# Phosphorus Dynamics in the Soil-Plant-Environment Relationship in Cropping Systems: A Review
## 6 Phosphorus Dynamics and Effects of Climate Change  
Different environmental factors modify P dynamics in the soil-plant system, such as temperature, water stress, wet/dry cycles, drought, and O\({}_{2}\)/CO\({}_{2}\) concentration [108]. These conditions can affect the dynamics in the absorption, transportation, and distribution of P from soil into the plant with contrasting effects.  
Global change involves important changes on these factors with important impacts on P cycling [105].  
The high CO\({}_{2}\) concentration reached in the atmosphere [109] anticipates an improvement in the photosynthetic rate of the crops, and some physiological variables, such as the Net Assimilation Rate, which reflects CO\({}_{2}\), can act as a fertilizer for the crops, contributing to the net primary productivity [110,111]. Nevertheless, an increase in the plant growth causes a higher nutrient demand, leading P to become the most limiting nutrient [112].  
The worldwide demand for fertilizers in 2017-2018 was 187 million tons of P, and this number is expected to increase up to 199 million tons for 2022-2023 due to demographic growth, which demands a higher productivity [113]. The indiscriminate use of phosphorylated fertilizers not only raises production costs, but also generates massive environmental pollution and a major reserve of P in agricultural soils [114]. In general, the response of fertilizers in the irrigated areas, especially the areas used to grow rice throughout the world, decreased around two-thirds, from 13.4 kg grain per NPK kg in 1970 to 3.7 kg grain per NPK kg in 2005 [115]. These fertilizers, due to their alkaline nature, also affect the dynamics of enzymes and bacteria that solubilize P. This is due to the alkaline-residual effect that those fertilizers present when entering in contact with water and dissolving in the soil, which leads also to changes in the microbial respiration [105].  
In addition, an indiscriminate use of P fertilizers such as MAP (12-52-0) and DAP (18-46-0), when applied in productive agricultural systems, generates a high amount of nitrous oxide (N\({}_{2}\)O), which is one of the most dangerous greenhouse gases, with a warming potential 298 times higher than that of CO\({}_{2}\)[116]. The Colombian Institute for Hydrology, Meteorology, and Environmental Studies reported that in 2004, the agricultural industry in Colombia produced 94.91 gigagrams (Gg) of N\({}_{2}\)O.  
There is an uneven distribution of high precipitations in different parts of the world, and the fact that 70% of soils worldwide are acid [117] should be also taken into account when applying phosphatized fertilizers acidulated with H\({}_{2}\)SO\({}_{4}\), HNO\({}_{3}\), or H\({}_{3}\)PO\({}_{4}\), which can further intensify soil acidity and hence P precipitation due to increasing amount of soluble Al and Fe [118,119].  
Table 1 shows some worldwide research on the main processes in which P intervenes in agricultural systems.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**P Forms** & **Area** & **Factors** & **P Activation Response** & **Crops** & **Reference** \\  & & & **on Soil or Plant** & & & \\ \hline C:P:N & Stoichiometric & Physiological, cellular, & & _Organ sativa_ & [PERSON] et al., 1992; \\  & relationships & morphological, and & & _Lepmias chinensis_ & [PERSON] et al., 2010; [PERSON] \\  & & & & _Pinicinicum maximium_ & et al., 2014; [PERSON] et al., 2016; \\  & & & & _Boutelona grazilis_ & 2016; [PERSON] et al., 2018; \\ P deficiency—H\({}_{2}\)PO\({}_{4}\)– & Radicle and proteoid & Physiological, cellular, & & _Payulas albedoides_ & [PERSON] et al., 2010; \\  & root emission & morphological, and & & synthesis & _Arabidopsis_ sp. & [PERSON] et al., 2013; \\  & & & & & [PERSON], 2016. \\  & & & Biosynthesis of & & & \\  & & & secondary metabolites, & & & \\  & biochemical processes & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \end{tabular}
\end{table}
Table 1: Dynamics of the procedures related to P in crops.