Effect of elevated soil temperature on radiation-use efficiency in peanut stands

In cool-temperate climate regions, low (below optimum) soil temperature is critical for radiation-use efficiency (RUE) of the peanut stands. Despite its negative effect, few studies have quantified the relationship. To study the effect of soil temperature on RUE of peanut stands, we conducted field experiments for 2 years with three soil temperature treatments-ambient, reduced, and elevated. Season-long, from sowing until harvest, mean temperatures of the three treatments were about 23.5, 21.7 and 25.7 degreesC, respectively. The stands grown under the elevated soil temperature converted significantly more of the absorbed photosynthetically active radiation (PAR) into dry matter. Such higher RUE was accounted mainly for the higher carbon exchange rate (CER) due to the synthesis of more chlorophyll pigments (Chl a + b) at early growth stages. Across treatments and years, RUE varied from 1.07 to 1.53 g MJ(-1). Irrespective of treatments and years, the RUE and soil temperature were positively correlated (r(2) = 0.99; P < 0.001). The regression equation was: RUE = -1.16 + 0.11T. Elevated soil temperature would enhance to accumulate relatively higher stand biomass per unit use of radiation that substantiates such linearity. It is concluded that elevating the soil temperature is a useful method of compensating for low air temperatures, allowing more efficient capture of resources especially in cool-temperate regions. (C) 2003 Elsevier Science B.V. All rights reserved.