Table 3.

Correlation efficient (r) between biochar application rates and paddy NH₃ volatilization after three fertilizer application (BF, TF and PF, respectively).

	n	PAV-BF	PAV-TF	PAV-PF	PAV-Total
Total	n = 27	0.37	− 0.05	0.34	0.29
PC	n = 15	0.42	− 0.20	0.10	0.16
HC	n = 15	0.45	0.14	0.61*	0.52*
WPC	n = 9	− 0.21	− 0.27	0.06	− 0.26
WHC	n = 9	0.88**	0.16	0.44	0.80*
SPC	n = 9	0.76*	− 0.10	0.33	0.52
SHC	n = 9	0.37	0.03	0.92**	0.51

n represents number of observations for correlation analysis; * and ** represent P < 0.05 and 0.01, respectively; WPC, SPC, WHC and SHC represent pyrochar (PC) and hydrochar (HC) prepared with wheat straw and sawdust, respectively.