جستجوی مقالات مرتبط با کلیدواژه « Nitrogen levels » در نشریات گروه « زراعت »

Improving forage yield and quality is a major concern for the producer. Sustainable crop production requires careful management of all nutrient sources in agroecosystems. Biological fertilizers, including Azospirilum, Azotobacter, Bacillus and Pseudomonas bacteria, can increase plant growth and yield through biological nitrogen fixation and increased solubility of macro elements such as phosphorus. Iron is the most important micro element for crops. Iron is required to perform many plant metabolism and growth activities. The experiment was conducted to investigate the effects of biological fertilizers combined with chemical fertilizers and iron micro element on yield and quality of maize (MV 500 cultivar) forage.

The experiment was conducted as a split plot based on randomized complete block design with three replications. The main plots consisted of different levels of urea fertilizer: Nitrokara biofertilizer, 150 kgha-1 urea + Nitrokara biofertilizer (Azorhizobium caulinodans), Super Nitro Plus biofertilizer (Azospirillum, Bacillus subtilis, Pseudomonas fluorescens), Super Nitro Plus biofertilizer + 150 kgha-1 urea without nitrogen fertilizer 450 kgha-1 urea, Nitrokara biofertilizer +300 kgha-1 urea, and Super Nitro Plus biofertilizer + 300 kgha-1 urea. The subplots consisted of two iron levels, including 10 kgha-1 iron chelate (Fe EDTA) and without iron application. The measured traits were crude protein, neutral detergent fiber, acid detergent fiber, ash, leaf to shoot ratio, ear to plant ratio and forage yield. Data were analyzed using MSTATC software.

Analysis of variance showed that the interaction effects of nitrogen fertilizer sources and iron levels were significant on crude protein, neutral detergent fiber, acid detergent fiber, ash, ear/plant ratio and forage yield. The highest crude protein and ash of maize forage were obtained from supernitroplus + 300 kgha-1 urea and iron application. Control treatment (without nitrogen and iron fertilizers) produced the most ADF and NDF values. The highest dry forage yield belonged to Super Nitro Plus + 300 kgha-1 urea with iron fertilizer and the lowest value obtained from control treatment without N and iron fertilizers.

The results of this study showed that the combined application of supernitroplus biofertilizer and urea fertilizer along with iron micro element increased maize forage quality and yield compared to the sole application of urea chemical fertilizer. Microorganisms constituting biofertilizers are very benefitial to the plant. They have the ability to enhance plant growth through increasing nutrient availability and uptake with minimal contribution to the environmental pollution, unlike the use of pure mineral fertilizers. The integration of biofertilizers and moderate mineral N fertilizer application accompanied with iron micro element is highly recommended in the production of maize forage.

  Stevia rebaudiana Bertoni in an ancient perennial shrub of South America, produces diterpene glycosides that are low-calorie sweetener sand about 300 times sweeter than saccharose (Savita et al., 2004). Stevia extracts, besides having therapeutic properties, contain a high level of sweetening compounds, known as steviole glycosides, which are thought to possess antioxidant, antimicrobial and antifungal activity. Stevia cultivation and production, especially in Iran, would further help those who have to restrict carbohydrate intake in their diet; to enjoy the sweet taste with minimal calories. In Iran, the best area that has the most similarity of favorable climate condition for Stevia cultivation is the north of Iran. However, poor soil aeration associated with excessive moisture usually influences plant establishment and growth negatively in this part of Iran. Heavy textured soils in northern regions of Iran are more susceptible to waterlogging after heavy rain, and hypoxia is likely to limit Stevia growth. Thus waterlogging is considered as one of the important limiting factors for Stevia cultivation in such regions. On the other hand, Oxidation-reduction systems in the soil, which are generally stable as long as the soil is bathed in oxygen, become unstable when the oxygen supply is restricted. Nitrate is stable in well-aerated soils but become unstable when the oxygen supply of the soil is cut off. Nitrogen is subjected to loss through denitrification because of the ability of facultative anaerobes to substitute nitrate for oxygen. Advantage can be taken from the reducing conditions in waterlogged soils to increase the utilization of nitrogen fertilizer. The objectives of the present experiment were to investigate the effects of waterlogging stress and the alleviation of the waterlogged damage by the application of nitrogen fertilizer in Stevia. Material and A greenhouse pot experiment was conducted in University of Guilan, in 2013. The experimental design was factorial using completely randomized design layout with three replications. Treatments included four waterlogging levels; (0, -5, -10 cm from soil surface and normal irrigation as control), in periods of 2 and 4 days of waterlogging and two levels of nitrogen (6‰ and no nitrogen spraying as control) by foliar spraying from source of urea. Because the economic organ of Stevia is its leaves samples were taken before flowering stage. Results showed that measured shoot traits including leaf percentage, leaf area density, specific leaf weight, leaf dry weight, leaf area, plant height, number of lateral branch, number of leaves were significantly different among treatments. Nitrogen application improved plant height (14%) (Bakhshandeh et al., 2016) but deceased leaf area density (14%) compared with control. Interaction of waterlogging duration and nitrogen fertilizer significantly influenced leaf percentage, specific leaf weight and leaf dry weight. During water logging period increase from two to four days, nitrogen application improved leaf percentage by 4.5%, specific leaf weight by 11%, and leaf dry weight by 14%. In addition, interaction between water logging level and nitrogen application significantly influenced specific leaf weight, number of lateral branch and leaf dry weight. For specific leaf weight in -5 cm water logging level, nitrogen fertilizer application resulted in 12% increase compared with the same water logging level but without nitrogen fertilizer. Nitrogen application under -10 cm water logging level improved the number of lateral branches by 9% compared with complete water logging level without nitrogen application. Also for leaf dry weight, nitrogen application under -10 cm water logging effect resulted in 11% increase compared with no nitrogen application. Generally, the results of this experiment show that nitrogen application under water logging stress improved growth features of Stevia although water logging stress reduce growth characteristics of Stevia. Nitrogen application under the highest waterlogging level improved leaf dry weight by 10% compared with no nitrogen application treatment. Because economic part of Stevia is its leaves, it is likely that nitrogen application under water logging stress improve this trait (Rashid et al., 2013). Results of this experiment showed that although level and duration of flooding stress caused a reduction in stevia leaf production but nitrogen application can ameliorate the negative effects of the stress on this trait. Since leaf dry weight is the economical yield of stevia, N application will improve yield if this plant under flooding stress