Effects of NP and Biofertilizers on Growth and Some Yield Attributes of Sunflower Helianthus Annus L
Abstract
Afield experiment was carried out in the demonstration farm of Sudan University of Science and Technology, College of Agricultural Studies, Shambat, for two consecutive seasons 2014/15 and 2015/16 to determine the effects of synthetic N (urea) and P (superphosphate) fertilizers and/or microbial biofertilizers on plant height (cm), number of leaves per plant, shoot and root dry weights, head diameter and 1000 seed weight of the sunflower hybrid Shambat. Nitrogen and phosphorus were applied at 100 and 50 kg/feddan, respectively. Biofertilizers were applied as a mixture of Azospirillum Brasilense (a nitrogen fixer) and Bacillus megaterium var. phosphaticum (a phosphate solubilizer). A combination of synthetic and biofertilizers was applied in addition to the control. NPtreatment gave the highest values of growth parameters in the first season followed by biofertilizers. In the second season biofertilzers then their combination produced the highest values. Head diameter and 1000 seed weight were enhanced by NPfertilizers. Significant differences in the first season were found only between NPand the combination of NP + AB in the number of leaves per plant and root dry weight, and in the second season the same treatments were significantly different only in shoot dry weight.
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Introduction
Sunflower (Helianthus annuus), belonging to the family Composite, is an important oilseed crop containing high quality edible oil. It is easy to cultivate and grown indifferent conditions and soils (Kaya and Kolsarici, 2011and Lopez-Valdez et al., 2011). It is an emerging oil producing crop in Sudan after Groundnuts and sesame. The total area under sunflower in Sudan, season 2003/2004 was 6300 ha (Zubillaga et al., 2002).
Nitrogen and Phosphorus are the two most important major essential elements for growth and development of plants. They are applied in the form of chemical fertilizers. Such fertilizers pose health hazards and microbial population disturbances in soil besides their high cost. Excessive nitrogen fertilization of sunflower not only generates that environmental risk, it may also affect the grain quality, decreasing its oil content and reduce yield through an increase of plant lodging (Scheiner et al., 2002). In addition, soluble phosphorus under wide range of soil conditions converts to unavailable form because of phosphorus fixation. In such a situation the biofertilizers playa major role inorganic agricultural practices that aim to enhance biodiversity, biological cycles and soil biological activity so as to achieve optimal natural systems that are socially, ecologically and economically sustainable (Samman et al. 2008).
Since the environmental and health problems arising from chemical fertilizers usage, attention has been drawn to the application of biological fertilizers in agriculture. Biological fertilizers or biofertilizers contain useful microorganisms, which could colonize the rhizosphere and promote plant growth through increasing the supply or availability of essential nutrients to the plants (Vessey, 2003). Soil microbes play an important role in many critical ecosystem processes, including nutrient cycling and homeostasis, decomposition of organic matter, as well as promoting plant health and growth as bio-fertilization (Han et al., 2007). Certain strains are referred to as plant growth-promoting rhizobacteria (PGPR), which can be used as inoculant biofertilizers. These bacteria include species of Azotobacter and Azospirillum, both of which provide direct and indirect effects on plant growth and pest resistance (Kennedy et al., 2004). Azotobacters and Azospirillum are free-living bacteria that fix atmospheric nitrogen in cereal crops without any symbiosis and they do not need a specific host plant (Mahrous et al., 2014).It is well-recognized that microbial inoculants constitute an important component of integrated nutrient management that leads to sustainable agriculture. (Akbari et al., 2011).
In recent years, biofertilizers have emerged as a promising component of integrating nutrient supply system in agriculture. Our whole system of agriculture depends in many important ways, on microbial activities and there appears to be a tremendous potential for making use of microorganisms in increasing crop production. Microbiological fertilizers are an important part of environment friendly sustainable agricultural practices (Bloemberg et al., 2000).Nowadays multi-strain biofertilizers containing microorganisms, having a definite beneficial role in supporting plant growth and developing sustainable soil fertility (Mekki and Ahmed, 2005) are receiving much attention.
Regarding the significant role of N, and Pin sustainable production of oilseed crops, an experiment was conducted to study the effect of biofertilizers on growth and some yield attributes of sunflower (Helianthus annuus. L).
Conclusion
In this experiment where sunflower plants were treated with synthetic NPfertilizers and/ or NPbiofertilizers, the growth parameters at the first season were enhanced by the synthetic NPfertilizers followed by the biofertilizers. In the second season biofertilizers caused the largest increase followed by the combination NP+AB. The head diameter and 1000 seed weight yield attributes were fairly increased by the synthetic fertilizers NP. Very few significant effects were recorded specially in yield attributes. We could conclude that biofertilizers could have abetter impact on measured parameters and much work has to be carried out concerning dose adjustment of synthetic biofertilizers in particular when employing combination treatments.
