 1000-seed weigh), seed yield, straw yield and biological yield of black seed. The highest and lowest leaf area index was observed in 100 kg N and control, respectively. The fast period of vegetative growth, leaf area index and dry matter accumulation were observed at flowering stage with a small decline afterwards until physiological maturity. Also, crop growth rate reached to its peak in flowering stage followed by a decreasing trend afterwards. In addition, number of branches decreased sharply at high densities. The highest seed yield was observed from 150 kg N per ha (895.7 kg.ha-1) and the lowest was for control (689.9 kg.ha-1). Biological yield had high correlation with straw yield (r2=0.99) and seed yield (r2=0.97).

Agronomic management strategies had significantly effect on growth, yield, and yield components of black seed. Generally, plant density and nitrogen rates are two effective techniques for agronomic management of the medicinal plants. Further, investigations on quantity and quality of medicinal plants including black seed in association with agronomic operations will provide additional information.

In arid and semi-arid regions, efficient use of water through improved cultivars with less water requirement and more drought tolerance is a basic important way to achieve assurance and stability of crop production. Water use efficiency (WUE) indicates the amount of consumed water for yield production and is defined as the ratio of dry matter or economic yield weight (g) to used water weight (m3). Indigo varieties are grown in many countries as ornamental plants for indigo color production and also as medicinal vegetative plants. Indigo (Indigofera tinctoria L.) is a valuable species of legumes that it's cultivation have an old background in Jiroft, Kahnooj, Bam and Iranshahr. It is known as a drought tolerant plant but in seedling stage, it is sensitive to water stress and requires sufficient water for seed production in flowering time. The aim of this experiment is evaluation of leaf and grain yield and WUE in existent and prevalent indigo ecotypes in Kerman south region in order to select the best ecotype for planting in this region in future.

This experiment was conducted during two years in Jiroft, Kerman, as split plot based on a randomized complete block design with three replications. Different irrigation levels (50, 75 and 100% of water requirements) and four ecotypes (Jiroft, Kahnooj, Rigan and Ghaleh-Gange) were considered as the main and sub plots, respectively. The leaf dry weight, seed yield, water use efficiency base on leaf and seed were measured.

The results of ANOVA indicated that drought stress has significant effect on all of the measured traits. In addition the effect of drought × year was considerable on seed yield and seed WUE, while it was not on leaf yield and leaf WUE. The most seed yield obtained in normal condition in second year and the most seed WUE was reported in same year in average drought stress. For all of traits, the highest means obtained from normal conditions except for leaf WUE, which was obtained from severe stress conditions. Ecotype effect was remarkable for all of traits. Ecotype×year and ecotype×drought effects were significant for leaf WUE. Ecotype×drought was significant about seed yield too. For ecotype×year effect, highest leaf WUE was related to Jiroft ecotype in second year and for ecotype×drought effect the highest means of leaf WUE and seed yield were related to Jiroft in severe drought stress conditions and normal conditions, respectively. However, the results of this research showed that Jiroft and Roudbar ecotypes had higher leaf dry weight (5100.9 kg.ha-1), seed yield (331.75 kg.ha-1) and water use efficiency of leaf (1.24 kg.m-3) compared to other ecotypes under severe water stress conditions.

The results of this experiment indicated that drought stress notably influences leaf and seed yield in indigo. With consideration of drought × ecotype effect, in severe drought conditions Jiroft and south Roodbar ecotypes had no significant difference and these two ecotypes had the highest means for all of traits. Management of production conditions in order to leaf yield improvement is necessary since the aim of indigo cultivation is leaf production and color industry. In this way, as warm and drought climate conditions in sought of Kerman and necessity of cultivation pattern change in order to water economize and increase economic value, cultivation of these two ecotypes is recommended in alternation after wheat and vine crops.

