جستجوی مقالات مرتبط با کلیدواژه « rotation » در نشریات گروه « کشاورزی »

This experiment was carried out in 2018 in the Lundville region of Astara for rice crop rotation, different amounts of nitrogen and potassium fertilizers, and varieties and dates of clover planting in the Gilan region. The experiment was evaluated in the form of s split-split plot with a completely randomized block design in three replications. The main factor includes nitrogen fertilizer with potassium at three levels (50, 100, and 150 kg per hectare) and the spreading of clovers in three different stages of rice growth, including after flowering, before harvest, and after harvest as split plot and secondary factors.

The results obtained from the variance analysis of the data showed that different levels of nitrogen and potassium fertilizers, distribution of clovers in different stages of rice growth, and clover cultivars on the height period, yield indices, and harvest index were significant in rice plants. Based on the results of comparing the average effects of treatments, it was observed that the highest yield of paddy per hectare was obtained under the conditions of application of 100 kg/hectare of fertilizer in the stage of spreading clovers after rice harvesting and from Iranian clover variety.

The use of nitrogen and potassium fertilizers along with crop rotation of rice and clover due to nitrogen stabilization and improvement of the soil substrate increased the height of the plant, increased the number of claws, spike length, the weight of 1000 seeds, and finally increased the yield of the rice plant.

The experiment was carried out in the research farm of the Faculty of Agriculture of Tarbiat Modares University in 2010 and 2009 for two years. The plants was sown in the crop rotation included vetchlings (Lathyrus sativus L.) as green manure and sunflower as the main crop and canola as fodder in the fall season. The experimental design was in the form of a split plot design based on randomized complete blocks with three replications, in which the main factor was the rotation system on 2 levels with and without green manure, including 1- green manure-sunflower-green manure- sunflower (GM) and 2- fallow-sunflower-fallow-sunflower (Fa) and the sub-plots were 5 types of nutritional systems including 1- zooponics organic fertilizer (Z100), 2-integrated fertilizer (75% organic zooponics + 25% chemical fertilizer (urea based on soil test) (Z75F25), 3- integrated fertilizer (50% organic zooponics + 50% chemical fertilizer) (Z50F50), 4- integrated fertilizer (25% organic zooponics + 75% chemical fertilizer) (Z25F75) and 5- fertilizer Chemical urea (F100). The results showed that the highest seed yield was obtained in the 100% chemical and 100% zooponics, and then in the 50% chemical + 50% zooponics fertilizing systems. Integrated feeding systems in both rotations efficiently increased the amount of soil organic matter.The fallow treatments had a higher amount of soil microbial biomass carbon and microbial respiration than the green manure treatments. The combined analysis of the data of two years of the experiment for the ratio of C/N showed that rotation had a significant effect and the mean comparison of the treatments showed that this ratio was higher in the fallow. Among the different fertilizing systems, 100% zeoponics treatment showed the highest ratio of C/N, and the lowest amount was found in 25% zeoponics + 75% chemical fertilizer. In general, by implementing integrated plant nutrition management through the use of green manure, zooponics and chemical fertilizers as an ecological approach, it is possible to achieve sustainable agricultural systems with the aim of reducing the consumption of chemical fertilizers and increasing the productivity of the soil.

Rapeseed needs a sufficient amount of nitrogen for optimal seed yield, but the efficiency of this plant in using nitrogenous (N) fertilizers is low, which causes an increase in N consumption in the cultivation of this plant. The need to maintain a high grain yield necessitates the use of a suitable timely program and manage the consumption of N fertilizers. Thus, a field experiment was conducted at the Research Station of Agriculture and Natural Resources of Khuzestan University during 2020-2021 growing season to evaluate the effect of preceding crop and N fertilizer on grain yield of rapeseed. The experiment was carried out as split plots based on a RCBD with three replications. Preceding crops (clover-barley mixture, rapeseed, corn, fallow, mung bean, rice and wheat) were allocated to the main plots and N levels (0.0, 100, 160 and 220 kg ha-1 N from the source of urea fertilizer) were assigned to the sub plots. Results indicated that the grain yield of rapeseed depends mostly on grain number, but the grain yield components (including pods number per plant, grain number per plant, grain number per pods) were mainly affected by the main effect of preceding crop and nitrogen. With the application of 100, 160 and 220 kg ha-1 N the number of grains per pod increased by 34%, 39% and 33%, respectively. The number of grains per plant was also increased by the application of nitrogen fertilizer, where all three levels of nitrogen fertilizer resulted in more than 200% increases in this grain yield attribute. The highest grain yield of rapeseed (3877 kg ha-1) was observed when mung bean was used as preceding crop and 220 kg ha-1 N fertilizer was applied, though it was not significantly different from the treatments of mung bean preceding crop and application of 160 kg ha-1 nitrogen fertilizer (with the production of 3105 kg ha-1 grain) and fallow preceding and 160 kg ha-1 N fertilizer. The lowest grain yield of rapeseed was obtained when corn and rapeseed were used as preceding crops and no N fertilizer was applied, as these preceding crops resulted in only 488 and 497 kg ha-1 grain of rapeseed, respectively. Rapeseed had the highest oil yield (1645 kg ha-1) with mung bean being the preceding crop and 220 kg ha-1 N application. It seems that for achieving the highest oil yield of rapeseed, mung bean preceding crop and 220 kg ha-1 N can be focused on for the next researches.

