Cropping in Semi-arid Northwest India in Greenhouse with Ground Coupling Shading and Natural Ventilation for Environmental Control

Research is ongoing to develop greenhouse technologies which economically control water and energy in order to improve farming in water-scarce, hot, semi-arid regions of north-west India. A greenhouse under investigation was coupled to earth-tube– heat–exchangers (ETHE) and also had provisions for shading, natural ventilation and mist nozzles. Tomatoes were grown in the greenhouse. In the cooler months, a regime of natural ventilation and top shading kept the greenhouse temperature close to ambient temperature. Mist was not used. Evaporation and later transpiration may have aided cooling. This cooling effort became less effective in warmer periods as the cooling load increased and dense foliage appeared to hinder ventilation. Forced ventilation via ETHE and top shading was then implemented. Inside temperature occasionally rose 2-3 °C above the ambient temperature. Cropping could be done through the spring and early summer. Heating was affectively achieved with ETHE in cold nights of December and January keeping the inside temperatures well above 12°C. Yields were 68 t/ha nearly twice the open field production, while the water used (266 mm) was nearly half of the open-fields usage. This appears to be a promising new way to improve livelihoods from farming.


INTRODUCTION
The Kutch region of north-west India (68.3 to 72.5 E, 22.5 to 24.5 N), spreads over 45,000 sq km, is semi-arid, and is characterized by a wide occurrence of salt-affected soils and poor quality water.It is bordered in the west by the Arabian Sea and in the north by the Great Rann of Kutch -a barren expanse of salt-crusted ground vacated by recession of sea.Rainfall is low (mean 300 mm, coefficient of variation 60%), while ambient temperatures are high (>31°C in all months, summer >35°C).Cropping is carried out in areas where groundwater is still suitable.Excessive withdrawal and inadequate recharge is rapidly depleting these aquifers making surface irrigation with conventional methods expensive and unsustainable.In most parts groundwater is not suitable for direct use.As a result, vast tracts remain uncultivated.Livelihoods from farming have always been difficult due to low and unstable yields.The temperature difference, ∆T, computed with global solar irradiance at noon (12:00) and mean day time wind velocities measured at a height close to 4 m at Kothara, is shown in column (3) of Table (1).In December, when day temperatures are typically near 32°C, an unventilated greenhouse will be hotter by 14 °C, or at 46 °C.The difference will be larger in other months; for example, spring (16°C), summer (17 °C) and in fall (15-17°C).The temperature range for good growth in general is 18-30 °C.For tomatoes, one of the popular greenhouse crops in many places, the temperature range is 12-32°C.Greenhouses will be overheated at all times without effective cooling.Natural ventilation is a simple solution requiring no energy.Shading is another simple solution which should be considered.Wind speeds are generally high in the region especially near the coast; and higher during the day -particularly in the hot seasons, spring and summer.Natural ventilation can be expected to affect high renewal rates (air changes per unit time), perhaps close to 40 per hour.In other words, the total volume of air contained in greenhouse is changed or renewed forty times in an hour.With such a renewal rate, ∆T will be reduced and can be computed by another expression by Kittas 7 .
The temperature difference (∆T) is reduced to 5-6 °C in winter and 7 °C in summer months (column 5).A closed greenhouse, without any measure of control, is usually at the same temperature as the ambient air at night.During the day, with natural ventilation, temperature will be above ambient by ∆T.The range of temperature that will prevail inside the greenhouse is shown in column 6. Natural ventilation is popular in the Mediterranean regions 7 and promises to be effective in this region also, but as seen from column 6, under conditions that prevail in Kutch region, it is only in December that this measure will be keep the inside temperature from exceeding 32 °C.In all other months, further cooling measures will be needed to reduce inside temperature to this level owing to the high heat load in the region.Heating requirements in the region are limited to nights in December to February.Cladding is the first barrier against entry of radiation into greenhouses thereby reducing the cooling load.Kittas et al. 8 reported that in the waveband 300-1100 nm, total transmission of irradiance into a polythene covered tunnel was 0.65, and using twin span glass house it was 0.54.Using multi-span fiberglass house it was 0.49.Shading devices can further alleviate heat load.When the glass house was shaded with a black mesh plastic net of 30% shading, the total transmission reduced to 0.401 and more dramatically to 0.171 with an aluminized shade screen of 70% shading.They showed by detailed measurements that devices may not be waveband-neutral and their effect also has a qualitative dimension.Maximum day temperature in naturally ventilated greenhouse will be higher by amount shown in column 5.
