جستجوی مقالات مرتبط با کلیدواژه « عملکرد گندم » در نشریات گروه « آب و خاک »

The lack of proper water productivity and the increase of water per capita over time have led to the drying up of rivers and lakes as well as the drop in the level of underground water. Currently, many countries are facing a great challenge in producing food from limited water resources. Lack of water along with improper exploitation of resources does not meet the growing demand of the current population for food. The lack of water resources for the production of various agricultural products, including wheat, is one of Iran’s main challenges and concerns and the primary solution is to improve and promote water productivity. In this regard, consuming less water should produce the most production. One of the biggest problems for wheat production is the lack of water resources and the fragmentation of different water management methods, fields, and irrigation systems. On the other hand, for water and farm management to have the greatest effect in increasing the yield, efficiency, and productivity of water consumption, it must have various inputs such as hybrid and modified seeds, chemical fertilizers and pesticides, the use of advanced tools and machinery, and appropriate planting operations, and harvesting should be done optimally, correctly, and at the right time-place.

The current study has targeted the main areas of wheat production in Iran. Due to its high nutritional value and strategic importance, wheat is cultivated in almost all areas of the country. According to the Pareto principle, the areas where 80% of wheat cultivation and production (irrigated and rainfed) are carried out are the main wheat production areas. Since in Iran, the statistics of the agricultural situation are mainly presented based on political divisions, therefore, the major regions will be the set of provinces in which the above hypothesis is true. Accordingly, 13 provinces of Golestan, Kermanshah, West Azarbaijan, East Azarbaijan, Hamedan, Ardabil, Lorestan, Central, Khuzestan, Fars, Razavi Khorasan, Kurdistan, and Zanjan have been identified as the main wheat production areas in Iran and in this study also, the main focus was on these areas. Since the vast country of Iran has a diverse climate, to ensure that all the country's climate groups are represented in the selected regions, an adaptation of these regions to the country's climate groups was also done.

The results showed that with the data of the 2020-2021 crop year, the reduction of agricultural water consumption by developing the method of irrigation the Raised Bed Planting Systems (RBPS) in the main areas of wheat production will lead to a reduction of 154.2 million m3 of water. The implementation cost of this solution based on the average implementation of each hectare is 50 million Rials in 2021, equal to 5059 billion Rials. Among the limitations in the stages of planting, planting, and harvesting wheat with the irrigation method of the raised bed planting systems, we can point out the need for cultivators equipped with furrows, but in the operation of planting, this method is facilitated. Regardless of the results of the research, limiting the movement of the wheels of agricultural machines to the furrows (traffic control), facilitating the operation, and the smoother movement of water in the furrows are some of the strengths of the raised bed planting systems. The advantages of this method can be mentioned as follows: increasing the yield of wheat per hectare, Improvement in soil ventilation and more growth of roots, Increasing the germination percentage of seeds and reducing seed consumption, reducing seed suffocation, reducing soil erosion, Reducing the amount of herbicides used, increasing the efficiency of using poisons and fertilizers, Reducing the risk of flooding and fungal diseases, and planting wheat on raised beds due to the elimination of irrigation borders as a combine-friendly method.

As a result, using the new method of cultivation the raised bed planting systems can lead to the improvement of water productivity of wheat in the country as a management tool. The raised bed planting system is the most modern method implemented in developed countries. In this method, the seed is planted on long and wide beds, which increases the economic efficiency of the raised bed planting systems. It is expected that the yield of wheat fields will increase by 15% compared to the traditional method. In the cultivation system on raised beds, both the raised bed and the irrigation furrows are prepared at the same time. Also, fertilizer and seeds are distributed on the beds at the same time.

