WOW !! MUCH LOVE ! SO WORLD PEACE !
Fond bitcoin pour l'amélioration du site: 1memzGeKS7CB3ECNkzSn2qHwxU6NZoJ8o
  Dogecoin (tips/pourboires): DCLoo9Dd4qECqpMLurdgGnaoqbftj16Nvp


Home | Publier un mémoire | Une page au hasard

 > 

Design of a geographic information supported database for the management of pressurised irrigation systems at the plantation du Haut Penja, Cameroon

( Télécharger le fichier original )
par Chick Herman AZAH
University of Dschang - Agric engineer 2009
  

précédent sommaire suivant

Bitcoin is a swarm of cyber hornets serving the goddess of wisdom, feeding on the fire of truth, exponentially growing ever smarter, faster, and stronger behind a wall of encrypted energy

2.5 Pressurized Irrigation Systems 2.5.1 Sprinkler irrigation systems

Sprinkler irrigation is a versatile means of applying water to any crop, soil, and topographic condition (Schwab et al., 1993; Fonteh and Assoumou, 1996). Sprinkler systems can be efficient on soils and topography that is not suitable or efficient for surface irrigation methods. In general, systems are described according to the method of moving the lateral lines on which various types of sprinklers are attached. Laterals may be stationary or movable. Sprinkler systems are highly efficient but there are general concerns about the maintenance and investment costs for these systems.

Hand-moved laterals have the lowest investment cost but the highest labour requirement. These systems are only suitable for short growing crops.

The side roll lateral system uses the irrigation pipe as the axle of large diameter wheels that are spaced about 12 m apart. These laterals are moved by a gasoline powered motor and thus require less labor than hand-move systems. Side rolls should be used for crops that will not interfere with the movement of the lateral or sprinkler pattern.

Centre pivots consist of radial pipelines that rotate around a central pivot by water pressure, electric motors, or oil hydraulic motors (Schwab et al., 1993). A variety of nozzle types, nozzle heights, and application rates can be used in centre pivot systems. Sprinkler systems are selected according to the field conditions for the most efficient operation.

Linear moved laterals use hardware similar to that of a centre pivot, but move in a straight line across the field. Solid-set systems have sprinklers that are placed over the entire field, where all or some of the sprinklers may operate at the same time. Sprinkler heads vary greatly from older impact heads to more modern spray heads that have an assortment of application and placement modes (Howell, 2003).

2.5.2 Micro irrigation systems

Micro irrigation is a method for delivering slow, frequent applications of water to the soil using a low pressure, low volume distribution system and special flow-control outlets (Schwab et al., 1993). If managed properly, micro irrigation can increase yields and decrease water, fertilizer, and labor requirements. Micro irrigation includes: micro sprinklers, drip irrigation, and subsurface drip irrigation (SDI).

Micro sprinklers, often referred to as micro sprayers or misters, typically consist of small emitters placed on short risers above the soil surface. Water is conveyed through the air, but travels only a short distance before reaching the soil surface. The wetted area of emitters in these systems is small, can be controlled fairly easily, and has different shapes to match desired distribution patterns. The advantages of micro sprinkler irrigation systems are the potential for controlling frost, greater flexibility in applying water, and lower susceptibility to clogging.

Drip systems deliver water directly to the soil surface or subsurface (SDI) and allow water to dissipate under low pressure in a predetermined pattern. These systems are advantageous because water is applied directly to or just above the root zone of the plant, thereby minimizing deep percolation losses, reducing or eliminating the wetted area from which water can evaporate, and eliminating losses associated with runoff. These systems are also advantageous because they reduce water consumption by weeds, while operating at a lower pressure.

Micro irrigation systems apply water on a high-frequency basis and create near optimal soil moisture conditions for the crop. Under proper management, micro irrigation systems save water because only the plant`s root zone is supplied with water and little, if any, is lost to deep percolation, consumption by non beneficial plants, or soil surface evaporation. In addition to being highly efficient, these systems also require relatively little labour input if designed properly. Yields of some crops have been shown to increase under these systems because the high temporal soil water level needed to meet transpiration requirements is maintained (Colaizzi et al., 2003).

The major disadvantages of micro irrigation systems are high initial cost and potential for the emitters clogging. In some cases, labor inputs may be quite high if rodents

burrow and chew system components. Proper design, operation, and maintenance can overcome many of these issues.

précédent sommaire suivant






Bitcoin is a swarm of cyber hornets serving the goddess of wisdom, feeding on the fire of truth, exponentially growing ever smarter, faster, and stronger behind a wall of encrypted energy








"Aux âmes bien nées, la valeur n'attend point le nombre des années"   Corneille