The black mesh plastic net was reported to be 'perfectly neutral as it maintained the PAR enrichment effect of glass' but aluminized shade screen 'counteracted' that effect.Shading devices have several other effects on greenhouse microclimate as shown by Baille et al. 4 who studied the effects of white paint (about 8 kg CaO per 100 kg water) over a glasshouse in coastal region of eastern Greece.Average transmission reduced from 0.62 before the paint to 0.31 after.The fluctuation around the mean too reduced due to the fact that paint made the radiation more diffuse.Temperature rises above ambient reduced significantly, so also the vapor pressure deficit of greenhouse air.The canopy became cooler than the air, and canopy-to-air vapor pressure deficit reduced appreciably.The transpiration rate increased by an average of 18 % after paint was applied.The sensible heat flux from the canopy reversed from large positive to a negative value.Crop water stress index reduced especially a few days after whitening.Besides being beneficial to the microclimate, paint as a shading device does not interfere with the ventilation process nor aerodynamics near the cladding as would the nets and screens.
With a view to select proper shading material for use in Kutch region, Sharan and Chitlange 21 made radiometric measurement on a set of shade nets marketed in India, in the 400-1000 nm range at 10 nm interval.They reported that black and white colored nets provided nearly uniform shading across the waveband.Blue and green nets provided higher shading near their characteristics wavelength and slightly lower than specified elsewhere.Assuming a net of 50% effective shading is installed over polythene clad greenhouse with transmittance of 0.65 (as in case of Kittas et al. 8 ) the overall transmittance will be 0.325.With such a shade net and natural ventilation, ∆T would be lower and accordingly the range of minimum and maximum temperatures reduced, as shown in the last column.Values are obtained using equation ( 2) with radiation level reduced to one third of that in column (1) and renewals of 40 per hour as before.These two measures would keep the temperature below 32°C in August, December; slightly above it in September, November, January and February.This represents a significant improvement.Although, shade nets of higher rating are available, the need to maintain adequate light intensity must also be kept in view.Now the need for more effective cooling is reduced to six months (March to July) and then in the fall, for which evaporative cooling should be considered.A fan-pad system is the most common means to implement this.Two other options are -sprinkling and fog.In a fan-pad system, water trickles continuously down thick cellulose pads that are installed on one wall of greenhouse.Fans located on the opposite wall pull the ambient outside air through the pads.Some water evaporates by extracting the required heat of vaporization from the air stream, rendering it cooler and more humid.In other words, sensible heat is converted into latent heat.Air can be cooled, at most, to the wet bulb temperature; accordingly its effectiveness is dependent on ambient humidity levels.It will be more effective in arid environments.Air, cooler and more humid near the pad, moves through the growing area absorbing heat and vapor before exiting from the other end.Water draining into the sump below the pads is recycled with replenishment to compensate for water lost.At the stage of planning, information on actual consumption of water in fan-pads was not available for Indian locations.Using the established design procedures (Indian Standard Code as also method outlined by Paul Nelson 10 ) it was determined that in the hottest part of the year (June), in Kutch area, fan-pads would evaporate at least 7 mm to 10 mm of water per day with top shading.This was a deterrent.It was decided not to employ fan-pad in the greenhouse facility that was being envisaged.
