Effects of long-term exposure to enriched CO2 on the nutrient-supplying capacity of a grassland soil

Abstract

Altered soil nutrient cycling under future climate scenarios may affect pasture production and fertilizer management. We conducted a controlled-environment study to test the hypothesis that long-term exposure of pasture to enriched carbon dioxide (CO 2 ) would lower soil nutrient availability. Perennial ryegrass was grown for 9 weeks under ambient and enriched (ambient+120 ppm) CO 2 concentrations in soil collected from an 11.5-year free air CO 2 enrichment experiment in a grazed pasture in New Zealand. Nitrogen (N) and phosphorus (P) fertilizers were applied in a full factorial design at rates of 0, 12.5, 25 or 50 kg N ha −1 and 0, 17.5 or 35 kg P ha −1 . Compared to ambient CO 2 , under enriched CO 2 without P fertilizer, total plant biomass did not respond to N fertilizer, and tissue N/P ratio was increased indicating that P was co-limiting. This limitation was alleviated with the lowest rate of P fertilizer (17.5 kg P ha −1 ). Plant biomass in both CO 2 treatments increased with increasing N fertilizer when sufficient P was available. Greater inputs of P fertilizer may be required to prevent yield suppression under enriched CO 2 and to stimulate any response to N.

Yield and Yield Attributes Responses of Soybean (Glycine max L. Merrill) to Elevated CO2 and Arbuscular Mycorrhizal Fungi Inoculation in the Humid Transitory Rainforest

“…Extensive reportsare available in the literature on the mechanisms that underpins this process (Aranjuelo et al, 2014). The increase in growth from elevated CO2 is likely to require more phosphorus, which is taken up from the available phosphorus pool in soil (Gentile et al, 2012;Jin et al, 2013). Several studies have reported that both the magnitude and the direction of the growth response of plants to elevated CO2 depend on P availability (BassiriRad et al, 1997;Jin et al, 2013).…”

A reduced fraction of plant N derived from atmospheric N (%Ndfa) and reduced rhizobial nifH gene numbers indicate a lower capacity for nitrogen fixation in nodules of white clover exposed to long-term CO<sub>2</sub> enrichment

“…Therefore, based on the leaf P concentrations, we can conclude that the P availability was in the range where nutrient limitation might occur. In a fertilizer experiment using soil from this FACE experi-ment in a controlled environment, Gentile et al (2012) found no difference in leaf P concentrations for aCO 2 and eCO 2 in Lolium perenne (ryegrass) plants but found a P limitation to growth under eCO 2 implying a higher demand for P in this treatment. To put our P status in some context, relationships drawn from fertilizer trials in New Zealand with ryegrass/white clover swards indicate a clover P concentration of 0.26 % is required to gain 90 % of the maximum response to P (Sinclair et al, 1997).…”

A reduced fraction of plant N derived from atmospheric N (%Ndfa) and reduced rhizobial nifH gene numbers indicate a lower capacity for nitrogen fixation in nodules of white clover exposed to long-term CO<sub>2</sub> enrichment

“…Therefore, based on the leaf P concentrations, we can conclude that the P availability was in the range where nutrient limitation might occur. In a fertilizer experiment using soil from this FACE experiment in a controlled environment, Gentile et al (2012) found no difference in leaf P concentrations for aCO 2 and eCO 2 in Lolium perenne (ryegrass) plants but found a P limitation to growth under eCO 2 implying a higher demand for P in this treatment. To put our P status in some context, relationships drawn from fertilizer trials in New Zealand with ryegrass/white clover swards indicate a clover P concentration of 0.26 % is required to gain 90 % of the maximum response 8278 T. Watanabe et al: Reduced N fixation of clover under elevated CO 2 to P (Sinclair et al, 1997).…”