Intercropping systems are one of the sustainable agricultural systems that defined as growing two or more plants simultaneously, lead to the use of more resources efficiently of nutrient water and land, improving plant productionIntercropping, as a new green revolution, is a sustainable strategy for the development of food production due to the lesser reliance of chemical fertilizer inputs compared with monocultures. In intercropping systems, plant nutrient uptake could improve the physical, chemical, and biological soil properties and higher nutrient mobilization in the rhizosphere. Arbuscular mycorrhizal fungi (AM) are preferred biofertilizers over other myriads of microorganisms that inhabit the interface between plant and soil. They are ubiquitous soil inhabitants and form the largest group which is predominantly associated with crops. Arbuscular mycorrhizal fungi can considerably improve plant growth, nutrients uptake, and transport, especially phosphorus, water status, and chlorophyll content. Previously studies demonstrated that higher productivity with AM fungi's application was attributed to higher nutrients availability such as P, K, Ca, Mg, etc. Thus, an experiment was conducted to evaluate the effects of barley's different intercropping patterns with grass pea and symbiosis with AM fungus on the forage yield and nutrients absorption, including N, P, K, Fe, Zn, Mn, Ca, and Mg.

In order to investigate the forage nutrients content and in intercropping of barley (Hordeum vulgare L.) with grass pea (Lathyrus sativus L.) under application of arbuscular mycorrhizal fungi, a field experiment was performed as a factorial layout based on randomized complete block design (RCBD) with ten treatments and three replications at the faculty of Agriculture, University of Maragheh, Iran, during 2017. The first factor included different planting patterns (monoculture of barley, monoculture of grass pea, 75% grass pea+ 25% barley, 50% grass pea+ 50% barley, 25% grass pea+ 75% barley), and the second factor was inoculated and non-inoculated with Glomus intraradices fungus. All data were statistically analyzed using analysis of variance (ANOVA) using MSTAT-C statistical software. The Duncan's multiple range test was used to compare means at a 5% probability level.

This study demonstrated that the macro and micronutrient content were significantly affected by different cropping patterns with the application of AM fungi. The greatest barley forage yield belonged to inoculated barley monoculture. Furthermore, the results demonstrated that the inoculated barley forage yield in monoculture was 47.48% more than the non-inoculated. The highest grass pea forage yield was achieved in monocultures and followed by a ratio of 75% grass pea+ 25% barley symbiosis with mycorrhizae fungus. Also, the highest nutrient content was achieved in grass pea monoculture with the application of AM fungi. Between different intercropping patterns, the highest nutrients content was obtained in the 75% grass pea+ 25% barley with the application of AM fungus. The higher nutrients uptake was attributed to increasing the absorption surface and improving nutrients availability with the application of AM fungi. Also, Varma et al. (2018) reported that the application of AM fungi in intercropping systems increased the transfer of the nutrients, especially nitrogen, to component plants that resulted in higher nutrients uptake in plants. These authors also reported that the higher nitrogen content with the application of AM fungi attributed to the higher activity of nitrate reductase and dikinase glucan enzymes that resulted in higher nitrogen availability for plants.

According to the results of this research, intercropping treatments of barley/grass pea with Glomus intraradices considerably influenced by the absorption of nutrients and forage yield. The content of concentration nitrogen, phosphorus, potassium iron, zinc, manganese, magnesium, and calcium were highest at all intercropping patterns coincided with the application of mycorrhiza fungi than the non-inoculated monoculture of barley. Also, between different intercropping patterns, the highest nutrients content was obtained in 75% grass pea+ 25% barley pattern accompanied by application of mycorrhiza that suggested as a better pattern to achievement high-quality forage for farmers. Therefore, intercropping of barley/grass pea with the application of mycorrhizae can improve forage quality of barley and grass pea from the point of view concentration of nutrients and were influential in production forage with high quantity.

Determining the precise water use efficiency is a critical issue in crop production temperature, precipitation, and evapotranspiration play an essential role in the hydrological cycle and crop production and as well as in assessing hydro climatological studies, plants water balance, water use efficiency, and water requirements measurements (Alizadeh, 2015). The purpose of this study was to evaluate the water requirement of tomato (Solanum lycopersicum L.) plants in Hormozgan province and compare it with other southern regions that are adjacent to this province, including Ahvaz, Dezful, Fasa, Isfahan, Kerman, Shiraz, and Yazd, in a 47-year long period from 1967 to 2013, using time series analysis.

