Response of soil basal respiration to fertilization across China’s croplands

Objectives Soil basal respiration (SBR) is an important indicator for soil quality. We investigated the SBR differences caused by fertilizer types, dosages, and by other factors, trying to quantitatively define the influence degree and key factors in farmland of China.

Methods The references were searched in keywords “fertilization”, “soil respiration”, “SOC mineralization”, “soil CO₂ efflux/soil CO₂ emission”, “farmland/cropland” that were published during 2000 and 2020 in the Web of Science, CNKI and CSCD database. Total of 586 pairs of experimental data were extracted and standardized to quantify the effects of fertilization (chemical and organic fertilizer) on SBR in different fertilization years, N application rates, climate zones, cropping systems, and land use types. The key factors related to the variation of SBR were analyzed by Meta-analysis.

Results Fertilization significantly increased SBR by 60.20%, compared to no fertilization. The increase of SBR caused by organic fertilizer was 81.45%, which was significantly higher than that by chemical fertilizer (47.78%). When fertilizer was applied consecutively for more than 30 years, the SBR increase by organic fertilizer was 1.38 times of that by chemical fertilizer. The range of SBR increase under N application rate of 100−200 kg/(hm²·a) (72.56%) was higher than those under >200 kg/(hm²·a) and under <100 kg/(hm²·a) (44.65% and 55.21%). Higher SBR by fertilization was recorded in mid-warm temperate zone (93.71%) than in subtropical and warm temperate zones (37.11%, 40.64%). The effects of mineral and organic fertilizers on soil basal respiration in mid-warm temperate zone (73.88% and 110.91%) were significantly higher than those in subtropical zone (28.99% and 45.00%). Fertilization led to higher range of SBR increase in dry land (105.01%) than in paddy field (28.90%) and drought-flood rotation feild (46.90%). Higher SBR occurred in soils under rotation system (101.60%) than under continuous cropping system (50.63%). Correlation analysis showed that SBR was positively correlated with organic carbon, total N, microbial biomass carbon and nitrogen. In addition, there was a significant positive correlation between SBR and alkali-hydrolysable N and microbial quotient under the treatments of organic fertilizers.

Conclusions Fertilization can significantly increase soil organic carbon content and soil basic respiration, the increment is impacted by fertilizer type, duration of fertilization, nitrogen input rate, climate, land use type, cropping system and soil texture. On a longer time scale (>30 years), organic fertilizer could significantly increase soil microbial biomass carbon and soil microbial quotient, thereby improve soil basal respiration more intensively than chemical fertilizers, and improve soil quality more efficiently.