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SSSA President's Message

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at the same time pushing huge quantities of

Jan Hopmans ffi:Tfi",f::Tj:l::Tffil1.,:"ii;"T:SSSA Presrdenr peak soil, that is, the world is ipproachingjwhopmans@ucdavis.edu its maximum land surface area available forTwitter: @janwhopmans agricultural production in the future.

Staggering is the amount of water re_

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Tn .y column in the Februa ry CSA

f Ncrus magazine,r I suggested thatIthe soil science community shouldrespond to this challenging timebecause of the broad societal interestin issues that strongly relate to soilscience, such as a changing climate,availability of fresh drinking water,environmental footprint of humans, and the future need forsafe and healthy food. This month, I would like to hieh_light the food security topic, and make the case that iilscience research will be crucial in meeting our future fooddemands. I do this, realizing that so much attention is paidto constraints of water and effects of a changing ctimatlon crop production, as well as to its environmental foot_print. Rightly so, yet the general discussion and literatureis largely absent of the enormous relevance of soils andthe biophysical limitations that soil may present towardsachieving the higher crop yields that are called for.

Let me start with reviewing the context of the needto feed two billion -o.e peopi" in the coming 40 years.First and foremost, essential inputs to crop pioduction areprovided by land, energy, water, and nutrients. With theexception of solar energy driving photosynthesis, their com_bined availability is determined by soil physical, chemical,and biological processes, as well as by eflective soil man_agement practices that minimize land degradation (such asby erosion or salinization) and protect thJ natural envi_ronment. Much innovative soil research will be recuired.including collaborations with our colleagues in the crop andanimal sciences, as well as with hydrologists and ecologists,to crack the immensely complicated fooJ security code.

Peak SoilMuch of the agricultural land is converted to urban and

industrial use. According to the UN, over the past 40 years,about 2 billion ha of soil, making up 30% of thl world,scropland, has been degraded and is now unproductive. Arecent USDA report states that between I9B2 and200Z, closeto 10 million ha of U.S. agriculturai land has been convertedfor development. In other parts of the world, produc_tive soiis are available, however, at the expense of naturalgrasslands, savannas, and forests. Opening these soils foragriculture is likeiy to have huge ecological impacts, while

quired for producing food. Though largely depending onthe relative proportion of animal and plant o.i,"rr-, .or-,_sumption, a typical daily diet requires about 1 L of waterfor each kilocalorie of food intake, corresponding to a totalof 2,000 L (near 600 gal) of water for a 2,0b0 kcal daily diet.In rainfed agriculture, most of that water is ,,green

water,,,coming from soil water storage by rainfall. However, inmany of the world's hydro-climatic regions, there is just notenough rainfall, and additional irrigation water is requiredfrom either pumping groundwater

-or reservoir storase. As

a result, about 15% of the world,s agriculture is irrigited,producing nearly 45% of the global food production, butusing about 70% of this developed ,,biue water,', globally.Therefore, much emphasis recently has been on availabiiityof blue water, either regionally or globally. However, withiew exceptions, there isn't much more water to develop. Inmany irrigated regions of the world,s river basins, streamflows have been decimated, beyond to what would beenvironmentally acceptable. To make matters worse, recentstudies confirm the yietd-reducing effects of increasingtemperatures by climatic change and the need to

"rpurldirrigated crop area to maintain crop productivity leveis.

April2014

Agricultural lntensificationConsidering all of the above, the most likely solution is

found in agricultural intensification, meaning that increas-

ing global food production can only happen by way ofproducing more food per unit land and per unit of avail-

able water. Agricultural soils will have to become moreproductive, and soil management practices will have to be

developed that are both more efficient and effective andreduce nutrient and water losses. Much can be said aboutthe need to increase crop nutrient use efficiency (i.e., nitrateand phosphorus), so as to reduce groundwater and surface

water contamination, as well to largely reduce the energyfootprints of production agriculture. But there is also a need

for more efficient use of soil-stored water (both green and

blue water) by minimizing soil evaporation in low-produc-tive agricultural systems. Some 80% of the worid's croP wa-

ter use comes from the green water that is stored in soils byrainfall. Therefore, huge investments in soil and agronomicresearch must be anticipated, to realistically achieve the

global goal of the projected doubling of required agricul-tural production. Without question, this involves advancingthe biotechnology field-seeking crop phenotypes that are

more drought, salt, or heat tolerant-but it will also need an

integrated approach that considers soil science holistically.

In summary, there is no silver bullet that will ensure thatfuture generations will be free from poverty and hunger. It

Connect with Jan Hopmansl"#?wset @janwhopmans

is iikely that some parts of the world will need to developfreshwater resources, especially in sub-Saharan Africa,and that other parts of the world wili expand their landarea into agricuitural production. However, much of the

required increased food production in regions with con-

straints in land and water resources will have to come fromagricultural intensification, requiring more efficient use ofnutrient and water inputs on avaiiable land' This will nothappen by business-as-usual agronomic practices but willrequire innovative soil research, coupled with technoiogies

in plant science and engineering.

Various sessions of the 2014 AAAS 2014 meeting inChicago presented the enormity of the global challenges inagriculture, but few addressed the limitations of soils. I ask

that you advocate for the importance of soils and soils re-

search using similar arguments as I presented above, when-ever the opportunity presents itself (e'g., when arguing forsoil faculty expertise at your home institution, collaboratingwith an interdisciplinary research team, or speaking aboutthe relevance of science and soil science in policymaking).

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