364 

 FOItESTS AXD FLOODS. 



Under this heading a letter in Nature (July 16, 1914) discusses 

 the significant circumstances that tilled soil absorbs more rainfall 

 than earth that has laid untouched. As an experiment, water was 

 poured into soil contained in pots consisting of two series : (a) in 

 which the soil was consolidated, (b) in which the soil was broken 

 up and loose. It was observed that the water entered the soil 

 of the undisturbed pots more slowly than the other, and that 

 the water more quickly passed through the soil in these pots than 

 the other. After having taken necessary precautions that the soil 

 had been entirely wetted throughout, the pots were weighed and 

 showed that the disturbed soil held a much greater amount of 

 water than the consolidated soil. 



It may be asked : What connection has this with forests and 

 floods? In the letter under consideration, it is maintained that 

 the soil in which trees are growing is looser than that which is 

 bare; consequently it is in its best condition for absorbing and 

 retaining the rainfall. It is maintained further that the decaying 

 vegetation on the surface under trees has also a beneficial effect, 

 as it absorbs water and acts as a mulch, preventing drying. 



It would seem to us that the conditions obtaining in the pots 

 are not perfectly comparable to the characters of a forest or 

 bare hill-land soil. The presence of a covering of decaying vege- 

 table matter in the forest introduces factors not involved in the 

 pot experiments. The main point brought out. however, is illu- 

 minative, and well worth bearing in mind. — Agricultural A^cws. 



GROUND LIMESTONE. 



When discussing the subject of liming, confused ideas are ck- 

 casionally met with in regard to the question of limestone versus 

 slaked lime or quicklime. Perusal of an article in the Journal of 

 Agriculture, of New Zealand (April 20. 1914), will show that all 

 the good effects resulting from the employment of quick or slaked 

 lime on the soil may be produced witli greater safety by ground 

 limestone. The effective nature of ground limestone naturally 

 depends to a large extent upon its mechanical condition ; the finer 

 the crushing the better the results. Chemically, limestone, like 

 lime, is alkaline, and tends to destroy the sticky nature of .soils. 

 It further supplies a base for the formation of nitrates in the soil 

 and liberates jiotash from the iri.'-oluble soil silicales and prevents 

 potash fertilizers from passing into an unavailable condition. 

 Limestone furthermore has a favoralile inlliuiui' (mi the availa- 

 bility of phosphates in the soil. 



In the article referred to. mentit)n i^ made of (he fact tliat ma- 

 terial containing limestone mav also contain a high percentage of 

 clay or other so-called impurities. It is quite possible that under 



