Agriculture revolution - III
RAIS AHMAD KHAN
ARTICLE (January 19 2008): DIVERSE TECHNOLOGIES: A) IRRIGATION TECHNIQUES: Historically farmers have used rivers, lakes or wells as sources of water for irrigating their fields. Later developments in ancient times speak of dams and canals to store and carry water to required sites. Basically rains and melting snows replenished the quantities consumed, besides directly irrigating or flooding the cultivated areas.

In ancient Egypt people depended on annual flooding of the river Nile to irrigate distant parched lands (a practice that still continues is some refined form).

With advent of modern energy sources, the possibilities of using pipelines to pump and carry water to distant localities became a reality, especially in cases where the raw water source was the sea. Desalination made it possible to irrigate areas where practically no rain (or very scant) had ever fallen.

Despite all these advances, the world faces a dwindling of fresh or sweet water resources and fighting wars to gain control of sources of water has become a frightening but distinct possibility. The future will witness this phenomenon occurring as often as, if not more than, wars of conquest for controlling sources of energy.

B) INNOVATIONS: Basically and traditionally, water for irrigation of fields has been a 'flooding operation'. The water flows not just to moisten plant-roots, but to inundate them and flow out, seeping into surrounding soil in the process, getting evaporated, or carrying away to waste the fertile top soil, seeds or chemicals used in agriculture.

This sheer waste is probably as much as 99% or more, of actual water used, while judiciously employed only 1% of the quantity would suffice, and does indeed do the actual job. This saving is accomplished in the drip irrigation system.

OTHER SYSTEMS IN USE ARE AS UNDER:

(I) 'PIVOT' OR SIMULATED RAIN SYSTEM In this technique piped water is carried to near or distant locations in pipes, where a few strategically placed towers with rotation arms of sprinklers (with radii spanning a diameter up to 4 km) shower an area in circles, like a rain-cloud. The practice is wasteful, but saves a lot of human labour needed otherwise. The frequency of the showers can be timed to suit the needs, unlike rains, which cannot be controlled for timing, quantity or frequency.

(II) 'MOISTURE' IRRIGATION In closed environment, like glass houses or enclosed and covered nurseries, water vapors or 'mists' are used to provide the moisture to sustain plants, and keep them moist to prevent their drying out for lack of water. This is particularly useful for plants that do not require a lot of water but do need a humid atmosphere all the time. In cold climates, steam is used to provide moisture as well as heat.

(III) HYDROPONIC SYSTEMS Basically these are a system of growing plants not rooted in soil but other media like perlite, fibrous pads of coconut or other tissues, or some other media instead of soil, soaked in water for plants to root. In some cases the roots rest in water itself in glass or plastic containers with no soil substitute used at all. This system is used for plants whose roots need to be kept moist or soaked in water all the time.

IV) PERIODIC PUMPING OR INJECTION METHODS If water is needed by plants only at pre-determined intervals in small quantities or spurts, hydraulic pumps of sizes suited to the job, and timed for periodic injection of water and the plants containers (or onto leaves and stems if necessary) are used, which function automatically, without manual help.

(IV) SPRAY SYSTEMS In cases where equipment costs are an inhibiting factor, but human labour is cheap, simple hand-held water containers with nozzles or spouts are used to spray plants. This system is in common use in gardens, parks, and for household plants.

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