6i 



THE TROPICAL AGRICULTURIST. 



[JotV I, 1885. 



and we find very nearly the same amount in the crop. 

 Tho phosphoric " acid, on the other hand, is much in 

 excess of the requirements of the crop, and it might he 

 reduced one-half. The salts of ammonia and the nitrate 

 each supply about the same amount of nitrogen — 87 lb. : 

 and of this the crop does not take up more than 50 lb. ; 

 there is, apparently, therefore, a considerable loss of this 

 substance; but at the same time, any reduction in the 

 amount of these manures would be followed by a reduction 

 in the crop. The loss of this costly manure ingredient 

 is a most serious matter, as unfortunately there is but 

 little prospect of recovering, in succeeding crops, any 

 appreciable amount of the 37 lb. not taken up by the 

 first. By means of the same mineral manures alone we 

 have grown — over the same period — one-half the crop we 

 obtained by the apphcation of minerals with nitrogen, 

 the soil having suppUed a sufficient amount of that substance 

 to give a product of iOU bushels; but one-half of the 

 minerals applied remained inactive in the soil; these, 

 however, might be made available to the crop by an 

 application of nitrogen. 



The quantity of potash removed in potatos is very 

 large. In the 400 bushels it amounts to about 130 lb. 

 Compare this with the amount removed by animals. An 

 ox weighing 1,400 lb., which was killed for the purpose 

 of 'analysis, contained only 2i lb. in the whole carcase 

 and ottal. Hay is another crop which takes a goood deal 

 of potash from the soil, and farmers in England rarely 

 "VOW either hay or potatos for sale unless there are facilities 

 tor the purchase of town dung. Artificial manures are 

 certainly not used alone by practical farmers in the growth 

 of their crops. 



In our experimental field, the character of the manure 

 is represented in the stem and leaves of the plant. 

 Ammonia and nitrate without minerals give a low stem 

 and greenish-brown leaves, which in the evening appear 

 almost black. Minerals without nitrogen give a thin, low 

 .stem and yellowish-green leaves ; while mineral and nitrogen 

 together give a luxuriant, and sometimes an over-luxm-iant, 

 stem, with leaves of a bright green. There is no difficulty 

 in accounting for these peculiarities. A plant takes up 

 wh.atever food is mo.st abundant in the soil, with the 

 hope, as I sometimes put it, that sooner or later it may 

 find the food which suits it best. In the dark-green 

 leaves the nitrogen is in excess; but starch cannot be 

 formed without potash, and the supphes of potash are not 

 uuflicient to use up the nitrogen. It is far more easy to 

 change the yellowish-green of the mineral-manured potatos 

 into a dark green than it is tn lighten the colour of 

 potatos which receive nitrogen ; a solution of nitrate of 

 soda will effect tho one in a very few days, but as both 

 potash and pUosphoric acid form the insoluble compounds 

 with the soil, they are much more slowly taken up by plants. 

 We always, however, obtain a larger crop of potatos 

 where we apply the mineral manures alone, than where 

 we apply the nitrogen without the minerals, though in 

 the next field, salts of ammonia applied without minerals 

 for thirty-nine years in succession, have grown larger 

 crops of wheat over the whole period than mineral 

 manures without ammonia. To explain this apparent in- 

 consistency we must consider the great difference in the 

 character of the two crops. 



Wheat in England is sown in the autumn, and being 

 a deep-rooted plant, it has a greater range of soil to 

 obtain a supply of mineral food than the spriug-sowu 

 potato. The relation between the potash and the phos- 

 phoric acid and nitrogen in the two crops is also very 

 different. In the wheat crops grown by salts of ammonia 

 alone, mixed samples, taken over a period of ten years, 

 give the products per acre of the total crop — straw and 

 grain— as follows : nitrogen, 3(i lb. ; potash, 23 lb. ; phos- 

 phoric acid, 13 lb. The relation, therefore, between these 

 two important minerals and nitrogen is as one to one. 



In the potato crop, on the other hand, the proportion 

 of nitrogen to the minerals is nearer one of nitrogen to 

 three of miiicrals, the demand upon the soil for potash 

 being much greater in the case of potatos than where 

 wheat or barley is grown. It must be a very large wheat 

 crop indeed which removes 50 lb. of nitrogen from the 

 soil ; but in some of our potato crops we carry off more 

 than 100 lb. of that substance per acre. 



As very few soils could furnish so large an amonut as 

 this from their own resources, when potatos are continously 

 grown, it becomes necessary to furnish a supply of potash 

 either in dung or chemical salts. The following table 

 gives the prorlucts of the crop grown in 1S?3, being the 

 ninth in succession without any change in the manures. 



amount of mineral matter and nitrogen per cent. in_ 

 dry tubers: — 



The character of the manure is most clearly shown in 

 the composition of the crop. lu No. 2, manured with 

 minerals, the minerals are five times as high as the nitrogen ; 

 while in No. 3, where ammonia or nitrates are useo, the 

 minerals are considerably less than doul)le the amount of 

 nitrogen. In both oases there is a waste of power^ shown 

 by small crops, and unused manures. The loss, however, is 

 not equal in both cases, as the minerals remain in the soil 

 to be taken up at some future time, while the nitrogen 

 is probably lost. — Sib John Lawes, in " Umal New yorkerJ' 

 — Gardeners' Chronicle, 



INJURIES TO 



CULTIVATOr.S BY 

 PESTS. 



IMPORTED 



A circular has been issued and widely circulated from 



the office of the Adelaide Observer upon the subject of 

 injuries done to crops, fruit, and farmers' produce gene- 

 rally, by imported pests of all kinds including the Coor- 

 ado beetle, the Oidium Tuckerii, and the Aphis lainger 

 or American Blight for which reductive if not intirely 

 obliterative remedies have already been discovered. The 

 author refers to the excessive danger done by the shot 

 hole fungus — Helmiuthosporium rhabdiferum — of which I\Ir. 

 Frazer S. Crawford has recently discovered the fruiting 

 spores. This destructive fungoid pest attacks the almond, 

 apricot, and peach crops, eating innumerable circular 

 holes in the leaves of trees, atfectiug the tender branches 

 by absorbing their juices, and disfiguring and dwarfing 

 the fruits. At one time this fungus was unknown in 

 the colony, and our apricot, peach and almond trees 

 used to be loaded with fruit of the largest size and 

 finest flavour. Now it is a very rare thing to see a 

 good peach or almond, except at American River, Kan- 

 garoo Island, where the disease has not yet been intro- 

 duced. An acre of apricots would contain about one hund- 

 red trees, and it woidd be an exceedingly moan estimate 

 at present to put the value of the yield of a good tree 

 at twenty shillings. "We have seen hundreds of dozens 

 of fruit upon the trees at the island, and at fourpeuce a 

 dozen that sum would he realized over and over again. 

 AVhat, then, would be the value of a remedy by which 

 the grower could secure the proper and healthy crops — 

 as of old — from the apricot and peach trees H For years 

 it has existed amongst us, and until now not one in a 

 hundred growers knew what it was that was injuring him,- 

 and not one at all knew the remedy. It is vtry simple, 

 and credit is due to Mr. Crawford for his enquiry into 

 the life history of the pest, as well as his suggestion of 

 a remedy — which is simply soft soap. I'robably the 

 kerosiue emulsion would answer e<)uany us well, and as it 

 is also destructive of scale and aphis it might answer better 



