Collapse Behavior of Pipe-Framed Greenhouses with and without Reinforcement under Snow Loading:A 3-D Finite Element Analysis

The present paper first investigates the collapse behavior of a conventional pipe-framed greenhouse under snow loading based on a 3-D finite element analysis,in which both geometrical and material non-linearities are considered.Three snow load distribution patterns related to the wind-driven snow particle movement are used in the analysis.It is found that snow load distribution affects the deformation and collapse behavior of the pipe-framed greenhouse significantly.The results obtained in this study are consistent with the actual damage observed.Next,discussion is made of the effects of reinforcements by adding members to the basic frame on the strength of the whole structure,in which seven kinds of reinforcement methods are examined.A buckling analysis is also carried out.The results indicate that the most effective reinforcement method depends on the snow load distribution pattern.

Evaluation of Two Cooling Methods for Closed Greenhouses

Special cooling methods are needed for normal growth of crops in closed greenhouses which permit no ventilation, especially during warm seasons. Experi- ments were designed to evaluate two cooling methods （Watergy chimney method and pool method） in a closed greenhouse in Beijing during warm seasons. Prelimi- nary results showed that average temperature at daytime （from 8：00 to 18：00） at 100 cm above ground surface in the closed greenhouse could be reduced by 8 with the Watergy chimney method. Average relative humidity fluctuated between 45% and 75% during daytime at 100 cm above ground surface within the closed greenhouse. With the pool method, average temperature was about 10 ℃ lower than that of the control greenhouse without pool at 50 cm above the ground surface. The peak temperature at 50 cm height was about 32℃ between 11：30 and 15：00 and, close to outside temperature. Temperature in this system satisfied normal growth of most crops, but relative humidity at 50 cm height were above 90% at daytime.

Effects of N, P and K on Output and Nutrient Cycle of Vegetables in Greenhouses

ObjectiveThe aim was to increase farmers’ income and reduce the waste of fertilizer by exploring effects of N, P and K fertilizations on vegetable yields and the accumulation of N, P and K in vegetable and soils. MethodThe fertilization tests were conducted on tomato, cauliflower and celery in greenhouses. ResultWhen N, P and K were not applied in tomato, cauliflower or celery, the yields reduced in 6.0%-13.8% and total annual income reduced by 39 220, 36 902 and 22 023 yuan/hm 2 respectively, suggesting that N, P and K are limiting factors of yield. The absorbed N amounts of tomato and cauliflower were higher compared with celery; the absorbed P amount of cauliflower was higher compared with tomato and celery; the absorbed K amount of tomato was the highest, followed by celery and cauliflower. The absorbed N in tomato fruit was lower than that of cauliflower and the absorbed N amount of other parts of tomato was also lower. Furthermore, the absorbed amounts of P and K by tomato and cauliflower fruits were higher than it absorbed by the other parts, especially the absorbed of K was significantly high. Total absorbed amounts of N, P and K from high to low were cauliflower, tomato and celery. After harvesting of tomato, cauliflower and celery, N, P and K in soils were all higher compared with soils before planting. Influenced by fertilizers, residual N content in soils grown with tomato and residual P content in soils grown with celery both doubled compared with base soils. Cauliflower plants were not applied with organic fertilizer, and residual N and K contents in soils were lower compared with tomato and celery. ConclusionResidual P content in soils is higher, which is a kind of waste and would cause pollution on soils. It is necessary to improve the proportion of organic and inorganic fertilizers in fertilization.

Cooperative Spectrum Sensing for Cognitive Radio-Wireless Sensors Network Based on OR Rule Decision to Enhance Energy Consumption in Greenhouses

Wireless sensors networks (WSNs) combined with cognitive radio have developed and solved the limited space of the frequency spectrum. In this paper, we propose different types of spectrums sensing and their own decisions depend on the probabilities that applied into fusion center, and how these probabilities’ techniques help to enhance the energy consumption of WSNs. In the same way, the importance of designing balanced distribution between the wireless sensors networks and their own sinks. This research also provides an overview of security issues in CR-WSN, especially in Spectrum Sensing Data Falsification (SSDF) attacks that enforces harmful effects on spectrum sensing and spectrum sharing. We adopt OR rule as four types of CRSN sensing protocolin greenhouses application by using Matlab and Netsim simulators. Our results show that the designing balanced wireless sensors and their sinks in greenhouses are very significant to decrease the energy, which is due to the traffic congestion in the sink range area. Furthermore, by applying OR rule has enhanced the energy consumption, and improved the sensors network lifetime compared to cognitive radio network.

