Estimating Nitrogen Availability of Heat-Dried Biosolids

Table 3

Biosolids and urea N fertilizer application amounts and timing for the ten treatments.

				Annual application rate (kg ha^−1 total N)
Year	N source	Application timing	Application dates	Soundgro	Milorg	Sumner	Zero N Control	Low Urea	Med Urea	High Urea
Trial A
Application Yr 2007	Biosolids	Single (1X)	16 Apr	630	592	907
	Biosolids	Split (0.5×2 appl)	16 Apr, 14 Jun	630	592	907
	Urea	Split (0.25×4 appl)	17 Apr to 20 Jul				0	90	180	270
Residual Yr 2008	Biosolids	Split (0.2×5 appl)	5 Mar to 8 Aug	168 U*	168 U	168 U
	Biosolids	Split (0.2×5 appl)	5 Mar to 8 Aug	168 U	168 U	168 U
	Urea	Split (0.2×5 appl)	5 Mar to 8 Aug				0	112	224	336
Trial B
Application Yr 2008	Biosolids	Single (1X)	25 Apr	441	414	635
	Biosolids	Split; (0.5×2 appl)	25 Apr, 3 Jul	441	414	635
	Urea	Split (0.2×5 appl)	25 Apr to 12 Sep				0	112	224	336
Residual Yr 2009	Biosolids	Split (0.2×5 appl)	4 Mar to 22 Jul	168 U	168 U	168 U
	Biosolids	Split (0.2×5 appl)	4 Mar to 22 Jul	168 U	168 U	168 U
	Urea	Split; (0.2×5 appl)	4 Mar to 22 Jul				0	112	224	336

168 U: In residual yr, 168 kg N ha⁻¹ of urea-N applied to all biosolids treatments, following same urea application schedule as urea the treatment plots.