As in due course of time, Pakistan may have to make use of its barren lands to meet the food requirement of its rapid growing population
By Dr. S.M. ALAM and Dr. R. ANSARI
Apr 09 – 15, 2001
There are many excellent works, one can point out, which sufficiently presents the early work, that was done with the hydroponics (soilless) culture of plants. Woodward in 1699 made the earliest use of water culture method without any solid material. During the 1700s, several workers attempted to find out, what caused plants to grow. Later on in 1800s, Sachs and Knop in Germany conducted experiments, which helped to determine that certain essential elements were contributors to plant growth. Out of this early research proved the basic for preparing and managing the nutrient solution for growing plants. It was during the hundred years period from 1850 to the mid l900s, that all the currently recognized essential elements required by plants all over the world were discovered.
The word “Hydroponics” is a term commonly used in describing solution culture, water culture, liquid culture, chemical culture, aqua culture, vermiculiculture soilless culture or any of a variety of invented names. In the scientific field, it is used as a general term for growing plants without soil, whether water, sand, gravel, or any other inert material. These techniques may be divided into several categories, such as with and without root supporting media and static aerated or following nutrient solution with or without its reuse. Sand or gravel culture, the nutrients solution either periodically flooding the growing bed or vessel of dripped through it, is still widely used technique. However, the water culture method was developed in 1929 by Prof. W.F. Gericke of University of California Researcher, who demonstrated on a semi-commercial basis that plants could be grown to maturity without any soil. No other aspect of plant production has caught the fancy of the public than soilless growing normally thought of the public as hydroponics. Popularized in the 1930’s by various books and writings on the object, hydroponics become a widely and frequently used technique for growing plants and vegetables in various countries of the world. However, this soil less culture procedure is not well suited, where precise control of the nutrient elements is desired. In 1930, there was a renewed interest in hydroponics. These most significant researches being done on soilless culture, primarily hydroponics, was being conducted at the Environmental Research Laboratory, Tucson, Arizona, USA and at the Glasshouse Crops Research Institute, Littlehampton, England. Later on, it was adapted in many other countries of the world. There are several factors, which control the growing of plants in soilless culture. These factors are control of pH, chemicals to be used in nutrient elements, electrical conductivity of the nutrients solution and temperature of the nutrient solution, and aeration of solution.
There are large barren areas (highly saline, sandy and gravelly areas) in Thar deserts, Thal and Cholistan, in the provinces of Sindh and Punjab, where normal agriculture is not feasible due to absence of good quality soil and enough sweet irrigation water. In such areas, hydroponic culture has proved an alternative for raising fresh vegetable crops. In this system, instead of soil, gravel or sand serves as the supporting medium and nutrient solution containing N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo, and Cl serve as plant food and due to the recycling of irrigation water, there is manifold saving on irrigation water. It may even be possible to use underground brackish water under hydroponics system.
Hydroponics use in Pakistan: As in due course of time, Pakistan may have to make use of its barren lands to meet the food requirement of its rapid growing population, it is considered worthwhile to explore the feasibility of growing fresh vegetables, using the local materials and with necessary modifications of the nutrient solution suited to our conditions.
Techniques and methods: At the first instance, for the experimental purpose, gravel and desert sands collected from Thar desert and Thana Bulla Khan were treated with 4% formaldehyde solution and washed thoroughly with tap water for several days prior to sowing vegetable seeds. Depending upon the seasons (Rabi and Kharif) various crops e.g. tomato (cvs. Fantastic, Roma VF, T-10, Summer Giant, Bountry, Marglobe, Marmande, Money maker etc), pepper (California wonder), bean, lettuce, watermelon, muskmelon, cucumber and kakri of different varieties, groundnut, garden pea, (American wonder), cotton, bajra, cauliflower (Chin Ka Moti), potato (atom Aloe-DRM), okra, sugarcane etc. were grown in desert sand and gravel media. Proper distance between rows and plants were maintained. All these crops were grown in 4 beds of glasshouse (38 sq.m each in area) and 8 beds of open pothouse (a 11.38 sq.m each in area), filled with gravel and desert sand. Regular spray of insecticides were made on different crops against white flies, aphids, powdery mildew etc. Hoagland nutrient solutions stocked in four different tanks of 1000 gallon capacity of concentrations (ppm) of N 182, P 120, K 160, Mg 50, Ca 300, S 64, B 0.5, Mn 0.5, Cu 0.5, Zn 0.09 Mo 0.3 and Fe 5 were irrigated to the each bed. The concentration of soluble salts and pH of the solution were checked regularly. The pH of the solution was maintained between 6.5 to 7.0 using H2 SO4. Optimum levels of nutrients in the tanks were maintained by analyzing the irrigated nutrient solutions.
Crop growth conditions: The growth of all the crops was generally better in the open pot house as compared to glass house with the exception of tomato and pepper plants, which were badly affected in pot house (i.e. tomato and pepper) due to viral infections, but grew well in glass house without any viral and white flies attack. It was generally observed that desert sand was proved to be a better medium for crop growth as compared to gravel. This may be due to likely more retention of water in the desert sand than gravel. Cucumber, kakri, watermelon and muskmelon varieties available in Pakistan are not suited to glass house condition, as these crops require cross fertilization by insects and lack of cross fertilization in glass house due to close system adversely affected the pollination or flower formation and fruit setting. Groundnut is not suited at hydroponics system.
