Effect of Nitrogen and Phosphorus Sources on Soil Chemical Properties and Elements Concentration in Sunflower (Helianthus annuus L.)

Soil fertility management is a key factor in achieving sustainable agriculture. Use of organic fertilizers is one of the methods that without environmental harmful effects with improvement of chemical and biological conditions increases soil fertility. Nitroxin contains a collection of the best strains of nitrogen fixation bacteria of the genus Azospirillum and Azotobacter. These bacteria through atmospheric nitrogen fixation and the balance of macro and microelements needed for plant uptake, stimulate the growth and development of roots and aerial parts of the plant. Phosphate Barvar2 is another bio-fertilizer which contains set of phosphate solubilizing bacteria of different genera Bacillus and Pseudomonas that can change soil insoluble phosphorus into available forms for plants. The purpose of this study was to evaluate some chemical properties of soil and nutrient concentrations in leaves and seeds of sunflower under the influence of chemical and biological form of nitrogen and phosphorus fertilizers to reduce the use of chemical inputs and to improve quality traits in sunflower. The experiment was carried out in a split factorial based on RCBD with three replications in a field in Eivanegharb (Ilam province) in summer of 2011. The main plot included four levels of phosphorus and nitrogen chemical fertilizer (0, 33, 66 and 100% of nitrogen and phosphorus fertilizer requirements) and subplot included factorial of Nitroxin bio-fertilizer application with two levels (inoculation and non inoculation) and Phosphate Barvare2 bio fertilizer with two levels (inoculation and non inoculation). Each plot consisted of 5 rows at a distance of 60 cm and a length of 6 m and 20 cm plant spacing. At the time of flowering, leaves were harvested for measurement of nitrogen, phosphorus, potassium, zinc and manganese. After harvesting, the amount of total nitrogen, phosphorus and potassium and pH of the soil and the concentrations of nitrogen, phosphorus, potassium, zinc and manganese seed were measured. The residual soil nitrogen: Based on these results, the effect of any of the factors tested for the residual soil nitrogen was not significant. The remaining soil phosphorus: With the increased use of chemical fertilizer, soil phosphorus increased so that the maximum (54.5 mg kg-1 soil) and minimum (40 mg kg-1 soil), available soil phosphorus levels were recorded in consumption of 100% of the required fertilizer and control treatments. Nitroxin and Phosphate Barvare2 applications increased percentage of soil phosphorus, i.e. 12.7 and 23.6 %, respectively, compared to no fertilizer application. The remaining soil potassium: Comparison of mean values showed that the increase in use of nitrogen and phosphorus fertilizer requirements reduced potassium levels in the soil, so that the maximum amount of soil potassium (624.9 mg kg-1 soil) belonged to control chemical fertilizer treatment and the minimum value of this attribute (514.4 mg per kg of soil) was related to the use of 100% chemical fertilizer consumption with no significant difference with use of 66% chemical fertilizers treatment. Soil pH: Among the experimental factors studied only bio-fertilizer Phosphate Barvar2 had a significant effect on soil pH at 5% probability so that the use of bio-fertilizer Phosphate Barvar2 significantly decreased soil pH. Leaf nitrogen: By increasing the amount of chemical fertilizer used, leaf nitrogen content increased, so that the maximum amount of leaf nitrogen (2.5%) was observed in the use of 100% chemical fertilizer consumption treatment. However, no significant difference was recorded in the use of 66% chemical fertilizers tratment. The lowest of this trait (2.2%) belonged to control chemical fertilizer treatment without significant difference with use of 33% chemical fertilizers consumption treatment. Seed nitrogen: Chemical fertilizer and Phosphate Barvar2 had significant effects on the amount of seed nitrogen content. With the increasing use of chemical fertilizers seed nitrogen increased so that the maximum (2.9%) and minimum (2.6%) seed nitrogen content belonged to use 100% of the chemical fertilizer and nonapplication of fertilizer, respectively. Mean comparison effect of Phosphate Barvar2 inoculation revealed that seed nitrogen increased by 3.7%. Seed phosphorus: Analysis of variance showed that the amount of seed phosphorus significantly was affected by the treatments, i.e. Nitroxin and Phosphate Barvare2 as well as the interaction of chemical fertilizer and Nitroxin. Application of Phosphate Barvar2 increased the amount of seed phosphorus by 14.8%. Seed potassium: Increasing application of chemical fertilizer requirement increased seed potassium. Among the 0, 33, 66 and 100% chemical fertilizer application treatments, Phosphate Barvare2 inoculation increased seed potassium by 23.3, 31.2, 31.3 and 11.4%, respectively. Seed zinc: According to the analysis of variance, effect of bio-fertilizer Phosphate Barvar2 and interaction of Phosphate Barvar2 and chemical fertilizer on the amount of seed zinc were significant different. However, only in 100% chemical fertilizer requirement, Phosphate Barvare2 inoculation showed significant difference in thistrait (63.4% increase). Seed manganese: The results showed that factors of Nitroxin and Phosphate Barvar2 and also the interaction of Phosphate Barvar2 and chemical fertilizer had significant effects on seed manganese content. Sunflower seed inoculation with Nitroxin increased the amount of seed manganese by 37%. According to the results, the maximum increase in the amount of nutrients studied in leaves and seeds of sunflower and soil was obtained in combined use of chemical and biological fertilizers.