Effect of nitrapyrin on functional diversity of soil microbial community in drip-fertigated cotton field

As one of the nitrification inhibitors (NIs), nitrapyrin (2-chloro-6-(trichloromethyl)-pyridine) exhibits some effective influences on controlling nitrification, reducing nitrogen leaching and nitrification-denitrification losses, increasing crop nitrogen uptake.However, information is still scant regarding the effect of nitrapyrin on the functional diversity of soil microbial community under drip irrigation condition in arid area.In view of this, a field trial (of randomized block design) was conducted to evaluate the impact of repeated supply of nitrapyrin with urea via fertigation on the functional diversity of soil microbial community in a drip-fertigated cotton field.Three treatments were established:CK0 kg (N)·hm^-2, Urea225 kg (N)·hm^-2and Urea+nitrapyrin225 kg (N)·hm^-2+2.25 kg (nitrapyrin)·hm^-2, each treatment was replicated three times.Biolog-ECO technology was used to explore carbon metabolism and community functional diversity of soil microbial.The results showed that the application of urea and urea plus nitrapyrin significantly increased metabolic capacity of 31 carbon sources (AWCD) and intensity of carbon metabolism (S) of soil microbial community compared with CK (P < 0.05), it also increased the diversity and richness of soil microbial communityShannon index (H'), Simpson index (D), McIntosh index (U) and Richness index (R)and improved the utilization of six types of carbon sources used by soil microbial community to some extent.Urea+nitrapyrin treatment increased AWCD, S, H', D, U and R of soil microbial community respectively by 13.83%, 9.33%, 1.29%, 1.34%, 11.26% and 11.79%(P > 0.05), it decreased Pielou evenness index (J)(P > 0.05) compared with Urea treatment.Principal component analysis and cluster analysis indicated that the application of urea and urea plus nitrapyrin significantly influenced the functional diversity of soil microbial community.However, there was no significant difference between Urea and Urea+nitrapyrin treatments.Furthermore, the addition of nitrapyrin increased the utilization of polymers, phenolic acids, carboxylic acids, amino acids and amines by soil microbial community, but decreased the utilization of carbohydrates compare with Urea treatment (P > 0.05).The results demonstrated that the repeated supply of nitrapyrin with urea via fertigation regulated soil micro-ecological environment, increased soil microbial metabolism and functional diversity of community.It inhibited the reduction of soil microbial activity due to long-term application of inorganic nitrogen fertilizers in drip-fertigated cotton fields in arid areas.