506 INVESTIGATION BY CULTURE EXPERIMENTS 



1894, 1895, 1896, and 1897 the one half of the oat plots were sown again with 

 carrots and the half of the plots devoted to wheat and barley were planted with 

 potatoes." 



Other changes from the original plans, and also some general 

 conclusions drawn by Doctor Saunders at the end of 20 years, are 

 given in the following statements quoted from the Report for the 

 year ending March 31, 1908. 



"These trials have shown that barnyard manure can be most economically 

 used in the fresh or unrotted condition ; that fresh manure is equal, ton for ton, 

 in crop-producing power to rotted manure, which, other experiments have 

 shown, loses during the process of rotting about 60 per cent of its weight. In 

 view of the vast importance of making the best possible use of barnyard 

 manure, it is difficult to estimate the value of this one item of information. 



"When these experiments were planned, the opinion was very generally held 

 that untreated mineral phosphate, if very finely ground, was a valuable fertilizer, 

 which gradually gave up its phosphoric acid for the promotion of plant growth. 

 Ten years' experience have shown that mineral phosphate, untreated, is prac- 

 tically of no value as a fertilizer. 



" Sulfate of iron, which, at the time these tests were begun, was highly recom- 

 mended as a means of producing increased crops, has also proven to be of very 

 little value for this purpose. 



"Common salt, which has long had a reputation with many farmers for its 

 value as a fertilizer for barley, while others disbelieved in its efficacy, has been 

 shown to be a valuable agent for producing an increased crop of that grain, 

 while it is of much less use when applied to crops of spring wheat or oats. 

 Land-plaster or gypsum has also proved to be of some value as a fertilizer for 

 barley, while of very little service for wheat or oats. Some light has also been 

 thrown on the relative usefulness of single and combined fertilizers. 



"After ten years' experience had demonstrated that finely ground, untreated 

 mineral phosphate was of no value as a fertilizer, its use was discontinued in 

 1898. Prior to this it had been used in each set of plots in Nos. 4, 5, 6, 7, and 8, 

 in all the different series of plots, excepting roots. In 1898 and 1899, similar 

 weights of the Thomas phosphate were used in place of the mineral phosphate, 

 excepting in plot 6 in each series. In this plot the Thomas phosphate was used 

 in 1898 only. 



"After constant cropping for ten or eleven years, it was found that the soil on 

 these plots to which no barnyard manure had been applied was much depleted 

 of humus, and hence its power for holding moisture had been lessened, and the 

 conditions for plant growth, apart from the question of plant food, had on this 

 account become less favorable. In 1899 the experiments were modified and an 

 effort made to restore some proportion of the humus and at the same time gain 

 further information as to the value of clover as a collector of plant food. In the 

 spring of that year ten pounds of red clover seed per acre was sown with the 



