Quantifying the Limitation to World Cereal Production Due To Soil Phosphorus Status

Abstract

Phosphorus (P) is an essential element for plant growth. Low P availability in soils is likely to limit crop yields in many parts of the world, but this effect has never been quantified at the global scale by process‐based models. Here we attempt to estimate P limitation in three major cereals worldwide for the year 2000 by combining information on soil P distribution in croplands and a generic crop model, while accounting for the nature of soil‐plant P transport. As a global average, the diffusion‐limited soil P supply meets the crop's P demand corresponding to the climatic yield potential, due to the legacy soil P in highly fertilized areas. However, when focusing on the spatial distribution of P supply versus demand, we found strong limitation in regions like North and South America, Africa, and Eastern Europe. Averaged over grid cells where P supply is lower than demand, the global yield gap due to soil P is estimated at 22, 55, and 26% in winter wheat, maize, and rice. Assuming that a fraction (20%) of the annual P applied in fertilizers is directly available to the plant, the global P yield gap lowers by only 5–10%, underlying the importance of the existing soil P supply in sustaining crop yields. The study offers a base for exploring P limitation in crops worldwide but with certain limitations remaining. These could be better accounted for by describing the agricultural P cycle with a fully coupled and mechanistic soil‐crop model.

Integrative Crop‐Soil‐Management Modeling to Assess Global Phosphorus Losses from Major Crop Cultivations

“…It implies that P may not be the major growth limiting factor in our simulations, but rather N (Kvakić et al, 2018;. In our simulations, the simulated optimal level of P inputs would not significantly increase crop yields in under-application regions, for example, in Africa.…”

“…In our simulations, the simulated optimal level of P inputs would not significantly increase crop yields in under-application regions, for example, in Africa. It implies that P may not be the major growth limiting factor in our simulations, but rather N (Kvakić et al, 2018;. However, it is still important to increase P inputs in the P limited regions to maintain soil fertility especially under a continuous cultivation (Ringeval et al, 2014;Zhang et al, 2017).…”

Low Phosphorus Availability Decreases Susceptibility of Tropical Primary Productivity to Droughts

“…We exchanged the original formulation of phosphorus sorption, which assumes a fixed fraction of labile phosphorus being dissolved in soil solution (Goll et al, ) with a more realistic Freundlich Isotherm, which is parameterized based on a compilation of isotopic dilution data ( n = 379; Achat et al, ; Kvakić et al, ). Three different soil classes are distinguished in respect to sorption dynamics, namely, Oxisols, Molisols, and “others.” Details are given in supporting information Text S1.…”

Balancing the Global Distribution of Phosphorus With a View Toward Sustainability and Equity

“…This article is a companion to Kvakić et al (2018) the central Pacific such as Banaba Island and Nauru have been completely exploited for decades now, although there is some discussion of remining the spoil piles given the high phosphate costs. Many of the more P-rich horizons from standard phosphate rocks have also been depleted, resulting in average P content of mined phosphate ore to decline from 15% P in 1970 to less than 13% P by 1996 (Smil, 2000).…”

“…It is the ultimate speed limit to our global food systems (Cordell et al, 2009) and hence our global societal structure. A paper published here by Kvakić et al (2018) provides for the first time a roadmap toward understanding the global distribution of P fertilizer application plus a crop-specific uptake model tied to climate. This work follows closely on previous work by some of these authors on P model development (Ringeval et al, 2017) and a backdrop of global fertilizer P distribution studies (e.g., Bennett et al, 2001;MacDonald, et al, 2011;Smil, 2000) that have advanced the field to the point where science-based controls can be placed on human choices (crop cover and type and fertilizer applications) coupled to climate to yield a basis for forwardthinking strategies to balance global fertilizer use policies.…”