Introduction 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. Materials and Methods 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 and Discussion 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. Conclusion 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.

Environmental and economic challenges resulting from the application of NITROGEN fertilizers have increased concerns about its productivity in the agricultural systems. This study was conducted to evaluate SSM-Wheat model to simulate NITROGEN budgeting with various NITROGEN application scenarios (Dry land-without NITROGEN, Dry land-low NITROGEN, Irrigated-without NITROGEN, Irrigated-conventional, Irrigated-high NITROGEN and Irrigated-very high NITROGEN) in rainfed and irrigated conditions in the wheat-based cropping systems of Gorgan region in Iran in a 21-years period (1990-2010). Results indicated that the average total losses of NITROGEN were significantly different among different scenarios. In all scenarios, the proportion of NITROGEN loss (81%), as gaseous was more than that of leaching (19%). NITROGEN loss by nitrification ranged between 5.9 and 59.2 kg.ha-1 with average 23.2 kg.ha-1 while NITROGEN volatilization ranged between 0 and 14.9 kg.ha-1 with an average 5.8 kg.ha-1. Also, the maximum NITROGEN leached was associated with irrigated wheat-high NITROGEN scenario that had significant difference with other scenarios. However, the lowest amount observed in the rainfed wheat-without NITROGEN scenario that had no significant difference with irrigated wheat-without NITROGEN scenario. The highest productivity was observed in irrigated wheat-conventional scenarios (26 kg.kg-1) and irrigated wheat high NITROGEN (25.9 kg.kg-1) which was significantly different than the other scenarios. Therefore, irrigated wheat- conventional scenario was identified as suitable scenario in wheat production in Gorgan, Iran, due to cost saving, low leaching, less environmental pollution, adequate irrigation and less fertilizer use.

Introduction: The nutrient synchrony is synchronization of ruminal fermentation rate of energy and NITROGEN which is a method to increasing microbial protein synthesis, improving NITROGEN efficiency, decreasing urinary NITROGEN excretion and improving animal performance. Microbial protein production is important for ruminants. Current concepts of ruminant nutrition focus on optimizing ruminal microbial protein synthesis. Microbial yield in rumen depends largely on the supply of carbohydrates and NITROGEN in the rumen. Balancing the rate of supply of NITROGEN and energy yielding substrates to rumen microbes has been proposed in order to maximize the capture of rumen degradable protein and to optimize microbial growth rate and its efficiency. A more efficient capture of rumen degradable protein would reduce the requirement for expensive undegradable protein sources and also reduce the excretion of urinary NITROGEN which case to environmental pollution and economical losses. Synchronization index expressed as the ratio between the hourly degradability of NITROGEN with organic matter or carbohydrates in the rumen where the highest value for the synchrony index is 1. 0. This research was done to evaluate the effect of synchronizing the rate of carbohydrate and crude protein ruminal fermentation on ruminal fermentation products, microbial protein synthesis, and NITROGEN BALANCE and blood parameters in sheep which were fed with similar components or structure high concentrate diets. Materials and methods: Chemical compositions and degradability parameters of crude protein and carbohydrate for alfalfa hay, wheat straw, barley grain, corn grain, sugar beet pulp, wheat bran and soybean meal were determined. Three diets were formulated for feedlot male lambs with same energy and metabolizable protein but containing different synchrony index 0. 64, 0. 78 and 0. 92 which calculated by using degradation parameters of carbohydrate and crude protein of feeds from the diet. The effects of synchrony index of diets by 6 rumen-fistulated sheep with an average weight of 30. 17± 1. 17 kg in metabolic cages were assigned in a duplicate 3×3 Latin square design (2×3 animals; 3 periods). Samplings were done in 3 periods (each period containing 14 days for adaptation and 5 days for sampling). Rumen fluid was collected for 5 consecutive days in the end of each period and ruminal fermentation parameters containing pH, NH3-N and volatile fatty acids were determined. Urine of sheep was collected end of each period for 5 days and microbial protein synthesis was estimated by measuring purine bases also NITROGEN BALANCE was calculated from the values of NITROGEN consumption and excretion. Bleeding (19th trial day) were done from sheep and blood parameters such as glucose, albumin and blood urea NITROGEN were determined. Results and discussion: There was no significant difference in ruminal pH among diets during fasting conditions or before feeding. Also there was no significant difference in ruminal pH between treatments at 3 or 6 hours after feed intake. With increasing synchrony index, ruminal NH3-N concentrate reduced especially at 1. 5 and 3 hours after feed intake. Total volatile fatty acids highest at 3 hours after feed intake for diet had highest synchrony index. With increasing synchrony index, total volatile fatty acids concentration increased almost by 20 percent. Also the propionate concentrates increased not only before feeding but also at 3 hours after feeding. Total volatile fatty acids and propionate concentration showed a linear trend between diets at 3 hours after feeding. Purine bases such as allantoin, uric acid, xanthine and hypoxanthine, total purine derivatives excreted or absorbed also microbial protein synthesis not affected by experimental diets. With increasing synchrony index, total excreted NITROGEN reduced but NITROGEN retained and its efficiency increased. Blood parameters such as glucose, albumin and blood urea NITROGEN not affected by treatments. Conclusion: with increasing synchrony index of the diets, microbial protein synthesis did not increase but total volatile fatty acids concentration and retained NITROGEN increased whereas ruminal NH3-N concentration and total excreted NITROGEN decreased. However, increasing nutrient synchrony index in high concentrated diets did not show the expected desirable results such as increasing microbial protein synthesis however did not also show undesirable results such as animal health. Due to the beneficial effects as increasing in fermentation and decreasing NITROGEN excretion or environmental pollution using the high synchrony index diets can be useful for feed formulation or providing the perfect mix of feed items to meet nutritional requirements of sheep.