It is still difficult to get Indian results on water consumption in fan-pads; but data now available from elsewhere confirms high water consumption.Sabeh 13 measured water used at Tucson, Arizona.When temperature in a 278 m 2 greenhouse growing tomatoes was on automatic control mode maintaining 24°C / 18°C day/night temperatures, the cooling system used 14.8 L / m 2 /day of water and crops used 8.9 L / m 2 /day of water.When control was based on a fixed air change rate, less water was consumed but temperature inside was higher.At flow rate of 0.017 m 3 /m 2 /s (about 10 air changes per hour) mean temperature inside was 31.1°C, and water used in cooling 10 mm, 16% higher than the crop.Simulations carried out by Al-Jamal 1 using a unsteady energy balance model of a polythene clad fan pad cooled greenhouse in Jordan, indicated that with ambient humidity at 10 g/m 3 , air change rate of 20/hr would keep greenhouse in the range of 20 -34°C, and use water at the rate of 4.87 m 3 /day or 23mm / day.Some other limitations of fan-pad are: "the lack of uniformity of climatic conditions, which are characterized by rising temperature and falling humidity along the length of the structure and in the airflow direction; electric power failure transforms the greenhouse into a heat trap; low cooling effect compared to fogging system; general diminution of efficiency with increasing humidity; and waste of water -to prevent blockage of wet pad water bleed is necessary," Arabel et al. 3 .Sprinkling uses large surfaces (blankets) for faster evaporation installed overhead in greenhouses and wetted by mist nozzles. 5.Air near the surface gets cooled and is moved out by forced ventilation.In a fog system, a large surface is created by turning water into fog (droplets in the range of 2-60 µ m ) using very high pressure pump and appropriate nozzles.These droplets fall slowly and are easily carried by air stream.Arabel et al. 2 made elaborate study of fog system and reported that it provided greater uniformity of temperature and humidity in greenhouse than fan-pad.High water consumption however is the common feature of all forms of evaporative cooling.
It is in this context that the use of earth tube heat exchangers is interesting.ETHE is a device that enables transfer of heat from ambient air to deeper layers of soil and vice versa, via pipes buried into the ground at depths where temperature stays nearly constant or at least the diurnal fluctuations has diminished.Santamouris 12 reported the experience of coupling the greenhouses to earth-tube-heat-exchanger placed deep into the ground for environmental control.Eighteen greenhouse installations drawn from different countries using ETHE were reviewed.Most were used for supplemental heating and met 28% to 60% of the requirement at different places.Actual use in cooling mode, if any, was not mentioned.But using simulated results for a greenhouse facility in Athens (37.5°N) they stated that ETHE would be an equally attractive supplement for cooling.Air temperature of the greenhouse in summer was predicted and compared with measurements from their 1000 m 2 glass-covered greenhouse coupled to a set of four underground parallel pipes made of plastic.The air change rate was not indicated.Simulations showed that continuous ventilation of greenhouse with air from the buried pipes will keep the inside air temperature below 40°C.Unventilated greenhouse commonly goes up to 45°C, they stated.Cooling capability of ground coupled systems is limited to the mean temperature of deeper layers of soil in a given place.But the fact that these do not use water and deep ground is a renewable source and sink of energy is interesting.
The above mentioned review led to the following: (a) climatic adversities notwithstanding, semi-arid areas do have features such as high solar radiation and long sunshine hours, which signify potential for high productivity, greenhouse technology is being used successfully in some such regions elsewhere to achieve that potential (b) environmental control, especially cooling, in such areas however is still a challenge; evaporative cooling is most effective, but also one that consumes largest amount of water, comparable or even more than the crop (c) development of control measures that are economical on water and energy would be desirable to successfully actualize via greenhouses the potential for high productivity in hot arid areas.In the context of Kutch region, a satisfactory solution would be one that, besides being economical on water and energy, is easy to maintain and run, able to cope with occasional electricity breakdown.It was decided to build a special greenhouse facility furnished with multiple measures -natural ventilation, shading, ETHE and mist nozzles for occasional supplementary evaporative cooling -and carry out investigations to determine which combination will be effectively address the problem.A R&D project was started with following objectives.1.To design and install a greenhouse facility at Kothara, consisting of a greenhouse with multiple measures -natural ventilation, shading, and ETHE and mist nozzles.2. To carry out investigations to determine the extent to which environmental control is achieved with the use of various measures.Also to determine the extent to which such a greenhouse can improve yields of important vegetables crops, conserve water and extend cropping season.