Nitrogen fertilizers are commonly used to increase economic performance in corn production. However, it should be noted that nitrogen added to the soil in crop ecosystems is not fully available to the plant and may be leached. In this context, many studies have investigated various crop production methods to improve soil health and reduce soil nitrogen losses. Crop rotation and no-till may be an appropriate method to improve soil health and increase soil organic carbon and total nitrogen. In this experiment, it was assumed that growing faba beans in rotation with forage corn and applying sustainable agriculture can greatly reduce the need for nitrogen fertilizer in corn and increase nitrogen use efficiency compared to monoculture corn. The objective of this experiment was to determine the appropriate plant density of faba bean and its effect on crop rotation with forage corn, and to evaluate the nitrogen fertilization efficiency of corn.
 
A two-year experiment was conducted in 2018-2019 as a factorial experiment based on a randomized complete block design with three replicates at the research farm of the Faculty of Agriculture and Natural Resources, university of Mohaghegh Ardabili, Ardabil, Iran. The experimental treatments were different plant densities of faba bean (25, 35, 40 and 80 plants m-2) and different nitrogen (N) fertilizer rates (0, 100, 200 and 300 kg ha-1) in forage corn. Shadan cultivar of faba bean was planted in this experiment and it was harvested manually at the physiological maturity stage. The corn variety was the single cross hybrid 201, which was planted at the density of 80000 plants ha-1 in the residue rows of faba bean. Nitrogen fertilizer (as urea) was applied three times at the V5 stage of corn. Three corn plants were harvested at the milk stage and then oven dried at 70 °C for 72 h and weighed. Traits studied in this experiment were include grain yield, 100-grain weight, harvest index, biological yield and weed control efficiency in faba bean and fresh and dry forage yield, protein yield, nitrogen recovery efficiency, nitrogen agronomic efficiency and nitrogen productivity in forage corn. Statistical analysis of data was performed using SAS 9.4 software, and significant differences between treatment means were tested using the Duncan's Multiple Range Test at P < 0.05.
 
Faba bean
The highest grain yield was obtained at plant density of 80 plants.m-2, 100-grain weight, and HI were observed at plant densities 40 plant.m-2 and the densities of 80 and 40 plants had the highest Reduction percentage in dry weight of weeds and biological yield. It seems that an increase in plant density, especially at the beginning of the growing season, results in complete coverage of the soil with plants and reduces the competitive ability of weeds. In addition, with higher plant density, solar radiation on the plant canopy increases, so less light is available for weeds and the germination rate of weed seeds decreases. The result of cultivation shows higher competitive power and the results were obtained.
Corn
Our results showed that using faba bean in rotation with forage corn can reduce the need for nitrogen fertilizer. The results of the mean comparisons showed that the highest dry forage yield of corn was obtained at the density of 40 faba bean plants+200 kg N ha-1, representing an increase of 155% compared to the control treatment. Corn yield is very sensitive to nitrogen deficiency. On the other hand, using of legumes in crop rotations can improve crop access to nitrogen. Addition, the highest protein yield was observed at the density of 40 faba bean plants+200 kg N ha-1 and 35 faba bean plants+200 kg N ha-1. Density of 40 faba bean plants+no application of N fertilizer had the highest nitrogen recovery efficiency and nitrogen agronomic efficiency. Thus, it can be concluded that the combined application of nitrogen fertilizer and the use of faba bean in the crop rotation increases the availability and uptake of nitrogen and also increases the efficiency of this element at a stage of plant growth when nitrogen uptake is high. Therefore, the corn yield was higher in these treatments
 
In this experiment, the effects of plant density of faba bean on the yield of this crop and the effects of crop rotation on nitrogen yield and efficiency of forage corn were studied. The results showed that the highest grain yield, 100-grain weight, biological yield, and bean harvest index were obtained at plant densities 40 and 80 plant. The results also showed that the density of 40 bean plants+200 kg N ha-1 had the highest increase in dry forage yield of corn compared to the control. It can be concluded that the density of 40 faba bean plants+200 kg N ha-1 in forage corn under similar climatic conditions may be a suitable method to reduce the use of chemical N fertilizer.