Results: It was observed from the present results that all the tomato varieties tested hydroponically thrived best in gravel beds under glasshouse conditions, producing an average of 40 tons fruit yield per hectare. Due to severe viral infection, all fields grown tomatoes were destroyed in the vicinity of Tandojam. The open bed tomatoes suffered this a lot. Pepper growth was satisfactory in glasshouse. At the later stage of growth, the attack of spider mite and powdery mildew reduced its yields, yet it produced 15.6 tons per hectare. In the open beds, lettuce grew very well in desert sand and gave an average yield of 36.5 tons per hectare. In coarse gravel, the yield was 16 tons per hectare. Snake melon (kakri), grew well in desert sand of open pot house and produced an average yield of 24.66 tons fruit per hectare, while gravel medium produced only 11.16 tons per hectare. Potato produced yield of 10.38 tons per hectare in gravel bed under glasshouse condition. Cucumber produced an average yield of 34.11 tons fruit per hectare in desert sand and 12.35 tons in gravel bed in open pot house. Cauliflower produced an average fruit yield of 17.4 tons per hectare. Crops like bajra, bean, potato and garden peas grew well in gravel as well as in desert sand. With the increasing knowledge of better production techniques and growth control in soilless culture over that of soil; the yields and quality of crops have increased considerably. The growers, however, are generally required to have more technical knowledge in order to produce the high yields.
Hydroponics use in other countries: Hydroponics workers in Sadiyat greenhouse Dubai (1970-71) grew vegetable crops and obtained yield as tons/acre/crop: cabbage (31), cucumber (102), egg plant (107), lettuce (25), okra (23), tomato (71), and turnips (70). Similarly, workers in USA (Florida State) obtained yield of these vegetables by growing in the field as tons/acre/crop: cabbage (12), cucumber (12), eggplant (8.3), lettuce (10.5), okra (5), tomato (30), and turnips (10). Yields of 200 mt/ha of tomato have been obtained in greenhouse hydroponic culture in a 9 to 10 months period depending on the plant populations. This can be calculated as 10 to 15 kg of tomato fruit/plant. Production costs for hydroponic tomatoes of high quality can range from $0.80/kg. Yields of more than 100 mt/ha of field grown tomatoes have been produced in Florida (USA) in a 4 to 5 month period. There may be areas of the world where hydroponics may be the only systems that kind be used to grow successfully food crops, which are important in human diets. The desert reasons of the world may be such places, where hydroponics has important application. The successfully commercialization of hydroponics is still and open question and it has gained popularity due to successful production of vegetables.
Advantages: (i) Crops can be grown in localities where normal cultivation is difficult or impracticable e.g. in arid area of saline or shallow soil. This opens up new regions for settlement. (ii) Nutrient solution is homogeneous, thus relatively easy to sample, test and readjust. (iii) Both nutrient solution and supporting media are contained in beds filled with gravel or sand, which can be sterilized to prevent root diseases in crops. (iv) Seepage can be stopped and surface evaporation be minimized so that less water is required for optimum yields. (v) Watering can be automatically controlled, thus reducing labour costs. (vi) Average yields are higher and cultivation is easy.
Disadvantages: (i) Initially, the construction of glasshouse and their structures are expensive. (ii) The design of equipment and operation requires a great deal of technical knowledge. (iii) Even with automatic operation of the hydroponic system a constant supervision is necessary. (iv) Some diseases are problem one and even under the uniform conditions of hydroponic gardening may spread quite rapidly. (v) Production costs for establishing and maintaining a hydroponic system are higher than for other more conventional growing techniques. Therefore, hydroponic growing has to be limited to high cash crops. It takes greater skill on the part of the grower to manage a hydroponic system and the margin of error is quite narrow. Small misjudgments in procedures can result in significant crop losses. The current systems that have been most widely used with relatively good success are the various bag culture techniques, using an organic root supporting media, such as sphagnum peat moss or an inert substrate like perlite, with nutrient solution being dripped into the bag.
There may be areas of the world, i.e. countries in Middle East, Arizona state in USA, many African countries and arid areas. Where hydroponics may be the only system that can be used to grow successfully vegetable crops, which are important in human diets. The desert regions of the world may be such places, where hydroponics has important application.
Conclusion: The research works conducted for over ten years in gravel and desert sands at Nuclear Institute of Agriculture, Tandojam, Sindh have shown that the hydroponic system using local materials is feasible under our conditions. However, a number of drawbacks such as non-availability of seeds suited to glasshouse conditions, steady electricity supply to run the electric motors, and protection from insects and diseases, pose difficulties. It has been established under the present experimental conductions, that different crops can be grown in coarse gravel and desert sands of Thar and other barren areas of the country in open and glass house beds, provided all the necessary facilities are available. In the open hydroponic system successful cultivation is possible if effective viral infection control measures become available. Hydroponics system is very profitable and valuable for growing crops in desert sand and gravel media. However, there are certain advantages and disadvantages of the system.