300 



Journal of Agricultural Research 



Vol. XII, N'o. 6 



the nitrate present in the water-soluble condition, we have direct evidence 

 that the water-soluble nitrate need only be renewed once in nine days even 

 at this critical period, while at all preceding and subsequent periods the 

 rate of renewal may be much slower. If we apply this same reasoning to 

 all of the ions, we develop the fact that there are always present in this 

 particular soil, in a condition capable of solution in water, at least — 



Nine days' supply of nitrate. 



Twenty-five days' supply of phosphate. 



One hundred and forty-four days' supply of potassium. 



Two hundred and sixty-five days' supply of calcium. 



Seventy-six days' supply of magnesium. 



Table II. — Rate of zvithdrawal by crop « as shown by periodic harvesting of soil I 

 iWithdrawals computed to parts per million of soil — 50 plants and i ,800 pounds of soil to the unit containerl 



May I (planted) 



Jtme 12 



June 26 



July 12 



July 24 



August 7 



August 21 



August 28 



Nitrate (NO3). 6 



Grams 



per 

 plant. 



•405 



(?) 

 . 520 



•594 

 . 629 

 .664 

 .694 



Parts per million 

 of soil. 



Entire. 



24.85 



31.90 

 36.40 

 38.40 

 40. 80 



42. 50 



Per 



day. 



0-59 



Phosphate (PO^).^ 



Grams 



per 

 plant. 



o. 000 

 .038 



•115 

 . 120 



• 144 

 . 184 



• 194 



Parts per million 

 of soil. 



Entire. 



2.32 



7. 02 



7-35 



8. 10 

 8.82 



II. 20 

 II. 90 



Per 

 day. 



0-055 



. 024 

 .054 

 .051 



Potassium (K). 



Grams 



per 

 plant. 



O. 000 



• ^33 

 (?) 

 (?) 

 .223 



•233 

 . 276 

 .294 



Parts per million 

 of soil. 



Entir e. 



Per 



day. 



8. 131 o. 194 



13-70 

 14.30 

 16. 90 

 18. 00 



133 

 043 

 186 



157 



Date. 



May I (planted) 



June 12 



June 26 , 



Jtily 12 



July 24 



August 7 



August 21 



August 28 



Calcium (Ca). 



Grams 



per 

 plant. 



o. 000 



. 012 

 •034 

 (?) 

 . 041 



(?) 

 .048 



•043 



Parts per million 

 of soil. 



Entire. Per day. 



o. 712 

 2. 092 



2-530 



2. 940 

 2.650 



o. 017 



. 016 

 . 014 



Magnesium (Mg). 



Grams 



per 

 plant. 



o. 000 

 .013 

 .031 

 .036 



(?) 

 .044 



•049 

 •051 



Parts per million 

 of soil. 



Entire. Per day. 



0.816 



1. 920 



2. 190 



2. 670 



2. 980 



3. 140 



o. 019 



.079 

 . 019 



017 

 , 022 

 023 



o Analyses based on varying numbers of plants: June 12, 69 plants; June 26, 42 plants; July 12, 42 plants; 

 July 24, 29 plants; August 7. 28 plants; August 21, 38 plants; August 28, 87 plants. 



6 Nitrate (NO3) and phosphate (POi) computed from the amounts of nitrogen and phosphorus in the 

 crop. 



The entire time the crop was in the ground was 119 days. The time 

 to elapse after the period of greatest depletion was 35 days for nitrate, 

 63 days for phosphate, 77 days for potassium, 63 days for calcium, and 63 



