Source-Sink Capacity Responsible for Higher Maize Yield with Removal of Plastic Film

Techniques based on the use of double ridges and furrows mulched with plastic film is very effective for improving water use efficiency and maize (Zea mays L.) yields in semiarid areas. Little is known, however, about the impact of removing the plastic film mulch during the reproductive stage (RS), i.e., during the July to September rainy season. We therefore performed a field experiment to investigate the effects of removing the film mulch during the RS. Two treatments were evaluated: (i) plastic film mulch in place during all growing stages (FM), and (ii) plastic film removed at the silking stage (RM). Relative to the FM treatment, the RM treatment decreased the cumulative soil temperature by 33 degrees C in 2010 and 45 degrees C in 2011 during the RS, thereby delaying leaf senescence and increasing the rate of photosynthesis. Grain growth measurements showed that the RM treatment extended the grain filling period by 3 to 4 d, resulting in greater ear biomass production, kernel numbers, and kernel volume. The greater grain production under the RM treatment was attributed to increases in source capacity or sink strength. Overall, the grain yields achieved under the RM treatment were greater than those for the FM treatment by 0.9 Mg ha(-1) in 2010 and 1.3 Mg ha(-1) in 2011, with concomitant increases in biomass production and harvest index. It may therefore be desirable to replace conventional film mulching with the RM treatment in regions with semiarid monsoon climates that have sufficient rainfall during the RS of maize growth to permit good yields.