Abstract
Objective The objective is to provide a scientific basis for improving rice paddy soil quality and for the application of new fertilizer, by investigating the effects of biochar-based fertilizer and organic fertilizer substituting chemical fertilizer partially on soil nutrients contents, microbial abundances and enzyme activities, and investigated the driving factors for soil enzyme activities. Method A field experiment was conducted in a typical rice paddy located in Hangjiahu Plain, which soil is Qingzini paddy soil. Four treatments, namely no fertilizer control (ck), conventional fertilizer (CF), biochar-based fertilizer (BF) and organic fertilizer substitution of 50% chemical fertilizer (OF), were laid out with the three fertilization treatments had consistent input of N, P and K amount. The field trail was initiated on June 2019 and soil sampling were collectted on November, 2019. Topsoils (0−20 cm) were sampled to investigate changes in soil carbon and nitrogen fractions, bacterial, fungal and archaeal abundances and enzyme activities involved in C, N and P cycling. Result Compared with CF, BF and OF treatments had no effects on soil pH, total C and N, available P and K and nitrate contents, but OF significantly increased soil ammonia and dissolved organic C contents. Compared with ck, OF treatment increased the content of soil microbial biomass carbon (MBC) by 164%, bacterial 16S rRNA gene abundance by 35% and fungal 18S rRNA gene abundances by 98% and fungi/bacteria ratio by 50%, while BF and CF had no effects on them. The three fertilization treatments had no effects on the activities of β-glucosidase, β-xylosidase and Leucine aminopeptidase, whereas BF and OF treatments significantly increased the activities of α-glucosidase (AG) by 111%和136%, β-cellobiosidase (BG) by 77%和100%, β-N-acetylglucosaminidase (NAG) by 109%和177% and acid phosphatase (PHOS) by 97%和199%, respectively. Redundant analysis indicated that changes in soil enzyme activities were strongly dependent on the contents of soil ammonia, dissolved organic C and N, and fungal abundances. Conclusion The application of organic fertilizer and biochar-based fertilizer significantly increased soil enzyme activities involved in C, N and P cycling, with the OF treatment further increased soil microbial abundance, which was beneficial for soil nutrient cycling. [Ch, 2 fig. 3 tab. 33 ref.]
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