| 摘要 |
<p>The system consists of a main pipe to which are connected perforated pipes (2) running parallel with the crop rows. the perforations are each provided with a small delivery tube (3). A needle is lodged within each tube, protruding in the form of a hook to facilitate handling and fixing in to the soil. The needles are used to keep the tubes free from obstruction and to secure the pipes beneath the soil. The needles can be made of steel, copper, aluminium or their alloys, so that the salts which these substances form with water act as a preventive against the formation of bacterial gels which may obstruct the pipes. The length of the needle in the pipe effects the rate of flow of the water.</p> |