Computational Fluid Dynamics Analysis of Greenhouses with Artificial Heat Tube

With the workmanship decrease in farms, the necessity to rationalize the use of other inputs and the development of technology has rapidly expanded the use of computer simulation in agricultural systems. One of the agricultural systems in which the modeling process of plant growth has been more engaged is the greenhouse production for horticultural crops. In Mediterranean climate, it is during the night that the energy losses are important and can be compensated with an artificial heat input. In this work an experiment was performed in a greenhouse in the north of Portugal. Temperature values in several points and air velocity in the aperture were measured during the night for three different cases: natural convective heating (case A);artificial heating tubes (AHT) (case B);AHT and natural ventilation (case C). A CFD simulation, carried out using FLOTRAN module of ANSYS, was also performed in two-dimensional configuration to obtain the indoor air temperature and velocity fields for the three cases. A very good agreement between experimental and numerical temperature values were verified, which allows to validate the adopted numerical procedure. In case A, the average temperature was 2.2℃. An average increase of 6.7℃ and 3.5℃ on the air temperature was obtained for the case B and case C, respectively. These results clearly emphasis the influence of each thermal load on greenhouse indoor air properties.

Utilizing Landsat TM Imagery to Map Greenhouses in Qingzhou, Shandong Province, China

To build a rapid and accurate method for greenhouse vegetable landinformation extraction using an index model derived from TM digital data of Qingzhou City, ShandongProvince, based on a systematic analysis of the spectral characteristics of different land use typesin the study area, a subset of the image was first made to eliminate the mountainous region notassociated with vegetable distribution, and then water body pixels were masked. With this the V_Iindex model for greenhouse vegetable land extraction was developed. The index model indicatedgreenhouse vegetable land for Qingzhou in April 2002 was concentrated in the southeast and aroundrural residential areas. Field data used for an accuracy evaluation showed that greenhouse hectaresdetermined with remote sensing were 95.9% accurate, and accuracy for the spatial distribution ofgreenhouse vegetable land cross checked with a random sample was 96.3%. Therefore, this approachprovided an effective method for greenhouse vegetable land information extraction and has potentialsignificance for management of greenhouse vegetable production in the study area, as well as NorthChina.

Determination and Analysis of Soil Organic Matter Content in Greenhouses around Lhasa City

The soil organic matter content in the greenhouses around Lhasa City was determined by potassium dichromate-sulfuric acid digestion method. The results showed that the soil organic matter content differed among different soil layers of the greenhouses around Lhasa City, and it was relatively low in the deep soil. The soil organic matter content also differed among greenhouses with different cultivation modes. In the same soil layer, the organic matter content in arched greenhouse was lower than that in semi-arched greenhouse. Among all the soil samples, the samples with organic matter content below the critical value （20 g/kg） accounted for 61.33%, and the samples with higher organic matter content （≥30 g/kg） accounted for 10.64%. The soil organic matter content in the greenhouses of different counties of Lhasa City ranked as Dazi County＇s〉Duilongdeqing County＇s〉Qushui County＇s. In overall, the organic matter content in the soil of greenhouses around Lhasa City was medium-low, and the fertility of the greenhouse soil was at the middle level.