In order to compare the water requirement of tomatoes in Hormozgan Province and other southern regions adjacent to the province, crop water requirement (CWR) and irrigation requirement (Irr.Reg) of Tomato was estimated in Bandar Abbas, Ahvaz, Dezful, Fasa, Isfahan, Shahrekord, Kerman, Shiraz, and Yazd. The CWR was acquired by estimating two components: reference evapotranspiration (ETo) and crop coefficient (Kc). ETo was calculated via the Penman-Monteith method (Allen, 2003). Time series analysis of total precipitation, average maximum temperature (Tmax) and minimum (Tmin) and diurnal temperature range (DTR) during the growing season of Tomato was calculated by using the non-parametric Mann-Kendall test (Mann, 1945; Kendall, 1975) in the studied areas during a 47-year long period from 1346 to 1392. The Pettitt test's presence of change-point in the series was also studied (Pettitt, 1979). It should be noted that ETo and CWR were calculated using the Ref ET and CROPWAT 8 software and the Man-Kendall and Petti test with r software.

The results showed no significant trend observed in crop water requirement (CWR) and irrigation requirement (Irr.Reg) of Tomato in Bandar Abbas, similar to Ahvaz, Fasa, Kerman, and Yazd. In comparison, the highest and lowest decreasing trend of crop water requirement was recorded in Dezful (with slope -5.42 mm) and Isfahan (with slope -1.56 mm), respectively. Also, the highest average tomato water requirement was observed in Yazd and Dezful (1135 and 1131 mm, respectively), while the lowest average tomato water requirement was observed in Shahrekord and Ahvaz (602 and 702 mm, respectively). On the other hand, high water requirement and irrigation of tomatoes in Dezful and Yazd can be attributed to an increase in the evaporation rate from the soil surface and transpiration from the plant surface due to the higher mean of the maximum (39 and 36.7 °C, respectively) and the minimum temperature (20.8 and 21.3 °C, respectively) and the sunshine hours of these two areas during the growing season compared with other areas. Bandar Abbas has the lowest water requirement and irrigation requirement of Tomato with the length of a growing season and growing season, similar to Ahwaz. In general, it can be stated that planting fall tomatoes in Ahwaz and Bandar Abbas is more cost-effective than summer planting due to reduced evapotranspiration. The t-student test results for comparing water requirement with irrigation requirement of Tomato showed that there was no significant difference between the amount of water requirement of tomatoes for all stations compared to the amount of irrigation requirement of Tomato due to the average low rainfall in these areas.

By analyzing the time series of evapotranspiration and climate variables and plant sensitivities to the minimum and maximum temperature for germination and growing, it is possible to decide about crop planting in a particular region, so the highest crop yield was achieved by maintaining more water resources in the region. In addition, due to climate change and the importance of Iran's food security in a warm and dry climate, acceptance and spending on appropriate strategies to adapt crop planting systems to warmer and more humid climates and new irrigation

Besides its commercial importance in the global wheat market, bread wheat (Triticum aestivum) is an efficient weapon in political and international relations. Its practical importance is increasing by the day. The planting date is an essential factor in crop production because meteorological parameters vary with the planting date changes. Singly or in combination, temperature, sunlight, and other meteorological factors influence plant growth and production. Planting date controls plant phenological total biomass production and influences the efficient conversion of biomass into economic yield (Khichar and Niwas, 2006). The purpose of determining planting date is to find the right time for a cultivar or a group of similar plant cultivars so that the set of environmental factors are suitable for seed germination and seedling establishment survival (Hore et al., 2002). It seems that planting various wheat cultivars by considering the high importance of wheat with different growth habits is necessary for agricultural experts and farmers to observe the different cultivars' responses to various planting dates and weather conditions. Various cultivars, each compatible with weather conditions in a specific part of the country, were selected for this experiment. This experiment intended to determine how cultivars responded to each planting date by taking its yield potential and temperature changes into account, identifying the optimum planting date for each cultivar, and introducing the suitable cultivar in the late planting date.

The split-plot experiment was conducted based on a complete randomized block design with three replications on the research farm of the Seed and Plant Improvement Research Institute in Karaj in two years (2015-2017). The bread wheat cultivars Baharan, Sivand, Sirvan, Mehregan, Chamran 2, Heidari, Zare, and Pishgam, formed the main plot factor and the various planting dates (12 October, 27 October, 11 November, and 26 November) the subplot factor. Yield and yield components such as the number of fertile spike per m2, number of grain per spike, number of grain per m2, 1000-kernel weight were measured at the end of the growing season to evaluate responses of the cultivars to the various planting dates. Also, the phenological stage was recorded during the growing season.

