Week 7:FYP1:- Chapter 2 (Literature Review)

5) HUMIDITY CONTROL

Healthy plants can transpire a lot of water, resulting in an increase in the humidity of the greenhouse air. A high relative humidity (above 80-85%) should be avoided because it can increase the incidence of disease and reduce plant transpiration. Sufficient venting, or successively heating and venting can prevent condensation on plants surfaces and the greenhouse structure. The use of cooling systems during the warmer summer months increases the greenhouse air humidity. During periods with warm and humid outdoor conditions, humidity control inside the greenhouse can be a challenge. Greenhouses located in dry, dessert environments benefit greatly from evaporative cooling systems because large amounts of water can be evaporated into the incoming air, resulting in significant temperature drops [5].

Since the relative humidity alone does not tell us anything about the absolute water holding capacity of air, a different measurement is sometime used to describe the absolute moisture status of the air: the vapor pressure deficit (VPD). The vapor pressure deficit is a measure of the difference between the amount of moisture the air contains at a given moment and the amount of moisture it can hold at that temperature when the air would be saturated. Pressure deficit measurement can tell us how easy it is for plants to transpire: higher values stimulate transpiration (but too high can cause wilting), and lower values inhibit transpiration and can lead to condensation on leaf and greenhouse surfaces. Typical VPD measurements in greenhouses range between 0 and 1 psi (0-7 kPa).

6) METHOD OF WATERING SYSTEM 

Watering is the most important cultural practice and most labor intensive task in daily greenhouse operation. Watering system ease the burden of getting water to plants when they need it. Knowing when and how much the water is two important aspects of watering process. To make the gardener works easily, the automatic watering system is created. There have a various type using automatic watering system that are by using sprinkler system, tube, nozzles and other. 

This project is used watering sprinkler system because it can watered the plants in a greenhouse from leaf to roots.  The system is often used for general plant care, as part of caring for small and large gardens. Normally, the plants need to be watered twice a day, morning and evening. So, the microcontroller has been to watered the plants in a greenhouse about two times per day.

7)  UNDERSTANDING PLANTS, SOIL & WATER

Plant needs the nutrients in soil to grow. They also require water, and it is water in the soil that carriers the nutrients to the roots of the plants. Then it is absorbed and used in building new plant cells. Water is also needed for photosynthesis. During photosynthesis, plants combine water with carbon dioxide to make food for them [6].

The greatest mistake in common gardening is improperly watering. Watering at evening is a definitely no. Fungus requires 3 living conditions and one of them is darkness which occurs after evening and the dampness due to watering. Usually soil is warmer than surrounding. Therefore it best we only water in the morning before peak photosynthesis occurs during the afternoon where most water is needed. Plant doesn’t perish overnight if you don’t water during the night. Don’t forgetting wet soil by the night is irresistible to slugs and snails.

Another common problem is frequent shallow watering, rather than occasional, pro-longed watering provided will do plants more harm than good by making the top 2 inch too wet, by discouraging the formation of lot puny roots near the surface, and by discouraging the development of deep tap roots [7].

Probe the soil to a depth of 6inch or so. If the soil is dry for the first 2 inch to 4 inch but damp at 4 inch to 6 inch, it means there is enough moisture in the soil bed for healthy plants to reach and use. It will be mistake to water now, because it would cause the tap roots on the plants to cease their trip downward. By waiting another day or two, you will encourage the plants to dig a little deeper and thus enlarge their feeding area.