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Answer: We recommend three pairs to an irrigated block; pairs at the top, middle and end of a row. An irrigated field is not uniform. Soil types and depth of topsoil can vary over short distances. Plants are not all the same size; the more leaves a plant has the more water it will require. Irrigation is also not uniform. In fact non-uniformity of irrigation presents a great challenge to soil based monitoring of water status. There are advantages in spreading out an inexpensive tool like a FullStop to capture this variability, rather than knowing in great detail what is happening in one spot that might not be representative of the field as a whole. Of course itÕs best to have both types of information. Drip irrigation is usually the most uniform method of irrigation, but the difference in output from drippers near main lines can differ by 20% from drippers furthest away. It is advisable to place FullStop pairs in at least 3 positions along an irrigation row. The uniformity of sprinkler irrigation varies greatly. An adequate system has a Distribution Uniformity (DU) of 70 to 75 %. A DU of 70% means that the driest quarter of the field receives 30% less water than the average. It is important to measure uniformity and place the FullStops in an area of known application rate or to place several sets of FullStops at varying distances from the sprinkler head. The output from micro-jets and mini-sprinklers can have large variations over very short distance e.g. the output can halve when moving from 1 to 3 m from a mini-sprinkler. Again it is important to measure uniformity and place the FullStops in an area of known application rate. It is not possible to be an efficient irrigator if the uniformity of application is poor, so fixing up the irrigation hardware is often the best place to start. |
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