Hydroponics is proven technique to grow herbs. All most every popular culinary herbs can be grow with hydroponics technique. The most important herbs are: basil, chive, chervil, dill, lavage, marjoram, Oregano, parsley (curly or plain), sage, savory, tarragon and thyme. The advantage with herbs is that it does not required big or sophisticated system, rather they can be grown successfully in small and basic arrangement.

Some important noteworthy Hydroponics Herbs :-

BASIL  :- It is the secret that accounts for many delicious southern Italian dishes containing tomatoes, such as spaghetti and ravioli sauces. This herb will lend a new and interesting flavour to practically all foods. It is one of the few herbs that actually increases in flavour when cooked.

CHIVE

The smallest of the onion tribe, chive has a subtle flavour. It is one of the best culinary herbs, making fatty foods more digestible and giving a special piquancy to almost anything. It is excellent when used on salads, soups, in cottage cheese, devilled eggs or in the famous Green Sauce that will be given later.

DILL

The lacy leaves of dill are delicately aromatic and when finely chopped yield a very special, sharp and interesting flavor.  Dill grows tall and graceful (two to three feet) and other things can be planted beneath it. However, don't grow dill next to fennel; they cross-pollinate and produce strange and useless offspring that are neither dill nor fennel.

LOVAGE

This giant herb has a strong scent reminiscent of yeast or the famous soup extract, Maggi. It gives strength to soups, stews, casseroles, salads and mixed vegetables. This extraordinary herb deserves a bit of experimenting. Lovage is an important flavoring for some vegetarians, for it provides the tastes normally associated with meat or soup bones.

OREGANO

this herb is a favourite in Italian, Spanish and Mexican dishes. Its hot flavour is best in tomato dishes, spaghetti, pizza, hamburgers, meat loaf, .sauces, stews and stuffings. Tomato or bean soup is much improved by the addition of a small quantity of Oregano. Oregano in cooking is as old as the Greek hills where it originated, and it has both stimulating and medicinal properties.

PARSLEY

Parsley underlines the taste of food. It has a remarkable gift for overcoming strong odours on the breath, even the powerful garlic is largely neutralized by it. In large amounts, it is a good natural tranquilizer. The finely chopped leaves are added twice in cooking; at the beginning when other flavours are brought out, and again shortly before serving. Parsley is a carefree crop, but very slow to germinate.

SAGE

The beautiful gray-green leaves of this wisest of all  the mints is a must in every kitchen. The ancients thought it prolonged life, the Chinese love it as a tea for medicinal purposes and the modern family uses this incredibly fragrant herb on a modest scale in cheese dishes and sausages.

THYME

You would almost think thyme was the twin sister of sage, since they go so well together. The beautiful, broad, dark green leaves of the English variety and the narrow gray-green leaves of the French type are the most flavourful and popular of all thymes. In early Greek and Roman days it was used on the body as an antiseptic. Today, however, it is without equal as an additive for soups, sauces and stuffing.

Chervil 

improves the flavour of any herb with which it is mixed, making it a constant ingredient in the fines herbs of French cooking. Chervil's mild flavor makes generous use necessary.

Growing time and yield of herbs in Hydroponics System

	Growing Time(days)		Yield (gm)
Variety	1st Cut	Replacement	1st Cut	Replacement
Basil	9 to 12	4 to 7	252	420
Chervil	12 to 16	7 to 10	140	224
Chive 15-20 7-10 3 5-8	15 to 20	7 to 10	84	196
Coriander 15-20 7 5 8	15 to 20	7 to 10	140	224
Dill 12-15 5-7 5 8	12 to 15	5 to 7	140	224
Marjoram 12-15 5-7 4 5	12 to 15	5 to 7	112	140
Mint 24-30 7-10 6 10	24- 30	7 to 10	140	252
Oregano 13-18 4-7 4 5	13 to 18	4 to 7	112	140
Parsley 13-18 7 5 8	13 to 18	7 to 10	140	224
Rosemary 15-24 10 6 8	15 to 24	7 to 10	168	224
Sage 12-18 6-9 8 12	12 to 18	6 to 9	224	336
Savory 14-20 7-10 8 12	14 to 20	7 to 10	224	336
Sorrel 14-19 7-10 8 12	14  to 19	7 to 10	224	336
Tarragon 20-30 10 5 8	20 to 30	7 to 10	140	224
Thyme 18-24 7-10 3 5	18 to 24	7 to 10	84	140
Watercress 12-15 6-10 5 8	12 to 15	6 to 5	140	224

