Application of biochar-coated urea controlled loss of fertilizer nitrogen and increased nitrogen use efficiency

Chemical and Biological Technologies in Agriculture

Table 4 Concentration of nitrogen (mg/kg) and pH in different fertilized soils collected after harvesting oil rapeseed

Treatments	pH	NH₄⁺–N (mg/kg)	NO₃⁻–N (mg/kg)	Total nitrogen (mg/kg)
CK	6.17 ± 0.20ab	7.34 ± 1.07e	22.09 ± 0.848c	254.06 ± 9.38d
U1	5.95 ± 0.10bc	14.42 ± 1.75bcd	58.99 ± 3.22a	294.42 ± 16.81d
U2	5.89 ± 0.04c	11.72 ± 1.57d	40.46 ± 4.15b	277.01 ± 26.99d
U1 + B	6.19 ± 0.13ab	17.45 ± 3.47ab	62.29 ± 4.13a	485.61 ± 72.93a
U2 + B	6.18 ± 0.15ab	12.48 ± 2.11 cd	44.12 ± 7.11b	384.18 ± 77.35bc
BCU1	6.10 ± 0.10abc	15.68 ± 2.41abc	63.41 ± 3.44a	321.87 ± 16.76c
BCU2	6.03 ± 0.15abc	12.59 ± 1.61 cd	45.19 ± 2.37b	280.20 ± 25.85d
BCU1 + B	6.27 ± 0.02a	18.99 ± 1.03a	64.79 ± 8.11a	441.68 ± 26.83ab

CK, no fertilizer; U1, urea at 100% N rate; U2, urea at 80% N rate; U1 + B, biochar combined with urea at 100% N rate; U2 + B, biochar combined with urea at 80% N rate; BCU1, biochar-coated urea at 100% N rate; BCU2, biochar-coated urea at 80% N rate; BCU1 + B, biochar combined with biochar-coated urea at 100% N rate
Different letters in the same column indicate a significant difference at the 5% level according to the LSD test