The purpose of this study was to investigate CropSyst model accuracy in simulating winter Alvand variety of wheat grain yields under different irrigation regimes. In this study, the CropSyst model was calibrated and evaluated for winter Alvand variety of wheat in the Eghlid region, Fars Province, under different irrigation treatments of 50, 75, and 100% of the field capacity. The agreement coefficient and normalized mean square error of calibrated model using Presley-Taylor evapotranspiration (ET) equation were 0.97, 11.4. The performance of the CropSyst was acceptable. Different irrigation regimes resulted in the difference in product performance and the min performance was obtained from the 50 percent regime. The productivity was different every year and the maximum yield was gained from 100% irrigation regime. Simulation error was minimum at 100% regime. Time of maturity was increased from 100 to 75 and 50% regime. Maximum of dry biomass and performance (ton/hectare) was obtained in 100% irrigation regime, and the minimum was obtained from 75% irrigation regime in the third year, so the performance of 50% regime was more than 75% in the third culture year. It could be from the complicated interaction of water, climate, soil, and plant in different years. The CropSyst can be used for winter Alvand wheat production simulation under different irrigation regimes (with no fertilizer deficit and no salinity).

In this study, a modified version of standard precipitatıon index (SPI), namely Agriculture-SPI,or aSPI was used to assese the impacts of drought on rainifed wheat yield in North Khorasan province,northeast of Iran. In the aSPI index, the effective rainfall is used instead of precipitation. The USDA-SCS, method was used for effective rainfall calculation. Both indices were worked out , using 30-years (1989-2018) monthly rainfall and temperature data. Rainfed wheat yield data for the period of 2004 to 2018 were also retrived from local oranizations and standardized for comparisons in different SPI time windows of 1, 3, 4, 5, 6, 7, 8, 9 and 12 months .The obtained annual yields were correlated with SPI and aSPI values in selected timescales. The results showed that in Bojnord station, the rainfall druring November-May period, in Shirvan, Faruj and Esfarayen stations April-June, in Maneh-Semelgan station, November-December period and in Jajarm station, October-June period rainfall, are the most signifcant variables affteting the rainfed wheat according to drought indices used in study region.

Wheat as the main food in the country is of particular importance. Wheat is not only an important economic agricultural commodity in the world, but also known as a powerful lever in political and global relations. Therefore, the analysis and forecast of the production status of this product in the country has always been the focus of attention. The purpose of this study is to predict the amount of wheat yield (X) using artificial intelligence in the annual time scale in Alborz province. For this purpose, using annual cultivation and production data, wheat yield was investigated in six cities of Nazarabad, Savojbalagh, Karaj, Eshtehard, Fardis and Taleghan with a period of 40 years (1981-2020). After calculating the yield (ton per hectare) and forming an annual time series, four artificial intelligence methods including the best neighbor algorithm (KNN), backup vector (SVM), gene expression planning (GEP) and Bayesin Network (BN) were used and the wheat yield was predicted for the following year. Results indicated a more precision in yield prediction in the years with more production; According to the results of the BN, GEP, SVM and KNN model, the correlation coefficient between the observed and anticipated wheat yield values was 0.84, 0.89, 0.89 and 0.92, respectively. Explaining that Karaj and Taleghan cities have the highest and lowest wheat production respectively. The results showed that the KNN method had the best accuracy among the others, as the values of R, RMSE and MAE varied from 0.84 to 0.92, 0.21 to 0/24 and 0.11 to 0.18. Overall, by comparing the proposed methods, the KNN method had the highest and the BN method had the least accuracy to predict the amount of wheat yield in Alborz province. The results of this study can be very useful in providing and managing food security in areas under study.

