Utilizing Zone-Tillage and Cover Crop Spatial Arrangements To Improve The Temporal and Spatial Availability Of Nitrogen In Organic Sweet Corn Production.

Increasing the synchrony between nitrogen (N) mineralization and crop N uptake is a major challenge in organic systems.  We propose a novel approach to improve N-synchrony by decreasing the time it takes for crop roots to access N pools through the targeted placement of organic N combined with zone-tillage.   Legume and cereal grass cover crops provide distinct services within a cropping system: legumes provide N, and cereal grasses provide a large quantity of carbon.  By segregating legumes and cereal grass cover crops into distinct zones (or strips), their functions can be targeted efficiently to maximize benefits to the crop.  Zone-tillage (ZT) confines soil disturbance to a narrow strip directly in line with future crop establishment, creating two distinct adjacent zones: tilled within the crop row (IR), and untilled between crop rows (BR).  Hairy vetch planted solely within the IR zone is incorporated to concentrate N directly in the crop rooting-zone.  Cereal rye planted in the BR may immobolize N where it is unlikely to be utilized by the crop.  

In 2012 and 2013, a field study was conducted at the Kellogg Biological Station in South-central Michigan to evaluate the effects of cover crop spatial arrangement (standard practice of mixed biculture, segregated strips, and a no cover crop control) and tillage (conventional vs. zone-till) on N availability and sweet corn yields.  Inorganic N availability was monitored both IR and BR throughout the growing season.  Insitu soil N mineralization was also measured within and between crop rows. 

In 2012, ZT combined with segregated rye and vetch strips resulted in a greater proportion of total inorganic N IR, compared to the mixed rye-vetch and full-width conventional tillage.   Within ZT, temporal patterns of N availability suggest that segregated rye-vetch strips improved the timing of N availability, however this benefit was not seen in conventional tillage.   Sweet corn yields were not affected by either cover crop spatial arrangement or tillage.  Future work will determine whether or not the concentration of legume derived-N within the crop rooting-zone increased N uptake efficiency and decreased N losses.