WORK OF THE DELTA EXPERIMENT FARM IN 1912. 5 



expensive, and rather wasteful, is made necessary by the physical 

 peculiarities of the peat soil, in which no machine digger so far tried 

 has done effective work. 



PREVIOUS INVESTIGATIONS. 



Progressive decrease in potato yields and a lowering of quality 

 under the present methods of cropping led to an investigation of the 

 potato situation in 1908 by the Office of Cotton and Truck Disease 

 and Sugar-Plant Investigations of the Bureau of Plant Industry, 

 and the results were published in 1909.^ These results seemed to 

 indicate that the decrease in yield and quality was due largely to 

 pathological conditions. Some preventive measures were described, 

 but it was stated that further investigation was necessary, particu- 

 larly in comiection with the improvement of cropping systems and 

 cultural methods. 



EXPERIMENTS WITH POTATOES IN 1912. 



In the spring of 1912 work was begun by the Office of Western Irri- 

 gation Agriculture looking to the improvement of cropping methods 

 on these lands. Since potatoes are the crop upon which the land- 

 holders depend for maximum returns, their place and duration in 

 any rotation are of great importance. In the work for the crop season 

 of 1912 the main aim was to determine what method of tillage, ferti- 

 Hzation, and rotation may be expected to give the best results in 

 potato production and weed control. 



It was thought that the potato wilt might be controlled by increas- 

 ing the vigor of the plants and that the damage from scab might be 

 reduced by acidulating the soil. For tliis reason the experiments 

 included methods of stimulating plant growth, particularly through 

 the use of commercial fertiUzers, and also included methods of acidu- 

 lation. The Burbank variety was used in aU the trials. 



The land used in 1912 comprised about 32 acres in three fields 

 (fig. 1), as follows: Field F, 15.5, field G, 6.6, and field I, 10 acres. 

 This land had been planted to potatoes in 1911 and was very weedy 

 when taken over for experimental purposes. 



In most of the experiments determinations were made of the 

 stand, the extent of potato ^\dlt {Fusarium oxysporum), the extent of 

 scab, a disease due to a fungus {Oospora scabies), and the yield of 

 marketable tubers and of tubers of unmarketable sizes. The method 

 followed in these determinations and the meaning of the figures used 

 in the following tables are described later. 



I Orton, W. A. Potato Diseases in San Joaquin County, Cal. U. S. Department of Agriculture, Bureau 

 of Plant Industry, Circular 23, 14 p., 1909. 



[Cir. 127] 