Cropping history can affect our knowledge about the compositions and diversity of weed communities in the soil. Weed Species composition and density are influenced by farming practices and vary from field to field and among areas within fields. Plants that escape control and produce seeds within the field can be considered as a major source of seed entering the soil. Crop rotation is an effective weed management tool which can change weed distribution pattern by increasing selection pressures. Two types of rotation including corn-winter wheat and fallow-winter wheat are the most common cropping systems in arid and semi-arid areas of Iran. The multiple tillage operations can affect the vertical distribution, germination and emergence of weed seeds in the soil. Weed seed bank density, species composition and diversity will change when crop management practices are altered.

A field experiment was conducted to evaluate the effects of corn-wheat and fallow-wheat crop rotations on weed seed bank dynamics and seedling population during 2016-2018 growing season at Shiraz University. The fields divided into 10 by 10 meter grids. Soil samples were taken from 0-15 and 15-30 cm depths by soil sampler (auger) with 10 cm diameter. These samples collected after seedbed preparation and before crop sowing from 144 points. The samples of each depth were mixed together, placed in black plastic bags, and transferred to the laboratory. Then, 250g of the total soil was weighed and separated. These samples was placed in silk bags and washed with low water pressure. Finally, weed seeds dried, identified and counted to the level of species using a binocular stereomicroscope. Those seeds that were resistant to forceps pressure assumed as healthy seeds. Weed seedling population were calculated using a quadrat before and after application of herbicide at the same points were seed bank was carried out. Geostatistics technique was used to investigate density and spatial distribution of weed seedlings in two different crop rotations.

The highest frequency of weed seed bank belongs to Portalaca oleracea, Amaranthus retroflexus, Chenopodium album and Lamium amplexicaule. Relative density of P. oleracea and A. retroflexus seeds increased in corn-wheat rotation compared with fallow-wheat. The results showed that weed seed frequency was significantly affected by crop rotation and depth of plowing. As corn-wheat rotation had 33% increasing and fallow-wheat 19.44% decreasing of weed seed in 15-30 cm soil depth. The size of the total weed seed bank in corn-wheat caused a greater seed accumulation in the surface layer of the soil (0-15 cm). Weed seed density in corn-wheat rotation increased 89.79% and 62.85% in 0-15 and 15-30 cm, respectively during two years. Shannon diversity index increased by 12% in corn-wheat and decreased by 5.4% in fallow-wheat compared with the first year. Margalf index of corn-wheat rotation at 0-15 and 15-30 cm of soil depths decreased 33.70% and 38.25%, respectively, compared to the fallow-wheat rotation in the first year. Sorenson similarity index of corn-wheat and fallow-wheat at 0-15 and 15-30 soil depths was 0.82% and 0.80% during two years. The slope of linear regression also indicates that fallow-wheat weed seed bank (0.79) decreased more than corn-wheat rotation (0.47). Spatial distribution of weed seedlings showed that there is a large similarity in distribution patterns of total weed population between before and after herbicide application in two different rotations during the second year. However, distribution pattern of seedlings in corn-wheat rotation at the first year herbicide application was different after application of herbicide. Therefore, herbicide application can affect spatial distribution and number of weed seedling species.

Corn-wheat rotation as a high input level cropping system with deep tillage increases the size of the weed seed bank, especially in the soil surface layer (0-15 cm). While fallow-wheat rotation as a low input level cropping system causes a decreasing in weed seed bank dynamics, increasing in the diversity and richness of the seed bank and improving the soil structure by wheat residual on the soil during fallow system. The results of this study will be valuable in aiding the prediction of likely weed infestations in rotation systems. This ability to predict the size of weed seed bank, pouplation, diversity and emergence would also provide valuable input to population dynamics models that can be used in weed management.

Introduction :

Achieve more production, efforts should be made to increase yield per hectare. One of the things that play an important role in increasing crop production, disease control, chastity control, improving soil fertility and structure is the implementation of proper crop rotation. Crop rotation increases the efficiency of production and yield through the continuity of soil vegetation, more efficient water use, preservation of soil nutrients, increase of soil organic matter and stability of soil grains, reduction of pests and diseases, and better control of weeds. Also, data collection in the conducted research is done in a traditional way, which is usually difficult, limited and very time-consuming due to the dispersion of farms and their size.

