Composting, Tillage, and Rotation Effects On Micronutrients and Soil Carbon.

Intensively cultivated high pH soils in Southeast Idaho have suppressed yield potentials that may be improved by applying compost, reducing tillage, and a longer rotation.  Application of compost may improve yield potential by increasing micronutrient fertility and soil organic matter (SOM).  The objective of this study is to determine the effects of crop rotation, tillage, and composting on SOM and micronutrients (boron, iron, zinc, manganese, and copper).  The rotation treatments were a four year wheat, wheat, alfalfa, and potatoes rotation and a two year wheat and potato (control).  Tillage and compost treatments were conventional tillage, composted with tillage, minimum tillage (tillage only before and after potatoes), and a control (two year rotation with intensive cultivation).  Compost source was steer feedlot manure and was fall applied at the rate of 11.2 Mg ha^-1.  Research plots were located on a Blackfoot silt loam and a Pocatello variant silt loam near Rexburg, Idaho.  Soil samples were taken in the spring and after harvest and compared to native soils from the original year which included undisturbed soils from the same soil type as the research plots.  Native soils had 15 - 27 g kg^-1 more SOM than the plot average which is a result of 75+ years of cultivation of the plot area.  Total C showed no difference between years or treatments, but mineralization rates of compost were influenced by soil temperature.  It may take more time for the minimum tillage and composting treatments to show difference as suggested by previous research.  Micronutrient analyses are currently being conducted and results are not yet available.  It is hypothesized that composting will increase micronutrient levels in the soil.