MATERIALS AND METHOD
Specifications for cladding, shade net, natural ventilation for the greenhouse and other units like the fertigation and mist nozzles, could be arrived at using accepted procedures and standards.To develop the specifications of ETHE to be connected to greenhouse however it was necessary to carry out investigations to generate local data.Sharan and Jadhav 17 monitored soil temperature regimes up to the depth of 3m for one year in Ahmedabad and, based on that, developed expression for annual wave propagation into the soil, Using diffusivity of local soil (0. 05469 m 2 /day) in the equation, it can be seen that the amplitude of fluctuation will become negligible (< 1 °C) beyond 6 m, with temperature becoming nearly constant, 26°C.Embedding pipes so deep will involve high trenching costs.It was decided to put the pipe at 3 m depth where temperature would be expected to vary 3°C around mean over the months.A single pass ETHE was installed next at 3 m depth to determine the actual heating and cooling potential (Figure 1).

FIGURE 1 EXPERIMENTAL SINGLE PASS EARTH-TUBE -HEAT-EXCHAGER
Details can be seen in Sharan and Jadhav 18 .It was made of a 10 cm diameter 50 m long mild steel tube.Three sensors (thermister AD 590) were installed inside, at the inlet, at middle ( 25 m) and at outlet (50 m).A direct drive industrial type 0.38 kW fan was used, a blower with radial blades, with air velocity in the tube being 11 m/s, and a flow rate of 0.0863 m 3 /s or 5.17 m 3 /min.ETHE was operated over three consecutive days each month for cooling tests and three nights of January for heating tests.When day tests were done, ETHE would be off during the nights -a break of 16-17 hours.It was observed from the sensor placed in soil near the entrance of the tube that the soil temperature regime was restored back to normal before start of new test.This is useful information as in the planned greenhouse facility it would be operated intermittently.Performance was broadly similar in cooling and heating modes.Tests in May showed that the ETHE cooled the ambient air by 10°C.Heating tests of January nights showed that it heated the ambient air by 10.6°C.Mean coefficient of performance (COP) in cooling and heating were 3.3 and 3.8 respectively.Most of the heat exchange, both in cooling and heating, occurred in the first 25 m length.Up to 12 hours of continuous operation did not show noticeable decline in performance.
Later, a mathematical model of the device was formulated 19 for use as a flexible simulation tool to study effects of changes in air velocity, flow rate, pipe dimension etc.The problem modeled was -a thin walled pipe buried horizontally at a depth below surface, air at a

Greenhouse facility at Kothara
Using the above results, a new facility was constructed at Kothara consisting of a greenhouse and a large ETHE connected in closed-loop.There was also provision for natural ventilation and supplementary mist nozzles, besides the usual fertigation and other internal units.The greenhouse was a single span, saw-tooth structure (20 m X 6 m X 3.5 m) with floor area of 120 m 2 and volume 360 m 3 .It is clad with 200 micron UV stabilized clear single skin PE film with transmittance of 0.8 (manufacturer's data).There are three closable vents, each 20 m x 0.5 m, two at the base of the side walls, a third at the top of higher side (Figure 4).Vents are screened with commercially available stainless steel wire mesh -15 strands per inch in each direction and whole size less than a 1 mm.Unscreened vent area was 25% of the floor area.A retractable shade net was put on top.Shade net was installed just above the cladding.Net used was green-black with shading of 50% (manufacturer data).There are 39 mist nozzles (manufacturers data operating pressure 4 kg/cm 2 , discharge 0.007 m 3 / hr ) installed 3 m overhead on a grid pattern.The ETHE connected to the greenhouse provides air flow rate equivalent to 40 changes per hour.It is made of eight pipes that connect to identical headers on both ends (Figure 5).Pipes are of mild steel with wall thickness of 3 mm, arranged in two tiers.The first tier is at 3 m and the second is at 2 m depth.Pipes are 23 m long and 20 cm diameter, placed 1.5 m apart laterally.Inside air from greenhouse is drawn, cycled through buried pipes and returned to the house.A centrifugal blower powered by 4 kW, 1440 rpm motor moves the air.
An eight-channel data logger (from Weather Technologies India) was used to record ambient temperature, global solar radiation, relative humidity, wind speed (three-cup anemometer) outside; and air temperatures at three locations, relative humidity at one location inside greenhouse.The outside sensors of temperature and humidity are placed two meters away from the greenhouse boundary and one meter above ground.The anemometer and the radiation sensor are located over a roof of a building 5 m high building 20 m away from the greenhouse.There are four sensors inside, three for temperature and one for humidity.All four are placed along the centre line one meter above the ground and weather shielded.One temperature sensor is placed at west end, one in the middle and one at the east end of the house.The humidity sensor is placed at the middle too.Data logger has LCD display, real time clock calendar, and serial output port for connecting it to PC with parallel interface to printer or memory module.

Cropping in greenhouse facility
Greenhouse has been under investigation for several years.Usually two crops can be raised from July to April.It is closed in most of May and June.Initially cropping was done through these months as well, but it becomes too hot, leading to poor quality undersize fruits.Several vegetables have been grown -tomato, okra, chilly, capsicum (bell pepper).Tomato has been grown over three rounds.Previous results were reported in Sharan at al. 20 , Sharan and Jethva 22 .
Here results of yet another round of tomatoes raised in the season of 2007-08 are discussed.Cropping practices were same as before except one change.Mist nozzles were not operated.This was because in previous rounds owing to poor water quality, mist caused deposits on the leaf surface leading to injury.Commercial hybrid (US 1080) was planted (45 X 45 cm) on 15 November, 2007.Fruit became ready for first picking 103 days after planting.The crop lasted more than 6 months through parts of June.Plants, pruned and trailed, grew to height of up to 1.6 m.Fertilizers were applied in liquid form via the drip line as per the stipulations of seed suppliers.Watering was done through drip, with duration and frequency decided by observation.Water quantity applied was noted using mean calibrated discharge of emitters and duration.Fruit size, shape and weight were normal to the type.Yield was 68 t/ha.The total water applied was 266 mm for irrigation and none for misting.Water used in open-field in this area would be twice as much and crop yield would be less than half.

