hamidreza tavakkoli kakhki

In order to investigate the effect of compensatory behavior of planting density, corm weight and planting depth on vegetative characteristics and yield of saffron stigma (Crocus. Sativus L.), a factorial split plot experiment with a randomized complete block design with three replications in the research center and Agricultural education and natural resources of Khorasan Razavi (Gonabad Research Station) was conducted in the cropping years 2018-2020. In this study, planting density treatment (in four levels of 60, 90, 120 and 150 corms per square meter) in the main plot and factorial planting depth (in two levels of 15±2 and 25±2 cm from the soil surface) and corm weight (in two Levels 4± 1 and 8 ± 1 gr) were located in the subplot. The results showed that increasing the density from 60 to 150 corms per square meter caused a significant increase in flower number, flower fresh weight and stigma dry weight, number of plants, number of leaves per plant, average length of a leaf and total leaf length per square meter. Accordingly, increasing the weight of coriander from 4 to 8 gr significantly increases flower number, flower fresh weight, stigma dry weight, number of plants, number of leaves per plant, average length of a leaf, total leaf length per square meter and total Leaf length per plant in the first and second years and reduced flower number, flower fresh weight and stigma dry weight in the third year. The results also showed that increasing the planting depth from 15 to 25 cm caused a significant decrease in all studied traits of saffron. The effect of dual and triple interactions on the studied traits was mainly significant. Overall, the results showed that the use of larger mother corms has a relative priority only in the early years and the importance of its effect decreases with increasing farm age. Based on this, it seems that it is possible to have a different strateg and with a combination of less depth and especially more density to compensate for the effect of corm weight and achieved more overall performance.

In order to investigate the effects of vegetation covering and shading on the economic yield of saffron (Crocus sativus L.) a split–plot experiment based on Randomized Complete Block Design (RCBD) with three replications was conducted at the Gonabad station for two cropping years (2018-2019, 2019- 2020). Experiments included main factor, density at four levels (90, 60, 120 and 150 corms per square meter) and sub-factors of crop residue management and shading at four levels (removal of saffron residues at the end of growing season as (control), presence of saffron residues at the end of the growing season, (control) + use of 2 (t.ha-1) barley straw and finally (control) + use of shading). Due to the nature of sub-factors, the data for the second year of growth were measured and analyzed. The results of analysis of variance showed that density and cover management had a significant effect (p≤0.01) on the vegetative characteristics of saffron (number, length and leaf area). However, the effect of density and the interaction effect of density × covering on vegetative traits had not significant effect. Also, the results of measured traits related to yield showed that the effect of corm density, covering management and the interaction of corm density × type of covering on number, flower weight and economic stigma yield were significant (p≤0.01). The highest amount of dry stigma yield and fresh weight of flowers with values of 5.16 and 411 (kg.ha-1), respectively, achieved from the treatment of 150 corms per square meter density and use of cereal straw covering and the lowest of these traits with values of 2.2 and 200 (kg.ha-1) was obtained from the density of 60 corms per square meter and control. Stepwise regression analysis for variables related to saffron economic yield showed that the number of flowers per unit area alone could explain 90.59% of the variation in saffron economic performance. Considering the positive effect of covering application on adjusting soil temperature compared to the maximum daily air temperature (at least 7%) and the simultaneous positive effect of this method of cropping management with induction of flowering stage in saffron, it seems that the use of different types of covering, especially cereal straw, is recommended to stabilize and improve saffron yield due to its low cost and easier access to covering saffron fields.

The nitrogen budget or balance is often evaluated by comparing various nitrogen inputs and outputs in soil–crop systems. Research on nitrogen balance can provide more detailed information on the nitrogen cycle and its losses by integrating soil nitrogen processes with the total nitrogen budgets. There are restricted researches for evaluation of nitrogen balances in the cropping systems. It is clear that accurate measuring of each component of nitrogen budgets in relation to soil processes is difficult. Wheat (Triticum aestivum L.) is the main cereal crop cultivated in Iran. According to published data the average nitrogen application rates in wheat cropping systems of Iran is 120 kg.ha-1 but, the excessive use of fertilizer nitrogen is very common in wheat fields. It is estimated that in Iran, about 2.2 million ha of wheat production areas are under irrigation. Alike, there are limited studies on nitrogen dynamics, budgets and its losses pathways in wheat production systems of Iran. Such studies are essential to understand the nitrogen behavior and balance in wheat cropping systems. This research was carried out with the aim of evaluating nitrogen balance of wheat cropping systems with different climatic conditions over the country by using CENTURY model.

