32 



Effects of Potash. 



The effect of potash is most readily noticeable in the quality of 

 the fruit, its carrying- capacity, sweetness, and a marked thinness of 

 skin. These are all factors in producing a good class of orange. Potash 

 is usually applied in the form of either sulphate or muriate; very 

 occasionally kainit is used. Experience has shown that the sulphate 

 is the most acceptable form in which to apply potash to bearing citrus 

 trees, and a good grade is preferable to a low one. Wood ashes are 

 quite a good source of potash also and should not be allowed to go to 

 waste. Nitrogen may be applied in various ways. Its effect is to 

 produce luxuriant growth of young wood and to increase leaf develop- 

 ment. Formerly it was largely applied in the form of sulphate of 

 ammonia and nitrate of soda, the latter being by far the readiest and 

 quickest in its action. 



More recently in South Africa organic nitrogen in the form of 

 dried blood has become available from the abattoirs of our large towns, 

 whilst the system of cover cropping with some leguminous crop supplies 

 a large amount of nitrogen to the soil. When this system is resorted 

 to it is unnecessary to apply as much nitrogenous fertilizer in any 

 mixture of a commercial nature which may be used. It may be added 

 that many other results are obtained by the use of cover crops. For 

 instance, a large amount of humtis is added to the soil which not only 

 improves it but is useful in assisting in the retention of moisture. 

 Planting a leguminous crop in September or October for ploughing 

 under later also prevents washing away of the soil in orcliards which 

 are laid out on a slope. We have also further sources of supply of 

 nitrogen in tlie guano supplied by the Agricultural Department from 

 the Guano Islands, and also in the fertilizers from the whaling stations 

 to be found round our coasts ; the latter siipply an exceedingly useful 

 article. Lime need rarely be applied alone to any of the soils on 

 which citrus trees are planted. It enters into the composition of most 

 fertilizers containing phosphoric ' acid, and is present especially in 

 Thomas's phosphate powder or basic slag in a large percentage. The 

 part played by phosphoric acid in nature's economy in connection with 

 the production of a healthy tree bearing good fruit is an important 

 one. It is found in the fruit, hark, peel, and seeds of the orange, and 

 induces maturity, both of wood and fruit, by its presence. An 

 inadequate supply of phosphoric acid often means late ripening of 

 fruit, and this is more especially the case when a quantity of stable 

 manure has been used. 



It is impossible to lay down one formula which will suit all soils, 

 and there may be some who would prefer to purchase their own 

 ingredients in suitable quantities and mix them on the farm. 

 Phosphatic manures most in use in South Africa are superphosphates, 

 bone meal, and basic slag. 



The diagram prepared by Dr. Geeken (and revised by Mr. 

 Brunnich, chemist to the Department of Agriculture, Queensland) 

 shows at a glance what fertilizers may be mixed before application 

 with safety and those which may not be mixed owing to the liability 

 of decomposition. 



It has been stated that phosphoric acid should form one-half of 

 the total fertilizer supplied, and on that basis one may safely work in 

 our soils, for nine-tenths of them are deficient in that particular 



