JAMAICA. 



BULLETIN 



OF THE 



BOTANICAL DEPARTMENT. 



New Series.] FEBRUARY, 1897. ^H^T 



SOIL FERMENTS IMPORTANT IN AGRICULTURE. 



By Dr. W. H. Wiley, Chief of the Division of Chemistry, U. S. 

 Department of Agriculture, in Year Book of TJ. S. Dept. of 



Agriculture for 1895. 



( Continued ). 



FALLOW FIELDS. 



In former times it was a common practice among farmers to allow a 

 field to lie fallow for one season in order to increase its fertility. The 

 advisability of this process is extremely questionable. Daring a mo- 

 derately dry summer there is pi'obably very little liss experienced by 

 ploughing a field after the spring rains and keeping its surface suffi- 

 ciently well cultivated during the summer to prevent the growth of 

 weeds. In the absence of heavy rainfall the stores of available nitrogen 

 in such a soil will undoubtedly be increased daring the summer, inas- 

 much as the processes of nitrification will be continued and the stores 

 of nitrogen thus oxidized, in the absence of absorbing bodies, will re- 

 remain in the soil. Even in case of rainfalls which may carry the so- 

 luble plant food below the arable soil, there may not be ony notable 

 loss, especially if such a downpour be followed by dry weather. In the 

 latter case, by the evaporation fro-n the surface and consequent capil- 

 lary movement of the soil moisture upward, the available plant food 

 carried beyond the reach of the rootlets of plants will be broiight again 

 toward the surface and rendered available. But in case of heavy 

 rains, producing a thorough saturation and leaching of the soil, the 

 losses in a field lying fallow during the summer will be very great, and 

 it is not well at any time to take the risk. Especially is this state- 

 ment true of fields which have lain fallow during the summer and 

 which are afterwards exposed to the saturating rains of the autumn 

 and winter. In these cases the nitrogen will be thoroughly extracted, 

 and all the soluble matters which may have accumulated during the 

 summer will be lost. It is advisable, therefore, in all cases, instead of 

 allowing the fields to lie fallow, to seed them with a catch crop, such 

 as barley, rye, or peas, which may retain the products of nitrification. 

 When the time comes for seeding the field with the intended crop, the 

 catch can be turned under with the plough, and, in the process of decay, 



