HYDROPONICS
Plant anatomy, physiology and growing requirements
Plant anatomy Plant anatomy describes the structure and organization of the cells, tissues and organs of plants in relation to their development and function. Flowering plants are composed of three vegetative organs: (i) roots, which function mainly to provide anchorage, water, and nutrients, and to store sugars and starch; (ii) stems, which provide support; and (iii) leaves, which produce organic substances via photosynthesis. The roots grow down in response to gravity.
· Aqu@teachIntroduction to hydroponics
The principles of hydroponics Hydroponics is a method for growing crops without the use of soil, and with nutrients added to the irrigation water (so called fertigation) (Figure 1). The main differences between traditional in-ground growing techniques and soil-less techniques concern the relative use of water and fertilizer, and overall productivity. Soil-less agriculture is also typically less labour-intensive, supports monocultures better than in-ground agriculture, and can be used on non-arable land (Somerville et al.
· Aqu@teachHydroponic systems
There are three main types of hydroponic systems (see also Module 1). In media bed hydroponics the plants grow in a substrate. In nutrient film technique (NFT) systems the plants grow with their roots in wide pipes supplied with a trickle of water. In deep water culture (DWC) or floating raft systems the plants are suspended above a tank of water using a floating raft. Each type has its advantages and disadvantages which are discussed in more detail below.
· Aqu@teachGreenhouse control systems
Control systems include those for lighting, heating, cooling, relative humidity, and carbon dioxide enrichment. Whilst it is helpful to have a fully controlled environment, aquaponic cultivation can also thrive without it, or with only some of the parameters being controlled. Light Maximum light transmission, of the appropriate quantity and quality (PAR, 400-700 nm), is crucial for optimal photosynthesis, growth and yield. If there is too much light in the summer, shade paint or white wash can be sprayed on the outside of the greenhouse.
· Aqu@teachGeneral cultivation practices
Staggered planting allows for continual harvest and transplant of vegetables. It is best to have an excess of plants ready to go into the system, as waiting for seedlings to be ready for transplanting is a source of production delay. Crop scheduling is covered in more detail in Chapter 7. Transplants from seeds Collecting seeds from growing plants is an important cost-saving and sustainable strategy, except when F1 hybrid plants are being grown (see below).
· Aqu@teachFertigation
Fertigation is the use of fertilizers in the appropriate combination, concentration and pH. Mineral nutrition is critical for optimal plant growth. Optimal nutritional conditions can vary between different plant species, for the same plant species at different times of its life cycle, for the same plant species at different times of the year, and for the same plant species under different environmental conditions. Even balanced aquaponic systems can experience nutrient deficiencies.
· Aqu@teach