Materials and Methods:

 His study was conducted to investigate the effect of crop rotations on wheat yield using satellite images in three crop years 2017-2018, 2019-2028, 2019-2020 in the fields of Shavor region of Khuzestan province. In this research, all the evaluated images are related to the Sentinel-2 satellite and all these images were obtained from the US Geological Survey website. The satellite images were taken at the flowering stage of wheat, and images without clouds and fog were used on February 25, 2019 (for the year before rotation) and February 19, 2021 (for the year after rotation). Also, for pre-processing and processing and extracting information, SNAP software, Sen2Cor and ENVI plugin were used, respectively. The steps of this research were done in three steps. In the first stage, five plant spectral indices EVI, GNDVI, GARI, NDVI and RVI were evaluated to identify the best index to estimate wheat yield. The spectral index, which has a higher correlation with the yield of wheat, was chosen as the base index and was used to continue the research. In the second stage, three farms were randomly selected from each rotation to evaluate wheat yield after their application. In this section, variance analysis was performed in the form of a completely random design in three replications (one replication for each farm). The treatments include four alternations of wheat-wheat-wheat, wheat-canola-wheat, wheat-rice-wheat and wheat-clover-wheat. At this stage, the comparison of means was done by Duncan's multi-range test and in the MSTATC software environment. The third stage is the changes in wheat yield in each rotation in two times before and after applying that rotation. For this purpose, the changes of the base spectral index before and after the application of periodicity were set as criteria.

Results:

The results of variance analysis of five spectral indices studied in this research showed that the coefficient of explanation of each of these indices with wheat yield at the time of flowering is NDVI with 76, RVI with 73, GARI with 71, EVI with 60 and GNDVI with 57 respectively. In this research, the NDVI spectral index has the highest correlation, R2 of 76%, and the minimum error, RMSE of 0.547 earned the results showed that the average and the dispersion coefficient of the NDVI spectral index of intervals have a significant difference at the probability level of 1%. So that in terms of the average, the lowest average of the NDVI spectral index is in wheat-rice-wheat rotation with a rate of 0.2650 and the highest average is in the wheat-clover-wheat rotation with a rate of 0.5603. According to the distribution coefficient, the minimum and maximum values belonged to the rotation of wheat-canola-wheat with the rate of 0.0505 and wheat-rice-wheat with the rate of 0.1970. The results of the corresponding comparison before and after the application of each rotation showed that not observing the rotation and wheat cultivation after two crop years led to a 10% decrease and the use of rice in the crop rotation led to a 50% decrease in the NDVI spectral index. Also, the use of rapeseed and clover in crop rotations has led to an increase of 2 and 30% in NDVI spectral index compared to before rotation. The results of the dispersion coefficient of the NDVI spectral index in the time before and after the application of rotation showed that in the continuous cultivation of wheat, the dispersion coefficient due to the decrease in yield uniformity in different parts of the field led to an increase of 27% and in the rotation of wheat-rice-wheat it led to an increase of 152 became a percentage However, the distribution coefficient of wheat-canola-wheat rotation and wheat-clover-wheat rotation resulted in a decrease of 57 and 32%, respectively, due to the increase in yield uniformity in different parts of the field.

Conclusion:

 Heat is one of the strategic products, and the evaluation of different rotations is of particular importance in increasing its yield. In this research, five plant spectral indices EVI, GNDVI, GARI, NDVI and RVI were investigated in order to identify the base index for wheat yield estimation. The results of the analysis of these indices showed that the NDVI spectral index with an explanation coefficient of 76% has the highest correlation with wheat yield. The comparison results of the NDVI spectral index correspondingly in each rotation in two states before and after the rotation showed that the continuous cultivation of wheat in an agricultural land after two crop years led to a 10% decrease in the NDVI spectral index and the use of rice in the wheat-rice rotation. - Wheat leads to a 50% decrease in the NDVI spectral index of wheat; But the use of canola and clover in the rotation of wheat-canola-wheat and wheat-clover-wheat led to an increase of 2% and 30% of NDVI spectral index, respectively. Also, the results of the comparison of the dispersion coefficient of the NDVI spectral index before and after the application of rotation showed that in the continuous cultivation of wheat, the dispersion coefficient increased by 27% due to the decrease in yield uniformity in different parts of the field, and in the wheat-rice-wheat rotation, the dispersion coefficient also as a result of the reduction of yield uniformity in different parts of the farm, it led to an increase of 152%.

