THE MONTHLY BULLETIN, 237 



lizer needs. These consist, first, in the fact that the ash of plants does 

 not always contain or indicate the amounts of a given constituent 

 which a plant needs the most during its growth. For example, as was 

 shown by Lawes and Gilbert many years ago in their controversy with 

 Liebig, turnips need large quantities of phosphorus for their successful 

 growth, yet their ash shows but relatively little phosphorus. The ferti- 

 lizer needs of soils can not, therefore, with the information which we 

 have in hand, be ascertained by the complete analysis of soils, unfortu- 

 nate as this statement may seem. The only method which we have that 

 is at all reliable is an empirical one, but it is none the less the best in 

 our possession. That is the method of trial in the field directly of a 

 series of fertilizers. 



Discouraging as this situation may seem to be with reference to 

 chemical anal^^ses of soils in relation to fertilizer needs, it is really not 

 so hopeless as it looks, and especially for Oilifornia soils. The reason 

 for this is that under our conditions, in which you are particularly 

 interested, the soils are so deep and are so well supplied with plant food 

 that we need rarely do aught else than add organic matter to increase 

 the soil's own ability to produce available plant food, if we will but 

 manage the soil right. Preferably to accomplish that end we must use 

 the methods of soil management Avhich help to dissolve and make avail- 

 able, from the insoluble store in the soil, the plant food elements. 

 These methods are deep tillage, the use of large quantities of organic 

 matter, the maintenance of good drainage, constant summer cultivation 

 or the use of straw or manure mulches — depending upon the condi- 

 tions — and the maintenance, through liming, of an alkaline reaction 

 in tlie soil, and of a good structure. With these methods used there 

 will be ample available plant food in most of our California soils, and 

 particularly in the deep ones. 



THE SPECIFIC EFFECTS OF PLANT FOOD ELEMENTS. 



Another one of our numerous misconceptions with respect lo soils 

 and their fertility is that every one of the essential elements — as we 

 love to call them — which is compounded in various forms in fertilizers, 

 has its own specific effects on plant growth in general and on the fruit 

 or product yielded in particular. Thus, for example, it is commonly 

 believed that potash will make a smooth rind on an orange, and that it 

 Avill give better color to fruit. It is believed that lime makes a sweeter 

 fruit, that phosphoric acid makes a large quantity of fruit, though 

 small in size, and that nitrogen makes a coarse grained fruit and a very 

 rough rind, in the case of a fruit like the orange. For none of these, 

 nor for many other such ideas, is there the slightest basis in scientific 

 data so far as I am aware, with the possible exception of the effects of 

 nitrogen. Even that is by no means securely established. I have 

 searched the literature assiduously many times through all the records 

 of plant physiologists and other investigators on plant nutrition, and 

 as yet I have been unable to find evidence which supports the view that 

 these elements exercise their specific effects as above noted. Even such 

 staunch adherents of the chemical view of soil fertility or the plant 

 food theory as Hopkins, deny the existence of proof for the specific 

 effects of plant food elements. And while such may exist — as future 



