Tham khảo Độ_phì_đất

  1. ↑ Bodenfruchtbarkeit, Retrieved on 2015-11-09.
  2. ↑ “Soil Fertility”. www.fao.org. Truy cập ngày 18 tháng 6 năm 2016.
  3. ↑ Brady N., Weil R. 2002 Nitrogen and sulfur economy of soils. pp. 543-571 in Helba (ed.), The Nature and properties of soils. Pearson Education, NJ.
  4. ↑ Sims, G. K., and M. M. Wander. 2002. Proteolytic activity under nitrogen or sulfur limitation. Appl. Soil Ecol. 568:1-5.
  5. ↑ Sims, G.K. 2006. Nitrogen Starvation Promotes Biodegradation of N-Heterocyclic Compounds in Soil. Soil Biology & Biochemistry 38:2478-2480.
  6. ↑ Bjonnes, R., 1997, Food vs Feed, People's News Agency; Frederiksberg C, Denmark
  7. ↑ Kötke, William H. (1993). The Final Empire: The Collapse of Civilization and the Seed of the Future. Arrow Point Press. ISBN 0963378457.
  8. ↑ Scherr, Sara (1996). “Land degradation in the developing world: Implications for food, agriculture, and the environment to 2020” (PDF): 7–8. Chú thích journal cần |journal= (trợ giúp)
  9. ↑ Smaling, Eric (1997). “Soil Fertility in Africa is at Stake”. Replenishing soil fertility in Africa replenishingsoi: 49.
  10. ↑ Cronon, William, Changes in the Land: Indians, Colonists, and the Ecology of New England, NY: Hill & Wang, 1983, p. 145-152.
  11. ↑ “Economic Manuscripts: Capital Vol. I — Chapter Fifteen”. Truy cập 20 tháng 12 năm 2018.
  12. ↑ Managing Soil Tilth; Colorado state university garden notes, Retrieved on 2014-10-04.
  13. ↑ Managing irrigation water quality, Oregon State University, USA, Retrieved on 2012-10-04.