Effectiveness of control measures
Control measures available are: a) Natural ventilation + shade net -typically used in combination, although some days in winter may not need shade; usually vents opened at 10:00 and closed at 17:00.b) Shade net + forced ventilation from ETHE -employed when heating is needed as on winter nights of December, January, usually turned on at 22:00 and off 06:00; it is also for cooling during day if greenhouse has tall and dense foliage which hindered natural ventilation.c) Shade net + ETHE+ mist spray -usually needed in hotter months March, April onwards; as stated in this round it was not deployed.
Figure 6 shows the temperature on November 15 with measure (a) in place.The peak inside temperature was 35 °C (mean of three locations), which was nearly equal to the peak ambient outside.The inside was marginally cooler than outside in the first half and warmer similarly in the afternoon.This appears to be the expected phase difference.Computations had indicated that measure (a) would reduce peak , Δ T , to only about 3 °C at mid-day in November (Table 1).It is plausible that some extra cooling was afforded by evaporation from largely bare and wet soil surface.Soon after planting for many days, the watering was done manually on the surface around seedlings.Mean inside humidity during the day was 62 %.Minimum and maximum temperature range computed for November is 15 -33 °C ( column 6 Table 1), in comparison to the range actually observed during the entire month (14-35 °C) .Figure 7 shows the temperatures inside and outside on December 14-15 with night heating on.ETHE was turned on at 22:00 hours and turned off at 06:00 hours next morning.It kept the inside temperature above 13 C. Day time peak temperature on 15th was 27 C. Expected range of temperatures inside as per earlier computations for December was 7 -28 °C, and actual range in the first half (before night heating started) was 11-32 °C .Heating was required at night from mid December to mid -January.Figure 8 shows the temperatures on January 14-15 with night heating, which was thereafter discontinued.Expected range of temperatures inside as per earlier computations for January was 8-34 °C, actual observed maximum was 32 °C.Ambient temperatures begin to rise after January.Expected range of temperatures inside as per earlier computations for February was 9 -35 °C; actual observed range was not available due to download malfunction in data logger.Figure 9 shows the temperature on March 15.Maximum temperature did not exceed 34 °C inside greenhouse and humidity was an average of 63 %.Inside was marginally cooler, most likely due to evaporation -transpiration cooling.By this time the crop was over 1.5 m tall with dense foliage.The mean humidity level also was higher compared to outside (53 %).Expected range of temperatures inside as per earlier computations for March was 17 -39 °C, observed 14 -36 °C.
Figure 10 shows the temperatures on April 15.By this time the tall and dense foliage trailed to structure above appeared to hinder natural ventilation.Accordingly, measure (b); shade net and forced ventilation via ETHE was used during the day.Vents were kept closed.Maximum temperature inside reached a peak of 34 °C, nearly same as the ambient.Mean humidity inside was 64 %, compared to 49 % outside.Expected range of temperatures inside as per earlier computations for April was 20 -39 °C, observed was 15 -37 °C. Figure 11 shows the temperatures on May 15.The greenhouse inside reached a peak of 36 °C, 3 °C higher than that of the ambient.Same measure of control (b) was in place.The average humidity inside was 70 % and 63 % outside.cleared soon after.To recapitulate, the top shade and natural ventilation in cooler months, top shade and forced ventilation with ETHE kept the inside temperature close to that outside.But as radiation levels and ambient temperatures rise in May and June, inside temperature did exceed by 1-3 °C.The humidity levels were generally lower than required for tomatoes, especially in cooler months (December, January).Since mist nozzles were not operated it could not be improved.For future, it is planned to change nozzle location to the end from which ETHE air enters the greenhouse.This is to prevent depositions on plants while humidifying the incoming air.