Conventional tillage methods increase energy costs and lead to the destruction and reduction of water and soil resources, and for a long time, have an adverse effect on soil properties and cause the formation of hard layers. Repeated tillage and deep plowing cause a quick release of carbon dioxide, causing soil and greenhouse effects and, in the long run, undesirable effects on soil characteristics. Compared with conventional tillage, protective tillage reduces the number of agricultural operations, which has many benefits. So that the loss of moisture and destruction of the soil structure would be reduced. Furthermore, the oxidation of organic residues of plants is reduced. Research has shown that the maintenance of a part of the previous crop residues on the surface of soil and the presence of superfluous roots of arable crops in the soil at a rate of two-thirds, reduce the amount of soil compaction in compared with uncoated and unpolluted land. Therefore, the present study was conducted to investigate the effect of different tillage methods and plant residue management on wheat and organic carbon of soil in Mashhad weather conditions.

 This research was carried out as a three-year experiment with wheat –rapeseed - wheat rotation as split plots in a randomized complete block design with three replications. In this design, different tillage methods were considered as the main plot and management of plant residues as a subplot. Tillage methods consist of three levels: conventional tillage (plowing + discing + leveling + farrowing + planting with seeding machine), low tillage (light discing + farrowing + planting with seeding machine), and no tillage (direct sowing with seeding machine). Also, the management of plant residues includes three levels: no residues, 30 percent of plant residues, and 60 percent of the previous crop residues. Characteristics of heading and maturity dates, wheat yield and yield components, and soil organic carbon content were investigated.

The results showed that the longest time for the occurrence of heading and maturity was observed in conventional tillage treatment. So that, it was only in this treatment the heading and maturity stages occurred on dates more than 170 and 202 days after sowing, respectively. Treatment of no residues with 168.22 days after the sowing date had the most extended date of heading. No-tillage treatment significantly decreased the number of spikes per square meter and 1000-seeds weight. However, there was no significant difference between the levels of plant residues in no-tillage treatment. No-tillage significantly reduced the grain yield of wheat. Though in no-tillage conditions and 30 percent of plant residues, grain yield was significantly higher than 60 percent, and no residues were in the same tillage conditions. The highest grain and biological yields were observed in conventional tillage treatments and in 30 and 60 percent of plant residues. Conventional tillage significantly reduced the soil's organic carbon content. Low tillage treatment at 30 and 60 percent of plant residues observed the highest organic carbon and nitrogen.

Although wheat's grain and biological yield in conventional tillage treatments were more than low tillage and no-tillage, low tillage improved the organic carbon content of the soil, and this phenomenon can have a positive effect on plant yield in the long run. Therefore, preservation of 30 percent of rapeseed residues with low tillage in wheat - rapeseed - wheat is recommended.

The objective of this research was to assess the effect of nickel (Ni) toxicity on rotated barley and faba bean characteristics under chemical and biological nitrogenous fertilizers.  

A greenhouse experiment with factorial arrangement based on randomized complete block design with three replications was conducted in two years of 2016-2017 at the Faculty of Agriculture, University of Tabriz. In the first part, barley seeds were sown using 36 pots with Ni levels of 0, 10, 100 and 200 mg.kg-1 and nitrogen (N) fertilizer (control, urea and Nitroxin). In the second part, faba bean seeds were cultivated in 72 pots. In this part, the crop rotation factor was applied in addition to N fertilizer and Ni treatments.

The results indicated that increasing Ni levels in soil markedly decreased plant height, leaf water content, chlorophyll content index, and root and shoot dry matters, but increased electrolyte leakage of barley and faba bean plants. The high level of Ni (100 and 200 mg.kg-1) was led to soil toxicity. While, the low nickel concentration (10 mg.kg-1) improved the growth of plants.  

It can be concluded that application of N fertilizer improved the growth conditions of plants under Ni stress. Cultivation of barley significantly decreased Ni toxicity in the soil, leading to an improvement in faba bean performance in rotation.

In this study, the effects of different levels of tillage and nitrogen fertilizer on wheat yield in rotation with chickpea were studied.

An experiment with 8 treatments in a split plot design based on randomized complete block design with two factors of tillage type including T0= low tillage and T1= no tillage and quantities of different nitrogen fertilizer application at four levels including N0= without nitrogen application, N30= 30, N45= 45 and N60= 60 kg.ha-1 pure nitrogen for 4 years in 3 replicates from 2015 to 2019 in moderate-cold region of Kermanshah was conducted.

Finally evaluated treatments technically and economically were. The highest amount of organic carbon (0.703%) belonged to T0N45 treatment. The results of soil analysis showed that the effects of tillage and nitrogen fertilizer application. The results showed that the highest yield occurred in the second crop year in T1N45 treatment. The results of economic evaluation showed that each treatment alone was economically profitable and among the treatments, T1N0 treatment had the highest benefit-to-expenditure ratio.