Water, land, and energy use efficiencies and financial evaluation of air conditioner cooled greenhouses based on field experiments

High temperature and humidity can be controlled in greenhouses by using mechanical refrigeration cooling system such as air conditioner(AC)in warm and humid regions.This study aims to evaluate the techno-financial aspects of the AC-cooled greenhouse as compared to the evaporative cooled(EV-cooled)greenhouse in winter and summer seasons.Two quonset single-span prototype greenhouses were built in the Agriculture Experiment Station of Sultan Qaboos University,Oman,with dimensions of 6.0 m long and 3.0 m wide.The AC-cooled greenhouse was covered by a rockwool insulated polyethylene plastic sheet and light emitting diodes(LED)lights were used as a source of light,while the EV-cooled greenhouse was covered by a transparent polyethylene sheet and sunlight was used as light source.Three cultivars of high-value lettuce were grown for experimentation.To evaluate the technical efficiency of greenhouse performance,we conducted measures on land use efficiency(LUE),water use efficiency(WUE),gross water use efficiency(GWUE)and energy use efficiency(EUE).Financial analysis was conducted to compare the profitability of both greenhouses.The results showed that the LUE in winter were 10.10 and 14.50 kg/m^(2) for the AC-and EV-cooled greenhouses,respectively.However,the values reduced near to 6.80 kg/m^(2) in both greenhouses in summer.The WUE of the AC-cooled greenhouse was higher than that of the EV-cooled greenhouse by 3.8%in winter and 26.8%in summer.The GWUE was used to measure the total yield to the total greenhouse water consumption including irrigation and cooling water;it was higher in the AC-cooled greenhouse than in the EV-cooled greenhouse in both summer and winter seasons by almost 98.0%–99.4%.The EUE in the EV-cooled greenhouse was higher in both seasons.Financial analysis showed that in winter,gross return,net return and benefit-to-cost ratio were better in the EVcooled greenhouse,while in summer,those were higher in the AC-cooled greenhouse.The values of internal rate of return in the AC-and EV-cooled greenhouses were 63.4%and 129.3%,respectively.In both greenhouses,lettuce investment was highly sensitive to changes in price,yield and energy cost.The financial performance of the AC-cooled greenhouse in summer was better than that of the EV-cooled greenhouse and the pattern was opposite in winter.Finally,more studies on the optimum LED light intensity for any particular crop have to be conducted over different growing seasons in order to enhance the yield quantity and quality of crop.

Variation and Dynamics of Soil Nematode Communities in Greenhouses with Different Continuous Cropping Periods

Continuous cropping in greenhouses can result in root-knot nematode outbreaks resulting from imbalances in the soil nematode community.However,the changes in soil nematode communities in greenhouses with continuous crop production are unclear.We compared soil nematode communities in greenhouses after 2 years(2-yr)and 10 years(10-yr)of continuous crop production by 18S rDNA high-throughput sequencing.Compared with the 2-yr greenhouse,soil in the 10-yr greenhouse showed acidification,nutrient accumulation and salinization.Bacterial-feeding nematodes(BF)were dominant in the 2-yr greenhouse over the whole growing season,but plant-parasitic nematodes(PP)were the dominant group in the 10-yr greenhouse during the late growing season.Meloidogyne gradually became the dominant group and had a relative abundance of 70.9%(maximum)in the 10-yr greenhouse.Rhabditidae,with relative abundance ranging from 99.8%to 26.8%,was the predominant group in the 2-year greenhouse.Forβ-diversity,hierarchical clustering analysis,unweighted UniFrac principal component analysis(PCA)and principal co-ordinates analysis(PCoA)all revealed that soil nematode communities in the two types of greenhouses were significantly different.Redundancy analysis(RDA)showed that soil nematode communities in the 10-yr greenhouse were related to high soil organic material,total nitrogen,electrical conductivity and disease index of root-knot nematodes.Fisher’s exact test and Pearson’s correlation coefficients revealed that Meloidogyne contributed to themain differences in soil nematode communities between the two types of greenhouses.Population dynamics of Meloidogyne were divided into dormant phase,low-level increasing phase and exponential phase during the whole season.The soil nematode communities within the 2-yr and 10-yr greenhouses had significant variation and different dynamics.This work contributes to a deeper understanding of changes in the soil nematode community in greenhouses with different continuous cropping duration.

