The Microclimate Suitability Analysis Of Late Autumn Tomato In Solar Greenhouse In Northern China

The solar greenhouse has an artificially regulated microclimate environment.Proper management providing suitable micro-environment according to the crop requirement is the key task to a better crop yield and economic benefits.So far,most of the solar greenhouse management is based on farmers'traditional experiences in China.The precise microclimate suitability of solar greenhouse crops was less taken into consideration in operation.It may imply some reduced production efficiency and waste of natural resources.For this,the experiment was carried out in a selected solar greenhouse in Raoyang County,Hebei Province,where is extensive and typical greenhouse production base located at.Based on two years'data from automatic microclimate system built in the solar greenhouse,in 2017-2018,air temperature?Ta?,soil temperature?Ts?,photo-synthetically active radiation?PAR?,relative humidity?RHa?,CO₂ concentration were analyzed on daily pattern as well as for whole growing season.The diurnal variation microclimate factors under different growth periods and weather conditions,and the suitability and stress degree of tomato microclimate in solar greenhouse at different growth stages were discussed based on the three basic points of tomato crops'suitability for various microclimate factors.The results obtained are as follows:?1?The maximum daily Ta is close to 50?,which is far higher than the upper limit of tomato growth and development;the minimum Ta in the middle and late period is lower than10?.The variation of Ts in the whole growing season ranged from 14?to 32?.Although it was somewhat low in the later stage,it could basically within the required range of tomato growth.In the late stage in house PAR is only under 200?mol·m^-2·s^-1,and the lack of light is serious.RHa is always in a high level of 99-100%.It should be taken care of against wetness.But under sunny days the minimum RHa can be reduced to 40%at noon time.So some special attention may be needed to prevent dryness in some key stages.The CO₂concentration in the solar greenhouse keeps a high level,like,800-1200ppm before sunrise.Nevertheless it decreases rapidly in the morning and keeps a significantly lower lever,generally below 400ppm,generally,with a minimum of 320-350ppm at noon.?2?For the microclimate suitability assessment,in greenhouse tomato has a 60%probability of being in a suitable Ta state only for 1 to 2 hours in the morning.Later on the rest of the daytime it is susceptible to extreme heat stress after near noon time.The probability of Ta higher than the non-growth-point?40??is 50%⁶0%.Nevertheless there is a probability of low-temperature stress with Ta<15?in the morning can reach 50%.The CO₂concentration generally stays low level.the probability of 300⁴00ppm is as high as 60%.Specially,the most key limited factor PAR is at a best situation at noon from 11am to 2pm,but in this period,the CO₂ concentration is at the lowest level?300³50ppm?,and with Ta in a extremely high?40⁵0??.This kind of combination must bring a negative effect to crop photosynthesis as well as crop productivity.when the CO₂ concentration is at the high enough,in the early morning,as well as later after noon,the PAR level is in a very low level.?3?To the above phenomena and problems,the following suggestions are proposed:For the problem of extremely high Ta at noon and low CO₂ concentration,more open window was suggested to enhance ventilation to get more atmosphere CO₂ coming into house and cooling Ta down more extensively.Additional light source and CO₂ fertilizer were also suggested as optional measures to improve the microclimate environment in the greenhouse,to promote better tomatoes yield and production efficiency.