ESSENTIALS OF PLANT 



Effect of the Soil and Season. The character of the soil and 

 the weather conditions prevailing during the growth of plants, 

 have a great influence upon the composition of their ash. The 

 seed is less influenced by these conditions, but the straw of 

 cereals is greatly affected. Indeed, it has been proposed to 

 determine the needs of the soil for plant food by analysis of 

 certain plants grown on it. 



At the Rothamsted Experiment Station, barley has been grown 

 on a certain field for over fifty years. Some of the plots receive 

 no fertilizer, and others receive various mixtures, but the treat- 

 ment has been the same during the entire period. Plots which 

 do not receive the complete fertilizer should be depleted of the 

 plant food not added in the fertilizer. There is very little varia- 

 tion in the composition of the ash of the grain. The phosphoric 

 acid and silica in the straw vary slightly, but great changes take 

 place in the percentages of potash and soda. 



While the yield of grain decreases from 45.62 to 36.63 bushels 

 per acre, the composition of its ash is little affected. The potash 

 in the ash of the straw decreases from 18.4 per cent, to 7.4 per 

 cent., accompanied by an increase in soda, though not in cor- 

 responding quantity. The ash in the straw from the plot re- 

 ceiving potash fertilizers contains four times as large a per- 

 centage of potash as ash of the straw produced without potash 

 during the decade 1882-91. Since in the first two ten-year periods 

 about 2,700 pounds straw per acre was produced on the no-potash 

 plot, while the 40 year average for the potash plot is 2587 pounds, 



1 Agricultural Investigations at Rothamsted, Gilbert, Bulletin 22, Office 

 of Exp. Station, U. S. Dept. Agr., page 78. 