Variety	Growth 1st Cut (Days)	Replacement (Days)	Yield 1st Cut (gm)	Yield Replacement (gm)
Basil	9 to 12	4 to 7	252	420
Chervil	12 to 16	7 to 10	140	224
Chive	15 to 20	7 to 10	84	196
Coriander	15 to 20	7 to 10	140	224
Dill	12 to 15	5 to 7	140	224
Marjoram	12 to 15	5 to 7	112	140
Mint	24- 30	7 to 10	140	252
Oregano	13 to 18	4 to 7	112	140
Parsley	13 to 18	7 to 10	140	224
Rosemary	15 to 24	7 to 10	168	224
Sage	12 to 18	6 to 9	224	336
Savory	14 to 20	7 to 10	224	336
Sorrel	14  to 19	7 to 10	224	336
Tarragon	20 to 30	7 to 10	140	224
Thyme	18 to 24	7 to 10	84	140
Watercress	12 to 15	6 to 5	140	224

The Growing media is one of the most important bur less discussed component. It is practically observed that it is significantly play role in crop yield and success of system.  A number of material in number of combinations are being used for hydroponics cultivation.  The Substrate must have some important characteristics.

Water holding capacity is one of the most important feature. While Particle size is controlling factor for both the water-holding capacity and aeration. High water-holding capacity and humid air spaces in the mix are important for germination and seedling and cutting growth, while good aeration and moderate water-holding capacity are essential for long-term plantings.

The pH balance is one of the considerable factors for substrate. The ideal substrate should be inert for nutrient salt and should not alter pH micro environment of system. The pH of substrate mix should not exceed a water pH of 5.5, with the optimum pH range between 4.5 and 5.5.

Adding nutrient to substrate is another good idea but a grower must keep the ratio as per his/her practical experience.  From a practical standpoint and for short-term cropping (growth period of less than 8 weeks), nutrient elements and the other essential elements would be added to the mix when constituted. 

Characteristics of some substrate components

Sand A common component it is added to provide porosity in fine mixes or weight when needed to keep plant containers upright in either fine or coarse mixes. However, sand should not constitute more than 20 to 25% of the mix. If more than 50% of a mix is sand, weight and reduced water-holding capacity become a problem. The recommended grade of sand is “builder’s” sand, which is a coarse-particle sand; 100% passes a 10-mesh sieve but only 30% a 40-mesh sieve.

Rockwool or Stonewool  Clean, (can cause skin irritation), sterile, lightweight when dry, reusable, high water holding-capacity (80%), good aeration (17% air-holding), no cation exchange or buffering capacity, provides ideal root environment for seed germination and long-term plant growth. Rockwool is probably the most widely used hydroponic growing medium in use in the world today for the production of tomato, cucumber, and pepper). Rockwool has excellent water-holding capacity, is relatively inert, and has proven to be an excellent substrate for plant growth but the disposal of used rock wool is becoming a major problem.  In India availability of material with right density and costing is issue.

Vermiculite is Porous, sponge like, sterile material, lightweight, high water absorption capacity (five times its own weight), but excellent with 10 to 20 % in substrate mix, easily becomes waterlogged, relatively high cation exchange capacity.

Perlite is Siliceous, sterile, sponge  like, very light, free-draining, no cation exchange or buffer capacity, good germination medium when mixed with vermiculite, but the problem associated is dust can cause respiratory irritation.

