Features International Sugar Journal

Managing soil health to drive crop productivity*

There is no disputing that soil health has taken a battering over the years with the arrival of industrial agriculture. There is also no disputing that for human security, the stewardship of soils is of utmost importance as the challenge of expanding crop productivity from the same area of land to meet the food needs of the rising population remains. Since the industrial revolution, soil erosion has accelerated and currently, the ability of soil, “the living epidermis of the planet,”1 to support the growth of our food supply is plateauing. This is compounded by the threat from expanding population competing for land devoted to agriculture. In their review, Amundson et al1 note that “between1970 and 2000, an area greater than the size of Denmark was urbanized, and that in the next 20 years, 1.5 million km2 of land (the size of Mongolia) will be urbanized”.

With United Nations designating 2015 as the International Year of Soils to recognize the importance of soils in food security, the ecosystem and the sustained life of our planet, awareness in the sugar industry has not been as raucous as it should be. Though, it has to be said, that in their recently published overview2, the EU Beet Sugar Sustainability Partnership commences with the chapter on soil fertility.

Since the advent of agriculture approximately 10,000 years ago, humans have been disturbing the soil. Undisturbed soils, unencumbered by the throes of human intervention retain their quality “indefinitely over time—their thickness, C content, and nutrients, for example—a condition that is equitable to sustainability”. Whereas a key feature of cultivated soils is that they are seldom “able to maintain the qualities of their original conditions, and these changes greatly affect their productivity1(figure 1). Soil scientists have certainly been actively addressing the challenge of maintaining soil productivity through farm practices that regenerate soil health. There is no one silver bullet. Combination of rotation, reduced tillage, increase in soil organic matter content via cover crops, supporting the formation of soil aggregates, maintaining soil biodiversity (that comprises earthworms, insects and molluscs, microfauna, microflora, actinomycetes, bacteria and algae), increase in both water capacity and infiltration, while at the same time decreasing erosion by wind and water certainly provides the armoury to address soil degradation.

Figure 1 Changes in the balance of important soil processes caused by human disturbance. (Human intervention in soil processes many times exceeds natural perturbations and thus exceeds the resiliency of soil to recover to its original condition.)

Measurable benefits from promoting and maintaining soil health, defined as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans” (Natural Resources Conservation Service, USDA) are many. These include increased crop yields, reduced energy, fertilizer, irrigation inputs, less nutrient and soil pollution of water bodies, reduced pesticide residue loss to air and water, and increased wildlife habitat. In the sugar beet sector in France, over the period 1977-2012, nitrogen fertilizer use dropped from 180 kg to 90 kg/ha, while sugar yield increased from 8 tonnes to some 14 t/ha2.

One remarkable observation made by Amundson et al is that the “key driving force” behind the expansion in agriculture has been the access to low-cost energy “which led to advanced agricultural machinery replacing human labor”, but equally important or more so, the availability of “NH4 fertilizer through the energy intensive Haber-Bosch process—constituting the first and most important green revolution.” Transformative effect on crop production by the use of N fertilizer has simply been phenomenal, which has kept pace with rising global population (figure 2). But as the authors suggest, it is only a matter of time before the supply of nitrogen and other macro-nutrients (in particular phosphate) availability is impacted by price and availability. Therefore, devising better ways to protect and recycle soil nutrients and making sure that they are used by crops efficiently rather than being washed away will remain a challenge.

Figure 2. The postWorld War II rise in nitrogen fertilizer use coincides with the spike in global human populations

Indeed, there is no other alternative but to act in haste and put into practice the sound principles of soil management. As one of the authors of the review1 Donald Sparks notes “Human civilizations have risen and fallen based on the state of their soils. Our future security really depends on our ability to take care of what’s beneath our feet.

 

*The comment was originally published in the December 2015 issue of ISJ.

References

1 Ronald Amundson, Asmeret Asefaw Berhe, Jan W. Hopmans, Carolyn Olson, A. Ester Sztein, Donald L. Sparks (2015) Soil and human security in the 21st century, Science, 348 (6235): 1261071-6

  1. EU Beet Sugar Sustainability Partnership (2015) Good practices (69pp)