however, it was found that mulching duration had significantly (F-test, P < 0.01) affected plant height during the early growing period (from June 6 to June 26): M0 < M40 < M60 < M90 ≈ Mw. This height difference can be explained by the higher soil temperature under mulch, which would enhance stem elongation according to Marinus and Bodlaender (1975). During the later growing period, removing mulch had little effect on plant height: treatment M90 had quite similar height to Mw. This was probably due to the small soil temperature difference between mulched and non-mulched soil during that period when crop canopy was very large and nearly shaded the entire soil surface.