— 40 — 



less soluble mineral matter there will be therein, and the more impove- 

 rished the soil will become. 



In this manner an uninterruplcd culture of cereals br/n,s;s about, 

 as an unfailing consequence, an intense, systematic drying up of tiie lower 

 lialf of tJie soil layer inJiabited by tlie roots of cereal grasses (the depth 

 of the layer inhabited by them equals 110 to 130 cm. but only 50 or 

 70 c. m. moistens yearly at the best of times) and an almost complete 

 cessation tiierein of the cliemical transformation of mineral salts into a 

 soluble condition, or, which is the same thing, a systematic impove- 

 risfiment there of. 



These chronic absense of useful water in an important part ot the 

 root-inhabited layer, explains the „ poorness" of the peasants fields. If these 

 fields sometimes, exclusively in moist years, receive water enough to 

 moisten the whole root layer, that water dissolves but an insignificant 

 unnormally small quantity of mineral salts; and in order to assimilate 

 and use them in building up their tissues, the plant must expend all the 

 water; that is to say, that from a large guantity of water a small quan- 

 tity of mineral salts is extracted. Obviously the abundance of soil water 

 does not go to the benefit of the plant in this case; it must exhale water 

 energetically, its cells hold too much water, the stalks become spongy, 

 easy to break, and high coloured. 



In this way one very moist year amongst a whole row, not of dry, 

 but even of average moist years, guarantees the crop: but that crop will 

 be far lower than it might have been, had the mineral matter been in a 

 higher state of solubility through the presence of water in the root layer 

 during the preceding years. 



Have looked into the distribution of water in three-course, on bare 

 fallow, and four-course rotations and then in uninterrupted culture, we see 

 that in a three - course rotation, when spring corn is sown after winter 

 corn, we get a condition favourable to the appearance of drought. On the 

 removal of the winter corn, the whole root layer turns out to be dry, and 

 the whole future of the barley crop depends exclusively on the autumn 

 winter and spring deposits. If they happen to be sufficient we can rely 

 upon an harvest; but if they chould be small the layer only moistens to 

 30 or 40 c. m. and there can be no hopes of a good harvest even with 

 a decent quantity of deposit like that of 1906 (page 29). Only an uncom- 

 monly moist spring, which so rarely happens in southern black -earth 

 districts, can raise the crop above the average. 



In a four-course rotation winter corn is followed by potatoes, the 

 root layer for which is not great. Therefore an important thickness of 

 humid layer is not requisite to guarantee the crop. Here, a complete 

 faillure cannot be expected, and even a moderately moist spring guaran- 



