Biochar for Improved Nutrient Retention and Agronomic Yields: A Field Study.

Increased storage of nutrients, like nitrogen, in the soil can decrease fertilizer inputs and increase the overall sustainability and efficiency of agriculture around the globe.  A hardwood biochar was applied to field plots (RCBD, 5 replications) in order to study the effects on nitrate retention in the soil. For the first growing season, biochar was incorporated into unfertilized plots at the rates of 0, 2, 4, 6, and 8% (w/w), one week before sweet corn (Zea mays) was planted.  Soil samples were collected one week after time of planting and again after corn harvest and analyzed for nitrate by colorimetric determination using flow injection analysis. Corn stalks were also analyzed for nitrate content and ears were harvested for marketable yield and quality analysis. Biochar application showed no significant effects on sweet corn yield or quality. This suggests that initial biochar application does not negatively affect sweet corn yield. Preliminary analysis of soil samples, taken one week after planting, shows a significant inverse relationship between nitrate concentration and increasing amounts of biochar. However, this effect was temporary and harvest-time soil samples showed greater nitrate concentrations in biochar amended plots.  For the second growing season (Summer 2013), a split-plot design was used comparing N-fertilized and unfertilized biochar-amended plots planted with sweet corn.  Samples were taken from 0-20cm, and 20-40cm to investigate nitrate retention in the soil horizon. It is expected that biochar amended plots will continue to show greater nitrate retention from 0-20cm, in the fertilized treatments with reduction in nitrate concentration below 20cm. This biochar-induced retention can positively affect both nutrient availability and overall sustainability of sweet corn production.