The change of crop height in Experiment 1 suggested that plastic mulch had restrained potato plant growth during the early growth. However, in both Experiments 2 and 3, mulch enhanced plant growth. This might be explained by the air temperature difference: in Experiment 1, air temperature was higher than in Experiments 2 and 3,
and thus the soil temperature
could have been beyond the optimum for potato.
In Experiments 1 and 2, crop height became similar after the mulch was removed. Mulching duration also affected crop height in Experiment 3: M60 was the tallest during the observation period. However, removing the mulch later had no effect on crop height.