جستجوی مقالات مرتبط با کلیدواژه « کارآیی بهره وری نیتروژن » در نشریات گروه « زراعت »

Drought is known as the most important factor limiting corn production in the world. Depending on the growth stage and severity of drought stress, it can decrease corn yield by 76%. In addition, the increase in drought stress can decrease the efficiency of elements such as nitrogen in this crop. Therefore, many ways have been studied to decrease the effects of drought stress on crops. The results show that the use of cover crops can be an important approach for agriculture to protect crops against climate changes. These crops improve crop yields and soil nutrients by reducing runoff and soil erosion. The use of legumes as cover crops can decrease the need for chemical nitrogen fertilizer by biological N fixation in these crops.

In 2019, a pot experiment was conducted in the greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran. The experimental treatments were faba bean cultivation (cultivated, non-cultivated), the different rates of nitrogen based on urea (0, 50, 100% of the recommended amount) and water deficit stress (40, 60, 80, 100% FC). In this experiment, 72 pots of 10 kg were used. First, the field capacity of the soil was determined, then the pots were filled with the air-dried soil. Ten grains of faba bean were planted in each pot, 5 of which were removed after germination. Shoots of faba bean were cut at the 50% flowering stage and mixed with the soil to the depth of 10 cm. Four corn grains were planted in each pot, two of which were removed after germination. In this experiment, the variety Shadan of faba bean and the corn hybrid 201 (single cross) were used. Different levels of nitrogen were applied at the V5 stage of corn, drought stress was applied ten days later and continued until the harvest stage of corn. Pots were weighed regularly for the application of drought stress. Corn was harvested at the pasty stage. Experimental characteristics included grain and shoot fresh and dry weights, grain and shoot protein content, nitrogen agronomic efficiency, nitrogen productivity, nitrogen recovery efficiency, and shoot and grain partial factor productivity. Statistical analysis of data was performed using SPSS software (version 26), and significant differences between treatment means were tested using Duncan's Multiple Range Test at P < 0.05.

Our results showed that all traits were influenced by interactions between faba bean cultivation × N fertilizer × water deficit stress. The highest grain yield was obtained of treatment the faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress, while no grains were observed in the treatment of non-cultivation of faba bean+100% of the recommended rate of nitrogen+application of severe water deficit stress, non-cultivation of faba bean+no nitrogen application+application of moderate water deficit stress and non-cultivation of faba bean+no nitrogen application+application of severe water deficit stress. The higher rate of nitrogen in the soil under severe water deficit stress can be considered as the limiting factor for crop growth, and therefore we observed lower yields in these treatments. Addition, our results showed that faba bean cultivation as cover crop increased some traits such as fresh and dry weight of shoot, agronomic efficiency and nitrogen recovery of nitrogen compared to non-cultivation of faba bean. The highest fresh dry shoot weight was obtained from the treatments of faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress and non-cultivation of faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress. Also, the highest shoot and grain agronomic efficiency was observed from the faba bean cultivation+100% of the recommended nitrogen rate+ no nitrogen application+application of moderate water deficit stress.

Overall, our results showed that the use of faba bean as cover crop can decrease the effects of water deficit stress and improve the growth status of corn, although the increase at higher water deficit stress level is lower than the other levels. Based on the results, it can be concluded that the use of faba bean as cover crop and and 50% of the recommended rate of nitrogen can be recommended under the same conditions (under water deficit stress).

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.

Response Surface Methodology (RSM) is a statistical tool for modelling and optimization of multiple factors which determine optimum process conditions by combining experimental designs with interpolation by first- or second degree polynomial equations in a sequential testing format. Nitrogen (N) and plant density are two factors crucial to the successful implementation of crop management practices used in corn production systems. Numerous studies have reported the effects of N fertilization on yield of corn. The optimum resource level in agro-ecosystems should be determined to decrease production costs, conserve resources and reduce environmental pollution which occurs as a result of excessive use of these resources. In this work, optimization of nitrogen fertilizer and plant density of corn using central composite design for RSM was done.
An experiment was conducted using central composite design with 13 treatments and two replications at the Research Field of Ferdowsi University of Mashhad during the growing season of 2015-2016. The treatments were allocated based on low and high levels of plant density (7 and 10 plants m-2, respectively) and nitrogen (0 and 300 kgN ha-1, respectively). Biological yield, grain yield, N utilization efficiency, N recovery and N use efficiency were calculated as independent variables and changes of these variables were evaluated by a regression model. Optimum levels of nitrogen and plant density were proposed to obtain the expected level of these traits based on economic, environmental and economic-environmental scenarios.
The results showed that the effect of linear component was significant on biological and grain yield and nitrogen efficiency indices of corn. Effect of square component was significant on all studied traits except for biological yield and N recovery. Interaction effect of full quadratic was significant on biological yield and N recovery. Lack of fit test had no significant effect on the studied traits except for NUE. The highest observed and predicted values of grain yield were obtained in 7 plants.m-2 with 150 kg N per ha (11.71 ton ha-1) and 10 plants m-2 with 300 kg N per ha (12.22 ton ha-1), respectively. The maximum observed and predicted values of N recovery were obtained in 10 plants.m-2 with 300 kg N per ha (86.45%) and 10 plants.m-2 with 300 kgN ha-1 (90.14%), respectively. The optimum levels of nitrogen fertilizer and density were 8.12 plants.m-2 with 225.27 kg N per ha, 7 plants.m-2 with 46.95 kg N per ha and 7 plants.m-2 with 69.42 kg N per ha for economic, environmental economic-environmental scenarios, respectively.
Increasing nitrogen fertilizer led to an increase in grain yield and a decrease in nitrogen use efficiency whereas increasing density caused an increase in grain yield and nitrogen use efficiency.

This study was carried out under temperate climate condition of Ilam province, Iran, during 2012-2013 growing season to determine the suitable crop rotation for enhancing nitrogen uptake, utilization, and use efficiency of wheat. A two factor experiment was laid out as split plot arrangement (RCBD) with four replications. The main plots consisted of 6 pre-sowing plant treatments (control, Perko, Buko, Clover, Oilseed radish and combination of three plants Ramtil, Phaselia, Clover), and sub-plots were allocated to four levels of nitrogen fertilizer (Zero, conventionally recommended fertilizer, 50% lower and 50% higher than the recommended fertilizer). Results showed that nitrogen use efficiency (NUE), nitrogen uptake efficiency (NUpE), nitrogen utilization efficiency (NUtE) and nitrogen efficiency ratio (NER) in wheat were significantly affected by crop rotation and nitrogen fertilizer and their interaction. The lowest and highest nitrogen use efficiencies were achieved in oilseed radish-wheat and fallow-wheat rotations. The greatest nitrogen use efficiency in oilseed radish-wheat was due to high utilization efficiency of nitrogen in the rotation. The greatest and smallest nitrogen utilization efficiencies (NUtE) were observed in oilseed radish-wheat and fallow-wheat rotations, respectively. Perko-wheat rotation with application of nitrogen at the conventional level for wheat brings about an acceptable economic yield and high nitrogen uptake and use efficiency and seems to be advantageous to other rotations.