عنوان مقاله [English]
Given the importance of nitrogen for improving the quantitative and qualitative yield of crops (Rodrigues et al., 2006) and the need for application of chemical fertilizers in intensive agriculture to get the maximum production, nitrogen supply in adequate amounts by ecologically avowed resources is known as one of the main challenges during transition from conventional to organic farming (Rodrigues et al., 2006).
Considering the sustainable nitrogen management, reconstruction and rehabilitation of agroecosystems depends on reduction the nitrogen losses due to leaching, soil erosion and volatilization (Kizilkaya, 2008). For this purpose, the use of eco-friendly bio based fertilizers that are derived from natural origin, known as effective and enforceable approaches. In this regards, the proper use of manure and free-living aerobic bacteria of soils, such as Azotobacter and Azospirillum as well as mycorrhizal inoculation which can be used as a biological fertilizers, can particularly be considered (Kizilkaya, 2008).
With regard to all mentioned above, the current study was aimed to evaluate the effects of biological, organic and inorganic resources of nitrogen on yield and yield components of black seed (Nigella sativa L.).
Materials and methods
The field experiment was conducted at Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, in years of 2009-2010. Experimental site was located in a semi-arid region, Khorasan Province, Northeast of Iran. The soil texture was silty loam, pH 8.36, electrical conductivity 3.72 dS.m-1, total N 0.095% and 0.195% organic carbon. The available P and K contents were 5.76 and 0.378 ppm, respectively.
Experimental design was arranged by using a completely randomized block design with three replications. Experimental treatments included chemical fertilizer (urea), urea + nitroxin, urea + mycorrhizae, urea + nitroxin + mycorrhizae, urea + biosulfur, manure, manure + nitroxin, manure + mycorrhizae, manure + nitroxin + mycorrhizae, manure + biosulfur and control.
Plots were designed with 4 m long and 2 m width (8 m2), 0.5 m apart each other. Seed sowing was done at 18th March on both sides of the furrows. Final plant density was determined equal to 200 plants m-2. At maturity stage, number of branch per plant, number of follicle per plant, seed weight per follicle and 1000- seed weight were determined based on randomly selection of eight plant. Moreover, grain and biological yields as well as harvest index of black seed were measured by considering the side effects.
For statistical analysis, Duncan multiple range test (p≤0.05) was used to separate the experimental means using SAS 9.1 software.
Results and discussion
According to the results, effects of urea and cow manure treatments on grain and biological yields of black seed were significant. However, cow manure, in comparison with urea fertilizer, had more significant effects in increasing mentioned traits of black seed. For instance, cow manure treatment increased grain yield by 25%, compared with urea treatment.
Generally, advantages of manure in comparison with chemical fertilizer can be related to the slow and more balanced release of nutrient contents as well as improving the physical and chemical soil characteristics over growing season. On the other hand, the results showed that biological fertilizers had no effects in increasing grain and biological yields of black seed, except biosulfur treatment.
From the results, there was a positive correlation between 1000- seed weight with grain yield. Moreover, similar correlations were found between number of branch per plant and grain yield, number of follicle per plant and grain yield as well as seed weight per follicle and grain yield. Nonetheless, relationship between harvest index and grain yield was determined as a negative correlation. These results are in agreement with those of Moradi et al. (2010) who found a significant decrease in harvest index of Fennel (Foeniculum Vulgare L.) affected by organic and biological fertilizers. It seem that under no application of organic or chemical fertilizers, black seed mother plants prefer to allocate more assimilation materials to the reproductive growth; therefore, plant harvest index can be increased possibly.
In sustainable agriculture, applying eco-friendly input can be considered as a principle approach for increasing plant production. Therefore, in regions with alkalic soils, applying the organic fertilizer (such as cow manure) and biological biofertilizer (e.g. biosulfure) can be suitable in reducing the problems caused by consecutive and excessive using of chemical fertilizers.