*3.4. Total Soil N*

The ANOVA at Efaw, did not show any significant difference (*p* = 0.3316) in TSN between treatments in 2018 (Table 5). Total soil N was 14% lower under NBC than observed under FN at 50 kg N ha<sup>−</sup>1. At 100 and 150 kg N ha−1, TSN was higher under NBC than FN by 6 and 5%, respectively. In 2019, similar observations were made where no significant difference (*p* = 0.6854) in TSN among treatments (Table 5). At 50 kg N ha−1, TSN was higher under NBC than FN by 10%.

**Table 5.** Mean total soil N for treatments plus the associated contrasts between N fertilizer and biochar-N combinations at Efaw and Lake Carl Blackwell, Stillwater, Oklahoma. 2018 and 2019.



**Table 5.** *Cont.*

C.V, coefficient of variation between treatments; S.E, standard error for replicated means (±SE, *n* = 3). Nitrogen fertilizer was applied as urea ammonium nitrate—UAN (28:0:0). Biochar was applied immediately following UAN and incorporated to a depth of 15 cm.

At LCB, results for 2018 did not show any significant difference (*p* = 0.64) in TSN between treatments (Table 5). At each fertilizer rate, single degree of freedom contrast did not indicate significant difference in TSN between NBC and FN (*p* = 0.143). Total soil N averaged 0.76, 0.75, and 0.78 g kg−<sup>1</sup> for FN and 0.82, 0.82, and 0.82 g kg−<sup>1</sup> for NBC at 50, 100, and 150 kg ha<sup>−</sup>1, respectively. Similar observations were made in 2019 where ANOVA did not indicate significant difference (*p* = 0.2424) in TSN between treatments (Table 5). Total soil N averaged 0.77, 0.75, and 0.81 g kg−<sup>1</sup> for FN and 0.81, 0.84, and 0.78 g kg−<sup>1</sup> for NBC at 50, 100, and 150 kg ha<sup>−</sup>1, respectively.
