210 DRY-FARMING 



In a sandy soil a small ])ercentage of water will cause 

 better germination than in a clay soil. While dif- 

 ferent seeds vary in their power to abstract water 

 from soils, yet it seems that for the majority of plants, 

 the best ix'rc(>ntagc> of soil-water for germination 

 purposes is that whicli is in the neigh])orhood 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 pur- 

 poses is about twice the maximum i)ercentage of hy- 

 groscopic water. This would not be far from the 

 field-water cajiacity as described in the preceding 

 chajjter. 



During the ajjsorption (jf water, seeds swell consid- 

 erably, 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, en- 

 abling the seed to absorb moisture with greater 

 facility. As seeds begin to absorb water, heat is also 

 produced. In man}' cases the temperature sur- 

 rounding the seeds is increased one degree on the 

 Centigrade scale by the mere process of water ab- 

 sorption. This fa^'(Jrs rapid germination. More- 

 over, the fertility of the soil has a direct influence 

 upon germination. In fertile soils the germination 

 is more ra])id and more complete than in infertile 

 soils. Especially active in favoring direct germina- 

 tion are the nitrates. When it is recalled that the 



