Crops Under Irrigation, 15 



CROPS UNDER IRRIGATION/ 



By A. J. McClatchie. 



Most irrigation is done in Arizona by one of two methods — through 

 furrows or by flooding. The furrows may be permanent or temporary. 

 Plants such as strawberries and small vegetables that require the 

 frequent application of small amounts of water, are by most growers 

 irrigated through furrows that are more or less permanent. Some 

 farmers break u{) by cultivation the crust that forms on the surface, 

 while others simply hoe from the furrows and the intervening ridges 

 the weeds that grow there. This method of irrigation should be 

 resorted to only in the case of such crops and under such climatic 

 conditions as make it difficult to irrigate by any other method. 



Furrow Irrigation. 



Running water through temporally furrows that are cultivated after 

 each irrigation is to be preferred wherever practicable. Experience at 

 this Station has shown that this is the method by which all crops that 

 can be so irrigated should be irrigated. The water applied penetrates 

 the soil, and a smaller percentage is lost by evaporation than by any 

 other method. Since the soil mulch formed by cultivation prevents the 

 rapid escape of moisture, crops will need less frequent irrigation by 

 this method than by any other. 



In irrigating by the furrow method, it is important that the streams 

 permitted to run in the furrows be small. Just enough water to cause 

 the stream to creep slowly along should be turned down each furrow. 

 The soil will thus become thoroughly saturated, and little water will 

 escape at the lower end of the field. The more slowly the water makes 

 its way down the furrows the better, provided it gets through during 

 the time that irrigating water is available. If so large a stream is 

 permitted to run in each furrow that the water reaches the lower end 

 quickly, the sides are thus made less pervious, and a large percentage 

 of the water escapes at the lower end — water that would percolate into 

 the soil if it ran more slowly. For equalizing the flow of water into 

 the upper ends of the furrows, straw or other similar coarse material 

 will usually be found most serviceable. If something is not used to 

 prevent the washing of the soil, the tendency is for too much water to 

 find its way down some furrows, and too little down others. 



Flooding. 



In the case of crops that cover the ground, such as lucerne and 

 grains, flooding is the method in general practice. In this region these 

 crops are flooded by running a large stream of water between two 



* Irrigalion at the Station Farm. Bulletin 41, Arizona Agricultural Experiment Station. 



