POT EXPERIMENTS WITH FERTILIZERS. I 57 



Care of the plants diiring the period of grozvth. — The pots in 

 which the plants grew were placed upon trucks which rolled 

 upon tracks and could be moved into and out of the plant shel- 

 ter. At night, and during stormy weather, and when high winds 

 would be likeh' to injure the plants, they were kept inside the 

 shelter house; at other times they were out of doors. Care 

 was taken to have the conditions of sunlight and moisture as 

 nearly alike as possible for the plants in the different pots. 

 The trucks on which the plants stood were switched from one 

 track to another whenever necessar}', so that the shorter plants 

 would not be in the shade of the taller ones. The plants were 

 kept under shelter during rainy weather, and water was sup- 

 plied to them artificial!)', as often as seemed necessary to keep 

 up a vigorous growth. The water used had previous!}' been 

 found by analysis to be practically free from nitrogen. Part 

 of the water was applied at the bottom of the pot by means 

 of the pipe entering from the outside, and part was poured 

 upon the surface, for the purpose of distributing it through 

 the soil. The water content of the soil was kept between 10 

 and 15 per cent, by weighing the pots with the soil and the 

 growing plant and adding sufficient water to bring the total 

 weight up to a given amount previously determined. 



Sampling and analyzi7ig the crops. — The total crop from 

 each pot was used as a sample for analysis. The grasses and 

 millets were cut one inch above the soil, and each sample was 

 put into a loose paper bag and was dried in the air, and later 

 was cut into pieces about one inch long and kept in sealed bot- 

 tles or jars until analyzed. In the case of the soy beans only 

 the seed from each pot was taken as a sample, no effort being 

 made to save the straw because the leaves drop off before the 

 seed is fully matured. 



The only analysis of the crops was the determination of the 

 percentage of total nitrogen in the samples. The data in the 

 tables giving the results with the different crops include for 

 each pot the amount of nitrogen in the fertilizer, the total 

 weight of the crop, the percentage and weight of total nitrogen 

 and the estimated percentage of total protein. 



The amount of crop that can be grown in a pot in the ex- 

 periments is so small that the results give little indication of 

 the effect of the different quantities of nitrogenous fertilizers 



