The use of greenhouses will help to regulate several key factors that greatly affect the yield and production of crops. These are factors are particularly annual growing season and temperature. A greenhouse will also allow other aiding factors to be utilized. Two in particularly will be: supplied carbon dioxide (CO2) and sound treatment.
Growing Season
Nothing can be more destructive to a crop than an inadequate growing season or a single night of freezing temperatures. A greenhouse controls these factors by providing the capability of shielding destructive weather and regulating the growth area’s temperature. This would mean that crop that crops can be grown year round and without any "interruptions" due to cold temperatures. If a weighted average of a group of main crops growth is around days a year, then a greenhouse could provide up to growth seasons a year (=).
Temperature
Increases that would be due to constantly having optimum daily temperatures have been calculated to be around .
Carbon Dioxide
It is said that supplied CO2 can increase crop yield by -. (See this site. A similar crop yield increase analysis & tabulation is also done there.) As CO2 is naturally produced in human respiration and with the way HC homes are designed with rooftop greenhouses, it will be easy to supply crops with some of the supplemental CO2. The rest could come from dry ice which is made from liquid CO2 and, if applicable, it could come from the burning of biomass fuel for energy.
Sound Treatment
It is not a myth that plants are affect favorably by certain customized sounds they hear during growth. (See this site where tremendous increases in yield (50 to 500%) are reported). In a greenhouse environment it will be easy to set up and control the sound equipment needed to apply this treatment. A conservative yield increase of only will be used here.
Hydroponic Units
The farming method of growth known as hydroponics ("water-work") is the ideal method for the Holy City’s agriculture need. It also provides several key advantages which contribute to higher crop yields which thus reduces the space needed for growth.
As a soiless medium which uses water instead, a resource which is of course readily available to the HC. In fact, it is said that hydroponic systems uses up to 30 times less water than soil systems. Water systems also allow for plants roots to "breathe" better as the system can be periodically drained to allow the roots to take in oxygen.
Hydroponically grown plants are also healthier than soil grown plants mainly because soil borne diseases, weeds, pests and parasites are not inherent in the water based system.
Hydroponics also allow nutrients to be efficiently supplied and absorbed during growth as they are more readily accessible by the plants’ roots. This allows for a reduction in the spacing between plants without affecting the roots nutrient supply. Also, plants expend much less energy in searching for nutrients as they are directly supplied to them, particularly with the use of Nutrient Films. This saved energy is instead used by the plant for produce growth and development.
Additional Links:
Photo: Hydroponic Wheat Growth
Supplemental Lighting
L.E.D.
Shelving
With shrub-type crops such as lettuce, cabbages etc, a circular layout can be used to further minimized needed space. In this layout the crops would be rotate periodically to have access to water and nutrients. With a circle’s perimeter being 3.14 (Pi) times its diameter, the area needed for growing these types of crops is reduced by this factor of 3.14. However, it is estimated that only of the HC crops would be able to use this arrangement so a minimal gain of only will be made in the spaced saved.
HC Agriculture Advantages
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