Where alfalfa is irrigated, it is usual to apply irrigating waters just after each cutting of the crop. It is a matter of some importance that the water shall be applied at once as soon as the previous crop has been harvested, otherwise time will be lost in growing the next crop. There are instances where it is necessary to apply water before the first crop is grown, but usually the moisture which falls in the winter and spring will suffice to produce the first crop of the season. Some irrigators apply water some time previous to harvesting the crop, but not so late as to leave the ground in a soft condition when mowing is begun. The amount of water required will vary with the soil, the season of the year, the distance of the ground water from the surface, and the precipitation. The more porous the soil and subsoil, the hotter the weather, the less the precipitation and the farther below the surface, up to a certain limit, the greater will be the amount of water needed. There are situations, as in some of the islands in the Yellowstone River, in which ground water is so near the surface that alfalfa grown on these is able to get enough of water from this subterranean source to produce good crops. Care should be taken not to apply water in excess of the needs of the crop, or the yields will be proportionately reduced. The amounts that will best serve the end sought can only be ascertained by actual test. Caution is also necessary where the winters are cold not to apply water late or in excessive quantities, lest a sappy condition of the plants shall be induced, which will make them succumb to the cold of the winter following. Moreover, on some soils alfalfa fields will produce good crops, if irrigated only the first season, until the roots get down to moisture, the irrigating waters being utilized when more needed.