In a sandy soil a small percentage of water will cause better germination than in a clay soil. While different seeds vary in their power to abstract water from soils, yet it seems that for the majority of plants, the best percentage of soil-water for germination purposes is that which is in the neighborhood of the maximum field capacity of soils for water, as explained in Chapter VII. Bogdanoff has estimated that the best amount of water in the soil for germination purposes is about twice the maximum percentage of hygroscopic water. This would not be far from the field-water capacity as described in the preceding chapter. During the absorption of water, seeds swell considerably, in many cases from two to three times their normal size. This has the very desirable effect of crowding the seed walls against the soil particles and thus, by establishing more points of contact, enabling the seed to absorb moisture with greater facility. As seeds begin to absorb water, heat is also produced. In many cases the temperature surrounding the seeds is increased one degree on the Centigrade scale by the mere process of water absorption. This favors rapid germination. Moreover, the fertility of the soil has a direct influence upon germination. In fertile soils the germination is more rapid and more complete than in infertile soils. Especially active in favoring direct germination are the nitrates. When it is recalled that the constant cultivation and well-kept summer fallow of dry-farming develop large quantities of nitrates in the soil, it will be understood that the methods of dry-farming as already outlined accelerate germination very greatly. It scareely need be said that the soil of the seed-bed should be fine, mellow, and uniform in physical texture so that the seeds can be planted evenly and in close contact with the soil particles. All the requisite conditions for germination are best met by the conditions prevailing in a well-kept summer fallowed soil. Time to sow In the consideration of the time to sow, the first question to be disposed of by the dry-farmer is that of fall as against spring sowing. The small grains occur as fall and spring varieties, and it is vitally important to determine which season, under dry-farm conditions, is the best for sowing.