Expanded clay Sterile, inert, range in pebble size of 1 to 18 mm, free draining, and physical structure can allow for accumulation of water and nutrient elements, reusable if sterilized, commonly used in pot hydroponic systems

Coconut fiber Made into fine (for seed germination) and fiber forms (coco peat, palm peat, and coir), useful in capillary systems, high ability to hold water and nutrients, can be mixed with perlite to form medium that has varying water-holding capacities, products can vary in particle size and possible sodium contamination.

Peat Used in seed raising mixes and potting media, can become waterlogged and is normally mixed with other materials to obtain varying physical and chemical properties.

Sawdust Fresh, un-composted sawdust of medium to coarse texture good for short-term uses, has reasonable water-holding capacity and aeration, easily decomposes which poses problems for long term use, source of sawdust can significantly affect its acceptability.

Rice hulls  Lesser known and used, has properties similar to perlite, freed raining, low to moderate water-holding capacity, depending on source can contain residue chemicals, may require sterilization before use

Hydroponics is proven technology for commercial cultivation. Now the technologies is been explored for its suitability for commercial greens.  Experiments have shown that hydroponically grown aromatic plants have higher productivity, in addition to accumulate 3–6 times more essential oil per unit of feeding surface, compared with field grown ones. The root environment of hydroponic plants is abundantly provided with water, nutrients and air, with a corresponding increase of the metabolic and absorbing activity of roots, which, in its turn, initiates development of plant over ground part with increasing biological and economical productivity several folds.

 Grass Suits for Hydroponics System

Palmarosa

Palmarosa (Cymbopogon martinii) is a widely distributed plant in India that yields a sweet, fragrant, aromatic oil. The flowering tops and foliage contain a sweet-smelling oil that emits a rose-like odor and is widely used in soaps, cosmetics, and perfumery industries. Oil of palmarosa is used in perfumery, particularly for flavoring tobacco and for the blending of

Soaps.

The plants attain a height of 150–200 cm with dense root growth. The harvesting spawn is near about 3 years. In optimal conditions harvesting may be started in 75 days. 3 cuttings are made during the first year of planting. From the second year onward, three to five cuttings are possible. From second year up to 5 cuttings are possible.

 Lemongrass

It is a perennial, multicut aromatic grass that yields an essential oil used in perfumery and pharmaceutical industries and vitamin. Lemongrass is widely used in Thai and Vietnamese cooking. Valued for its exotic citrus fragrance, it is commercially used in soaps, perfumes, cosmetics, and disinfectants, and is a raw material for manufacturing ionones and vitamin A.

During the first year of planting, three cuttings are obtained and, subsequently, five to six cuttings per year are taken, The plants attain a height of 200 cm. During the first year of planting, three cuttings are obtained and, subsequently, five to six cuttings per year are taken, up to 3 years.

Citronella

Citronella Citronella is a perennial, multiharvest aromatic grass, the shoot biomass of which, on steam distillation, yields an essential oil extensively used in fragrance and flavor industries. The oil is widely used in perfumery, soaps, detergents, industrial polishes, cleaning compounds, and other industrial products. In optimum condition it can grow upto 200 cm high. Its multi harvest plants and harvesting intervals can be 45 to 60 days.

Electrical conductivity is a measure of the nutrient solution’s concentration through its ability to conduct electricity. Pure water does not conduct electricity, but any water having solutes (elements) added to it has the capacity to conduct electricity. The EC of a nutrient solution can significantly affect plant growth. . Electrical conductivity (EC) is frequently used as a means of determining elemental replenishment needs in closed recirculating nutrient solution growing systems.

An EC measurement of the nutrient solution is used to determine nutrient element top up levels. Note that the EC value indicates the total strength of the solution but nothing about the balance of nutrients within it, so, its use in the management of hydroponic solutions is limited.

