[Illustration: Harvesting Seed Potatoes near Houlton, Aroostook County, Maine.] Barnyard manure would answer all purposes and would be an ideal potato fertilizer, except for the fact that it so often carries with it the spores of such diseases as blight, scab and rot. Still, barnyard manure in a partly rotted condition is very widely used by potato growers. Clover sod is an excellent source of nitrogen, as heretofore explained. The clover is, perhaps, the best of the leguminous crops for green manuring purposes. Many successful potato farmers depend largely upon clover, supplementing it with a small amount of high-grade complete fertilizer in the rows. Where phosphoric acid is necessary, it can be had in the form of ground bone or acidulated rock, and potash can be had in the form of sulphate or as kainit. Where the scab is prevalent, it may prove better to use kainit, on account of the salt which it contains, as will be presently explained. =Planting.=--It requires from seven to ten bushels of tubers to plant an acre. Some growers use as much as fifteen bushels. The date of planting, depth, distance between rows, etc., are details for individual determination. Flat culture is better than ridge culture, so far as conservation of moisture is concerned. It is important that good Northern-grown seed be planted; tubers which have not lost their strength by excessive sprouting. Storage in a cool, dark, dry place is best for potatoes. Whether planted early or late, or at successional dates, must be determined by the market requirements of the grower. =Varieties.=--The varieties of potatoes are many, and while it is wise to experiment in a small way on new kinds, it is best to depend for business purposes on standard sorts that have been fully tested. =Irrigation.=--After the farmer has exhausted his best efforts in the preparation and fertilization of the soil, and after good seed has been planted and the best possible culture given, there may come a season of prolonged drouth that will defeat his purpose of securing a large crop. This result is not common, but neither is it rare; and where farmers are looking toward the high culture of certain special crops, it would be well for them to consider the matter of artificially watering their potato fields. [Illustration: An Average Tuber of Table King, One of the Best All Around Potatoes.] =Diseases and Enemies.=--Not counting dry weather, which sometimes robs the farmer of two-thirds of his crop, there are four diseases which exert a disastrous influence on the potato, and which are liable to occur any season. Two of these diseases are of the leaf and stem and two of the tubers. The two leaf troubles are respectively known as blight or downy mildew and the Macrosporium disease. The two tuber troubles are scab and rot.