Plant phosphorus acquisition links to phosphorus transformation in the rhizospheres of soybean and rice grown under CO2 and temperature co-elevation

Abstract

Climate change is likely to influence the reservoir of soil phosphorus (P) as plants adaptably respond to climate change in the perspective of P acquisition capability via root proliferation and mediating biochemical properties in the rhizosphere to access various soil P fractions. It is particularly important in cropping soils where P fertilizer plus soil P is required to synchronize crop P demand for the production sustainability under climate change. However, few studies have examined the effect of CO2 and temperature co-elevation on plant P acquisition, P fractions and relevant functional genes in the rhizosphere of different crops. Thus, the present study investigated the effect of elevated CO2 and warming on P uptake of soybean and rice grown in Mollisols, and soil P fractions and relevant biochemical properties and microbial functions in the rhizosphere with or without P application. Open-top chambers were used to achieve elevated CO2 of 700 ppm combined with warming (+ 2 °C above ambient temperature). CO2 and temperature co-elevation increased P uptake in soybean by 23% and 28% under the no-P and P application treatments, respectively; and in rice, by 34% and 13%, respectively. CO2 and temperature co-elevation depleted organic P in the rhizosphere of soybean, but increased in the rhizosphere of rice. The phosphatase activity negatively correlated with organic P in the highland soil while positively in the paddy soil. The P mineralization likely occurs in soybean-grown soils under climate change, while the P immobilization in paddy soils. CO2 and temperature co-elevation increased the copy numbers of P functional genes including phoD, phoC, pstS and phnX, in soils with P application. These results indicate that the P application would be requested to satisfy the increased P demand in soybean under climate change, but not in rice in paddy soils where soil P availability is sufficient. Therefore, elevated CO2 and temperature facilitated the crop P uptake via biochemical and microbial pathways, and P functional genes played an essential role in the conversion of P.