Seed-mixtures.--When grass is wanted for hay as well as fertility, the clovers and timothy compose the greater part of a desirable mixture wherever the clovers and timothy thrive. Probably this condition always will continue. The clovers are needed to supply nitrogen to the soil and to put protein into the hay for livestock. They give way, in large part, or entirely, the second year. Alsike is more nearly perennial than the red which practically lasts only through its second season, when its seed crop has been made, and its function performed. The sod is chiefly timothy in the second season. A little red-top is desirable, and the percentage should be heaviest for quite wet land or very dry land. When fertility is the first consideration, and the sod is left only two or three years, the following mixture is good, and is for one acre: Red clover 10 pounds Alsike 2 pounds Timothy 8 pounds Red-top 2 pounds When a mixed hay is wanted the first year, the following mixture may be found better for the purpose: Red clover 6 pounds Alsike 2 pounds Timothy 12 pounds Red-top 2 pounds Mammoth clover seed may be substituted for the red without change in number of pounds. The amount of timothy and red-top in the second mixture suggested calls for a liberal supply of plant-food, and this is true of any heavy grass mixture. If fertility is not present, the seeding of grass should be lighter, but the clover should not be less in amount for a thin soil than for a good one. The question of fertilizers is discussed in Chapter XX. CHAPTER IX SODS FOR PASTURES Permanent Pastures.--There is a large total area of land that can be brought into profitable production of food only by means of pasture grasses. A small part is too low and moist for tillage, but a larger part is too rough or too infertile. It can be made to yield profit in grasses that are harvested without expense by animals. The grasses afford feed and at the same time protect the soil from waste. The efficiency of much pasture land is kept low by poor stands of grass, the encroachment of weeds, bushes, and briers, close grazing, and the failure to supply fertility. When making a sod for mowing, the aim is to select varieties of plants that mature near the same time. Pastures need varieties maturing at different times, and this is a matter under control when temporary pastures are used. Permanent pasture land soon becomes occupied by the grasses best fitted to soil conditions or most able to crowd other plants. [Illustration: Good Pasture Land in Chester County, Pa.]