170 



EXPERIMENTAL FARMS. 



Weight of Important Fertilizing Constituents withdrawn from the soil. 



Of these essential elements it is here made clear that the chief demands for the de- 

 velopment of the plant are upon the available potash and nitrogen in the soil. The phos- 

 phoric acid stands third, the ratio of potash to phosphoric acid from our analysis being 

 4 to 1. 



Since the plants are finally ploughed under, thus returning the substances former- 

 ly abstracted and assimilated from the soil, the only real loss, theoretically, of plant food 

 is that contained in the fruit. The quantity of fruit obtained per acre varies widely, 

 viz , from 75 bushels to 300 bushels, a good average yield weighing probably 10,000 lbs. 

 From the report for 1892 of Dr. Goessmann, Director of the State Experiment Station, 

 Amherst, Mass., U. S. A., the following averages were obtained : Ash in fruit, - 52 per 

 cent; potash in ash of fruit, 53-81 per cent; phosphoric acid in ash of fruit, 17*9 per 

 cent. Estimating the weight of fruit at 10,000 pounds, we find that 52 pounds of min- 

 eral matter, containing 28 pounds of potash and 9 pounds of phosphoric acid, are re- 

 moved per acre. The ratio here of phosphoric acid is 3 to 1. Unfortunately, the 

 amount of the nitrogen was not ascertained. 



The loss of plant food that the soil sustains through the gathering of the fruit, is 

 not, compared with other crops, an excessive one. At the same time, it is to be remem- 

 bered that the soil has to provide, in addition to those required by the fruit, the fertil- 

 izing constituents as given in the above table though, as already pointed out, the greater 

 part of the latter will eventually return to the soil. 



A soil to be well manured must contain a large excess of available plant food over 

 and above the amount that can be utilized by the crop, since it can not be supposed 

 that the roots will be able to absorb, by virtue of their disposition in the soil, more 

 than a comparatively small proportion of such fertilizing ingredients. 



The strawberry is usually considered an " exhausting crop " ; as far as the real loss 

 of plant food through gathering the fruit is concerned, the facts scarcely bear out this 

 opinion. To replace or restore to the soil the substances so removed by the fruit, would 

 not in itself require a very heavy application of manure. It is found, however, as a 

 matter of practical experience that, to make strawberry culture successful, the soil must 

 be fed very liberally. High manuring for strawberries is a common practice. We may 

 advance several reasons why such is necessary and why this practice does not conflict 

 with what has already been said and shown here. 



The growing season is short, and more especially the fruiting period. During a 

 comparatively brief time there is a large demand for immediately available forms of nitro- 

 gen, phosphoric acid and potash (and especially the first and last of these,) a demand 

 that must be met if the best results are to be obtained. Even the richest soils contain 

 only small amounts of such plant food, and hence the necessity for the presence in the 

 soil of a large quantity of manure that will readily yield its fertilizing ingredients. 

 This more particularly is found to be the case when the rainfall during the fruiting 

 season is below the average. 



