4 BULLETIN 228, U. S. DEPARTMENT OF AGRICULTURE. 



plants during the second period through the forced reduction in the 

 leaf and stem area of the plant. This would tend to prevent the 

 normal development of the root system, which in turn would increase 

 the water requirement during the third period, since a relatively 

 greater proportion of food material would be diverted to the roots. 



When the water requirement is based on the total dry matter pro- 

 duced during the season (May 24 to November 4) without reference 

 to the time at which the growth occurred, series B is practically as 

 efficient as the check series. The respective ratios were 642 ± 6 and 

 656 ±11, the difference, 14 ±13, being without significance. This is 

 of interest in view of the fact that the water requirement of each of 

 the three crops is higher in series B than in the check series. The 

 explanation of this seeming anomaly is to be found in the relative 

 yields during the second (midsummer) period, during which time 

 series B produced only 18 per cent of its total dry matter, while the 

 check series produced 38 per cent. 



The amount of dry matter produced under frequent cutting is also 

 of interest. The check series produced practically the same amount 

 of dry matter during the second period as during the first. Series B 

 produced only 30 per cent as much during the second period, the 

 small plants being unable to elaborate plant material as rapidly as 

 the larger plants of series A. Series B was also maintained during 

 the midsummer period with an actual expenditure of only one-third 

 the water required by the check series. This forced economy in the 

 use of water through frequent cutting seems not to be without effect 

 on subsequent production. Series B produced only 48 per cent as 

 much dry matter during the third period as the check series, while 

 during the first period, notwithstanding the shorter period of growth, 

 series B produced 60 per cent as much dry matter as the check 

 series. 



BEARING OF RESULTS ON THE MANAGEMENT OF ALFALFA LANDS. 



The results here recorded indicate that the total consumption of 

 water can be controlled to a considerable extent by pasturage or fre- 

 quent clipping without serious injury to alfalfa plants. This affords 

 a means of limiting the growth of the crop so that its demand for 

 water will not exceed the available moisture supply. With a limited 

 amount of stored moisture it is evident that the greatest production 

 can be obtained by allowing the crop to grow when the water require- 

 ment is the lowest, i. e., in the spring or fall, and b}^ keeping the leaf 

 surface at a minimum during the summer through clipping or pastur- 

 age. Numerous field observations by the writers have shown the 

 efficacy of reducing the size of the aerial portion of a plant as a 

 means of moisture conservation during periods of drought. 



Although frequent cutting or clipping is not practicable under field 

 conditions, the same result can be attained by grazing. Whenever 



