Lodging in rice can be alleviated by atmospheric CO2 enrichment

Abstract

Abstract The projected increase of atmospheric CO2 concentration [CO2] is expected to increase yield of agricultural C3 crops, but little is known about effects of [CO2] on lodging that can reduce yield. This study examined the interaction between [CO2] and nitrogen (N) fertilization on the lodging of rice (Oryza sativa L.) using free-air CO2 enrichment (FACE) systems installed in paddy fields at Shizukuishi, Iwate, Japan (39°38′N, 140°57′E). Rice plants were grown under two levels of [CO2] (ambient = 365 μmol mol−1; elevated [CO2] = 548 μmol mol−1) and three N fertilization regimes: a single initial basal application of controlled-release urea (8 g N m−2, CRN), split fertilization with a standard amount of ammonium sulfate (9 g N m−2, MN), and ample N (15 g N m−2, HN). Lodging score (six ranks at 18° intervals, with larger scores indicating greater bending), yield, and yield components were measured at maturity. The lodging score was significantly higher under HN than under CRN and MN, but lodging was alleviated by elevated [CO2] under HN. This alleviation was associated with the shortened and thickened lower internodes, but was not associated with a change in the plant's mass moment around the culm base. A positively significant correlation between lodging score and ripening percentage indicated that ripening percentage decreased by 4.5% per one-unit increase in lodging score. These findings will be useful to develop functional algorithm that can be incorporated into mechanistic crop models to predict rice production more accurately in a changing climate and with different cultural practices.