Excess phosphorus exists

In an analogy, it can be said that plants can "eat" more than they need. Scientists at the Agricultural Research Service (ARS) in West Lafayette, Indiana, argue in an article that, regarding phosphorus, corn plants will continue to absorb the nutrient 25% to 80% more than necessary to reach their full grain yield. The situation was called "luxury consumption", in literal translation. The work is by Chad J. Penn, James J. Camberato and Matthew A. Wiethorn.

The scientists showed in their study that the absorption of phosphorus (P) in corn occurred in three phases with two stages of "luxury consumption"; (i) increased absorption with an increase in grain production and total biomass until reaching maximum grain production, (ii) greater P absorption with an increase in total biomass, but with a decrease in grain production; and (iii) absorption with little or no increase in total biomass and a continuous drop in grain yield.

Thus, the two stages of "luxury consumption" of P were defined by them as continuous absorption with a decrease in grain production, followed by absorption with little or no increase in total biomass and a continuous decrease in grain production. From this, they say, the optimal P content to achieve maximum grain yield (Pgy) and biomass (Pbm) can be defined at approximately 580 and 730 mg P plant-1, or 1,23 and 1,35 g kg-1, respectively.

Scientists add that excess P absorption probably produces a plateau in grain yield, which presents a great inefficiency in relation to the use and savings of phosphate fertilizers. Ultimately, this excess P is used to build greater biomass without any grain yield benefit.

One implication of this two-step luxury consumption is that, depending on the intended use, plant P uptake (and therefore soil P levels) vary.

Simply put, they say, more P will be needed if the goal is to produce maximum biomass, such as for biofuel, silage production or carbon sequestration, compared to maximizing grain production. On the other hand, if the end user does not benefit from the additional P content that is achieved with increased P uptake, then it would be more economical for the producer to employ lower P fertility simply to achieve Pgy.

Finally, they point out that of great interest is the significant decrease in grain yield with excessive absorption of P in addition to Pgy. This was probably due to interactions between P and other nutrients.

The full article can be read here: how much phosphorus uptake is required to achieve maximum maize grain yield?