October, '16] NITRATES IN ORCHARD SOILS. 9 



Table No. 5. 



Summary of Nitrate Determinations, Water Soluble Parts per 

 Million of Dry Soil. 



Average per Plot. 

 Surface soil. 



Subsoil. 



From the above data it will be seen that the amount of nitrates 

 recovered in the soil samples under sod is considerably reduced 

 as compared with Plots 4 and 5. The ratio of nitrates between 

 sod, tillage and tillage with cover crops is as 1:5.4:10.6 in the 

 surface soil and in the subsoil as 1:3.3:3.7. At no time during 

 the experiments have we obtained a sample under sod that showed 

 more than 14.78 parts nitrates per million and the average for 

 the four years is 3.18 p. p.m., while for clean tillage it has gone as 

 high as 63 p. p.m. with an average of 17.40 p. p.m., and for tillage 

 plus a leguminous cover crop it has shown as high as 132 p.p.m. 

 and the average is 33.91 p.p.m. for the four years. 