In both no tillage and low tillage systems, it was observed that the ratio of present value to interest expense decreased with increasing nitrogen use. Finally, considering the ratio of present benefit - cost ratio difference showed that T1N45 treatment, namely rainfed wheat cultivar with low tillage and 45 kg/ ha nitrogen fertilizer, be known as the best economically treatment in Sararood region of Kermanshah.

Given the various advantages of applying conservation tillage methods in the agriculture, including reducing the effects of climate change by decreasing the carbon dioxide emissions to the atmosphere caused by carbon sequestration in soil, this study was conducted with two wheat-cotton and wheat-sesame rotations at Agricultural Research Station Bakhtajerd, in Darab, the southeast of Fars Province, which had a warm and dry climate; this work was carried out in a loam soil during four years. The aim of this investigation was to compare the carbon sequestration (CS) in the soil after application of different conservation tillage methods with the conventional method. The results showed that in wheat-cotton rotation, the maximum and minimum amount of CS in the 0-20 cm depth of soil with the average 17.160 and 13.810 t/ha could be obtained by using no-till and conventional tillage, respectively. Therefore, no-till increased CS by 24.26% in wheat and cotton cultivation, as compared to the conventional tillage. The economic value of this CS increment for the environment was $2459 per hectare. In the wheat-sesame rotation, the highest and lowest CS was obtained with an average of 25.850 and 12.505 t/ha in no-till and conventional tillage, respectively. Namely, direct seeding of wheat and sesame increased the CS at the 0-20 cm depth of soil by 107%, as compared to the conventional tillage with the economic value of $9809.5 per hectare. Under similar conditions, in wheat-cotton and wheat-sesame rotations, the conventional methods could be replaced by no tillage.

Soil quality appraisal is essential for sustainable agricultural production and should provide some information for decision. In this means soil quality indicatorsare introduced as criteria for assessment. This research was conducted to determine a suitable crop rotation system in parsabad region of Ardabil province, based on diffrent soil quality indicators.Three adjacent sites under rice cultivation that their second cultivation were fallow, clover and wheat with at least 4 consecutive years under this crop rotation, were selected. Soil sampling was performed on a random pattern from depth of 0-50 cm (30samples in each plot) after secend cultivation harvest. Statistical results revealed that the frequency distributions of all variables were normal. pH and microbial biomass (C) had the lowestand highestCV among the three selected rotations respectively. Analysis of Variance (ANOVA) and comparison test revealed that there were significant differences between the soil quality indicators. Organic matter content, total nitrogen, microbial respiration, cation exchange capacity, aggregates’ mean weight diameter and microbial biomass C were significantly greater in Rice-clover rotation systems than those in the other systems. However, bulk density and textural fractions components were not significantly different in the crop rotation systems.Overall results of this research showed that the ricerotation with legumes such as clover over a long time improved the soil quality.

Optimal use of irrigation water requires to the precise irrigation planning and the accurate crop coefficient estimation is the prerequisite of that particularly in the global scale. The aim of research was the comparison of preprocessing approaches of artificial neural network: regression and data reduction (principle component analysis and rotation) for crop coefficient estimation using NDVI, RI, TVI, MSAVI, SAVI, mTVI, EVI, MNDVI and TVX for wheat crop coefficient of East Azarbaijan Province. The performance of regression and data reduction approaches indicated the error criteria decreasing of data reduction approach, for example RMSE increasing from rotation to regression and from principle component analysis to regression was 11.8 and 22.7%, respectively. The used approaches of crop coefficient estimation has overestimation as the average increase of crop coefficient in the validation period showed 7.7, 6.13 and 4.6% increasing of crop coefficient from FAO to the regression, principle component and rotation approaches, respectively. Therefore, using the rotation in the data reduction analysis increased the accuracy of estimation. Decreasing of correlation coefficient-39.13% - from MSAVI to NDVI indicated that the improved indices basis on the study area condition increased the performance of crop coefficient estimation using satellite images.

Soil contamination with heavy metals would accumulate these elements in plant tissues and decrease qualitaty and quantity of agricultural producs and thus endanger human and animal healths. Previous crop residues and rates of fertilizers applications (especially phosphorus fertilizer) are the most important effective factors on accumulation of cadmium in crop tissues. Another influential factor affecting soil shrinkage is crop rotation which induces the solubility of cadmium. This research was aimed to assess the effects of conventional cropping system on cadmium concentrations in wheat at its different growth stages by using a split plot in time experiment based on completely randomized block design with three replications in the 2014-2015 growing season in Shavoor Agricultural Research Station (Khuzestan province). Main plot consisted of cropping system (rice-wheat, fallow-wheat) and sub plot of growth stages at three levels (tillering, flowering and ripening). Different wheat seed cadmium concentrations due to two cropping systems were different significantly at 1% probability level. Cadmium concentration in the seeds at rice-wheat cropping system (0.31 mg.kg-1) was higher than fallow-wheat system (0.27 mg.kg-1) which is higher than World Health Organization standards. Result of analysis of variance showed that the effect of cropping systems and different growth stages of wheat on root and stem cadmium concentrations were significant at 1% probability level. Rice-wheat cropping system resulted in higher cadmium concentration in root (1.09 mg.kg-1) and stem (0.73 mg.kg-1) compared to that of the fallow-wheat cropping system. Accumulation of cadmium in stem or root at different growth stages of wheat were not significant but it was totally additive, because range of variation of cadmium concentration from planting to harvest was low.

