﻿Water utilization by spring wheat. • 28 



COMPARISON OF CULTURAL METHODS. 



The conservation and use of moisture in plats on which different 

 cultural practices have been employed, are sufficiently comparable 

 at the different stations to allow definite deductions to be made. 



For the average of all stations, plats A and B show no notable 

 differences in the quantity of moisture conserved. The differences at 

 individual stations are only minor. In the northern section of the 

 Great Plains the advantage of one or the other at the stations where 

 one is superior favors plat A. This is without doubt due to the fact 

 that in most years there is a better opportunity to obtain moisture by 

 holding the winter snow than by conserving the moisture that falls 

 after harvest. The soil at harvest has been shown to be dry approxi- 

 mately 90 per cent of the time; therefore, cultivation at that time 

 usually conserves no moisture, because none is present. By pre- 

 venting weed growth, fall plowing is better able than spring plowing 

 to conserve the moisture that falls between harvest and winter. How- 

 ever, the moisture that falls after harvest is not usually all used up 

 on land not fall cultivated. The season between harvest and freezing 

 is not long, and the demand of plants for moisture at that time is not 

 high. Where there is sufficient precipitation after harvest to induce 

 weed growth, there is usually enough so that the moisture supply 

 is not exhausted by the time freezing kills the weeds. 



In years with a heavy precipitation after harvest, plat B usually 

 conserves more moisture than plat A. The greater number of times 

 that plat A possesses the higher moisture content in the spring shows 

 the superiority of catching snow over retaining fall precipitation in 

 conserving moisture at the northern stations. 



At the southern stations the difference between the two methods 

 in conserving moisture when a difference exists has been in favor of 

 plat B. In this region there is little snow ; consequently, the superi- 

 ority of plat A in catching snow is of little importance. There is 

 also an earlier harvest and a later fall than at the northern stations. 

 This gives plat B a longer period for moisture storage and also gives 

 the weeds on plat A a greater chance to remove the moisture that 

 falls after harvest. In spite of this, the difference between the two 

 plats in the quantity of moisture stored has generally been small. 



That the greater depth of plowing practiced on plat B has not 

 increased the root development of this plat over that of plat A is 

 indicated by the fact that the two plats have been practically dupli- 

 cates in the utilization of the moisture present. 



Unfortunately, the slight superiority of one plat over the other in 

 moisture storage in different sections of the Great Plains is such that 

 it is not possible to benefit greatly from it in farm practice. The 

 southern stations, where plat B has conserved more moisture than 

 plat A, are particularly subject to soil blowing during the winter 

 months. This operates against the use of fall cultivation on an ex- 

 tended scale. 



At the northern stations, where plat A has been slightly superior to 

 plat B, there is a practical limit to the spring work that can be done 

 without unduly delaying seeding. In that region the earlier seeding 

 that may be practiced on fail plowing frequently more than makes 

 up for any superiority of spring plowing in the quantity of moisture 

 conserved. 



