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tees the crop of potatoes. Then, after potatoes, a certain reserve of useful 

 water remains in the soil for the next spring corn, and with a moderately 

 moist spring the crop of barley is guaranteed by a small reserve of wa- 

 ter, and a clean soil, after the culture of potatoes. Therefore in a four- 

 course rotation, there is no moment in the culture which could create in 

 the root layer a condition favourable to the appearance of drought. 



With an unbroken culture of cereals every year, the reserve of 

 useful water is entirely used up at the period of reaping, and every 

 year the farmer finds himself threatened with drought. Practice confirms 

 the instabilety of farms built up on an uninterrupted culture of cereal 

 grasses solely. There must be a change of culture, but not restricted to 

 changing one cereal grass by another, as barley by wheat. The root- 

 systems of cereal grasses are nearly alike, and so are the limits in 

 which they can make use of serviceable water. In a change of culture 

 one must reckon, not so much with, the varieties of the parts about gro- 

 und, as with the varieties in the dimensions and structure of their root- 

 systems. Maize and barley differ greatly in their above ground features, 

 but they both dry up the root layer, towards the reaping period, completely. 



The chain of seed changes or rotation should be made with the 

 idea of root changes. Song rooted plants should alternate with short-rooted 

 and dence rooted (with a thik network of small roots) with meagre-rooted 

 (with a open network). In our four-course rotation after long rooted (win- 

 ter wheat or rye) follows short-rooted (potatoes). Then again long - rooted 

 (barley, oats). If after spring corn, we place thorough ploughed short and 

 meagre-rooted (flax) and after that agaitn long-rooted (spring grasses) we 

 get a six-course rotation probably the most perfect for southern steppe 

 black-earth of a lightish type. And so, the cause of drought is not con- 

 fined only to the fall of a small quant'ty of atmospherie water. The cause 

 of drought is more complex and is rooted pre-eminently in the incorrect 

 technical methods of farming-late turning up of the fallow in spring (June 

 fallow fig. 12), in an incorrect organisation of crop rotation and in the 

 system of letting land I'e untouched. The farmer himself prepare the way 

 for drought in the course of a whole series of years by failing to look 

 after the accumulation of water in the root layer of the soil and by the 

 way the increase in the quantity of soluble matter. Our blackearth soil, 

 on condition that a certain reserve of useful water is left in the root-layer 

 as, often as possible, gives a prolific harvest, in a year with a less than 

 average quantity of falling deposit; for the water which enters the soil 

 finds there a sufficient reserve of dissolved mineral salts; and the plants 

 in order to assimilate it and use it in building up their cells expend less 

 soil water than they would from impoverished soil, in getting the same 

 quantity of mineral salts. 



