COOPERATIVE EXTENSION SERVICE, PURDUE UNIVERSITY, WEST LAFAYETTE, INDIANA
(Fertilization) AY-256
Managing Nitrogen Fertilizers for Maximum Efficiency in Reduced Tillage Systems
David B. Mengel,
Department of Agronomy, Purdue University

Soil erosion is a major problem facing farmers in many areas of the U.S. today. One practice which has demonstrated marked success at controlling erosion is conservation tillage. Reducing tillage and leaving a protective cover of crop residue does reduce erosion. However, in many situations, the practice can also lead to reduced uptake efficiency of nitrogen fertilizers. The objectives of this publication are 1) to describe some of the features of conservation tillage that can influence N use efficiency, 2) to explain the results of some recent research in the area, and 3) to outline alternatives for developing effective and efficient N fertilization programs for corn under different tillage systems.
NITROGEN EFFICIENCY UNDER CONSERVATION TILLAGE
In general, conservation tillage involves less mixing of the soil than conventional tillage systems and leaves more crop residues on the surface to serve as a protective mulch. However, the degree of mixing and residue incorporation varies greatly with the system used. Researchers in Indiana measured the percent of the soil surface covered by residue immediately after planting under a number of tillage systems. Their results (Figure 1) show residue cover ranging from less than 1 percent for moldboard plowing to over 90 percent for no-till. Chisel plowing, while considered a conservation tillage system, only left from 6 to 29 percent of the surface residue covered, depending on the type of residue being tilled (cornstalks, bean stubble, etc.) and the type of chisel being used.
100
80 ►
% of Residue Cover
Moldboard Ridge Spring Chisel No-till Plow	Disk
Tillage
Figure 1. Tillage System Used and Percentage of Residue Cover After Planting.