Mahbubeh Gheitasi; Ali Reza Hosseinpur
Abstract
Introduction: Leafy vegetables such as spinach (Spinaciaoleracea L.) contain high levels of nitrate. Using nitrification inhibitors (NIs) such as 3,4-dimethylpyrazole phosphate (DMPP) is one of the strategies for reducing nitrate accumulation. Nitrification inhibitors are compounds that delay the biological ...
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Introduction: Leafy vegetables such as spinach (Spinaciaoleracea L.) contain high levels of nitrate. Using nitrification inhibitors (NIs) such as 3,4-dimethylpyrazole phosphate (DMPP) is one of the strategies for reducing nitrate accumulation. Nitrification inhibitors are compounds that delay the biological oxidation of ammonium to nitrite by depressing the activity of Nitrosomonas bacteria in soil. Soil properties such as texture, pH, organic matter, moisture, temperature and mineral nitrogen have important effects on the efficiency of NIs to delay nitrification. A pot experiment was conducted to investigate the effects of NI 3,4-dimethylpyrazole phosphate (DMPP) on soil mineral nitrogen (ammonium and nitrate) content, yield and nitrate concentration of spinach.
Materials and Methods: A completely randomized factorial design was carried out employing three factors consisted of nitrogen fertilizer type, soil type and spinach variety with three replications at Shahrekord University. Nitrogen fertilizers included urea, ammonium sulfate nitrate (ASN) and ASN plus DMPP (0.8 %). A no N fertilizer application was considered as control treatment. The soil factor contained 3 different soils with different physical and chemical characteristics. Two spinach varieties were smooth-leaf (Giant Santos) and wrinkled-leaf (Viking). The dose of applied nitrogen in all experimental treatments was 150 mg kg-1 soil that was applied in two split doses before sowing and after one month. The textures of three selected soils were loamy sand, loam and silty clay for the soils number 1, 2 and 3, respectively. Three selected soils were non-saline (EC1:2=0.14-0.31 dS m-1) and alkaline (pH1:2=7.9-8.0). Organic carbon and calcium carbonate equivalent (CCE) ranged from 0.26% to 0.35% and 28.5% to 36.2%, respectively. At 30 and 60 days after sowing, soil subsamples were taken to determine ammonium and nitrate content. The ammonium and nitrate concentrations (extracted with 0.5 M K2SO4) were determined calorimetrically using a spectrophotometer at a wavelength of 667 and 410 nm, respectively. At the end of the experiment, shoot fresh weight was determined and plants was mixed and dried to measure nitrate accumulation.
Results and Discussion: The results indicated that the application of ASN with DMPP led to significant increase of ammonium compared with ASN and urea fertilizers in three soils. At 30 days after sowing, the amount of this increase for ASN plus DMPP in comparison of ASN and urea were 182% and 78% for the soil number 1 (loamy sand), 105% and 65% for the soil number 2 (loam) and 89% and 74% for the soil number 3 (silty clay), respectively. By contrast, the application of ASN with DMPP led to significant decrease of soil nitrate in comparison of ASN and urea fertilizers in three soils. At 60 days after sowing, the amount of this decrease for ASN plus DMPP in comparison of ASN was 52%, 40% and 27% for the soils number of 1, 2 and 3, respectively. It means that the application of DMPP has slowed down the process of ammonium oxidation to nitrite. In fact, the addition of DMPP retained soil nitrogen as ammonium form for longer time. The application of NI DMPP also had positive effect on decrease of nitrate concentration in the soil. Unlike nitrate, ammonium is less susceptible to leaching and thus the application of DMPP can reduces nitrogen loss from the soil. However, the application of ASN with nitrification inhibitor DMPP in soils No. 2 (loamy sand) and No. 3 (loamy) significantly reduced shoot fresh weight of both spinach varieties compared with the similar treatment but without NI. This decrease was due to the toxic effects of high level of soil ammonium on the plant growth. While, in the soil No. 3 (silty clay) in Viking variety, the use of ASN plus DMPP resulted in significant increase of spinach shoot fresh weight to 29% in comparison with the same treatment but without NI. The highest and lowest values of shoot fresh weight (229 and 16.2 g pot-1, respectively) were obtained by Giant Santos variety in soil No. 3 (silty clay) with ASN plus DMPP and soil No. 1 (sandy loam) with no added N fertilizer. The application of ASN with nitrification inhibitor DMPP induced significant decrease of shoot nitrate concentration in spinach in comparison of ASN and urea. The amounts of this decrease for ASN plus DMPP in comparison with ASN and urea were 25.7% and 31.5% for the soil number 1 (loamy sand), 29.1% and 37.1% for the soil number 2 (loam) and 33.9% and 34.0% for the soil number 3 (silty clay), respectively. This decrease was due to ammonium nutrition of spinach plants.
Conclusion: In all studied soils, application of ASN with nitrification inhibitor DMPP is recommended for diminishing nitrate content in both spinach varieties (Giant Santos and Viking).
F. Ehsanpour; Sh. Kiani; alireza hosseinpuor
Abstract
Low phosphorus use efficiency in calcareous soils is one of the problems of wheat production in the fields, all over the world. This experiment was conducted to elucidate the effects of nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) and phosphorus (P) levels on the yield and P use ...
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Low phosphorus use efficiency in calcareous soils is one of the problems of wheat production in the fields, all over the world. This experiment was conducted to elucidate the effects of nitrification inhibitor (NI) 3,4-dimethylpyrazole phosphate (DMPP) and phosphorus (P) levels on the yield and P use efficiency of wheat (Triticum aestivum L.). A factorial experiment in randomized complete block design was carried out with two factors of type of nitrogen fertilizer (1- control: with no added N fertilizer, 2 and 3- ammonium sulfate fertilizer (ASF) with and without nitrification inhibitor DMPP, 4 and 5- ammonium sulphate nitrate fertilizer (ASNF) with and without nitrification inhibitor DMPP with rate of 100 mg N Kg-1 soil) and different levels of P (0, 30, 60 and 90 mg P kg-1 soil) on spring wheat cv. Pishtaz during 2010 at ShahreKord University with three replicates. According to results, application of nitrification inhibitor DMPP with both of ASF and ASNF resulted to meaningful increase of soil available P at the end of experiment as well as significant increase of NH4+ and also significant decrease of NO3- in the soil during experiment as compared to similar treatments but without NI. The results indicated that application of nitrification inhibitor DMPP with ASNF at all P applied led to significant increase (P
Sh. Kiani
Abstract
A pot experiment was conducted to elucidate the effects of nitrification inhibitor (NI) 3, 4-dimethylpyrazole phosphate (DMPP) on the nitrogen uptake, yield components, yield and grain protein content of spring wheat (Triticum aestivum L.) cv. Bahar during 2011 at ShahreKord University. A factorial experiment ...
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A pot experiment was conducted to elucidate the effects of nitrification inhibitor (NI) 3, 4-dimethylpyrazole phosphate (DMPP) on the nitrogen uptake, yield components, yield and grain protein content of spring wheat (Triticum aestivum L.) cv. Bahar during 2011 at ShahreKord University. A factorial experiment in randomized complete block design was carried out with two factors of type of N fertilizer (1- control with no added N fertilizer, 2-urea 3- ammonium sulphate nitrate (ASN) and 4- ASN plus DMPP) and soil type (10 soils) with three replications. The results indicated that application of nitrification inhibitor DMPP with ASN led to significant increase (P
