Disadvantages and possible solutions
Please advise the problems and disadvantages of Poly house farming. We are going to start a poly house farming (4000 sq meter) in Kerala, India. We are aware of its benefits and advantages. But we want to know the major disadvantages of it, if any. If any experienced, experts on this topic are available here, please advise.
There is one major disadvantage that comes to our mind. Last time I checked, in Kerala the government gives 75% subsidy for Naturally Ventilated Poly house. While only 50% is available for fan and pad system. The argument is that Kerala's climate doesn't need Fan and Pad. This could not be further from the truth. Having visited numerous poly-houses, here are some of the common complaints:
> Excessive Heat, particularly during the summers can make the poly house a slaughter house for plants. This isn't the case for open field cultivation every-time.
> Inorder to counter this excess heat, many farmers are resorting to excessive misting leading to excess moisture - which then makes the polyhouse a breeding ground for Fungi.
> Since they do not have sensors to measure things accurately, they do not have any idea about the appropriate temperature, moisture and water needed for the plants or achieved after misting/irrigation so are bound to overdo or underdo it. This may override the very benefit of constructing polyhouses.
> Farmers have little control over airflow and temperature in naturally ventilated polyhouses unlike artificial ones, this may limit their choice of produce to ones that suit the climate.
> Naturally Ventilated Polyhouses have to be unnecessarily taller than those with fan and pad, leading to wastage in metal costs and labor charges during construction phase.
> Stagnant air and lack of air circulation makes the breeding ground for insects. Though farmers try to limit entry, the insects are smart to get in somehow.
> Lower replenishment of CO2 supply.
> Low quality films cause easy wear and tear in heavy rains, making crops vulnerable.
> For many subsidy are yet to be released - this puts the polyhouse builder and the farmer in uneasy situations
> The saddest part is that, many of the polyhouse farmers had to cut down several coconut trees just because the "specifications" needed clear land. In the west there are greenhouses built by using trees as supports, in between the redwoods and they run pretty well.
There are solutions to many of the problems above -
> To counter the heat and stagnant air, Ventilation systems should be used especially during the hot summers. Note: If you are planning to use evaporative cooling pads - make sure air flow pathways are properly regulated otherwise it might result in the same problems caused by excessive misting. Since ventilation systems don't fall under subsidy in Kerala, you may have to shell it out from your own pocket.
> Most polyhouses in India, unlike in the west, don't seem to have any sensors. The farmers here are like Blind men searching for a black cat in a pitch dark room at night. This lack of technology adoption is partly responsible for the yield gap. Using agricultural probes and sensors will help quantify and asses plant health and give an idea on how much to irrigate.
> Regarding the felling of trees - The argument given to me by one person is that it "blocks the light". Considering the width of the coconut trees, plenty of space between them and the fact that the earth revolves, the "block the light" argument is pretty much absurd. There are options like Phillips Horticultural lights which are at a fraction of the cost of "cutting down full grown coconut trees". The revenue from the coconuts would be sufficient to cover electricity charges of LEDs even if the agricultural electricity is not subsidy. Fabric support sheds could have been provided to prevent coconuts from falling into greenhouses. Not to mention that this argument doesn't apply for species that need shade to grow where the presence of trees is desirable.
Polyhouses unlike open field agriculture, often require more technical guidance. Hence, another possible demerit is the lack of support - many farmers complained about feeling abandoned after polyhouses were constructed. Being independently well versed in technical aspects of running polyhouses is of great importance before venturing into the business. Polyhouses require intensive investment so do also make sure to make thorough research for your produces at your local market place through practical on the ground terms.
There are cases of growers running polyhouses having a difficult time trying to sell produce - many a times this is not due to lack of demand but due to difficulty in finding people who will transport food. Incase your grower society/co-op doesn't have your own pre-cooling unit or reefer truck yet, then you might suggest them to apply for scheme where government support is available for reefer/precooling units.
