THE POTATO 109 



conditions, some of which fluctuate even on a 

 given farm from year to year. The composition 

 of the soils, the subsoil, the annual rainfall, the 

 humidity of the air, temperature, the time of 

 seeding and many other things have appreciable 

 effects upon the amount of water necessary for a 

 given crop for maximum results. It is a question 

 of knowing how little instead of how much to use. 

 The soil can retain only a certain amount, and 

 whatever is applied more than this is lost by perco- 

 lation into the subsoil and beyond the food gather- 

 ing area of the roots of plants. An appreciably 

 large per cent, of irrigation water is lost in this way. 

 New land will take more water the first year than 

 thereafter, and for the third year less is required 

 than for the second. The time to apply water is 

 when the crop needs it and not before. This is 

 determined in alfalfa by a darkening in the green 

 of the leaves. The moisture content of the soil 

 should be closely watched, and by the exercise of a 

 little good judgment no serious mistake in apply- 

 ing water need be made. Too little as well as too 

 much moisture in soils injures plants. The 

 amount of water to be put on at one application is 

 dependent on the crop and the soil, but generally 

 about five acre inches is sufficient for an irrigation. 

 On sandy loam, and making allowances for some 

 loss as waste and evaporation, this amount will 

 wet the soil about as deep as plant roots go. 



"In localities where water for irrigation is scarce, 

 fall or winter irrigation is often practised. It 

 has a number of things to commend it besides the 

 principal fact that if the water is not stored in the 

 land it is lost. By using the water in this way, 

 where there is a scarcity, additional land can be 

 farmed and made to yield remunerative crops. 



