Synthesis and Evaluation of some Pyrazoles for N-regulation of Soil-applied Urea in Rice-Wheat Culture

In order to develop suitable ecofriendly nitrification regulators, eleven pyrazole derivatives were synthesized in the laboratory by condensation of appropriate α, β-unsaturated carbonyl compounds with hydroxyl ammonium chloride and characterized using physico-chemical techniques. These compounds were evaluated for regulation of soil apllied urea nitrogen in a typic Haplustept (IARI- f arm soil), in vitro and in vivo employing rice-wheat culture. The fertilizer and regulator combinations produced more dry matter (grain and straw) yield as compared to control and/or urea alone. Compared to 17.90 g pot⁻¹ dry matter yield in control the yields in treatments consisting of urea plus 3-methyl- 5-diphenyl pyrazole and 3-phenyl-5-(4-methoxyphenyl) pyrazole combinations were 37.9 and 38.3 g pot⁻¹, respectively. The dry matter yield in urea alone treatment was 23.3 g and that is urea plus DCD, the reference regulator was 34.6 g pot⁻¹. Higher N-uptake and apparent N-recoveries in the treatments (20–25%) than those in urea alone, indicated that the chemicals did not deter the soil health while retarding the nitrification of soil applied fertilizer.