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Improving Fertilizer N Use By Corn

Jeff Wessel Jeff Wessel
Research Assistant
Department of Crop Sciences
(217) 244-1287; wessel@illinois.edu
Fred Below
  Fred Below
Associate Professor
Department of Crop Sciences
(217) 333-9745; f-below@illinois.edu

While nitrogen fertilizer is a crucial input for optimizing corn productivity, its use is being scrutinized increasingly as a contributing factor to decreases in water quality. Thus, growers are faced with the challenge of finding ways to increase yield and profitability while using nitrogen fertilizer in an environmentally acceptable manner. Because the cultural practices employed can have a large impact on crop productivity and nitrogen use, we have focused our recent research on identifying how different cultural practices influence N use by the corn crop.

Decisions governing the use of cultural practices such as tillage systems and rootworm larval control depend largely on the perceived impact they have on yield, profitability and, in some instances, soil erosion and lodging. Often when selecting a particular cultural practice, growers pay little attention to the potential effects on corn N requirements. In our research in this area, we sought to determine the influence of two cultural practices (tillage and corn rootworm larval control) on corn N requirements.

Three tillage systems: mulch (1), zero (2), and strip (3).

Figure 1. Three tillage systems: mulch (1), zero (2), and strip (3).

We varied the rate of N fertilizer additions (using six rates ranging from 0 to 200 lbs N per acre) made to fields receiving three different tillage practices (zero, strip, or mulch till) and to fields receiving either treatment or nontreatment for corn rootworm larvae. We selected tillage systems because of the accompanying changes in temperature and moisture status, as well as the perception that soil organic matter or its distribution are altered. We chose rootworm larval control because damage from these pests affects the N-absorbing organ of the plant. To date, the tillage study has been conducted at five environments and the rootworm study at three environments.

When N fertilizer was applied at rates commonly used for corn production in Illinois (120 to 200 lbs N per acre), there was no difference in grain yield among the three tillage systems. However, when the N supply was limiting (0 to 80 lbs N per acre), grain yield increased with increases in tillage (mulch > strip > zero), which we attributed to a tillage-induced enhancement in soil mineralization. Although variable according to location and the degree of root damage, there was a tendency for rootworm larval control to decrease the level of fertilizer N required to maximize grain yield.

rom left to right, an increasing degree of root injury from corn rootworm.

Figure 2. From left to right, an increasing degree of root injury from corn rootworm.

These initial results show that cultural practices do influence the fertilizer requirements of corn and suggest that, in some instances, N rates can be reduced as a function of rootworm control or tillage.

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