Results indicated that planting dates had significant effects on grain yield, biological yield, number of seeds per spike, number of spikes per m2, and harvest index. The highest yield was 12 November among the planting dates, and the Sivand cultivar had the highest grain yield (7708 kg.ha-1). The interaction effects of planting date and cultivar were significant on grain yield, biological yield, and some yield components. The highest grain yield (9529 kg.ha-1) was observed in the Heidari cultivar planted on 12 October and the lowest (5474 kg.ha-1) in the Chamran cultivar planted on 26 November. Delays in planting reduced grain yield by 16-36% compared to the most suitable planting date (12 October) because of the reduced vegetative and grain-filling periods.

The highest grain yield at each of the planting dates was achieved for one of the cultivars. Therefore, the cultivars adapted to different climates exhibited their highest yields at different planting dates. Based on results, it is recommended that the Heidari and/or Sirvan cultivars be planted in Karaj and regions with climates to Karaj on 12th October.  In cases of limitations concerning planting dates (unfavorable weather conditions, insufficient planting equipment, etc.), the recommended dates for planting the Mehregan and Sivand cultivars are from 27 October to 26 November to minimize yield loss caused. It seems that 12 October is the best planting time for the study region because it allows better use of the environmental conditions, including more desirable temperature, more extended growing season, higher soil moisture content, and suitable seedling establishment.

Canola is one of the most important sources of vegetable oil. It is a valuable oil crop plant the second-highest produced in the world, following soya. In dry farming areas with heavy cereal production, canola becomes crucial as an alternative to cereals. Due to its adaptation to Iran's climate, its cultivation has received much attention. Kaolin is a non-toxic aluminosilicate (Al4Si4O10 (OH)8) clay mineral that is used in organic farming as a foliar solution. Kaolin spray reduces leaf temperature through rising leaf reflectance, which decreases the transpiration rate more than the photosynthesis of plants grown at high solar radiation levels. The application of kaolin was reported to protect plants against drought stress. Kaolin efficacy in reducing temperature and mitigating environmental stresses can also affect fruit-quality parameters. Several studies also showed an increase in the yield of different crops after kaolin application, particularly under water stress conditions. It is also used to prevent crop insect damage, plant sunburn, and heat stress. Kaolin does not interfere with the leaf gas exchange by creating a porous coating. According to other research, this substance can change the insects behavior. The kaolin particles stick to the insects' tarsi, reducing their movement ability, feeding and laying eggs. Considering the importance of increasing oil production, in this study, the effect of different concentrations and time of kaolin application on canola aphid and its natural enemies and yield and yield components were examined to determine the best conditions for using kaolin on rapeseed.

The field experiment was carried out on Hydra 401 canola variety field in Mahdasht, Karaj, Iran, during 2017-2018. Canola seeds were planted in a depth of 2–3 cm. The first irrigation was done two days after planting, and then irrigation was done seven days apart. Phosphate and urea fertilizer were added to soil as required during the experiment based on the soil test results. The experiment was conducted as a factorial randomized complete block design with four replications and 16 treatments. Experimental factors were kaolin concentration (0, 3, 6, and 9 percent) and the Phenological stages of canola (germination, rosette, budding, and flowering). Field sampling was performed to determine agronomic traits, including seed yield, biological function, harvest index, and 1000-seed weight. Fifteen plants were also selected from each plot. Their pests (Brevicoryne brassicae L.) and natural enemies (Coccinella septempunctata L., Hippodamia variegata Goeze, Chrysoperla carnea Stephens.) were sampled. Samplings were performed one day before the treatments, on the third day of treatments, and once a week from insects (pests and natural enemies). This study was conducted under natural contamination conditions to adapt to field conditions. No aphids were manually added to the treatments for infection. Insects were counted and recorded in all areas of the selected plant. Mean data were used for analysis. Data analysis was done using Design Expert 10 software.

