300 Agricultural Gazette of N.S.W. [April 3, 1920. 



Humus adils nitrogen to the soil. Humus is iiisoliihle, but in the soil it is acted upon 

 y certain bacteria, wiiich make it available as a plant food. 



The air consists of about four-fifths nitrogen, but this is not available to most plants. 

 Certain of them, legumes (beans, peas, clover, &c. ) have the power of drawing the 

 nitrogen from the air, and storing it in i-ool nodules — hence the value of leguminous 

 crops. The crops can be fed off, and then ploughed in, the ground being enriched both 

 by the manure and by the nitrogen on these nodules. Nitrogenous manures must not be 

 applied tobguminous crops. 



Phosphorus does not occur in nature in tlic free stale, but usuallj' in the fo:m of 

 phosphates. Phosphoric acid is next in importanc; to nitrogen, and is contained in all 

 soils, though in variable quantities ; it forms the stiffening matter in the stalks of jdants, 

 such as cereals, and is necessary to produce strength and vigour in young j^lants. When 

 humus decays it makes phosphoric acid availaijle, hence deficiency in humus means less 

 phosphoric acid. Bones and phosphatic rocks (among the chief sources of phosphor'c 

 aci 1) are not soluV)lc in water, and they are chemically treated to change tlie various 

 phosphates into superphosphate, sulphide super, and Thomas' phosphate. Other sources 

 of phosphatic manures are guanos, or manures of birds, which are found on the islands 

 in the Pacific and Atlantic Oceans. 



Potash is the most important mineral plant food, and is necessary to procuce woody 

 tissues and starcli. It is specially beneficial to fruit plants, root crops and potatoes. 

 Like phosphoric acid, porash Ijecomes available through the decay of humus. Moreover, 

 farmyard manures contain potash in soluble form, and wood ashes also supply it, though 

 in comparatively small quantities. This is the reason why new lands which have been 

 cleared by burning off respond so well to potatoes, as the potash the tree absorbed from 

 the soil remains in the ashes. 



Certain soils (wet and boggy soils, for example) are wanting in certain materials 

 necessary to plant life, being sour or acid. In many cases this is noticeable by the 

 reeds, sedges, &c., that flourish to the exclusion of all else. The usual test for acidity 

 in soils is blue litmus paper. If acid, the litmus turns red. As there are other factors 

 which also act on litmus in the same waj', this is not always a reliable test. Even 

 cultivated soils nearly always possess an acid reaction. The remedy in such cases is 

 drainage with the application of lime, say 1 ton per acre, or 8 oz. per square yard. 

 iSorae growers apply as much as 3 tons per acre. 



Departmental Note. — The Chemist points out that the paper does uot refer to lime 

 — an important requirement of soils, which has often to be artificially supplied. 



Middle Dural. 



At a meeting of this branch on 20th February, the questions asked in the 

 January Agricultu7-al Gazette were discussed. 



As to the topping of maize, members considered it ■v\u)rth doing ; it 

 decidedly improved the size of the cob and grain., and it provided green 

 fodder for stock. The best time to top was just after the flower or tassell 

 had become dry. 



For green manuring, barley and green peas were regarded as about the 

 best, the legumes being well sown with the cereal. If sown early they got 

 the winter rains and did not rob the trees of moisture. 



The best way to deal with peach tip moth, it was stated, was to pinch ofi' 

 the tips as soon as they wilted, as at that time the grubs would be about half 

 grown and would be easily destroyed, and the tree would shoot again quickly. 

 The tips should not be left until (juite dead as the grub would then have 

 escaped. Bandaging had not been tried, as it involved more work. 



Departmental Note. — The Chief Inspector remarks that his experience is that the 

 yield of maize is reduced by topping when done early enough to yield tops of good 

 feeding value. If done later -so as not to affect the yield, the operation has not been 

 warranted on account of the cost and the smaller amount of fodder of lower feeding value 

 obtained. 



The Government Entomologist remarks that if everyone pinched the tips infested with 

 peach tip moth as .soon as they showed signs of wilting, it would be all right, but very 

 few do this and when the tips are dead it is too late. Attention to the young shoots 

 with bandaging will certainly much reduce the damage to the peaches the pest do later on. 



