118 FOOD FOR PLANTS 



composition determines its usefulness. This service 

 soil weighs on an average 2,000 tons per acre. 



There is enough sulphate of lime or gypsum pres- 

 ent, as well as acid, in the average acid phosphate, 

 to materially help the black alkali of many alkaline 

 soils, but gypsum alone may be used also for correct- 

 ing alkali. 



Since we never recommend the use of Chilean 

 Nitrate alone, except at the rate of from one hundred 

 to two hundred pounds per acre, this relatively small 

 amount could have no material influence whatever in 

 increasing the alkali content of soils. The continued 

 use of Nitrate under rational methods of fertilizing, 

 would not add to, but rather diminish the quantity 

 of alkali in the soil. The associated gypsum and 

 acid phosphate thus used would tend to loosen heavy 

 clay soils which need improvement in texture and 

 the acid residues from these materials would likewise 

 benefit alkaline soils. 



In this connection, it is important to observe that 

 care must be exercised, in soils containing black 

 alkali, to avoid materially increasing the content of 

 carbonate or bi-carbonate of lime, since this would 

 help promote the destruction of humus. It is, there- 

 fore, suggested for these particular soils, that the 

 large and constant use of lime be avoided. When 

 lime is needed, have your soil examined by an expert, 

 and do not put on any more lime in any form than 

 advised for your particular case. In other words, 

 take good care to preserve your humus. Do not 

 destroy it by excessive liming on any account. 

 Neither wetness nor stickiness will result from the 



