Relative Location of Strips Influences Sweet Corn Yields, Potentially Leachable Nitrate, and Trace Gas Flux Under Strip Tillage.

Strip tillage (ST) is a form of conservation tillage in which strips are tilled only where the crop will be planted; the rest of the soil remains undisturbed.  When continuous ST is used, the relative location of strips from one year to the next may entail pest, crop, and soil management tradeoffs.  A field experiment was conducted to examine the impacts of strip placement on sweet corn (‘Luscious’) yield, potentially leachable nitrate (NO₃^-), and flux of nitrous oxide (N₂O) and carbon dioxide (CO₂).  Three treatments were examined in a field that had been in ST cabbage the previous year: 1) conventional (full-width) tillage (CT); 2) ST with the strips located in the same position as the previous year (STsame); and 3) ST with the strips offset from their previous year’s position (STdiff).  N fertilizer applications were banded 15 cm deep in rows (IR) in ST treatments, and surface broadcast and incorporated in CT treatment.  Deep soil cores (1 m) were collected in September 2011 and April 2012, cut into 20 cm sections, and analyzed for NO₃^-.  Trace gas flux was measured approximately weekly using a static chamber method; chambers were located IR and between crop rows (BR).  Sweet corn yield was highest in the STdiff treatment and was lowest following CT; yield in STsame was intermediate.  Soil NO₃^- was similar at all depths in all treatments in September 2011, but more soil NO₃^- was found at the 80-100 cm depth in the CT treatment in April 2012.  This suggests that greater amounts of NO₃^- may be lost to leaching in CT compared to ST, though residual NO₃^-  was low in all treatments.  N₂O flux was greater IR than BR in all treatments.  CO₂ flux in both BR and IR was similar in all treatments.  Results from these experiments demonstrate that yields can be maintained or improved with ST and that the N losses to the environment may be lessened by adopting ST with deep N banding.