Effects of Film Mulch on Soil Temperature in Sand Dune Field

Abstract

Characteristics of film mulching in a sand dune were investigated through the field experiment.Three plots, black PE film mulch, transparent PE film mulch and control were set up in the experiment. The following items were compared with for those three plots: (1) Heat balance, (2) Effects of canopy and planting hole of film, (3) Multiple correlation coefficient with meteorological factors, (4) Maximum frequencies of order for soil temperature.The results are summarized as follows;1) About 96% of the all daily net radiation was exchanged to the latent and sensible heat flux and 4% was to the soil heat flux in the black film mulch plot. In the case of transparent film mulch, 75% of all heat flux was latent and sensible heat flux and 25% was soil heat flux. This tendency of the heat balance in a sand dune area was nearly same as that of an upland field.2) The soil temperature near the ground surface in the no-mulch plot without a canopy was the highest in the daytime because of the development of a dry sand layer, but the temperature was markedly lowered by covering with a imitation canopy. The effect of cover by the canopy was not observed in soil temperature at night.3) Both canopy and planting holes caused a decrease in the maximum soil temperatures (5cm depth) in the black film mulch plots. However, only the canopy did affect the temperature in the transparent film mulch plot (43°C at the mulch, and 50°C at the control).4) The most significant meteorological factor on the maximum soil temperature (5cm depth) was the duration of sunshine in the black film mulch plot and in the transparent film mulch plot the precipitation was the maximum, regardless of planting with or without holes on the films (Table 5).5) Frequencies of order for soil temperatures among three plots, black PE mulch, transparent PE mulch and control were also calculated in order to compare effectiveness of the mulching between the sand dune area and an upland field previously studied. As shown in Table 6, the maximum frequencies in the sand dune area (21%-73%) were lower than those in the upland field (74%-97%) in most cases. This indicates that effects of the mulching in the sand dune area are relatively unstable.