Effects of Different Heating Systems on Cucumber Yield in Greenhouses and Cost and Gas Volume Consumed in Varamin Region

This research was conducted to investigate the effects of three heating systems on cucumber yield,and cost and gas volume consumed in greenhouses located in Varamin region,Tehran province,Iran.Conventional heating systems used in the greenhouses are:central heating system(including boiler+hot water pipes),gas heater system(including double-walled tank+blower)and traditional furnace system(including ignition chamber+torch+pipes carrying a mixture of hot air and flammable gases).The study was carried out for two consecutive cucumber cultivation periods from January to June.Average values of crop yield,volume and cost of gas consumed were determined separately for each heating system.Results of the study indicated that the central heating system with the highest crop yield(295 t/ha),and the lowest volume(100,000 m^(3)/ha)and cost(840 USD/ha)of gas consumed was the best and most suitable heating system for greenhouses producing cucumbers in Varamin region and other regions with the same and similar climate as well as regions with active greenhouses in the cold season.

Effect of Different Heating Systems in Cucumber Production Greenhouses in Varamin Region on Crop Yield, Volume and Cost of Gas Consumed

This research was conducted to study the effect of different heating systems in cucumber production greenhouses in Varamin region,Tehran province,Iran on crop yield,volume and cost of gas consumed.Three types of conventional heating systems,namely the central heating system(including boiler+hot water pipes),gas heater system(including double-walled tank+blower)and traditional furnace system(including ignition chamber+torch+pipes carrying a mixture of hot air and flammable gases)were studied during two consecutive periods of greenhouse cucumber cultivation in the cold season(from January to June),and average values of crop yield,volume and cost of gas consumed were determined separately.Results of the study indicated that the central heating system with the highest crop yield(295 tžha^-1),and the lowest volume(100,000 m3žha^-1)and cost(210,000,000 Rialsžha^-1)of gas consumed was the best and most suitable heating system for greenhouses producing cucumbers in Varamin region and other regions with the same and similar climate as well as regions with active greenhouses in the cold season.

Capturing Heat from a Batch Biochar Production System for Use in Greenhouses and Hoop Houses

Biochar is charcoal produced at comparatively high temperature and used as an agricultural amendment, which also sequesters carbon. Most of the research on biochar manufacture in the United States has either focused on large-scale continuous systems with multiple products or small batch systems with biochar as the only product. At James Madison University in Harrisonburg, Virginia, we have worked on a batch system to make high quality biochar while capturing the heat for use either as a backup system for hot water heating, or to heat a greenhouse in winter. The system is now in its third iteration. In the first, we used a small intramural grant to experiment with low cost material using a minimalist design. While the unit captured some heat, operation of the design was smoky and hazardous to handle. The second design, funded by a larger intramural research grant, captured considerable heat, made 8-10 kg of biochar per burn and captured up to 250 MJ per batch of biochar made, but remained smoky. The third generation pyrolysis unit was constructed on Avalon Acres Farm in Broadway, Virginia, funded by a 25 × 25 grant through James Madison University （JMU）. This unit makes the same amount of biochar, with less smoke, and sends the captured heat to a storage tank to help heat a greenhouse and home on the site. Our average efficiency of heat transfer is 12.5% of the total heat value of the starting woody biomass, a number we believe can at least double.

Effects of Climate Factors in Greenhouses on the Growth Development and Quality of Houttuynia cordata Thunb.

[Objectives]This study was conducted to demonstrate whether greenhouse planting can solve the problem of insufficient supply of fresh H.cordata Thunb.in winter and spring.[Methods]The effects of meteorological factors on the growth and quality of H.cordata Thunb.were analyzed.[Results]The highest temperature and lowest temperature in greenhouses were 6-12℃and 5-10℃higher than those in the open fields,respectively,and the average temperature difference between the greenhouses and the open fields was large in the early stage,but small in the late stage.The effective accumulated temperature≥10℃was 3463℃in the greenhouses and 2046℃in the open fields.Although the humidity in the open fields was higher than that in the greenhouses,the humidity in the greenhouses was relatively stable and that in the open field changed greatly.The light intensity of the greenhouses was lower than that of the open fields.In terms of the periods from film covering day to seedling emergence,seedling emergence to full emergence,and full emergence to crop closure,greenhouse planting was shortened by 47,11,and 5 d,respectively,compared with open field planting,but the period from crop closure to flowering was extended by 40 d.The plant height of the plants planted in the greenhouses reached 0.1 cm on January 7,while those planted in the open fields did not have seedlings until February 25,and the plant height,daily growth rate,yield and effective components in volatile oil of the plants planted in the greenhouses were significantly higher than those planted in the open fields.The growth,development and quality of H.cordata Thunb.reached the extremely significant or significant level with temperature,but had no significant correlation with humidity and light intensity,indicating that temperature had the greatest impact on the growth,development and quality of H.cordata Thunb.when planted in the greenhouses.[Conclusions]This study provides a theoretical basis for protected cultivation and explores new planting methods for the further development of its industry.

