INFLUENCE OF GROWTH OF COWPEAS UPON SOME 

 PHYSICAL, CHEMICAL, AND BIOLOGICAL PROPERTIES 

 OF SOIL 



By C. A. LeClair.i 

 Assistant Professor of Soils, University of Missouri 



INTRODUCTION 



In the past 25 years much experimental work has been done with 

 cowpeas (Vigna sinensis) in relation to cultural methods, fertilization, 

 and variety tests, but practically nothing has been written with regard 

 to the direct effect of the plant upon the soil. Some have expressed the 

 belief that cowpeas are capable of producing a loosening effect upon the 

 soil, but no authentic experimental data are available. 



HISTORICAL SUMMARY 



An exhaustive study of research literature revealed that previous 

 work along the particular line referred to has been exceedingly limited. 

 The data at hand bear only indirectly upon the work of this experiment, 

 but are worthy of consideration. 



With regard to the effect of shading on soil, Biihler ^ reports having 

 carried on an experiment on four broad plots of ground. One was 

 exposed to sun and wind; the others were shaded by horizontal wooden 

 trellises placed around each plot 40 cm. above the ground and so arranged 

 as to cut off one-fourth, one-half, and three-fourths of the sunlight from 

 respective screened plots. 



Data at the end of the experiment showed that at midday the shaded 

 plots had a lower temperature than the open plot by from 2 to 10 

 degrees centigrade. However, the cooling by night under the shaded 

 plot was very slight, being less than 2 degrees centigrade, which explains 

 the effectiveness of a windbreak in preventing injury by frost. In rainy 

 weather the variation of temperature either by day or by night was 

 much smaller. 



The relative evaporation from plots throughout the test was as follows : 



Percentage of 

 Treatment. evaporation. 



No shade 100 



One-fourth shade 84 



One-half shade 71 



Three-fourths shade 62 



1 The writer desires to acknowledge his gratitude to Prof. M. F. Miller, of the Missouri Experiment Sta- 

 tion, under whose direction these experiments were carried out. 



2 Biihler, A. Influence des treillis abris sur la temperature du sol et sur 1 'evaporation. In CicI et Terra, 

 ami. 17, no. I, p. 21-22. 1896. 



Journal of Agricultural Research, Vol. V, No. 10 



Dept. of Agriculture, Washington, D. C. Dec. 6, 1915 



bb Mo.-i 



(439) 



