Comments on 'Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen: A Global Dilemma for Sustainable Cereal Production,' by R.L. Mulvaney, S.A. Khan, and T.R. Ellsworth in the Journal of Environmental Quality 2009 38:2295-2314/Reply to Comments on 'Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen: A Global Dilemma for Sustainable Cereal Production,' by R.L. Mulvaney, S.A. Khan, and T.R. Ellsworth in the Journal of Environmental Quality 2009 38: 2295-2314

摘要

(2009) compare soil N concentration in selected treatments of the Morrow Plots measured in 1955 and 2005, for three soil depths (0-15, 15-30, and 30-46 cm) and three crop rotations: continuous corn, corn-oats (oats replaced by soybean since 1967), andcorn-oats-alfalfa hay. In the HNPK treatment, it was 336 kg hasup -1 (1967-1997), reduced to 224 kg hasup -1 from 1998. [...] for the last 8 yr of the study period, the rates of N applied in HNPK and NPK were the same. [...] the observation that soil Nand C declines in the HNPK treatment were greater than in the unamended and NPK treatments is entirely understandable on the basis of the cessation of manure applications.