A GIS-based plan with TOPSIS multi-criteria technique was used to assess the feasibility of implementing conservation agriculture in the Maroon Basin of Khuzestan Province. For this purpose, a total of 17 information layers mechanization-farming including machinery (level of mechanization, operation factor, number of conservation tillage and drill), climatic (temperature and precipitation), topographic (slope and elevation), soil properties (texture, pH, salinity, phosphorus and organic carbon) and water resources (potential and salinity) are considered, to determine the areas most suitable for the crop rotation of canola, chickpea and wheat. Thematic layers for the above parameters were prepared in a GIS environment, classified into 5 categories according to FAO guidelines as: highly suitable, suitable, moderately suitable, marginally suitable and not suitable and weighted with AHP method. Then, prepared layers are ranked with TOPSIS techniques and overlapped in GIS. The results showed that 1.6% (5030 ha) and 14.5% (44595 ha) of the studied area is highly suitable and suitable for implementing conservation agriculture, respectively.

IntroductionHeavy metals, as one of the most important factors contaminating natural environments and agricultural ecosystems, are found in almost all industrial regions. Toxic effect of high concentration of heavy metals is also observed in plants. One of the specific characteristic of heavy metals which has high influence in occurrence of toxicity of heavy metals is their bioaccumulation. Heavy metals are not biologically inseparable and decomposable and remain in environment which finally threaten human health. Therefore, removing, or at least, reducing their concentration in agronomical systems is closely related to human health. Cadmium is a heavy metal which is an unnecessary element for plants and enter agronomical systems through pesticides usage. However, cadmium is easily absorbed by plant roots and its toxicity is 20 times more than that of other heavy metals. There are chemical, physical and biological methods for removal of heavy metals from agronomical soils. Phytoremediation is a low cost and environmental compatible method for heavy metal removal from soils. This research was aimed to compare the ability of wheat, clover and rapeseed for removal of cadmium from agronomical soils to achieve the goal of reduction of heavy metal for incoming crop in rotation.
Materials and methodsThe current research was conductedas3×3 factorial experiment based on randomized complete block design with three replications. The first factor was plant type including wheat, clover and rapeseed and the second factor was heavy metal concentrations including 0.0, 50 and 100 mg kg-1 soil. Soil samples were contaminated with cadmium concentrations of 0.0, 50.0 and 100 mg per kg soil. Experimental plots (with height and diameter of 40 cm) were filled with 10 kg contaminated soils. Four weeks after planting, all plants parts (including root and shoot) were harvested and oven dried at 75°C for 72 hours. Finally, cadmium concentration was determined in all plants.
Results and discussion The highest cadmium uptake was observed in wheat under the concentration of 50 and 100 mg kg-1 soil. Increasing cadmium concentration from 50 to 100 mg kg-1 soil had not significant effect on the ability of wheat, clover and rapeseed for cadmium uptake from soil. Plants with high biomass are capable for more heavy metals uptake which is line with the findings of this research where wheat with higher biomass removed more cadmium from soil in comparison with clover and rapeseed. However, nonsignificant difference between clover and rapeseed for cadmium uptake was not compatible with this opinion where rapeseed produced higher biomass. Although different physical, chemical and biological methods are used for removal of heavy metals from soils, phytoremediation has the highest effect for removal of cadmium from soils.
ConclusionThe current research confirmed the results of other experiments about the ability of phytoremediation for removal of cadmium from soil. Furthermore, the results revealed that wheat, in addition to its nutritional value, has a high ability for reduction of cadmium from contaminated soils and can be considered as a good crop in crop rotation programs.

