Aerial Nitrogen Fluxes and Soil Nitrate in response to Fall-Applied Manure and Fertilizer Applications in Eastern South Dakota

Table 3

Summary of statistical tests and model factors.

Descriptor	Total soil nitrate in the top 0–60 cm of soil	Surface soil nitrate in the top 0–15 cm of soil	Olsen-P	Soil OM	Soil pH	Soil EC	Soil K	Corn leaf nitrogen concentration	Total N	Total C	Ammonium	Corn yield	Corn grain nitrogen concentration	Nitrous oxide	Ammonia flux	Soil water nitrate concentration
Fixed effects	Trt, Y, GS							Trt, Y, GS	Trt, GS			Trt		Trt, Y
Random effects	Block							Block	Block			Block		Date, block
Distribution type	Log	Log	Log	Nor	Nor	Log	Log	Nor	Log	Exp	Log	Nor	Nor	Log	Log	Nor
Covariance structure	UN	AR(1)	VC	VC	VC	CS	VC	AR(1)	AR(1)	AR(1)	AR(1)			VC	VC	AR(1)
Effects	Type III tests of fixed effects P value
Trt	0.0009	<0.0001	0.001	0.058	0.241	0.002	0.0002	0.0802	0.28	0.999	0.232	0.58	0.098	0.0106	0.0185	0.1989
Y	0.0331	0.4575	0.132	0.809	0.793	0.002	0.168	<0.0001						0.3204	0.4245	0.0305
GS	<0.0001	<0.0001	0.017	0.004	0.032	<0.0001	0.0006	<0.0001	0.005	0.97	0.22
Trt  GS	0.1157	0.0001	0.082	0.309	<0.0001	<0.0001	0.012	0.5657	0.1	1	0.219
Trt  Y	0.4603	0.4136	0.771	0.411	0.95	0.455	0.985	0.8584						0.1712	0.1921	0.8708
Y  GS	0.0114	0.0018	0.109	0.679	0.062	<0.0001	<0.0001	0.0001
Trt  Y  GS	0.3077	0.2078	0.0005	0.214	0.243	0.118	0.0004	0.2351

All statistical tests were performed using PROC GLIMMIX and included interactions among fixed and random effects. Abbreviations for fixed effects: Trt = treatment; Y = year; GS = growth stage. Abbreviations for distribution type: Log = lognormal; Nor = normal or Gaussian; Exp = exponential. Abbreviations for covariance structure: UN = unstructured; AR(1) = first-order autoregression; VC = variance components.