The Bulletin 17 



phosphoric acid. If the farmer, after buying acid, mixes with 

 it lime and lets the mixture stand for some length of time, it is 

 probable, under ordinary conditions, a material quantity of the 

 available phosphoric acid may be changed to the insoluble form." 



Now, if the luixiiig of acid phosphate with ground limestone is going to 

 cause the acid phosphate to be less available to the crop, wc can see no 

 reason why the fertilizer manufacturer should, on financial grounds, 

 have any objection to raise, as such action on the part of the farmer 

 would cause him to buy more acid phosphate in order to produce normal 

 crop yields. The fertilizer manufacturer, therefore, might welcome 

 rather than oppose the mixing of ground limestone with acid phosphate. 

 On the other hand, if the mixing of ground limestone with acid phos- 

 phate is going to prevent the formation of the insoluble phosphates 

 of iron and aluminum, and promote the foinnation of di-calcium phos- 

 phate, and thus prolong the availability of the phosphate in the soil, 

 and enable the farmer to utilize, not a small part, but the whole of his 

 application, and, in this way increase crop production, and at the same 

 time lower the cost, the fertilizer manufacturer might, pursuing a narrow 

 and shortsighted business policy, object to the farmer making any such 

 mixture of his acid and limestone. 



On the same page we find the broadcasting of lime advocated to the 

 exclusion of mixing it with the fertilizer ingredients, as follows: "In 

 using lime on a soil that is to receive an application of acid phos- 

 phate alone, or mixed with other materials, the best plan to follow 

 will be to add the lime broadcast, work it into the soil with a har- 

 row, and then apply the acid phosphate, or acid phosphate mixture 

 in the drill just before the crop is planted." This method of apply- 

 ing lime or limestone insures the least possible contact with the acid 

 phosphate in the fertilizer mixture, and insures the greatest amount of 

 reversion possible with the iron and aluminum oxides of the soil. The 

 locking up of the soluble phosphates into iron and aluminum compounds 

 seems to occur very quickly after the material is applied to the soil, and 

 it can be easily seen that this method of application will allow the great- 

 est possible mischief to be done before sufficient limestone can come in 

 contact with the soluble acid to arrest the process. To illustrate: An 

 acre of soil 6 inches deep weighs about two million pounds. On the 

 average North Carohna soil 1 per cent of limestone, broadcast and 

 worked into the soil, will be necessary to do any appreciable amount of 

 good in preventing the formation of iron and aluminum phosphates. 

 ISTow, it would take 10 tons of limestone to the acre to add 1 per cent of 

 lime carbonate to the soil to a depth of six inches, and no farmer is likely 

 to add this amount of limestone to his land at one time. Moreover, if 

 1 per cent of these red clayey soils were limestone added broadcast and 

 worked in to a depth of 6 inches and the acid phosphate put in the drill, 

 a simple mathematical calculation will show that the acid phosphate 



