276 



THE AGRICULTURAL NEWS. 



bEFTEMBEK 



1911. 



FRUITS AND FRUIT TREES. 



PINE-APPLE GROWING AND MAN- 

 GANESE SOILS. 



Tbis subject has received much attention of late, |iar- 

 ticularly in Hawaii, and an opportunity is given to present 

 further information concerning it by the publication, in the 

 Havjaiidii Voreiiler and Agriculturist ior June 1911, of an 

 article dealing with the matter, in relation to the soils of 

 Wahiawa in the Hawaiian Islands. It is stated that pine- 

 apple plants growing in this soil are stunted, likely 

 to be attacked by pests and diseases, possess a sickly ajjpear- 

 ance, and are wanting in the healthy green colour that 

 attends a normal content of chlorophyll in the leaves. The 

 admission is made thai these conditions may be due to cir- 

 cumstances other than the presence of an excess of manganese 

 in the soil, among these being lack of drainage, root rot, and 

 deleterious sub.stances in liquid manure; but it is agreed that 

 the manifestation of untoward conditions in this case is due 

 to the eflfect of the manganese compounds in the soil. 



Reference is made to the fact that manganese is vvidely 

 distributed in soils, but always exists as compounds. The 

 subject is comjilicated by the considerations that manganese 

 dioxide can lose oxygen and give rise to manganous salts, and 

 that it can combine with such substances as lime to form 

 compounds, call manganites, which decompo.se somewliat 

 easily under ordinary conditions. 



Attention is called to the circumstance that citric acid has 

 been found capable of dissolving considerable amounts of man- 

 ganous hydroxide, and that acids, generally, can dissolve the 

 oxides of manganese. Further, various water plants have been 

 shown to be able to absorb combined manganese from water con- 

 taining compounds of that element, manganese dioxide being 

 deposited in the ejiidermis of the leaves. Other work, carried 

 out more especially in .hipan, has demonstrated that plants 

 other than pine apples exhibit a toxic conditioti when they 

 are subjected to the action of manganese salts in large 

 amounts. The results of the.se investigations are ajjplied to 

 pine-api)les growing in Wahiawa soils, particularly in view of 

 the large acidity of the plant, although it is doubtful if man- 

 ganese dioxide could be deposited in the pineapple in a way 

 similar to that in the ca.se of wat?r plants, in view of the 

 high citric acid content of the former. 



Trials have shown that sugarcane can be grown success- 

 fully on manganese-containing soils which could hardly 

 support pine-apples, and this fact suggests that there must 

 be some considerable ditlercnce between these two crojis. in 

 relation to their absorption of substances from the soil. The 



matter receivts elucidation when the ash of each of these 

 plants is analyzed, for it is .seen that the pine-apple takes up 

 much more mangane.'o than the sugar-cane, while at the same 

 time, the proportion of ash to the total weight of the plant 

 is much greater in the case of the former. The circimstanoe 

 may be due to the greater acidity of the plant, but the 

 important matter is that, where manganese is present in the 

 .soil, this will naturally lie absorbed to a much greater 

 extent in the case of pineapples than in that of sugarcane. 



As has been indicated, the formation of manganites from 

 manganese dio:;ide, with basic substances such as lime, 

 requires due consideration. Several such bodies are formed, 

 with lime, and they are all very poisonous to plant life. 

 An interesting illustration is given, in which a heavy 

 dose of (luicklime was applied to a field of soil possessing 

 a high manganese content, where pine-apples were growing, 

 when the plants practically ceased to grow, lost nearly all 

 their chlorophyll, and had to be removed. The circumstance 

 would point to the formation of some highly poisonous com- 

 pound, through interaction between the lime and the manga- 

 nese compounds in the soil, and provides an exami)le in which 

 the application of lime was not beneficial, as is usually taken 

 to be the case, but quite otherwise. 



The article concludes with the suggestion that, with 

 liresent knowledge, it may be a.ssumed, at any rate tempora- 

 rily, that the poisonous effect observed with pine apples grow- 

 ing in the manganese soils of Wahiawa is due primarily to 

 the action of calcium manganite, and .secondarily to that of 

 other salts and acids upon this body. 



CASSAVA FROM REUNION. 



In L' Aijricidtin-e Prafi(jiie des I'ai/.t C/iauili for July 

 1911, particulars are given of an analysis of 'manioc en 

 cossettes ' exported from Ucunion, which was made at the 

 Jardin Colonial. This is a product obtained by drying the 

 ca.ssava and exporting it in the form of small 'cakes'. The 

 figures are as follows : — 



J'er cent. 

 Water 1 1 -70 



Starch 84' 1.^ 



Nitrogenous matter 1-31 



Ash 1-70 



The cassava was stated to be well prepared and free 

 from large fibrous bundles, and to be considered as a product 

 of very good quality. 



