好文精选66篇之35——磷危机与土壤
发表时间：2020-10-15 09:27:18
Farmers are facing a phosphorus crisis. The solution starts with soil.
Overuse of fertilizer has led to phosphorus shortages and water pollution. But farms might not need so much to grow healthy crops.
7 MINUTE READBY JULIA ROSEN
ON AN OVERCAST day, Roger Sylvester-Bradley walks along a hawthorn hedge, collecting a thick rind of mud on his leather boots, before stepping into a gently sloping field of barley.
He stoops to pluck an ankle-high seedling from the ground and examines its healthy mop of fine white roots. Turning them in his hands, he says, “when you see a plant that’s deficient in phosphorus, it doesn’t look like this.”
That’s something of a surprise to Sylvester-Bradley, a crop scientist at ADAS, an agricultural consulting company in Cambridge, England. Phosphorus occurs naturally in soil and is a critical nutrient for plant growth. For centuries, farmers have added extra to their fields to boost harvests, but Sylvester-Bradley and his colleagues are studying ways to produce food using less of it.
The reasons are twofold: First, phosphorus runoff from farms contributes to widespread water pollution. Second, we don’t have phosphorus to waste.
Nearly all of the phosphorus that farmers use today—and that we consume in the food we eat—is mined from a few sources of phosphate rock, mainly in the United States, China, and Morocco. By some estimates, those could run out in as little as 50 to 100 years. Geologists know of other deposits, but they are harder to access and contain less phosphorus. Thus, the price will likely rise, making it harder for growers to afford fertilizer and for people to afford food.
Here and at other experimental sites in England, Sylvester-Bradley and his colleagues have taken a first commonsense step toward addressing the problem: They stopped adding phosphorus fertilizer to half the barley field to see how the plants would fare. Eight years later, they have only just started to observe the first effects on crop size and yield. The plants have survived on the excess nutrients in the soil—so-called legacy phosphorus—which some say represents a key piece of the phosphorus puzzle.
Researchers have calculated that, in countries like the United Kingdom and the United States, there is already billions of dollars’ worth of fertilizer in the ground that could help offset demand for mined phosphorus. Using it up would also curb phosphorus runoff.
