High Nitrogen Fertilization of Tobacco Crop in Headwater Watershed Contaminates Subsurface and Well Waters with Nitrate

Table 4

Orthogonal contrasts for nitrate concentrations in soil solutions between different positions in landscape, between collection times, and between land uses.

Contrast	Depth (m)
	0.2	0.5
Positions in the landscape
1 × 2	ns	ns
1 × 3	ns	ns
1 × 4	*	**
Land use
Tobacco × grassland	ns	*
Tobacco × forest	ns	ns
Collection periods
1 × 2	*	*
1 × 3	*	*
1 × 4	*	*
1 × 5	*	*
1 × 6	*	*
1 × 7	*	*

5% significant; 1% significant; ns: nonsignificant. Collection periods: 1 = November 10, 2005 (60 days after transplanting (DAT)); 2 = November 28, 2005 (78 DAT); 3 = December 09, 2005 (89 DAT); 4 = January 06, 2006 (117 DAT); 5 = January 20, 2006 (131 DAT); 6 = January 27, 2006 (138 DAT); and 7 = February 10, 2006 (145 DAT). Position in the landscape: 1: upper slope, 2: mid slope, 3: lower slope, and 4: plateau.