The results showed that kaolin could increase agronomic characteristics in canola. In the current study, the highest seed function, biological function, and harvest index were observed in 6% treatment about 1888.87 kg.ha-1 in the rosette stage, 3038 kg.ha-1 in the rosette stage, 66.77% in the budding stage, respectively. The highest 1000-seed weight was determined in 3% treatment about 3.90% in the rosette stage. Results of kaolin application on cabbage aphids revealed that this mineral could help to reduce the canola aphid population so that the lowest population was observed at the germination stage in 9% treatment with an average of 31.33 aphids. The results also showed that kaolin affects natural enemies and reduces their population.

The results of this study revealed that kaolin affects agronomic characteristics like seed function, biological function, harvest index, and 1000-seed weight. Kaolin was also could control the cabbage aphid population. Kaolin also had adverse effects on the studied natural enemies. It seems that using kaolin at the 6% concentration due to the canola phenological stage can increase the production of this plant in the country.

Cultivation of cover crops associated with their proper management can be a sustainable alternative to conventional weed control methods. In addition to their beneficial effects on weed control, these plants can improve soil structure and organic matter, increase water holding capacity, control soil-borne diseases, reduce soil erosion, and subsequently enhance crop yields. The use of suitable cover crops and optimizing the planting date can improve the advantages mentioned above, especially desired weeds control. They were considering the importance of sunflower production development and the need to introduce the ecological approaches in weed control; the present study aimed to investigate the efficiency of some cover crops and their optimum planting date, the influence on weed structure population and morphological traits, and sunflower seed yield (cv. Lakumka) under climatic conditions of Galougah city, Mazandaran province.

In order to study some cover crops and their optimum planting date on controlling the weeds in sunflower production, an experiment was conducted in Galoogah city (Mazandaran province, Iran) based on a factorial split-plot arranged in a randomized complete block design (RCBD) with four replications during two growing seasons (including 2016-2017 and 2017-2018). Experimental treatments were considered to cover crops such as wheat, barley, berseem clover, hairy vetch, and different planting dates, including planting two months before, simultaneous, and two weeks after the sunflower planting. Moreover, two treatments without any cover crop cultivations, including with and without weeding, were designed as controls.

The study results revealed that the cultivation of mentioned cover crops, regardless of types and planting dates, had a significant role in weeds control and increasing the seed yield of sunflower. In all treatments, the highest weeds dry matter was observed two months before the sunflower planting treatment. Also, barley cover crop had the lowest weeds dry matter in both experimental years in two months before the sunflower planting. It could maintain the weeds dry matter lower than other cover crops during various stages of sunflower growth. The lowest weed dry matter was observed in simultaneous planting with sunflower for all cover crops. Planting cover crops two weeks after sunflower planting also reduced the weeds dry matter. However, its efficiency was lower than the simultaneous planting of cover crops with sunflower. The highest and lowest sunflower height were observed in the treatments of berseem clover at the same time of planting and in wheat cover crop planting two months before planting of sunflower (181.76 and 105.98 cm), respectively. The highest leaf area index (3.97) was related to berseem clover cover crop in simultaneous planting date with sunflower, which was 14 and 69% more than control treatment without covering crops in weeding non-wedding conditions in two years of experiment, respectively. The lowest sunflower leaf area index was obtained from the wheat cover crop on the planting date two months before sunflower planting (first and second year 0.96 and 1.08, respectively). The highest sunflower dry matter (485.61 g.m-2) was observed in berseem clover cover crop simultaneous with sunflower planting, which was not significantly different from control treatment in weeding conditions. The lowest sunflower dry matter (108.27 g.m-2) was obtained in wheat planting two months before sunflower planting. Finally, the highest seed yield of sunflower was obtained in simultaneous planting of berseem clover with sunflower (2859.06 kg.ha-1), which was 17% higher than the control treatment without any cover crops in weeding condition (2381.1 kg.ha-1).

Simultaneous planting dates of cover crops with sunflower led to seed yield similar to weeding treatment. Even planting of berseem clover and hairy vetch had 17 and 14% enhancement in sunflower seed yield. Therefore, berseem clover cover crop planting simultaneously as sunflower planting, reduced weed growth, and increased seed yield of sunflower, it can be introduced as a solution for optimal sunflower production in sustainable agriculture.