Biochar contributes to sustainable production by improving soil and plant characteristics. In previous studies, less attention has been paid to the effect of particle size and amount of biochar on soil hydraulic properties and plant water use efficiency. The aim of this field study was to investigate the effect of different amounts of biochar with different particle sizes on plant available water (PAW) and stomatal resistance, root dry weight, yield and Wheat water use efficiency (WUE). Factorial experiment with a randomized complete block design was performed with three factors of type, amount and particle size of biochar. Wheat straw and apricot firewood biochar, in the sizes of 0- 0.5 (S1), 0.5-1 (S2) and 1-2 (S3) mm with amount ​​of 0.5 (R1), 1.5 (R2) and 3 (R3) percent were added to the loamy sand soil. Wheat straw biochar with S2 particle size in R3 amount and apricot firewood biochar with S1 particle size in R3 amount further increased PAW. The lowest stomatal resistance in S3 particle size of wheat straw and apricot firewood biochar was observed in R1 and R2 amounts ​​of these biochars, respectively. Wheat root dry weight was less affected by the amount and particle size of those biochars. A significant increase in wheat yield compared to the control was observed in wheat straw biochar with S2 particle size at amount of R3. In some treatments, the yield was significantly lower than the control. The results of this study showed the greater effectiveness of wheat straw biochar in particle size of S2 and amount of R3 on WUE increase.  The effect of a change in the particle size of biochar on studying properties varied depending on the amount of biochar that added to the soil and the characteristics of raw materials for biochar production. The results of this study showed that the effect of biochar on soil properties is not the same.

Wheat is considered a strategic crop in the country and even in the world. It covers a large area under cultivation (approximately 50% of the country's irrigated lands).The main objective of this study was to review and analyze wheat WP in Iran and compare it with data of some other world countries. For this purpose, national and international scientific references were collected and reviewed, and the reported values for wheat WP (at the national, basin, and provincial scales) were arranged, calculated, and summarized, and necessary analyses and some conclusions were derived. According to the results, the range of wheat WP values in Iran and the world is very wide (0.25-2.2 and 0.3-3.9 kg/m3, respectively), depending on the geographical areas, water and soil conditions, different irrigation systems, climate, etc. The country's wheat WP (on a national scale) is estimated at 0.87 kg/m3, which is in the middle range compared to world. However, based on the reported wheat WP at the provincial level, the average wheat WP in the country is equal to 0.75 kg/m3, which is again in the (lower) middle range in comparison with the global values. Comparison of  WP mean value at provincial level (0.75 kg/m3) with the average WP of 10 major wheat producing countries (0.93 kg/m3), indicated that the country's wheat WP is about 25% lower than the average of these countries. Moreover, the Iranian national wheat WP and the global scale average of this index is about 0.93 and 1.1 kg/m3, respectively. Therefore, the value of the country's wheat WP is not very low compared to the global average, and there is a relatively small gap (just 22%) with the global average. However, it is far from the values of the leading wheat producing countries (1.4 kg/m3), such as most Western European countries, South Africa, and Egypt in the Middle East, with a relatively large distance (50% lower). In conclusion, the range of wheat’s WP are very wide in different provinces and regions of the country, therefore there are many opportunities to increase it event up to twofold. This target could be achieved in the country in the medium term with the necessary investments and planning.

The present study was conducted with the aim of studying the feasibility and determining the qualitative and quantitative suitability of irrigated wheat crop in some saline lands in the south of Khuzestan Province. Based on semi-detailed soil studies in the region, 13 series of soils were identified. The physiological needs of the wheat plant were determined and graded using available resources. Then, qualitative and quantitative assessment of land suitability was performed by parametric method (Square root) and, finally, the relevant maps were prepared in GIS environment. The results showed that climatic variables did not limit wheat production. Also, there were qualitative land suitability classes from relatively suitable class (S2) to unsuitable (N), and the most important limiting factors were salinity limits (4.7-115 dS), alkalinity (9.9-77%), calcium carbonate (40-60%), fertility characteristics (acidity) and soil wetness. The results of quantitative land evaluation also showed that 16260 hectares equivalent to 57% of the land available in the region for wheat cultivation was in class S2 (relatively suitable), 1380 hectares (4%) in class S3 (critical suitability), and 12680 hectares (37%) in class N (unsuitable lands). According to the results, in most units, the quantitative classes of land units for wheat cultivation corresponded to the qualitative class of land suitability, or had a higher suitability due to better management of this crop in the region. Therefore, due to the fact that most of the study area had salinity and alkalinity limitations, to increase production and create a sustainable agricultural system, land improvement operations are necessary.

The effective use of rainwater is a key issue in agricultural development in arid and semi-arid regions. The tillage system as an important soil management measure can affect the rainwater retention, soil moisture content, and in consequence crop yield in rainfed lands. This study was conducted to evaluate the effects of slope gradient and tillage direction on rainwater use efficiency (RWUE) in rainfed lands in Zanjan Province. The field experiment was performed in five slope gradients (12.6, 15.3, 17, 19.4, and 22%) and two tillage directions (along slope and on contour tillage) at two replications. Mass soil water content was determined at 5-day intervals and runoff was measured after rainfalls. Wheat grain yield was determined for each plot and RWUE was computed using the proportion of wheat grain yield and precipitation. Base on the results, runoff, soil moisture, wheat grain yield, and RWUE were affected by tillage directions, so that runoff in contour line tillage decreased about 6.4 times compared to along slope tillage and in consequence increased soil moisture, wheat grain yield, and RWUE about 8.7, 24.8, and 24.8%, respectively. Increasing runoff production in contour line tillage at steeper slopes was associated with a lower capacity of cultivated furrows that strongly declined soil water retention and negatively affected wheat grain yield and RWUE in the lands. This study revealed that the efficiency of the contour tillage in water retention and RWUE decreases in steeper slopes in rainfed lands.

The Bukan plain with its largest wheat production in the province is referred as the West Azerbaijan grain storehouse. Water and soil salinity can cause crop redution. In this research, a computer model of SALTMED was used to simulate wheat yield under different salinity conditions of irrigation water. Field experiments were conducted for five irrigation water treatments with salinities of 3.5, 4.5, 5.5 and 6.5 dS m-1 and a control treatment (Simineh Rood water with 2 dS m-1 salinity) in a completely randomized blocks design. R2, NMRSE, CRM and ME values ​​were calculated at different soil depths for different treatments. The results showed that the SALTMED model had a high accuracy in simulation of the soil moisture and salinity as well as the crop yield. The coefficient of determination for simulating soil moisture was 0.87, soil salinity 0.85 and crop yield 0.92. According to the results, with increasing salinity level of irrigation water, the model accuracy in simulation of the soil moisture was increased, but the model error was decreased in simulating of the crop yield. The simulation results of the SALTMED model showed that the accuracy of the model for crop yields was better than that of soil moisture and for soil moisture was better than that of soil salinity.

Optimal use of available water resources and their management is very important according to modern science. This has led to the importance of using plant models to study the effects of low water on agricultural yields. In order to investigate the effect of moisture stress on yield and growth traits in three cultivars of horizon, clear and narin and weeding and validation of vegetative model AQUACROP for these cultivars were performed in 96-97 crop year on a research farm located in Birjand. The research was conducted in the form of a factorial randomized complete block design with 6 treatments and three replications. Irrigation treatments included 100 (control treatment), 75 (medium stress) and 50 (severe stress) percentage of wheat water requirement and 3 other treatments related to two new cultivars of Ofogh and Narin and one old and native cultivar Roshan. The results of the mean comparison of the mean mean of the simple effect of moisture stress, the simple effect of cultivars and the interaction effect of stress on different cultivars were significant in different traits. After analyzing and comparing the average plant traits of the AQUACROP plant model for stresses of 100 and 75%, the water requirement was measured in two parameters of grain yield and biomass. After the validation stage, the model validation model was performed with 50% water stress. The results of the model validation showed that the model calculations showed a close and acceptable simulation value compared to the measured value of grain performance according to NRMSE and R2 evaluation indicators. Also, to ensure the accuracy of the model, using the measured performance data, the bright figure in the 2009-2010 crop year was validated by changing the re-meteorological data. The NRMSE index value of the simulated and measured grain mass for the mean moisture stresses of 100 and 75% in the horizontal and horizontal digits of Rosin, Narin and Narin cultivars was 0.99, 0.88 and 1.51%, respectively. These values were observed in the model validation in 50% stress to 1.49, 3.14 and 0.88%, respectively. According to the values calculated in the statistical indicators, it can be concluded that the model can provide us with an acceptable efficiency for measuring different wheat cultivars, which is very important in the region due to the high and increasing number of different wheat cultivars.