Toxicity of Pyrifluquinazon against Greenhouse Whitefly on Tomato Produced in Greenhouses

The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), is a major pest of tomato, Solanum lycopersicum L. Management in both the field and greenhouse is often based on foliar applications of insecticides. A lack of control along with resistance development requires development of alternatives to currently available insecticides. Pyrifluquinazon is a recently developed insecticide by Nichino/Nihon Nohyaku Co., Japan and is marketed in the US by Nichino America. The insecticide inhibits feeding by aphids, thrips, mealybugs and scale insects resulting in death. Because limited information exists on pyrifluquinazon effectiveness against whiteflies, tests were initiated to establish its toxicity against the greenhouse whitefly on greenhouse produced tomato. Data reported herein indicate that pyrifluquinazon was highly effective against adult greenhouse whiteflies. When adults were transferred to tomato shortly after the application had dried, mortality counts taken after 48 h produced LC50 and LC95 values of 0.2469 and 2.4826 μg·g-1, respectively. Although few adults were observed on tomato foliage 24 h post-exposure, little mortality was observed until the 48 h observation. When adult whiteflies were placed on tomato 3 d after pyrifluquinazon application, the LC50 value was 0.3343 μg·g-1 which did not significantly differ from the 0 h LC50 value. A significant increase in LC50 value was observed when adults were placed on tomato 5 d after pyrifluquinazon application. In a greenhouse efficacy trial, both the recommended pyrifluquinazon rate (46.8 g active ingredient [AI] ha-1) and a reduced rate (11.7 g·AI·ha-1) significantly reduced numbers of whitefly adults when compared to the non-treated control for 10 days. The 46.8 g·AI·ha-1 rate was as effective as the insecticide standard, imidacloprid. Pyrifluquinazon applied to tomato foliage in the greenhouse offers a useful alternative to currently available insecticides for control of greenhouse whitefly. Further, its unique mode of action may represent a new tool in management of insecticide resistance.

Temperature and Humidity Control in Greenhouses in Desert Areas

Water consumption can be reduced by using a greenhouse for agriculture in desert areas. We analyzed the effect of control of ventilation, sprinkler water, and solar radiation?shielding on changes of temperature and humidity in a greenhouse under various desert area conditions. We calculated the changes in temperature and humidity in a greenhouse for a whole day in four seasons, and the calculation results of water consumption with and without a greenhouse were compared. When ventilation, shielding, and sprinkler water were controlled under suitable conditions to grow orchids in a desert area, water consumption in July was only 7% of that without a greenhouse.

Managing Energy Consumption of Wireless Sensors Networks in Multiple Greenhouses

An extensive area implementation of fully observed greenhouses motivates on research, especially in remote greenhouses. However, implementation of wireless sensor networks (WSNs) is still needed for investigation. Cognitive radio sensor networks (CRSNs) took advantage of using the cognitive radio (CR) concept to which allowed wireless sensor networks to dynamically access into white space channels which is unused channels. In this paper, we adopted the Generalized Implicit-OR as CRSN sensing protocol to reduce the energy consumption and increase the network lifetime in multiple numbers of greenhouses. Our results showed that enhanced energy consumption and improved network lifetime compared to ordinary WSN.

