lulz. Manure causes way wider isotopic variaion than synthetic fertilizer (and always has). https://wwwrcamnl.wr.usgs.gov/isoig/period/n_iig.html https://wwwrca

lulz. Manure causes way wider isotopic variaion than synthetic fertilizer (and always has). https://wwwrcamnl.wr.usgs.gov/isoig/period/n_iig.html https://wwwrcamnl.wr.usgs.gov/isoig/period/n_iig.html “ Soil-derived nitrate and fertilizer nitrate usually have overlapping compositions, preventing their separation using 15N alone.”