Nowadays, the use of proper irrigation methods to increase the productivity of water use in the agricultural sector due to the limited water resources is considered essential. The aim of the present research was designed with the economical assessment of irrigation different methods (drip irrigation, center pivot and fixed classical sprinkler irrigation) in using new(solar) and traditional (network) energies in irrigated wheat production. This research carried out in Alborz province in 2016 and 2017. In this research, at first, water requirement of this product was determined by Karaj condition and then, the cost and benefits of irrigation different methods using electricity network and solar power in the production of wheat was determined. For economic analysis in order to selecting the best irrigation method used Partial Budgeting Method. In this method, used Cost and Benefits and Marginal Net Benefits. According to the results, water saving in drip irrigation, center pivot to fixed classical sprinkler irrigation were estimated 22.8 and 17.6 percent, respectively. That means the net Benefits of wheat production in fixed classical sprinkler irrigation, center pivot and drip irrigation using electricity network were estimated 84.6, 85.6 and 90.7 Iranian million rials per ha and using solar power were estimated 72.4, 79.7 and 85.3 Iranian million rials per ha. In general, drip irrigation system using electricity network was recommended as better treatment and economic in wheat production, because, substitution of others systems instead of this method, Marginal Net Benefits in this substitution would decrease.

Awareness of the physical, chemical and biological quality of soil in agriculture and natural resources is essential for optimal land management and achieving maximum economic productivity. Soil has various functions, including crop production ability, carbon storage, water retention, nutrient cycling, water filtering and etc. Thereby, the quality of soils can be taken into consideration depended on the purpose of their use. The soil quality indices are often regional; therefore, a set of indices cannot be used consistently to determine soil quality in all areas. In this study, the Nemero Soil Quality Index (NQI), the Weighted Additive Soil Quality Index (SQIw), and the Additive Soil Quality Index (SQIa) were determined using the total data set (TDS) and minimum data set (MDS) and the impact of properties affecting the soil quality and the yield of irrigated wheat were investigated, in Nazarabad region.

This study was carried out in 26000 hectares of Nazarabad agricultural lands, known as an area with irrigated farms in western Alborz province. The Nazarabad area was sub-divided into a network consisting of 95 squires of 1650 m × 1650 m. The surface soil (0-30 cm) was sampled from the farms located in the middle of each squire (9+5 soil samples from 95 farms) and the irrigated wheat was sampled from 32 farms. Then, soil physical properties including sand, silt, and clay percentages, soil structural stability (MWD), bulk density (BD), particle density, soil porosity (F), field capacity (FC) and permanent wilting point (PWP), available water (AW), saturated hydraulic conductivity (Ks) and soil chemical properties including salinity (EC), pH, organic matter (OM), equivalent calcium carbonate (TNV), available phosphorus )p < sub>ava(, available potassium )Kava(, sodium absorption ratio (SAR) and soil microbial respiration (SMR) were measured. Effective properties on soil quality were selected using SPSS 24 by principal component analysis method (PCA). For this purpose, components with Eigen values greater than one were selected and in each component, properties with high loading coefficient up to 10% lower than the highest loading coefficient were selected MDS affecting soil quality. Then, the Nemero Soil Quality Index (NQI), the Weighted Additive Soil Quality Index (SQIw) and Additive Soil Quality Index (SQIa) were determined using TDS and MDS. For validating soil quality indices, the correlation between the yield of irrigated wheat and NQI, IQIa and IQIw indices were determined in MDS and TDS.

The results showed that the correlation between the soil quality indices (NQI, SQIw and SQIa( using total data set and MDS were significant (p <0.01). In addition, a significant correlation was observed between methods of MDS and TDS in IQIw (r=0.76), IQIa (r=0.73) and NQI (r=0.68) indices. According to the results, there was a significant correlation (p <0.01) between the yield of irrigated wheat and IQIw (r=0.68), IQIa (r=0.67) and NQI (r=0.62) using MDS method; and using total data set method this correlation was 0.61, 0.58 and 0.58, respectively. The results indicated that using NQI, SQIw and SQIa indices based on MDS, 42, 57 and 57% of the study area were in very high quality category and 29, 25 and 24% were in high quality category, respectively. However, using NQI, SQIw and SQIa indices based on TDS, 16, 16 and 18% of the study area were in very high quality class and 42, 39 and 45% were in high quality class, respectively.

The results showed that in Nazarabad region, the yield of irrigated wheat was affected by texture, p < sub>ava, B, SAR, Bd and TNV. There was no significant difference between IQIw and IQIa and NQI indices. In addition, the correlation between soil quality indices based on MDS and total data set was significant, and the correlation between the yield of irrigated wheat and the soil quality indices was stronger while using MDS rather than the use of TDS. Therefore, the use of MDS is more appropriate due to better results and fewer properties and less cost. According to the results obtained from Nazarabad region using NQI and SQIw indices, nearly 82% and 72% of the area are in the very high and high quality class, about 6% and 8% are in the moderate quality class and about 7% are in very low and low quality class, respectively. The studied area is less restricted in terms of physical properties such as soil texture and bulk density. Consequently, due to the high quality of soils in Nazarabad region, it is possible to improve the yield of wheat by proper management.

Despite studies on the performance of superabsorbents in improving soil physical conditions, as well as increasing the yield and productivity of water consumption, economic issues have received less attention from researchers. Therefore in this study to investigate the effects of water stress and superabsorbent polymers on yield and yield components of wheat in 2015-2016 growing years, a factorial experiment was carried out in a randomized complete block design with three replications. Treatments consisted of combination of three levels of irrigation to supply 100, 70 and 50% crop water requirement (FC, 0.7FC, 0.5FC respectively) and three levels of superabsorbent (Stockosorb) with the amount of 0, 50 and 100 kg.ha-1 (S0, S1, S2 respectively). The results of economic indicators showed that the highest net income was allocated to S0,FC and S1,0.7FC treatments. The highest gross income to production cost ratio was allocated to the S0,0.7FC treatment, which had a significant difference with the control treatment (S0,FC) at the 5% level. The maximum (+44.2%) and minimum (-11.7%) of net income to irrigation water amount ratios were belong to S1,0.7FC and S2,0.5FC  treatments, as compared to control treatment (S0,FC), respectively. Therefore, in the best (S1,0.7FC treatment) condition, compared with control treatment, superabsorbent and water stress interaction effects increased gross income and net income equal to 12.2 and 1.1%, respectively. The investigating interaction effects of treatments showed that the superabsorbent application is recommended only in S1,0.7FC treatment condition due to increasing yield and cultivation area  (leading of reducing water consumption) and economic justification.