We used CENTURY model (Parton et al., 1994) to evaluate nitrogen dynamics and nitrogen balance in wheat cropping systems. For this purpose 14 wheat cropping system located in diverse climates were selected. Soil data was collected from Soil and Water Research Institute and weather data from 2000 to 2014 were obtained from Iran Meteorological Organization for 14 selected stations. The CENTURY model simulates the long-term dynamics of Carbon (C) and Nitrogen (N), for different Plant-Soil Systems. The model can simulate the dynamics of agricultural crop systems. The crop system of CENTURY have different plant production sub-models which are linked to a common soil organic matter sub-model .The soil organic matter sub-model simulates the flow of C, N through plant litter and the different inorganic and organic pools in the soil. CENTURY model runs in monthly time step with monthly precipitation (cm), monthly mean minimum and maximum temperature (°C), site latitude and longitude, sand, silt and clay (%), soil bulk density (g.cm-3), rooting depth (cm), C and N content of the top 20 cm of soil and management information such as planting date, first and last month of wheat growth, number and amounts of applied fertilizers, amount of irrigation water and its schedules are required. For model validation we used two statistical measures including Normalized Root Mean Squared Error (nRMSE), Willmott (1982) index of agreement (d value) and linear regression coefficients between actual and predicted values.

Results revealed that the highest nitrogen input in wheat cropping systems (9.5 - 12.5 g.m-2) was observed in Northwest, West and Southwest and the lowest (7.3 - 9.4 g.m-2) were in East and Southeast areas of the country. Also, nitrogen output plan in wheat cropping systems was similar to nitrogen input. In addition, stepwise regression analysis indicated that fertilizer application rate with partial coefficient of 97.33% and grain nitrogen with partial coefficient of 92.79%, respectively, were the most important variables in relation to nitrogen input and output in wheat cropping systems of Iran.

According to the results, it seems that in relation to nitrogen input, the role of agronomic management such as fertilizer application, coincidence of fertilizer application time with plant requirement and increasing nitrogen use efficiency (NUE) which is mostly dependent on agricultural management are important issues. But in the case of nitrogen outputs from wheat cropping systems, in addition to agronomic managements, use of improved cultivars with higher nitrogen uptake efficiency is more important.

The relation between agriculture and energy is very tight. Agriculture itself is an energy user and energy supplier in the form of bio-energy. Energy consumption in agriculture has intensified in response to increasing populations, limited supply of arable land and desire for an increasing standard of living. In all societies, these factors have encouraged an increase in energy inputs to maximize yields, minimize labor-intensive practices, or both. Effective use of energy is one of the conditions for sustainable agricultural production, since it provides financial savings, fossil resources preservation and air pollution reduction. In developing countries, agricultural growth is essential to fostering economic development. In Iranian economy, more than 33% of the total population is engaged in agriculture sector.  Recent years with the rise in world energy prices the governments has taken steps to reduce fuel and energy consumption. Energy in agricultural sector  are divided into two groups of direct and indirect, direct energy is required to perform various tasks related to crop production processes such as land preparation, irrigation, threshing, harvesting and transportation of outputs. Indirect energy consists of the energy used in the manufacture of fertilizers, seeds, herbicides and farm machinery and so on. Recently, application of integrated production methods are recently considered as a means to reduce production costs, to efficiently use human labor and other inputs and to protect the environment.

This research was carried out to evaluate the effect of conservation agriculture system on energy indices in conventional rotation systems including wheat, barley and cotton. The experiment was conducted at Gonabad Research Station as a moderate climate condition between 2012 and 2016 by using split plot design in a randomized complete block design (CBD) with three replications. Two substantial criteria were investigated such as different tillage methods including conventional plowing, reduction of tillage (Minimum tillage) and direct cultivation (No tillage) as a main plots, as well asamount crop residue involving absence of residues 30 and 60%of the remains as a subplots. The area for each subplot and main plot was 600 and 1800 m2, respectively. In this study, energy indices were calculated using equations .Besides, data analysis and mean comparisons were performed via SAS (SAS, 2002) software and Duncan test, respectively.

According to results, electricity, chemical fertilizers and fuel inputs shared the highest energy consumption from the total amount of energy in the conventional crop rotation with 43, 23 and 12%, respectively. On the other hand, the lowest energy consumption related to the input of human resources with an average of 0.7%. In addition, variance evaluation and statistical analysis of energy indices demonstrated that only energy efficiency index for wheat and barley at level (p≤0.05) dramatically affected by tillage methods. . However, the effect of residues and interaction between soil tillage × residues on other energy indices was not significant. Comparison of average values ​​of energy use efficiency index in the conventional rotation illustrated that the highest and lowest values ​​of this index were observed in two methods without soil tillage or direct planting and soil tillage or customary tillage. Therefore, the average of energy use efficiency index for wheat and barley crops in non-tillage method was represented increasing 21 and 9%, respectively, than that of conventional tillage and minimum tillage methods.

Consequently, based on data analysis, it seems that the implementation of conservation agricultural systems with various tillage procedures (non – tillage or minimum tillage) to enhane energy use efficiency is exclusively recommended for wheat and barley agronomic systems in climate condition of this study.