LEARNING AND PARTNERSHIPS
The sequential presentation above may give the impression of a pre-planned research project.In reality the work sequence evolved driven by the results achieved and insights gained.The engagement that has now spanned several years began by a visit to the region to observe and understand the problems when a severe drought occurred in Kutch region causing widespread shortage of food, fodder and water; and leading in turn to large scale cattle fatalities and displacement of people.The author traveled to rural parts expressly to identify problems to work on.Direct observation and conversation with people led to conceptualization of possible solutions.A concept paper was drafted arguing that open-field cropping will always be a low yielding, risk-prone business under the prevailing climatic and agronomic conditions.Covered cultivation could be a better way to use scarce water, grow high value produce on a steady basis.But at the time there was no experience in the country on greenhouse cropping in hot arid regions.A symposium was therefore convened to discuss the feasibility of this approach.Participating engineers and other scientists pointed out that unless cooling was possible without the use of water, greenhouse cultivation would not be an advantage.This led to researches on ETHE, starting from measurement of deep soil temperature.Only after the results showed the possibility of using deep strata of soil as sink and source, an outline of future work emerged.
As the outline began to be clear, it was necessary to define the goal of the endeavor.Goal was set as -a practical solution -development of greenhouse especially suited to the environment of the region and one which would help farming community to improve incomes.In remote rural areas of this region, many basic problems have remained unsolved because research endeavors usually ended up contributing to knowledge (publications), but not products or solutions that people could use.An emphasis on -solution or product -is important.
It became necessary to set-up an experimental station in the rural part of the region.At that stage however there was no funding, and no physical facilities to work.Cummins Foundation (India) was approached to help with funds and Gujarat Energy Development Agency (GEDA) with infrastructure.Former supported innovative application of engineering to solve problems in rural areas and therefore responded positively by providing funding to rent accommodation and for small office staff.Latter provided us access to their small campus in the village of Kothara.GEDA also funded our initial researches in ETHE.These two partnerships were crucial in getting started.Partnership with GEDA continues.Development of solutions entails greater uncertainties than is usually the case with well (and narrowly defined) research projects.It is important to find partners who appreciate this.Sharing the results of the work, progress and set-backs with the partners frequently is helpful in retaining them and also in finding others.Regular reports and when possible visits to the site by the partners are a good practice in such endeavors.
Development and Outreach Station ( DOS ) , Kothara hosts up to six engineering summer interns each year who work with ETHE , greenhouse and other projects.A total of 35 interns have worked there over the years.Requests from graduate students have also come from overseas (Spain, Mexico, Kuwait, Brazil ) seeking clarifications via emails on ETHE research for their own areas.

BENEFITS TO THE REGION
Benefits to the region accrued as the new technology was introduced.The first commission to build a air-conditioning system using ETHE came from the Ahmedabad zoological garden which wanted it for the dwelling of tigers 16 .The zoo authorities saw the cooling and heating mode results and noted that ETHE could be appropriate for animals especially as it did not add humidity to dwelling which is unhealthy for the animal that lack sweat glands.The installation pioneered the use of such device in a zoo.It is regularly used as training and demonstration unit for other zoo keepers who come for refresher courses periodically.Subsequently two similar systems were made for milk cows at animal science departments of two agricultural universities, Anand and Junagadh.These units are also useful for teaching environmental management in cattle houses.Requests continue to be received from dairy cattle owners for such installations.Enquiries also come for adaptation of ETHE for human residences and work places.Given our focus on agriculture and livestock, we responded only in a limited manner.One large auditorium at the Science City, Gandhinagar and one small residence of an architect were built to improve comfort.Two local entrepreneurs have been trained in fabrication, installation and maintenance of ETHE systems.

FIGURE 2 MESHFIGURE 4
FIGURE 2 MESH PLOT OF SOIL TEMPERATURE AFTER 4 HOURS ( T* = 40 o C T 0 = 26 o C

InternationalFIGURE 7 FIGURE 9 FIGURE 11 TEMPERATURES
FIGURE 6 TEMPERATURES INSIDE GREEN HOUSE AND AMBIENT

FIGURE 12 TEMPERATURES
FIGURE 12 TEMPERATURES INSIDE GREEN HOUSE AND AMBIENT The expected range of temperatures inside as per earlier computations for May was 21 -38 °C, observed was 20 -38 °C.Figure12shows the temperatures on June 8 with same measure of control.The peak inside temperature was 38 °C, outside 37 °C.Mean humidity inside was 74%, outside was 64%.Expected range of temperatures inside as per earlier computations for June was 20-37 °C, observed was 22 -37 °C.Fruit size in June became smaller, crop was