Considering the importance and special status, the critical conditions of water scarcity in production systems, and the lack of traceability of wheat water in Khuzestan, in this study, green, blue and gray water footprints of wheat product were estimated. The studied areas were Ahvaz, Dezful, Shooshtar, Behbahan, Izeh and Khorramshahr. The total water footprint of wheat was obtained from the sum of green, blue and grey water footprint. Then, the relationship between wheat water footprint and actual yield was compared. The results showed that among the study areas, Khorramshahr needed more water (1704 m3 t-1) to produce the product and thereafter, Ahvaz (1228 m3 t-1), Behbahan (1083 m3 t-1), Izeh (1012 m3 t-1), Dezful (959 m3 t-1) and Shushtar (915 m3 t-1). To produce 1 ton of wheat, Izeh needs 778 cubic meters of green water, and after that, Khorramshahr was ranked second with 458 cubic meters of green water. However, Izeh had the lowest blue water footprint, and the zoning of Khuzestan province in terms of the blue water footprint of wheat showed that the blue water footprint in the southern half of the province is more than the northern half. Grey water footprints also follow a similar blue-water trend. Whereas Shooshtar has the lowest water footprint with the highest yield, and Khorramshahr has the lowest wheat yield and the highest water footprint among the other studied cities.

The yield of Wheat is influenced by various factors including climate, land management practices and soil properties. It is important to investigate the relations between soil physical and chemical properties and the yield of wheat. In this study, the physical and chemical properties of the soil top layer (0-30 cm) and the yield of Wheat were determined in 34 wheat fields of Nazarabad region in Alborz province, during wheat crop year of 2018. Principal Component Analysis (PCA) was used to select the effective parameters on wheat yield and multivariate linear regression was applied to analyze the relationship between wheat yield and soil properties. Finally four regression equations were presented. Principal Component Analysis (PCA), stepwise linear regression, the highest correlation method and all the measured properties were used respectively to prepare four equations to estimate the Wheat yield. The evaluation of each equation was performed by Geometric Mean Error Ratio (GMER), Geometric Standard Deviation of the Error Ratio (GSDER), Normalized Root Mean Squared Error (NRMSE), and determination coefficient (R2). The results showed that wheat yield varies from 2750 to 10500 kg/ha in the region and the proposed equation using clay, Pava, Cu, porosity, calcium carbonate equivalent and pH with GMER, GSDER, NRMSE and R2 values of 0.99, 1.19, 0.17, and 0.64 respectively, is the most appropriate equation for determining of wheat yield. Therefore, in regions with climatic conditions and soil physical and chemical properties similar to the study area, the yield of wheat can be estimated with an acceptable level, based on the proposed equation.

This study was carried out to evaluate the effects of soil and foliar applied chemical fertilizers and foliar organic acids (as leonardite; a mixture of humic and fulvic acids) on yield and yield components and nutrient uptake by wheat. The experiment was laid out in Gorgan University of Agricultural Sciences and Natural Resources Farm during 2013- 2014, using a split-plot design with four replications. Treatments included potassium application and without potassium in the main plots and foliar applications of nitrogen, potassium, and leonardite from two different sources (Humic Power, mega humat) and a control without foliar application in subplots. Maximum root length before heading was obtained by Humic Power (11.6 cm) and, at harvest, by megahumat (16.4 cm), both in potassium treated sub plots. Root weights also followed the same trend. This may be due to growth stimulating effects of humic acids. Greatest phosphorous uptakes were 19.2 and 48.75 kg.ha-1 by straw and grain, respectively, by foliar application of megahumat in soil potassium applied plots. Foliar applications of nitrogen and potassium also enhanced nitrogen and potassium uptake, respectively. The interactions between foliar and soil applied treatments on stem length and straw yield were significant by analysis of variance. Their combined application significantly improved plant height and straw yield. This research showed that yield by foliar application of leonardite (from both sources) was greater than yield by foliar use of nitrogen and potassium irrespective of soil potassium applications. Soil potassium applications enhanced yield and nutrient uptakes by foliar treatments.