Development of Multi-purpose Small-sized Rotary Tiller for Greenhouses

IGLP-62 multi-purpose small-sized rotary tiller is a tool of production urgently needed for “Vegetable Supplying System”in China. It is mainly used for rotary cultivation as well as for fertilizer mixing and stubble mulching in greenhouses. And it can be used for open vegetable plots and orchards as well. The machine is characterized by the integration of rotary tilling with driving. It has a good performance of clod crushing and high capacity. It is equipped with a power-take-off shaft to drive a water pump, thresher or rice mill. Thus the machine solved the long-standing problem of heavy manual labour in greenhouses. So it is a kind of ideal hand cultivation machinery of horticultural type.

A state of art review on time series forecasting with machine learning for environmental parameters in agricultural greenhouses

Agricultural greenhouse production has to require a stable and acceptable environment,it is therefore essential for future greenhouse production to obtain full and precisely internal dynamic environment parameters.Dynamic modeling based on machine learning methods,e.g.,intelligent time series prediction modeling,is a popular and suitable way to solve the above issue.In this article,a systematic literature review on applying advanced time series models has been systematically conducted via a detailed analysis and evaluation of 61 pieces selected from 221 articles.The historical process of time series model application from the use of data and information strategies was first discussed.Subsequently,the accuracy and generalization of the model from the selection of model parameters and time steps,providing a new perspective for model development in this field,were compared and analyzed.Finally,the systematic review results demonstrate that,compared with traditional models,deep neural networks could increase data structure mining capabilities and overall information simulation capabilities through innovative and effective structures,thereby it could also broaden the selection range of environmental parameters for agricultural facilities and achieve environmental prediction end-to-end optimization via intelligent time series model based on deep neural networks.

Sensitivity analysis of the DehumReq model to evaluate the impact of predominant factors on dehumidification requirement of greenhouses in cold regions

In this study,the sensitivity of a novel dehumidification requirement model(DehumReq)is analyzed to evaluate the effect of the predominant factors on the dehumidification needs of the greenhouses.The hourly dehumidification demand and sensitivity coefficient(SC)are estimated for three different seasons:warm(July),mild(May),and cold(November),by using the local sensitivity analysis method.Based on SC values,the solar radiation,air exchange,leaf area index(LAI),and indoor setpoints(temperature,relative humidity(RH),and water vapor partial pressure(WVPP))have significant impact on the dehumidifi-cation needs,and the impact varies from season to season.Most parameters have a higher SC in summer,whereas solar radiation and LAI have a higher SC in mild season.The dehumidification load increases 4 times of its base value with increasing solar radiation by 200 W/m^(2),and the highest LAI(10)caused 5 times increment of the load.The changing of WVPP from its base value(1.5 kPa)to maximum(2.9 kPa)reduces the load 70%in summer.Air exchange was found to be the most crucial parameter because it is the main dehumidification approach that has a large range and is easily adjustable for any greenhouses.Sufficient air exchange by ventilation or infiltration will reduce the dehumidification load to zero in May and November and minimizes it to only nighttime load in July.For the other parameters,higher ambient air RH and indoor air speed will result in higher the dehumidification load;whereas higher inner surface condensation will result in lower dehumidifi-cation load.The result of this study will assist in the selection of the most efficient moisture control strategies and techniques for greenhouse humidity control.

Simple model for predicting hourly air temperatures inside Chinese solar greenhouses

For an efficient energy greenhouse,temperature is the most important climate parameter,which not only affects crop growth and health but also determines the management of energy consumption.So reliable monitoring of temperature is of great significance,and often hourly values are required.However,due to the low level of automation for Chinese solar greenhouse,the loss or poor quality of climate data often occurs.In order to accurately supplement the missing data,as well as for the generation of future temperature,a 24-hour indoor temperature prediction model was established.It uses a piecewise Bezier curve equation that takes the characteristic temperature as the control point which was determined by the outside weather recording.The 130 d of observed hourly temperature data were used to build and validate the model,and the results showed that the temperature model proposed was accurate and sufficient for the simulation of the trend curve of hourly temperature change inside a solar greenhouse.(EF=0.98,R2=0.89).After validation,this temperature model proposed can be useful for the quantitative analysis of crop growth and optimal management.