From the tropical regions of the Amazon to Africa, these areas are expected to play a greater role in food production as the world’s population continues to grow, and a winning strategy is to increase crop yield per acre while sparing the tropical forests.
There is a down-side to intensifying crop production, particularly in tropical regions. In a study that took a closer look at intensive farming in tropical climes, researchers found that it would require increasingly larger amounts of phosphorus fertilizer because it is often found in very low levels in tropical soils, and many of the soils bind the phosphorus, making it less available to the crops.
Phosphorus is the 11th most common element of Earth, but it has to be mined. It cannot be manufactured or destroyed and there are no synthetic substitutes for it. The element is essential to all life for the creation of DNA, cell membranes, and for bone and teeth formation in humans.
Phosphorus is one of three nutrients used in fertilizers, the other two being nitrogen and potassium. Phosphorus is found in a handful of countries around the world, with 72 percent of the reserves located in Morocco and Western Sahara. It could be likened to fossil fuels, except that it is essential to food production.
The study found that applying intensified farming (increasing the crop output per acre), on phosphorus-binding soils could end up resulting in the sequester or capture of from one to four metric tons of Phosphorus in those soils annually. In comparison, about two million metric tons are used in North America annually.
There is a reason for the big difference in phosphorus use. Europe and North America are in temperate zones and the soil doesn’t have low levels of phosphorus. But in the tropical regions, humans have to pay a “phosphorus tax.” This means that twice the amount of fertilizer is used to just get an average annual yield.
“In some parts of the tropics, for every ton of phosphorus harvested in food, you have to donate one ton to the soil,” said Eric Roy, a scientist at the University of Vermont who led the new study. “We call that the phosphorus tax.”
The study also found that if land-use scenarios of the Millennium Ecosystem Assessment were to come to pass, the phosphorus tax imposed on the tropical soils would more than double by 2050. “That’s similar to the amount of phosphorus fertilizer currently consumed in North America and Europe combined,” said Roy.
But the concerns raised by this study go a step further. We have to think about the future of agricultural intensification and whether or not it will be economical and sustainable over the long term. “There are very real economic and political considerations to building a global food supply based around a finite resource that is mostly found in a few countries and which we will be dependent on for decades because these soils are not going to saturate anytime soon,” said Brown University associate professor Stephen Porder, who worked with Roy.
Roy seems to think that the real problem is with food security, especially because it can become vulnerable to geopolitical dynamics with the price of phosphorus being right in the middle. But food security is certainly tied to more than just phosphorus-binding soils. We also need to address food waste, and the increasing use of pesticides.
This interesting study, “The phosphorus cost of agricultural intensification in the tropics,” was published in the journal Nature Plants on April 18, 2016.