This study was conducted to investigate wheat production and precipitation water productivity response to planting dates of Sabalan wheat variety at the Dryland Agricultural Research Institute in Maragheh located at the north-west of Iran. Four planting dates of 23 Sep.¡ 2 Oct.¡ 12 Oct. and 22 Oct. Treatments were laid out in complete randomized blocks for three years. Results revealed that grain yield affected by planting dates. The planting date of 23 SPt. (with single irrigation at the sowing time) with seasonal precipitation of 504 mm produced the highest yield of 3422 kg ha-1. To describe the relationship between grain yield and received water from precipitation and single irrigation a linear model (r =0.96) was developed with high agreement between measured and predicted values. Also¡ results showed that received water productivity averaged 0.46 and ranged from 0.32 to 0.68 kg m-3. Planting date of Sep. 2 with single irrigation at the sowing time produced the highest water productivity and grain yield. Therefore date of Sep.2 for planting with supplemental irrigation and date of 2 Oct. can be recommended as the optimum planting date of wheat in in dryland condition of Maragheh and similar climate condition.

The simulation models of yield response to water are expected to play an increasingly important role in the optimization of water productivity (WP) in agriculture. In this study, the CERES-Wheat model was used to simulate of wheat yield response under different irrigation-cultivar treatments with three irrigation treatments in main plots and Five wheat cultivars in sub plots consisted of C1:C-75-5, C2: C-78-4, C3:C-78-8, C4: C-79-6 and C5: C-79-16 in Mashhad region during the years of 2002-2003 and 2003-2004. According to the results, the relative root mean square error of grain yield simulation by CERES-Wheat model was 7 and 10 % for 2002-2003 and 2003-2004 years, respectively. Because, the relative root mean square error was less than 10 percent, so done well simulation. Also, the root mean square error calculated for grain yield for both years was less than 10 percent of the observed mean. The results are indicating a good match to the simulation results of the model. The value water productivity based on crop evapotranspiration and irrigation water value in I3-C-79-6 treatment has the value highest for both years of 2002-2003 and 2003-2004. Therefore, the noted irrigation management (I3) and wheat cultivar (C-79-6) can be recommended in the study area. The overall findings of this study to confirm the optimal performance of the model CERES-Wheat in the growth process simulation and the water impact on yield in the study area.

Effects of different tillage systems on dispersion ratio, status of aggregation, degree of aggregation, mean weight diameter, geometric diameter, the rain-fed wheat yield and the yield components were investigated by a field trial using a completely randomized block design with five treatments in four replicates during 2009-2010 growing season at Gorgan University of Agricultural Science and Natural Resources Research Farm located at seyedMiran, Gorgan. Tillage treatments used moldboard plough (20-25 cm) with disc, roto-tiller (12-17 cm), double disc (8-10 cm), Chisel plough (25-30 cm) and No-tillage. Results showed that the maximum and minimum dispersion ratios occured with chisel and moldboard plough respectively which indicate various tillage methods hardly influence aggregate stability in soils with high specific surface. With no concerns for loss in aggregate stability, tillage intensities may be intensified for greater yield goals. Maximum status and degree of aggregation occurred with moldboard ploughing with the consequent increases of potassium root uptake and the yield of wheat at before heading and harvest stages both.

The spatial and temporal variation of wheat virtual water، as one of the strategic product in Sistan and Blouchestan Province، has been investigated. To this end، the 12 year weather data، yield، cultivated area and irrigation method were used. The 12 year average of the net wheat water use was 303 million cube meter from which 9. 2 percentage was supplied by green water. Regardless of the irrigation efficiency، the net virtual water varied among 1. 59 (Khash City) to 6. 18 (Zabol City) meter cube per kilogram and its 12-year average was 3. 42 meter cube per kilogram in the whole province. Considering the real water volume allocated to the wheat، the 12-year average of the imported and exported virtual water in the entire province was 1043 and 43. 2 million cube meter، respectively، and Zahedan and Zehak were، respectively، the biggest importer and exporter of the virtual water. Results showed that decreasing the water loss by 10 percentages through improving irrigation efficiency would increase the sel-sufficiency in whaet production by 18. 2% and decrease the dependency to virtual water import by 3. 62 percentages due to 11. 7 percentage decrease in wheat water use.