The raw water used for the hydroponic solution may itself contain dissolved nutrients which will contribute to the strength of the solution. A water quality test will ascertain which nutrients are present and their concentrations, and should be taken into account when making up the hydroponic solution

 Units of measurement

decisiemens per meter (dS/m)

millisiemens per centimeter (mS/cm)

microsiemens per centimeter (μS/cm)

(1 dS/m = 1 mS/cm = 1000 μS/cm = 1 mmho/cm)

(1 μS/cm = 0.001 dS/m)

EC (in dS/m) x 640 = TDS [in mg/L (ppm)]

(approximate measurement, depends on type of salt)

cf. (conductivity factor) of 10 = 1 dS/m

Electrical conductivity adjustment of the nutrient solution is recommended when the plants are to be stressed, as water uptake by the plant is reduced when the EC of the nutrient solution and/or rooting

Medium is increased. Change in the electrical conductivity (EC) of a solution surrounding the root, or may alter the pH of the surrounding solution.

High EC in the rooting medium can result in plant wilting on high atmospheric demand days because insufficient water is being taken up through the plant roots to keep the plant turgid.

The target EC of a nutrient solution can vary according to the crop being grown, stage of growth and climatic conditions. Most nutrient solution formulas have a fairly low [<3.0 dS/m (mmhos/cm)] EC when initially made.

In hot, low-humidity days, if the water loss is not replaced, the EC of the nutrient solution will rise. The EC of the nutrient solution, and particularly that of the solution in the medium, becomes critical when it exceeds 4.0 dS/m.

In an NFT system most leafy greens such as Basil, Choy Sum, Tat Soi, and Coriander Pak Choy grew best in the nutrient solution managed in an EC range of 1.5-2.5 dS/m.

Nitrogen is probably most discussed Nutrient element in hydroponics community. And it deserve so because Nitrogen probably has a greater total influence on plant growth than most of the other essential elements. A plant leaves contains N, around low of 2.00 to a high of 5.00% of the dry weight. Nitrogen is a major constituent of amino acids and proteins that play essential roles in plant growth and development. Here we will figure out thins to remember for Hydroponics cultivator.

Nitrogen Deficiency Symptoms in Hydroponics

Nitrogen deficiency appears as a lightening of the normal green color associated with a healthy plant appearance. First symptoms of N deficiency appear on the older leaves, which become light green in color. Nitrogen deficiency will shift the morphogenetics of the plant, reducing growth, bringing an early onset of flowering and early completion of the life cycle.

The Sulphur Mimic

Sulphur deficiency symptoms can mimic those of N deficiency, although S deficiency symptoms appear over the entire plant, while N deficiency symptoms initially appear on the older tissue, and then advance over the entire plant as the severity of the deficiency increases.

Excess is dangerous too

There is as much danger in N excess as deficiency, particularly for fruiting crops. Excess Nitrogen in hydroponics system frequently does more permanent damage to the plant than does N deficiency. Excess N produces lush plants with dark green foliage. Such plants are susceptible to disease and insect attack and have greater sensitivity to changing environmental conditions.

Ammonium versus Nitrate

NH4+ in the nutrient solution stimulates the uptake of NO3–. It has been shown that as little as 5% of the total N in solution as NH4 + in a flowing nutrient solution system is sufficient.  Experience has shown that the percentage of NH4 + ions in the nutrient solution should not exceed 50% of the total N concentration; the best ion ratio is 75% NO3 – to 25% NH4+.

Ammonium Toxicity

Ammonium can be toxic to plants when it is the major source of N, resulting in slowed growth and development. Lesions will develop on the stem and leaves, and leaves will develop a cupping appearance. The vascular tissue may begin to deteriorate. Another factor that needs to be considered when selecting the proper ion ratio of NH4 + to NO3 – in the nutrient solution is plant species. Fruiting plants, such as tomato and pepper, are particularly sensitive to NH4 + nutrition.

Roots and Elemental Uptake

It is known that the N concentration in the nutrient solution can influence the character of root growth. As the NO3– concentration increases, the number and length of root hairs decreases. Concentrations of the other major elements, P, K, Ca, and Mg, have no similar effect. Even a change in the NH4 + content  of the nutrient solution has no effect on root hairs.

Key Takeaway

Nitrogen is considered most important nutrition element in Hydroponics system. Nitrogen deficiency and excess can be easily figure out during plants growth stage. But one must check Ammonium and Nitrate ratio in Hydroponics Nutrition Recipe.