142 MASS. EXPERIMRxNT STATION BULLETIN 237 



Last Year's Crops Affect This Year's Onions. 



To estimate better the value of lime for onions, attempt is made in 

 Table 2 to eliminate as far as possible previous crop effects. Of the total 

 fields of set onions in the survey, 88 were on land which would be called 

 "oJd" onion land, whereas 21 followed tobacco grown the year previous. 



Taiu.e 2.-Influence of Soil Reaction on Yeld of Set Onions on Land with 

 Different Crop Histories. 



Of the 88 fields of onions on the old onion land about half were verv 

 acid, and low yields of o.nions were obtained. On the less acid soils, pH- 

 5.1 to 6.1, yields were increased by about 20 per cent; and on the still 

 m,ore neutral soils, pH-6.1 to 6.5, yields were about 40 per cen,t higher 

 than those on the very acid soils with pH-4.3 to 5.1. 



Onions following tobacco were in general very poor. Lime had been 

 applied in a few cases, but this either had not been well worked into the 

 soil, or had not been applied in amounts sufficient to neutralize the depres- 

 sing effect of tobacco. The table shows by computation a difference of 

 nearly 33 per cent between the yields on the most nearly neutral fields, 

 pH-6.1 to 6.5, and those on very acid soils, pH-4.3 to 5.1. Even the highest 

 yields secured, however, could not be considered to represent a profitable 

 crop. There was a greater response to lime on the old onion land than on 

 the tobacco land. The yields on tJie old onion land were very much better 

 in each soil reaction range than on tobacco land cropped to onions in the 

 year of the survey. These poorer yields may be ascribed either to the 

 effect of the previous crop of tobacco, or to the fact that where lime was 

 applied to tobacco after plowing, it remained chiefly on the surface, leav- 

 ing the layer from three to six inches down very acid. It is also interesting 

 to note that the dhamces of a good crop, even on very acid soil, are very 

 much greater on old onion land than on land formerly in tobacco. 



W'hile it is occasionally neceissary to shift from tobacco to other 

 crops, or vice versa, yet the finst crop following tobacco should not be 

 onions. Unfortunately the state of our knowledge does not permit us to 

 say what this crop should be. This problem is now under investigation in 

 the newly instituted onion research work at the Experiment Station. 



Lime Must Be Well Distributed. 



Table 3 illustrates the fact that wihile the surface three inches of soil 

 may be well limed, the three to six inch layer immediately uinderneath 

 remains quite acid, at least for the first year following liming. This may 

 mean that for many fields the lime must be applied to both sides of the 

 furrow slice before maximum yields can be expected. 



