Timely Topics: Fantasy Fertility - Not Sustainable

Contributed by Dr. Clifford S. Snyder, Director, IPNI Nitrogen Program

Higher crop yields place increased nutrient-supplying pressures on the soil. It is well known that crop roots absorb nutrients from the soil solution through root interception (as roots explore new soil volumes), mass flow (as water moves through soil pores), and diffusion (as nutrients move in the soil solution from a zone of higher concentration to alower concentration) processes. 

Soils with higher fertility levels are better able to supply plant nutrients during times of environmental stress and also during peak crop uptake demands. Wise, economic additions of fertilizer and/or manure help replace the available nutrients removed from the soil by crop harvests, erosion, leaching, and other losses. Neglecting such nutrient replenishment leads to declines in:

1) soil fertility, 2) crop productivity, 3) cropping system resilience, and 4) indices of soil health; which threaten sustainability.

Soil testing is a very important tool in assessing current levels of soil fertility, and in monitoring changes over time; an essential sustainability practice. However, soil testing is not a perfect tool …. and experienced agronomists know that they should also use complementary plant tissue analyses, as well as estimates of crop harvest nutrient removal, to assess and manage optimum plant nutrition in each field and sub-field area.

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