The aim of this study was to evaluate the long-term (16-years) NITROGEN efficiency after the application of organic and mineral fertilizers at two sites Lukavec (S1) and Suchdol (S2) with different soil and climatic conditions in the Czech Republic (Central Europe) and to determine grain yield and NITROGEN content with regard to the requirements of protein content for baking quality of wheat. After the application of NPK treatment the highest average values from both sites of grain yield (6.22 t ha-1), NITROGEN content (2.01%) and NITROGEN uptake (123.6 kg ha-1) were determined, which means 78%, 26% and 121% increases compared to the unfertilized treatment. At the less fertile S1, located on Cambisol, the significant effect of NITROGEN fertilization on yield was observed. The yield of the NPK treatment was by 144% higher compared to the unfertilized Control treatment. The limit of 11.5% of protein content for bakery wheat was not achieved for any of treatments at S1, at S2 for unfertilized treatment and treatments with organic fertilizers. Lower values of recovery efficiency of NITROGEN and N inputoutput BALANCE were found at S2 situated on Chernozem.

This research was conducted to study the effects of physical form of total mixed ration (in Block and Mash form) in sheep nutrition. In a 2×2 change-over design with two treatments and 5 replicates, 10 Shal lambs with average initial weight of about 31 kg were fed for two periods and 22 days per period. An unique ration (to supply fattening lambs) was formulated and prepared in TMR, then it was shared out in two parts where one part processed in Densified Block Ration (DBR) and the other part fed as mash TMR form. Results showed that the dry matter, organic matter and nutrients intake were increased when the animals received DBR compared to the mash TMR (P< 0. 05). The digestibility of DM, OM, CP, NDF, ADF, EE and gross energy were not affected by the physical form of the diet but NITROGEN retention and NITROGEN BALANCE were increased when the lambs received DBR (P< 0. 05). The daily times for eating, rumination, total chewing and resting time were not statistically different when the animals fed DBR or mash TMR whereas the amount of DM, OM and nutrients intake per minute were increased (P< 0. 05) by feeding of DMR. Feeding of DBR resulted in higher (P< 0. 05) weight gain and feed conversion ratio in comparison to the mash TMR. In general, feeding of pressed complete ration could improve animal performance; however more researches are required to find out the optimum feeding levels of DBR in Iranian lambs.

In order to investigate thewater productivity of rice in Rasht, a study was carried out in a RCBD during 2005 and 2007 years, with 3 replications in Rice Research Institute of Iran, Rasht. Irrigation management (3 regimes) was the main factor and N application (4 levels) was the other factor. In this study, simulation modeling was used to quantify water productivity, and water BALANCE components of alternate for water–NITROGEN interactions in rice. Results showed, the significant (28–56%) share of evaporation into evapotranspiration, using the actual yield (measured) and simulated water BALANCE (ORYZA2000), the calculated average WPET was significantly lower than the average WPT: 37%. The average WPI, WPET, WPT and WPETQ were 1.01, 0.89, 1.41 and 0.65 kgm-3. Also Results showed that, Irrigation with 8 days interval and 60 kg N ha-1, was the optimum combination.

