Soil Chemistry Aspects of Predicting Future Phosphorus Requirements in Sub‐Saharan Africa

Abstract

Phosphorus (P) is a finite resource and critical to plant growth and therefore food security.Regional-and continental-scale studies propose how much P would be required to feed the world by 2050. These indicate that Sub-Saharan Africa soils have the highest soil P deficit globally. However, the spatial heterogeneity of the P deficit caused by heterogeneous soil chemistry in the continental scale has never been addressed. We provide a combination of a broadly adopted P-sorption model that is integrated into a highly influential, large-scale soil phosphorus cycling model. As a result, we show significant differences between the model outputs in both the soil-P concentrations and total P required to produce future crops for the same predicted scenarios. These results indicate the importance of soil chemistry for soil-nutrient modeling and highlight that previous influential studies may have overestimated P required. This is particularly the case in Somalia where conventional modeling predicts twice as much P required to 2050 as our new proposed model.

The impact of phosphorus on projected Sub-Saharan Africa food security futures

“…We projected Sub-Saharan Africa’s elemental phosphorus requirements using the IMAGE 3.2 database (described in the introduction) which, in turn, uses SSPs as an underlying framework 24 , 25 , 30 . IMAGE 3.2 projected crop production was coupled to the soil efficiency 28 using the Geochemical Dynamic Phosphorus Pool Simulator (GDPPS) which calculates efficiency based on the concentration of iron and aluminium oxides in the soil 45 , 46 . We projected SSP1–5 at a continental level and assessed specific countries under middle of the road SSP2 only.…”

“…This study predicted future phosphorus requirements across Sub-Saharan Africa using data from the geochemical dynamic phosphorus pool simulator model (GDPPS) 46 . GDPPS uses a theory-driven geochemical fitting to overcome limitations induced in the conventional DPPS model where soils are highly weathered such as tropical locations 41 , 46 . Required yields were made according to the SSPs built into IMAGE 3.2 (see introduction for details) 24 , 25 .…”

“…We developed GDPPS to calculate the phosphorus application as a function of the available phosphorus in the soil, the inputs and the phosphorus needed for crop uptake 46 . The independent key variable phosphate uptake is controlled by the amount of crop production as determined for an SSP within IMAGE 3.2—this is calculated at a gridded scale of 0.5° × 0.5° 41 , 46 , 52 . Phosphorus use efficiency in SSA has relatively high values and fluctuates over a small range (0.8–1) these do not affect our results since they are a function of our model 39 .…”

A pilot study on dietary and faecal calcium/phosphorus ratios in different types of captive ruminating herbivores

“…It has to be taken into account that captive intermediate feeders are fed a more grazer‐like diet and can adapt to this rather well. Even under these circumstances, the intermediate feeding antelope species may have adapted to their natural habitats, that is Africa and India, where phosphorus is scarce (Alloway, 2008 ; MacDonald et al., 2011 ; Magnone et al., 2019 ). Historic reports of phosphorus deficiency resulting in osteophagia and botulism (‘lamsiekte’) show that domestic ruminants, mostly cattle, brought to Africa could not cope with the low phosphorus intake without supplementation (Bigalke, 2012 ; Green, 1949 ; Sigwart, 1929 ; Theiler, 1927 ).…”

Phosphorus requirement for achieving the Sustainable Development Goal “Zero Hunger”

“…By doing so they can reduce P fixation and improve production beyond 2030. SSA in particular has large areas of P fixing soils 19,20 but it is nevertheless on track to achieve the SDG2 target, and only needs a modest extra P input of 4 Tg by 2030. Yet, it is worth noting that in SSA input and uptake of P are rising from an extremely low level per unit area (Figure SI4a), and P fixation will not be overcome just yet (Figure 1b).…”