Interactive Effects of Cover Crops and Topography On Soil Nitrate Levels.

The ability to keep nitrate at an optimum level for crop production is an important ecosystem service provided by soil. Nitrate is the primary absorbable source of N for most plants and its concentration should be high enough to support plant growth. On the other hand, the excess amount of nitrate can be leached into underground water or transformed into greenhouse gases. Therefore, synchronizing nitrate supply with crop demand to minimize excess supply is key to minimizing losses to the environment. The objective of this study is to assess how cover cropping affects soil nitrate levels across topography. The study was carried out in ten fields of Long Term Ecological Research site at Kellogg Biological Station, MI. Three agricultural management practices compared were: management with conventional nitrogen inputs, management with cover crops + low nitrogen fertilizer inputs and certified organic management with cover crops. Microbplots with and without cover crops were established in topographical positions of depression, slope and summit. Soil samples were collected bi-weekly/monthly during the growing seasons of 2011 and 2012 form microplots. The preliminary results indicated that topographical effects were equally strong in all three studied managements. The incorporation of cover crops into soil increased the levels of nitrate within soil throughout the growing season.