Introduction: Crop productivity is highly constrained by water and NITROGEN limitations in many areas of the world.Therefore, there is a need to investigate more on NITROGEN and water management to achieve higher production as well as quality. Irrigated sugar beet in the cropping systems of Khorasan province in northeastern of Iran accounts for about 34% of the land area under sugar beet production (~115, 000 ha) with an average yield of around 36 t.ha-1. However, there is a huge yield gap (the difference between potential and water and NITROGENlimited yield) mainly due to biotic and abiotic factors causing major reduction in farmers’ yield. Accordingly, yield gap analysis should be carried out to reduce the yield reduction and reach the farmer’s yield to the potential yield. The current study aimed to simulate potential yield as well as yield gap related to water and NITROGEN shortage in the major sugar beet-growing areas of Khorasan province of Iran.Materials and methods: This study was carried out in 6 locations across Khorasan province, which is located in the northeast of Iran.Long term weather data for 1986 to 2009 were obtained from Iran Meteorological Organization for 6 selected locations. The weather data included daily sunshine hours (h), daily maximum and minimum temperatures (oC), and daily rainfall (mm). Daily solar radiation was estimated using the Goudriaan (1993) method. The validated SUCROSBEET model (Deihimfard, 2011; Deihimfard et al., 2011) was then used to estimate potential, water and NITROGEN-limited yield and yield gap of sugar beet for 6 selected locations across the Khorasan province in the northeast of Iran. This model simulates the impacts of weather, genotype and management factors on crop growth and development, soil water and NITROGEN BALANCE on a daily basis and finally it predicts crop yield. The model requires input data, including local weather and soil conditions, cultivar-specific parameters, and crop management information. Soil water module was used to determine soil water BALANCE under water-limited conditions. Some questionnaires were then sent to extension agents to obtain information from the main sugar beet producing fields in each location.Results and discussion: The SUCROSBEET model reasonably well predicted root yield across the study locations. The model could be used to simulate sugar beet yield under potential, water and NITROGEN-limited situations. Simulation results of SUCROSBEET model showed that the lowest and highest sugar beet potential yield were obtained in Sabzevar (100 t.ha-1) and Neishaboor (137 t.ha-1), respectively. Total yield gap (the difference between potential and farmer’s yield) ranged from 74 to 109 t.ha-1, in Sabzevar and Neishaboor, respectively. Despite the fact that most of the farms had been irrigated up to 20 times over seasons, there were still yield gap of an average 42 t.ha-1 due to water shortage. To reach the potential yield in the study locations, more than 2000 mm water is required in Sabsevar and Torbat-Jam and 1400 to 1500 mm in Ghoochan and Neishaboor, respectively. On average, to fill NITROGEN-limited yield gap, 440 to 530 kg.ha-1 of NITROGEN for sugar beet uptake are also required. However, the farmers in various locations have been able to apply only 50% of the sugar beet NITROGEN demands during the past decade. The results of the current study also suggested that the farmer yields of about 16-48 t.ha-1 in the irrigated locations across Khorasan province, were not constrained by low genetic yield potential. It is also needed to irrigate more than two times in some locations for reaching water-limited yield to potential one.Although there is a high potential for production of sugar beet (more than 130 t.ha-1), the ratio of yield production to water consumption (known as water productivity) is not suitable in the study locations and production of sugar beet would not be cost-effective. Another issue which has not been considered in the simulations is qualitative traits of sugar beet (such as sugar content, Alkaloids, molasses sugar, sodium andpotassium in storage organ, etc.) particularly under different levels of NITROGEN applications. Although increasing NITROGEN application would be resulted in higher yield and lower yield gaps, supplied NITROGEN more than crop demand could be accumulated in storage organs and reduce white sugar yield. For instance, every 15 kg additional application of NITROGEN reduced sugar content by 0.1 percent and reduced extraction coefficient of sugar. It is also worth noting that the current version of SUCROSBEET model is not capable to simulate qualitative traits of sugar beet and a few subroutines are needed to add to the model for future investigations.Conclusion: The results indicated that although there is high yield potential for sugar beet in Khorasan province, water productivity would not be reasonable. In addition, yield gap in sugar beet cropping systems which reflects the actual yield gap in irrigated environments is essentially due to non-adoption of improved crop management practices and could be reduced if proper interventions are made.

This experiment was performed to evaluate the carbon (C) BALANCE and global warming potential (GWP) as affected by tillage methods, maize residual management and NITROGEN levels. For this purpose, a field experiment was conducted as row split-plot arrangement based on randomized complete block design with three replications in Ferdowsi University of Mashhad, Iran in 2011 and 2012. The experimental treatments were tillage systems (conventional and reduced tillage) and residual management (remaining and leaving of maize residual) assigned to main plots and different levels of urea fertilizer (0, 150, 300 and 450 kg.ha-1) was randomized as subplot in tillage treatment. The results showed that carbon sequestration was affected by residual treatment in both years and residual management × N fertilizer interaction in second year. Addition of residual in soil was caused to increasing 48% and 69% of C sequestration in first and second years, respectively. Across the treatments, residual management had the highest effect on C BALANCE. So, C BALANCE was positive in remaining maize residual and that was negative in leaving condition. GWP was higher under conventional tillage, residue remaining and higher N fertilizer levels in comparison with reduced tillage, residue leaving and lower N fertilizer application.