Saturday, September 25, 2010

Nitrate: kg in the soil

Up to now I have recorded the nitrate concentration in the water in the detectors (in mg/L or ppm). With a few assumptions, I can estimate the amount of nitrate in the soil in kg/ha, which is how we normally think of nutirent levels. Assuming the water content in the soil when the detector collects is 35%, and the collected sample is representative of the soil water as a whole, the mass of nitrate can be calculated.

The values in the graph are calculated over the top 50 cm of soil (I averaged the shallow and deep detectors), and are surprisingly high. It is probably a consequence of the relatively high organic matter levels. The decline in nitrate through the season is hopefully mostly plant, but there would be leaching losses as well.

No comments: