No. 4.] KEEPING UP FERTILITY. 113 



will see that is the case all through. On this grass land 

 there are four plots which during the six years have not 

 received anything whatever. They are in difl'erent parts of 

 the field, and I wish you to remember that the figures repre- 

 sent only the increase in the yield where fertilizers were 

 used compared with the plots which received nothing. 

 Now, one year, 1892, my assistant by accident put some 

 nitrate of soda on one of these plots which should have 

 received nothing. For the two previous years I had had a 

 chance to see what that plot was doing. I had been grow- 

 ing corn there, and it had not been doing any better than 

 the other three nothing plots in the acre. By accident, as I 

 say, he got at the rate of one hundred and sixty pounds of 

 nitrate of soda to the acre on tliat plot. The result was we 

 got almost as large a crop of hay there as we did where we 

 had been using manure every year, but we did not get any 

 rowen, and we did not get any larger crop of hay the next 

 year. The yield went right back again where it belonged. 

 The eflect of nitrate of soda on grass early in the spring is 

 almost magical. This is an illustration of a principle which 

 I have stated in ray paper ; but perhaps I had better clinch 

 the point right here. The effect of nitrate of soda is almost 

 magical upon every crop which makes its chief growth very 

 early in the season. That is an explanation in })art why 

 nitrate of soda has been so beneficial wherever it has been 

 used on grass and oats. Nitrate of soda for corn is not of 

 much use, but for oats and hay there is a large increase. 

 AVhile oats and grass make their chief growth in the cool 

 spring weather, corn needs hot weather. 



Question. Do you recommend applying it early to grass ? 



Professor Brooks. Yes, as soon as the grass will begin 

 to grow ; and I will explain why this should be so. The 

 rains of the fall and winter leach the soluble nitrogen out of 

 the soil, and the crops which have got to make their growth 

 early in the spring must be fed with soluble nitrates. Those 

 that do not make their best growth until after considerable 

 warm weather, like corn, can get their nitrogen fi-om the 

 soil, because natural agencies working on the organic mate- 

 rial of the soil chanofe its nitrogen into available form. The 

 following important ditierence in the use of fertilizers you 



