2 BULLETIN 164, U. S« DEPARTMENT OP AGRICULTURE. 



It is harmful to wheat seedlings in water cultures, even in such low 

 concentrations as a few parts per million, and the plants are killed in 

 solutions of 500 parts per million in a few days. 1 The toxic effect is 

 less marked upon the tops of the wheat plants than upon their roots. 

 Vanillin is also harmful in nutrient culture solutions composed of cal- 

 cium acid phosphate, sodium nitrate, and potassium sulphate. It is 

 an oxidizable substance and is less harmful in solutions of some of 

 these nutrient salts than in others, especially those high in nitrate. 2 

 Sodium nitrate and calcium carbonate, 3 which themselves induce 

 oxidation, ameliorate the harmfuiness of vanillin. 



The isolation of vanillin from soils and its harmfuiness to plants in 

 aqueous solutions has made a study of its effect in soils and under field 

 conditions essential. The results of such experiments with cowpeas, 

 garden peas, and string beans will now be given, together with the 

 action of vanillin on clover in soil in pots and with wheat plants grown 

 in several soils of different characters. 



EFFECT OF VANILLIN ON GLOVER IN POTS. 



An experiment to determine the effect of vanillin on clover was 

 made by growing clover in Chester loam soil in large pots. Ordinary 

 clay flower pots holding 6 pounds of soil were used. One pot was 

 untreated; the other had a total of 300 parts per million of the 

 vanillin added to it. 



When the soil was potted, 100 parts per million of the vanillin was 

 added and clover then sown, 0.5 gram of seed per pot. The clover 

 was sown April 12, and came up well. On April 28, 50 parts per 

 million of va nillin were added in solution through a funnel passing 

 into the soil nearly to the bottom of the pot, thus avoiding direct con- 

 tact with the tops or roots of the clover. On May 15 another 50 

 parts per million were added, and on June 1 and June 10, 50 parts per 

 million were added, making the total application 300 parts per mil- 

 lion. The experiment was discontinued June 21, 1912. The effect of 

 vanillin was noticeable from the first. 



The harmful effect of the vanillin is shown by comparing the un- 

 treated pot and the vanillin-treated pot shown in Plate I. The vanil- 

 lin-treated plants were healthy in appearance but stunted in growth. 



The green weight taken at the termination of the experiment was 

 8 grams from the untreated pot and only 3.8 grams from the vanillin- 

 treated pot, a decrease of 53 per cent. 



The soil used in this experiment was a soil of moderate productive- 

 ness, and vanillin applied to it at different periods of the growth of 

 the plants was distinctly harmful. Other experiments were made to 



i Schreiner, Reed, and Skinner, Bui. 47, Bureau of Soils, U. S. Dept. Agr. (1908). 

 2 Schreiner and Skinner, Bui. 77, Bureau of Soils, U S. Dept. Agr. (1911). 

 a Schreiner and Eeed, Am. Chem. Soc, 30, 85 (1908). 



