| Characteristics of the changes of relative humidity and absolute humidity inside plastic-made greenhouses were studied in Hezhou Demonstration Garden of Modern Agricultural Techniques, Guangxi Municipality. Observations were separately conducted at four different detecting sites, three inside the greenhouse (respectively in upper, middle and lower horizons ) and one outside the greenhouse, including measurements for the daily changes of relative humidity and absolute humidity under the conditions of sunny, cloudy and rainy day respectively, and long term changes of relative humidity and absolute humidity in a whole winter season. Measurements were taken at an interval of one hour for daily changes observation and at 6:30, 11:00, 17:00 and 21:30 respectively for long term changes observation in a whole winter season. Effects of dehumidified treatments such as plastic mulch and drip irrigation on changes of atmospheric humidity in middle horizon within greenhouse, dynamics of soil moisture and tomato plant growth were also studied under strictly-controlled water and fertilizer management. The main results were showed as follows.(1) It was showed that daily changes of relative humidity inside greenhouse were remarkable in sunny day and cloudy day, taking on a single valley curve, with a wider range of change in sunny day in comparison to those in cloudy day; and there were no obvious daily changes in rainy day. Daily changes of absolute humidity inside greenhouse took on a single peak curve in sunny day, and two peaks curve in cloudy day and rainy day, with a similar range of daily variation.(2) No obvious differences of monthly average relative humidity from upper, middle and lower horizons inside greenhouse were found for the same observational time in different month or in the same month, but there were marked differences of monthly relative humidity from the same horizons inside greenhouse which were observed at different time of the same month. Monthly average relative humidity in various horizons inside greenhouse or outside greenhouse showed gradual increase trends in a period from December to March. There were no obvious differences of monthly average relative humidity from different horizons inside greenhouse or outside greenhouse which were observed at 6:30, 17:00 and 21:30 within the same month, but significant differences were showed at the observational time 11:00.(3) It was found that dehumidification effects of plastic mulch and drip irrigation in greenhouses were significant. By using plastic mulch and drip irrigation techniques, monthly average relative humidity in middle horizons respectively decreased 3-11% and 2-6%, and monthly average absolute humidity in middle horizons was reduced 0.8-4.0 hpa and 0.4-1.5 hpa compared to conventional growing techniques.(4) Following use of plastic mulch and drip irrigation techniques, tomato plant height was reduced by 7.19-21.24% and 3.24-8.70%, plant stem diameter increased by 12.96-23.39% and 10.19-19.35%, average leaf area of individual plant increased by 44.10-91.92% and 30.00-82.50%, leaf area index increased by 0.09-1.47 and 0.07-1.36, average crop growth rate increased by 1.89 g/m2/d and 1.15 g/m2/d, average relative growth rate decreased 0.007g/g/d and 0.008 g/g/d, average net assimilation rate increased by 0.66 g/m2/d and 0.10 g/m2/d, plant biomass increased by 18.61% and 11.39% and economic yield increased by 37.50% and 19.88%, respectively. It was also found that dry matter distribution rate in aboveground section (including stem, leaf, flower and fruits) was markedly raised and dry matter distribution rate in underground section was obviously reduced by those techniques.Liang Chengfu (olericulture)Directed by professor Liu Mingyue and vice-researcher Chen Zhengfa...
|
PDF Full Text Request