February, 1910,] 



151 



Miscellaneous. 



POTASH-A MANURE FOR 

 ORCHARDS, VINEYARDS, AND 

 GARDENS. 



By Albert H. Benson, m.r.a.c. 



(Prom the Queensland Agricultural 

 Journal, Vol. XXIII., Pt. 3, 

 September, 19W.) 



The value of potash as a manure for 

 orchards, vineyards and gardens is only 

 now beginning to be recognised by our 

 Queensland growers. It has been used 

 in small quantities, generally in the 

 form of a mixed fertiliser, for some 

 years ; but it is only recently that it is 

 being used systematically. 



The reason for this I will deal with 

 latei* on, as, in the first place, I wish to 

 show the important part that potash 

 plays in the growing of fruits and vege- 

 tables. If one makes a careful study of 

 the analyses of the ash of the principal 

 commercial fruits and vegetables, one 

 cannot fail to be impressed with the 

 important fact, that potash forms a 

 very large percentage of the ash ; in 

 fact, so much so, that it may be said to 

 be the dominant ingredient of the ash. 

 Potash is usually present in the largest 

 proportions in the ash of fruits, roots, 

 and pulses, but it is present also in 

 large quantities in the ash of wood, 

 leaves, and roots of fruit trees and vines, 

 and in the roots and foliage of vegetables. 



In the case of the ash of fruits, the 

 average potash contents for all commer- 

 cial fruits amount to nearly 50 per cent, 

 of the total weight of the ash. Some 

 fruits, notably stone fruits, run con- 

 siderably higher, in some cases the 

 potash amounting to 70 per cent, of the 

 total ash. 



This being the case, it seems at first 

 sight an extraordinary fact, that so far 

 we have used such a small quantity of 

 potash as a manure; especially when 

 we take into consideration the fact, that 

 many of our soils are by no means rich 

 in this essential plaut food, particularly 

 so iu a readily available form. 



How is it then, one may ask, that we 

 have been able to grow such good crops 

 of fruits and vegetables for years past 

 without the application of potash 

 manure ; and why is it now necessary 

 to apply such manures in order to keep 

 up the yield of fruit or vegetables ? The 

 answer to those questious is, that the 

 bulk of the land on which we are grow- 

 ing fruit is virgin land, and that this 

 land has, up till the present, shown little 

 signs of deficiency in available potash. 

 In other words the available potash in 

 new land, particularly when there has 



been a heavy growth of forest or scrub 

 timber burnt off, has been sufficient to 

 produce good return?, in some cases for 

 several years, and it is only now that 

 this available supply is becoming ex- 

 hausted by the heavy crops of fruits 

 or vegetables that have been taken off 

 the land that we are beginning to find 

 out the value of potash as a manure. 



There is one very noticeable feature in 

 manuring with potash, and that is, it 

 is only when the supply of available 

 potash in the soil is exhausted or 

 seriously depleted that we see the bene- 

 ficial effect of manuring with potash. 

 This accounts for those cases when it 

 has been found that the application of 

 potash has had apparently no effect, 

 as where there is a sufficiency of avail- 

 able potash in the soil for the proper 

 development of the crop, the addition 

 of an extra supply of potash has had 

 no effect. In these cases the grower 

 has been disappointed, and has even 

 gone so far as to say that potash is 

 no good as a manure. The fault has 

 not been with the manure, but that 

 the soil was already sufficiently rich 

 in this plant food. The question now 

 arises, how is the grower to tell when 

 his land requires potash ? This can 

 only be answered by an analysis of the 

 soil, or, better still, by a little experi- 

 menting on the part of the grower. A 

 few pounds of sulphate of potash applied 

 to a row of English or sweet potatoes, 

 or to a patch of tomatoes, will soon show 

 the grower if his land wants potash, as, 

 if in want of this plant food, the l'esults 

 of the manure will be very evident. 



The total amount of potash contained 

 in a soil, as shown by analysis, is often 

 very misleading, as it is only that 

 portion which is soluble or readily avail- 

 able that can be utilised by the plant. 

 The bulk of the potash iu the soil is in 

 an insoluble form that only becomes 

 slowly available. This is clearly shown 

 in the case of the soils in the Stauthorpe 

 district. Here the bulk of the soils are 

 formed by the disintegration of the 

 granite rocks for countless years. The 

 granite is rich in felspar that coutains 

 from 7 to 8 per cent, of potash, yet 

 once the available potash in the soil 

 is depleted, the addition of a potash 

 manure to the soil has a very marked 

 effect in the production of potatoes, 

 tomatoes, carrots, pulses, and of all 

 fruits. 



Another instance of the necessity of 

 having a sufficiency of available potash 

 iu the soil, is clearly shown by the 

 analyses of some banana soiis from the 

 Liverpool Creek district, North Queens- 

 land. Two soils were selected, one on 



