Abstract
Biochar addition is a promising solution to improve soil nitrogen (N) availability and enhance crop productivity. However, a comprehensive understanding of the impact of soil N dynamics on crop productivity under biochar addition remains elusive. Here, we conducted a meta-analysis from 93 peer-reviewed field experiments to synthesize the linkage of crop productivity to soil N dynamics under biochar addition. The results show that biochar addition significantly enhanced crop productivity by 12.8% and plant N uptake (PNU) by 22.6%, and there was a strongly positive relationship between crop productivity and PNU. Biochar addition also significantly increased the contents of soil total N (TN), inorganic N (IN), microbial biomass N (MBN), and biological N2 fixation (BNF) by 3.34–18.7%, but reduced nitrous oxide (N2O) emission by 15.9%. Further analysis with the aggregated boosted tree model indicated that the TN and BNF played the most important roles in biochar-induced change in crop productivity. However, while crop productivity was positively correlated with TN under biochar addition, it showed a negative correlation with BNF. These findings suggest that biochar addition could enhance crop growth and productivity through increasing the soil N resource and N uptake, but this was not true for some N2-fixing crops, probably because they were usually constrained by nutrients other than N.
Highlights
Increasing crop productivity in the agroecological system is conducive to (1) increase the utilization of carbon dioxide and mitigate global climate change [1], (2) to improve the biodiversity and functioning of ecosystems [2], and (3) to provide enough food for the global growing population [3]
FiF(gaiu)gruperlae2n.2t.M(Mcereaoanpns)saNanndudp99t5a5%k%e ccaoonnndffiidcdreeonnpcceepirinontdeteurrvcvatialvslisotyof ftihntehcleupdepriecnregcnetcnargotaepgcyehicaehlndgaen(Ysgi(ee%sld)()%o, f)cbrooifopcbhaioabrcohveaeffgrerceotfsufenocdnts on (a) plant N uptake and crop productivity including crop yield (Yield), crop aboveground biomass (CAB), and crop belowground biomass (CBB); the sample size of each variable is displayed over the corresponding bar. (b) Relationships between the response ratios of crop productivity vs. plant N uptake
There was no correlation between crop productivity and the response ratio (RR) of microbial biomass N (MBN), inorganic N (IN), NH4+-N, NO3−-N, N2O emission, NH3 volatilization, or N leaching under biochar addition (Figure 4 and Table 1)
Summary
Increasing crop productivity in the agroecological system is conducive to (1) increase the utilization of carbon dioxide and mitigate global climate change [1], (2) to improve the biodiversity and functioning of ecosystems [2], and (3) to provide enough food for the global growing population [3]. Improving N availability and use efficiency is thought to effectively enhance crop growth and productivity [5,6]. A better understanding of how soil N dynamics contribute to crop productivity has important implications for alleviating the global food crisis and climate change. Previous studies have indicated that biochar addition could improve N use efficiency and increased N uptake in crop by reducing soil N2O emissions and N leaching, enhancing crop productivity [11,12]. Some studies reported that biochar addition did not change crop N uptake and productivity, despite increasing soil total N content and greatly reducing soil N2O emissions and N leaching [13,14,15]. To the best of our knowledge, the linkage of crop productivity to soil N dynamics under biochar addition has not been well characterized on a global scale [20]
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