Competition between potassiumand ammonium fixationwas studied in somesoilsofthe northern and southernKhuzestan province. Samples were taken from0-30and30-60cmdepthsin cultivation systemssuch assugarcane, rotational cropping, date palm, and uncultivated lands. Then, 0, 50, 100, 200, 400, 600, 800, 1000 mg kg-1 concentrations ofpotassiumand ammoniumwere added to these soil samples. The statistical analysis showed that with increasing concentrations from zero to 1000 mg kg-1 potassium and ammonium for all treatments, potassium and ammonium fixation increased in all systems and depths. In cultivated system, ammonium was fixed from 2007.50 to 1952.08 mg kg-1 in the surface and subsurface layers, respectively, while uncultivated land fixed 1880.62 to 1941.87 mg kg-1 ammonium. In contrast to ammonium, the same trend was not observed for potassium. Ammonium has also more tendency to fixing than potassium due to the presence of smectites and depleted illite clay minerals in these regions. The correlation coefficients between physicochemical properties and fixation showed that organic matter and clay content had negative effect on these cation fixations, but these effects were not statistically significant. Also, soil pH, the amount of lime and sand had insignificant and negative effect on ammonium fixation -0.034, -0.029 and -0.021 and cation exchange capacity and silt percentage show negative effect that was insignificant at -0.068 and -0.017, respectively.

This experiment was conducted to study the residual effect of some wheat herbicides on following corn (Zea mays L.) crop under different tillage systems in Karaj province. Tillage treatments included: conventional tillage, minimum tillage and, no-tillage. Herbicide treatments were: 1- bromoxynil MCPA (EC 40%) 1.5 lit/ha, 2- triasulfuron dicamba (WG 70%) 150 gr/ha, 3- mesosulfuron-methyl iodosulfuron-methyl-sodium (62 WG) 400 gr/ha, 4- metsulfuron methyl sulfosulfuron (w/v %5) 36 gr/ha, 5- tribenuron methyl (EC 8%) clodinafop propargyl (DF 75%) 20 gr/ha and 0.8 lit/ha respectively, as well as unweeded control (without herbicide). Soil sampling for bioassay tests made from surface layer (0-12.5 cm) and, sub-surface layer (12.5-25 cm). Bioassay experiment was conducted with Cress (Lepidium sativum) as a test plant and corn. Cress emergence percentage and cress and corn dry matter and height was assessed. Results indicated that herbicide bio- availability was depended on tillage system; in fact herbicide bio-availability was minimum in no-tillage systems. Triasulfuron dicamba, mesosulfuron-methyl iodosulfuron-methyl-sodium and metsulfuron methyl sulfosulfuron were the most persistent herbicide based on bio-availability, respectively. Therefore, these herbicides may damage the following corn crop in rotation although, corn was more tolerant to metsulfuron methyl sulfosulfuron. On the other hand, the persistence of bromoxynil MCPA and tribenuron methyl clodinafop propargyl herbicides in the soil was negligible and damage seems unlikely by theses herbicide in rotation.

In order to evaluate the effect of crops rotation on agronomical and non agronomical characters of cotton in Karkandeh Station in Golestan Proviences .The first and second years planted cotton and stems were cut to pieces and ploughed in soil . In the third and fourth years 15 treatments includes: soybean ,barley, onion , ploughing ,ploughing흍 nitrogen ,tomato , wheat ,lettuce, broad bean ,green bean ,green pea ,sesame ,sorghum,colsa based on randomized complete block design with four replications were planted. The yield, boll weight, percentage of earliness, sympodial length, monopodial number, monopodial length, disease indexes of wilt and Verticillium wilt percent were measured. Population of Verticillium dahliae,in dried soil were assessed before and after treatments by using semi selective Alcohol agar medium. The results were compared using Duncan's multiple range test. The results showed that the highest yield of cotton in cotton urea cotton, and plowing plowing and cotton , sorghom cotton, and lowest yield in succession, canola forage barly cotton and Cotton Cotton garden cress, widest monopodial length forage barly cotton cotton and the highest of sympodial length,cotton 늊 犋涢 , that the highest of monopodial number , barely spinach cotton and , the highest percentage of earliness barely spinach cotton were measured. Percent increase in the population of ofVerticillium dahliae in cotton Cotton Cotton Cotton Cotton sequence from first to fifth respectively 52/5, 25, 5/13, 5/6 and 0, respectively.The results showed that, population ofVerticillium dahliae, were incresed after cotton in first year(35%- 70%),in second year(14%- 36%),third year(12%- 15%),fourth year(4% - 9%) and fifth year without increase. Population ofVerticillium dahliae, were increased after wheat(66.7%),barley(68%),colsa(33.3%0,forage barly(48.5%- 54.5%),lettuce(25%- 39%),onion(52%),soybean(36%), ploughing(36%), ploughing흍 nitrogen(50%), green bean (12.5%) and sorghum(62.5%). population ofVerticillium dahliae, were decresed after tomato(6.6%), and sesame(26.6%).