Nitrogen fertilizers, plays an essential role in crop production and additionally its application has environmental drawbacks. So, nitrogen dynamics between cropping systems and environment is one of the most important agronomic management practices. Improving nitrogen use efficiency (NUE) is an important target in wheat cropping systems, it increases profitability through greater yields and reduction of the greenhouse gas emissions associated with the production and it could be reduce environmental hazards. There are many definitions related to NUE in the context of crop production and as well as in the literature review. One of the fundamental definition related to Moll et al (1982). According to Moll et al. (1982) definitions’ NUE as grain dry matter yield per unit of nitrogen available from the soil and fertilizer and divided it into two components 1-Nitrogen-uptake efficiency that is crop nitrogen uptake to nitrogen available and 2- Nitrogen-utilization efficiency which is grain dry matter yield to crop nitrogen uptake. Wheat is one of the most extend cultivated crops in the world. It is estimated in Iran, about 2.3 million ha of wheat cropping systems are under irrigated cultivation. The specific objectives of the present study were to 1- investigation and analysis nitrogen use efficiency variations and its components in wheat cropping systems by using simulation model.2-Determine how nitrogen use efficiency and its components (component analysis) is affected by nitrogen fertilizer levels. We used CENTURY model to evaluate nitrogen use efficiency in wheat cropping systems. For this purpose 14 wheat cropping system from different locations were selected. Soil data was collected from Soil and Water Research Institute and weather data from 2000 to 2014 were obtained from Iran Meteorological Organization for 14 selected stations.The CENTURY model simulates the long-term dynamics of Carbon (C), Nitrogen (N), for different Plant-Soil Systems. The model can simulate the dynamics of agricultural crop systems. The crop systems have different plant production submodels which are linked to a common soil organic matter submodel. The soil organic matter submodel simulates the flow of C, N through plant litter and the different inorganic and organic pools in the soil. CENTURY model runs in monthly time step with calculating monthly precipitation (cm), monthly mean of minimum and maximum temperature (c°), site latitude and longitude, sand, silt and clay (%), soil bulk density (g/cm3), rooting depth (cm), C and N content of the top 20 cm of soil and management information such as planting date, first and last month of wheat growth, number and amounts of fertilization, amount of irrigation water and its schedules are required. For model validation we used three statistical measures including Normalized Root Mean Squared Error (nRMSE), Willmott (1982) index or (d index) and linear regression coefficients between actual values and predicted values. Results, revealed that average nitrogen use efficiency in wheat cropping systems of Iran was 28.3 kg grain per kg of nitrogen applied. The highest and lowest mean nitrogen use efficiency were 36.02 and 21.26 kg grain per kg N that observed respectively in (Tabriz, Shiraz, Gorgan) and (Kerman, Zabol, Birjand). Regression of nitrogen use efficiency vs. yield showed that with increasing nitrogen use efficiency, yield is raised (b=0.14 kg kg-1). Separation of nitrogen use efficiency to its components indicated that on range of value (80-120 kgha-1) use of nitrogen, relative contribution of nitrogen uptake and utilization efficiency separately were 64 and 36 percent. When use of nitrogen fertilizer was increased up to value (121-160 kg ha-1) relative contribution of nitrogen uptake and nitrogen utilization was changed to 33 and 67 percent, respectively. It seems that, when in cropping system nitrogen uptake will be dominant, agronomic management practice and in versus, if nitrogen utilization efficiency will be more important choice of superior cultivars are emphasizes the improvement of nitrogen use efficiency.

In order to investigate the effect of planting density and maternal corm weight on some characteristics of daughter corms and agronomic characteristics of saffron (Crocus sativus L.) a field experiment was conducted at the Agricultural and Natural Resources Research Center of Mashhad. This experiment was carried out as a factorial split plot in time based on complete block design with three replications and 12 treatments during the years 2010-2014. The experimental factors were 3 levels of density (40, 80 and160 corm in m2) and 4 levels of mother corm weight (≤3, 3-6, 6-9 and 9-12 g per corm) as a main plot and time as a sub plot. The results showed that density, maternal corm weight and year had significant effects on daughter corm’s weight, but the effect of interaction density × corm weight and density × weight × year were not significant for the most characteristics. The mean comparison of interaction effect of density × weight for number of daughter corm showed that maternal corm weight (9-12 g) × planting density (160 m2) had the highest number for daughter corms (771 m2). Maternal corms with higher initial weight produced the highest number of corms in different corm classes. In addition, the results showed that maternal corm with lower initial weight produced heavy daughter corms compared to other maternal corm weight classes. Flower weight and stigma dry weight of saffron (m2) were increased by increasing planting density and maternal corm weight flower number. The highest dry stigma (0.65 g.m-2) yield was produced by maternal corm (9-12 g per corm) weight class.