[Effects of tillage patterns on photosynthetic and chlorophyll fluorescence characteristics of maize in rainfed area of Northeast China].

In 2010-2011, a field experiment was conducted in Northeast China to evaluate the effects of different tillage patterns on the temperature and moisture in topsoil layer and the leaf photosynthesis and chlorophyll fluorescence of maize. The effects of tillage patterns on the soil temperature and moisture mainly manifested at sowing-jointing stage. In treatments flat planting with ridging at early jointing stage (PL) and flat planting without ridging (PP), the soil moisture content at the depth of 0-40 cm was significantly higher than that in treatment ridge planting (LL), with the increment being 5.6% and 5.2%, 4.6% and 7.3%, and 3.9% and 4.8% at emergency, seedling, and jointing stages, respectively. The minimum temperature at the soil depth 5 cm at seedling stage in PL and PP was 1.4 and 1.3 degrees C higher than that in LL, respectively. Due to the improvement of soil water and thermal conditions, the leaf photosynthetic rate (Pn) and transpiration rate (Tr) at jointing stage in PL and PP were significantly higher than those in LL, whereas the PS II potential activity (Fv/Fo) and PS II maximal photochemical efficiency (Fv/Fm) had no significant differences among the treatments, indicating that the stomatal factors such as stomata conductivity and stomata limitation were the main factors inducing the photosynthesis differences among the treatments. Furthermore, the Pn and Tr at grain filling stage in LL and PL were higher than those in PP, mainly due to the high water-logging risk in PP in strong rainfall season. Consequently, treatment PL could promote maize photosynthesis through improving soil water and thermal conditions, and further, increase maize grain yield.