[Effects of different mulching and drip irrigation patterns on photosynthetic characteristics of maize leaves in the Hetao Irrigation District, Inner Mongolia, China].

Photosynthesis controls crop growth and yield, and differences in planting methods and soil moisture can significantly affect the photosynthetic characteristics of crops. Grain filling stage and milking stage are two important stages of maize from flowering to maturity, which are essential for maize grain formation and dry matter accumulation. The effects of different mulching and drip irrigation patterns on the photosynthetic characteristics and maize yield at grain filling and milking stages were investigated in a field experiment in the Hetao Irrigation District, Inner Mongolia. Maize leaf photosynthesis during the grain filling stage was not significantly different under the different treatments. During the milking stage, photosynthetic and transpiration rates under both partial (B2 ) and full (Q2 ) film mulching with drip irrigation level 2 (350 mm) were significantly higher than those in both the partial (B1 ) and full (Q1 ) film mulching with drip irrigation level 1 (200 mm). Photosynthetic and transpiration rates, water use efficiency and stomatal conductance under the B1 and Q1 treatments were significantly higher in the grain filling stage than in the milking stage. Diurnal variations in photosynthetic and transpiration rates, stomatal conductance and water use efficiency of maize leaves during the grain filling and milking stages were synchronous and showed an upside-down "U" pattern, but the intercellular CO2 concentration showed the opposite pattern. Stepwise regression analysis showed that photosynthetically active radiation, air temperature and relative humidity were the main environmental factors influencing photosynthetic characteristics of maize leaves under the different mulching and drip irrigation treatments. In addition, maize yield was significantly higher under the B2 and the Q2 treatments than under the B1 and Q1 (increase of 29.3% and 50.9%, respectively), but no significant differences were found between the B1 and Q1 treatments, indicating that drip irrigation level affects the yield of maize and its photosynthetic capacity more than mulching mode in arid regions.