Early growth of muskmelon in mulched minitunnels containing a thermal water tube. II. Air, soil, and water tube temperatures and vegetative growth

Field experiments were conducted during 1997, 1998, and 1999 to determine e ffects of 10 combinations of mulched minitunnel and thermal water tube on a ir, soil, and water-tube temperatures and on vegetative growth of 'Earligol d' netted muskmelon (Cucumis melo L. Reticulatus Group) within the tunnels. Use of mulched minitunnels significantly increased air, soil and water tem peratures during the preanthesis phase in all years compared with control t reatments. Inclusion of water tubes and venting the tunnels decreased air t emperature fluctuations in the tunnels. During the first 10 to 15 days afte r transplanting, plants grown in nonperforated tunnels had higher relative growth rates (RGRs), net assimilation rates (NARs), and dry weights (DWs) t han those grown under perforated tunnels and control plots. Plants in tunne ls containing thermal water tubes generally had higher RGRs, NARs, and DWs than those without tubes. During the later part of the experiment, from 11 to 16 days after transplanting until anthesis, however, there were no consi stent effects of mulched minitunnels on RGR, NAR, and plant DW. Tunneled mu skmelons had significantly higher RGRs, but generally lower NARs than those grown without tunnel. Use of mulched minitunnels significantly increased p lant DW at anthesis in 1997, but not in 1998 and 1999. Plants grown in the minitunnels containing a thermal water tube generally had higher RGRs, NARs , and DWs than those without water tubes. Ventilating nonperforated tunnels generally increased RGR, NAR, and plant DW. Plants grown in the tunnels re ached anthesis 10 days earlier than those without tunnels.