Vol. XI. No. 259. 



THE AGRICULTURAL NEWS. 



109 



STUDENTS' CORNER. 



APRIL. 



First Period. 



Seasonal Notes. 



Distinguish between artificial and natural manures, 

 stating why manures are required for soils on which crops 

 are grown. What is likely to happen, especially in the 

 tropics, from the use of artificial manures, with the employ- 

 ment of little or no natural manure? Discuss the use of 

 artificial manures from the point of view of economy, partic- 

 ularly in relation to the fact that, in most cases, many by- 

 products of the estate are available for manurial purposes. 

 Proper consideration of these subjects will lead to the conclu- 

 sion that the main use of artificial manures should be to 

 supplement natural manures such as pen manure and green 

 dressings. What are the constituents for which artificial 

 manures are most generally valuable, and which of these 

 constituents of the manure costs the most? Taking the analy- 

 sis of an artificial manure of which you have had experience, 

 calculate the cost of each constituent in one ton of the manure, 

 and compare the cost of the manure itself with that of others 

 which do not contain the same proportions of the different 

 constituents. It is to be remembered that one of the chief 

 objections to the purchase of cheap, low grade manures is that 

 they contain a certain amount of matter that is of little or no 

 manurial value, usually called 'filler', the presence of which 

 actually entails greater expenditure in freight, and in applying 

 the manure to the purpose for which it has been bought. 



What do you understand by water soluble, citric acid 

 soluble and insoluble phosphate? How is the so-called insolu- 

 ble phosphate treated in order to make it more quickly avail- 

 able to plants, and what changes that are taking place in the 

 soil assist in its becoming soluble? How is the phosphatic 

 manure known as bone meal treated to make it soluble, and 

 under what name is it known after this treatment? State 

 ■what you understand by the manures that are called acid 

 phosphates or superphosphates. What is basic, or Thomas, 

 slag? 



What occurs to organic matter in the soil which, causes 

 it gradually to disappear? State what products are available, 

 under conditions with which you are familiar, for use for the 

 purpose of restoring the proportion of such matter in the soil. 

 It should be remembered that this question is of larger im- 

 portance in the tropics than in temperate countries, because 

 of the greater rate at which the destruction of such matter 

 takes place in the soil. Explain the employment of green 

 manuring in this connexion, and state what plants your exper- 

 ience would lead you to consider best to be employed for the 

 purpoe^e. ' Distinguish carefully the effects of manuring with 

 ordinary plants, as compared with those from turning legu- 

 minous plants into the soil. Care is required in using stable 

 manure and green dressings, lest this should lead to the intro- 

 duction into the soil of seeds of harmful or useless plants, 

 which may interfere with the growth of the crop for which 

 the manure or dressing has been applied. 



It sometimes happens that the plants of a leguminous crop, 

 particularly in the case of one that has been introduced for 

 the first time, do not thrive. This condition may be a result 

 of the fact that the soil does not contain the actual strain of 

 bacteria that live in symbiosis with the plant, in the nodules 

 that should form on the roots. In such cases, efforts may be 

 made to introduce the required bacterium, and this is done: 

 (1) by applying soil from an area where the same plant, or 

 one closely related, has been grown recently; (2) by 

 using artificial cultures of the required bacteria, the culture 

 being placed in a large quantity of water containing salts 

 for the nutrition of the bacteria, and the seed of the plant 

 being soaked in the water a few hours after the intro- 

 duction of the culture; or even (3) such soil as is men- 

 tioned in the first of these methods has been soaked in 

 water, and the water poured off and used for moistening the 

 .seeds to be planted. Of the ways described, the first has 

 been found most successful. In regard to the second, men- 

 tion the names of any bacterial preparations that have been 

 prepared for use in connexion with this purpose, on a large 

 scale. In such work, it cannot be expected that any im- 

 proved results will follow the addition of the bacteria where 

 these are present already in sufficient amount; the lack of 

 recognition of this matter has led to a deal of confusion in 

 the interpretation of the results of experiments performed in 

 connexion with the matter under consideration'. 



Questions for Candidates. 

 Preliminary Que.stions. 



(1) Give a list of the operations required in raising 

 sugar-canes from cuttings, under conditions in which yoti 

 have had experience. 



(2) State carefully how Bordeaux mixture is usually 

 made. 



(3) What is the importance of sunlight to green plants? 



Intermediate Questions. 



(1) Give an estimate of the cost of raising an acre of 

 sugar-cane, under conditions with which you are familiar. 



(2) What are the chief precautions to be followed in 

 making and applying Bordeaux mixture? 



(3) How would you show by means of a simple experi- 

 ment the effect of sunlight on the rate of transpiration 

 in plants? 



Final Questions. 



(1) Provide statements showing the approximate cost of 

 raising an acre of canes : (1) when implemental cultivation is 

 employed, (2) when hand labour is the sole resource. 



(2) Give an account of any means that has been em- 

 ployed for the speedy making and use of Bordeaux mixture 

 on a large scale. 



(3) What is the effect of sunlight in relation to the 

 changes that take place in the soil? 



Experiments described in the Comptes Rendus de 

 rAcadc'iiiie des Scieiires for May 1, 1911, p. 1884, have shown 

 that when frc.sh vanilla pods, even those that are completely 

 green, are subjected to the ultra-violet rays an exhalation of 

 perfume is caused. This action is brought about more 

 quickly, and the exhalation is stronger, if the stalk of the 

 fresh fruit is placed in a solution containing manganese 

 chloride at a strength of one part of the salt in 1,000 parts 

 of water. 



