254 LIME 



creases nitrification and fixation. The fact that lime hastens 

 decomposition is frequently charged against it. This is a 

 great mistake, for decomposing organic matter is of very 

 great value to crops and should be encouraged, within 

 reason of course. Active organic matter helps to release 

 the stores of unavailable plant food. Organic matter in the 

 soil should be maintained so that it may be destroyed. A 

 mere piling up of organic matter in the soil, organic matter 

 that does not decay, is useless except for holding moisture 

 and improving soil texture. 



(b) Making Potassium Available. — Lime releases potas- 

 sium from insoluble silicates and humates. Calcium takes 

 the place of potassium in these compounds and potassium 

 is made soluble as the carbonate. 



(c) Making Phosphorus Available. — Lime also changes 

 iron and aluminium phosphates to calcium phosphate and 

 thereby makes the phosphorus compound soluble in the soil 

 moisture (Section 135, a). Also by maintaining a supply 

 of lime in the soil, phosphate fertilizers are prevented from 

 changing to iron and aluminium phosphates. 



It must be borne in mind that valuable as lime is in free- 

 ing unavailable potassium and phosphorus, it does not add 

 either of these elements to the soil, it rather exhausts the 

 soil. This is of course beneficial — the freeing of plant food 

 in the soil — but additions must be made in the form of 

 phosphate fertilizers if the supply is to be maintained. 



(d) Improving the Physical Condition. — Lime also im- 

 proves the structure of soils by flocculating heavy clays and 

 binding together loose, sandy soils. 



(e) Checking Plant Diseases. — Lime destroys some fun- 

 gous diseases of plants, notably the club-root or finger-and- 

 toe disease of cabbage and turnips. 



(/) Harmful Effects. — Lime, on the other hand, is favor- 

 able to potato scab. It prevents the growth of such crops as 

 the cranberry, watermelon, blueberry, and trailing arbutus. 

 It is not known why this is, whether they can live better 

 on other forms of calcium than the bicarbonate or whether 

 they prefer an acid soil. Too heavy applications of caustic 

 or burnt lime particularly destroy organic matter to an 



