Compaction and Nitrogen Placement Effect on Root Growth, Water Depletion, and Nitrogen Uptake

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Abstract
Zones of compaction and/or high nutrient concentration that exist with selected tillage systems can alter plant root growth. It is hypothesized that these alterations affect water and nutrient uptake patterns. A greenhouse experiment was conducted to study the effects of horizontally and vertically oriented compaction zones and nitrogen (N) fertilizer placement on corn (Zea mays L.) root growth patterns, soil water depletion, and N fertilizer uptake. Compaction treatments included a simulated plow pan, simulated wheel tracks in one or both interrows, and uncompacted soil. 15N‐enriched ammonium nitrate was point injected 0.1‐m deep at a rate of 80 kg N ha−1 either under the plant or in a simulated interrow region (0.13 m to the side of the plant); a check treatment (no N) was also included. Compaction and N treatments were factorially combined in five randomized blocks. Corn plants were grown for 26 d without rewatering. Measurements taken at 26 d included: shoot and root growth, plant 15N content, and soil water content, and distribution. Compaction treatments did not significantly affect total root growth, but N fertilization tended to decrease it. Root growth compensation, both enhancement in zones of favorable nutrient supply and redirection of growth to zones of more favorable physical conditions, was observed. Nitrogen placement had a greater impact on N uptake when compaction zones were present than when they were not present. Water extraction from a given zone was directly related to root density in that zone.
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