Application of nitrogen inhibitors is an effective way to improve nitrogen fertilizer use efficiency of rice. The effects of nitrogen inhibitors (urease inhibitor N-butylthiophosphoramide

NBPT and nitrification inhibitor 3

4-dimethylpyrazole phosphate

DMPP) and their combinations on yield

nitrogen efficiency and soil nitrogen were studied by field experiment

aiming to provide scientific basis for formulating scientific nitrogen management and reducing nitrogen loss of paddy field in plain along the Huaihe River. A field experiment (between June 2018 and October 2018) using rice cultivar of "Changnuo" 1 as test materials was conducted in Huaiyuan County

Anhui Province (a typical rice growing area along the Huaihe Plain). Five treatments were set up

which were CK (no nitrogen fertilizer)

U (urea only)

U+NBPT (urea plus NBPT)

U+DMPP (urea plus DMPP) and U+NBPT+DMPP (urea plus combined application of NBPT and DMPP). The results showed that addition of NBPT or DMPP into urea increased the yield

nitrogen absorption and utilization

in which the effect of NBPT was better than that of DMPP

and the combination of NBPT and DMPP showed synergistic effect. Compared with U treatment

the rice yield of U+NBPT

U+DMPP and U+NBPT+DMPP treatments significantly increased by 6.8%

4.3% and 8.6%

respectively

and plant nitrogen absorption increased by 9.6%

6.5% and 12.2%

respectively

and the difference between the treatments were significant (P<0.05). Furthermore

the addition of NBPT or NBPT+DMPP in urea both significantly improved the nitrogen recovery efficiency (NRE)

nitrogen agronomic efficiency (NAE)

nitrogen uptake efficiency (NUP) and nitrogen partial productivity (NPFP) (P<0.05). However

urea combined with DMPP also increased in varying degrees

but the difference did not reach a significant level (P>0.05). In addition

the addition of DMPP or NBPT+DMPP in urea both significantly enhanced soil NH4+-N content and microbial biomass nitrogen (SMBN)

while reduced soil NO3--N content at maturity

and increased the ratio of NH4+-N to NO3--N. However

adding NPBT only had no obvious effect. In summary

adding urease inhibitor NBPT or nitrification inhibitor DMPP into urea could effectively improve rice yield and nitrogen use efficiency in plain along the Huaihe River

and the effect of urea added with combination of NPBT and DMPP was the best.