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Spatial Variability of In-Season Nitrogen Uptake by Corn Across a Variable Landscape as Affected by Management

^a Dep. of Soils and Plant Nutrition, Rubber Research Inst. of Sri Lanka, Dartonfield, Agalawatta, Sri Lanka
^b Dep. of Land Resource Science, Univ. of Guelph, Guelph, ON, N1G 2W1, Canada

View larger version (81K): [in a new window]   Fig. 1. Accumulation of rainfall and crop heat units during each month from May to October in the 1997, 1998, 1999, and 2001 growing seasons. The 13-yr average rainfall is from 1967 to 1980.

View larger version (29K): [in a new window]   Fig. 2. Variation in N uptake by corn at three contrasting landscape positions (averaged over management treatments in the 0N plots) during the 1997, 1998, 1999, and 2001 growing seasons. The vertical bars indicate the standard error.

View larger version (29K): [in a new window]   Fig. 3. Variation in N uptake by corn in the three management treatments: (i) barley followed by corn under no-tillage (Barley-NT), (ii) barley followed by corn under a spring plowing and secondary tillage operation (Barley-CT), (iii) barley under-seeded with red clover that was plowed down in the following spring and plots planted to corn (Barley + RC-CT) (averaged over landscape positions in the 0N plots) during the 1997, 1998, 1999, and 2001 growing seasons. The vertical bars indicate the standard error.

View larger version (47K): [in a new window]   Fig. 4. Variation in N uptake by corn as influenced by the fertilizer N application (averaged over landscape positions) in the three management treatments: (i) barley followed by corn under no-tillage (Barley-NT), (ii) barley followed by corn under a spring plowing and secondary tillage operation (Barley-CT), (iii) barley under-seeded with red clover that was plowed down in the following spring and plots planted to corn (Barley + RC-CT) during the 1999 and 2001 growing seasons. The vertical bars indicate the standard error.

View larger version (35K): [in a new window]   Fig. 5. Relation between the aerial dry matter (DM) accumulation and N concentration in DM (Ni) in 0N and +N treatments in the 1997, 1998, 1999, and 2001 growing seasons with respect to the critical N concentration developed by Plenet and Lemaire (1999).

View larger version (32K): [in a new window]   Fig. 6. Effect of management treatments: (i) barley followed by corn under no-tillage (Barley-NT), (ii) barley followed by corn under a spring plowing and secondary tillage operation (Barley-CT), (iii) barley under-seeded with red clover that was plowed down in the following spring and plots planted to corn (Barley + RC-CT) on the ratio between Ni and Nc concentration in the aerial dry matter at three growth stages and its variation with organic C content. The solid horizontal line indicates the minimum N concentration in the aerial dry matter for the maximum growth (i.e., Nc). Other lines were generated using the regression models given in Table 5.