Oct. 25, 2016
With a global population expected to reach 9 billion people by 2050, improved management of key essential nutrients such as phosphorus (P) will be necessary to boost crop yields and stay one step ahead of steeply rising food demand.
Phosphorus is present as phosphate in every cell of our bodies. It is a nutrient required by all living things for basic life-sustaining processes, such as energy storage. Global supplies of phosphate are finite, and most of the largest phosphate reserves are in areas of the world that are prone to political instability, such as Africa and the Middle East.
The phosphorus situation is also challenged by many agricultural soils with insufficient levels of plant-available P, and some soils with a high capacity to fix applied P in slowly available forms due to reactions with calcium, magnesium, aluminum or iron. Crops grown in these soils are not able to obtain sufficient P to meet their needs and cannot reach their full yield potential.
If an applied rate of P is less than optimum for a crop under existing conditions, and a practice such as fertilizer placement is changed that increases nutrient use efficiency, yield will usually increase, at least in the short term. However, in other cases, nutrient use efficiency can increase with no effect on yield if a rate exceeding optimum levels is reduced to optimum.
According to the International Plant Nutrition Institute (IPNI), its soil test summary and evaluation of phosphorus balance – the difference between P application and removal by the crop – does suggest that P is being under-applied in rather significant portions of the U.S. Corn Belt. In such cases where soil fertility levels are less than optimum, an increase in P application rates is called for, even though that rate increase will likely reduce nutrient use efficiency. In other cases, the summary shows P is being over applied and use reductions would be appropriate and would increase nutrient use efficiency without reducing yield.
The lowest soil test P levels in North America are generally found in the Great Plains, but many farmers there are responding to that and slowly building those levels up by increasing P use relative to crop-removal rates.
In contrast, states in the central and eastern Corn Belt generally have higher soil test P levels today than in the Great Plains, but soil levels are either stable or slowly declining due to application of less P than what is being removed by crops. Farmers there have been to a degree living off P that was built up in their soils from past fertilization. In some cases in the same region, P levels were higher than the optimum range, and they are now moving down into the optimum range, which is good for both economic and water quality reasons.
“The key to producing higher yields and feeding the growing world population is not simply applying more fertilizer, as one might think,” said Kenneth Avery, chief executive officer at Verdesian Life Sciences. “Rather, it is finding sustainable solutions for nutrients such as phosphorus to be used more efficiently and effectively to produce more food.”
“Increased plant uptake of P translates into less of that nutrient being left in the soil, where it is subject to off-site movement into waterways,” Avery said. “It also allows farmers to be good stewards of the land and help minimize the environmental footprint left by P applications.”
Like many other agricultural industry leaders, Verdesian is a 4Rs Nutrient Stewardship Partner. The four tenets of this program recommend applying nutrients from the right source, at the right time, at the right place and rate. “The 4Rs Nutrient Stewardship Program provides a science-based framework for building sustainable systems,” Avery said.
Unlike nitrogen, which is subject to a great amount of movement within the soil, air and water, phosphorus mostly doesn’t go anywhere once applied. Phosphorus placed in direct contact with the soil is quite immobile. The biggest quantity of phosphorus loss is usually by soil erosion. If phosphorus sources like fertilizer or manure are left on the soil surface without enough time for retention or if the soil surface is over-enriched in phosphorus, the soluble P lost in run-off can contribute significantly to water quality problems.