LII.1ING ORCHARD SOILS 



The soils in l.Iassachusetbs are naturally acid. In uost productive soils the 

 soil acids, clay and hunic acid, are combined i;ith bases such as calcium, nagnesiura 

 and potassium. 



Soils become progressively more acid and less productive as calcium, magnesium 

 and potassium are lost from the soil by leaching and/or by crop removal. The 

 harmful effect of this acidity on crop yields has been mainly attributed to exces- 

 sive quantities of hydrogen ions, soluble alimiinum, manganese, iron and to defi- 

 ciencies of calcium, phosphorus or other essential nutrients, 



Ilany agricultural practices speed up the acidification of the soil. In 

 orchards the continued use of sulfur to control fungus diseases T/ill increase soil 

 acidity and accelerate the leaching of calcium, magnesiiun and potassium, Orchard- 

 ists using sulfur and follovdng the current pest control schedule for apples may 

 use 200 to 300 pounds of sulfur per acre per year. Since it takes approximately 

 three pounds of limestone to neutralize one pound of sulfur, knovdng how many 

 pounds of sulfur compounds he buys for the year and the per cent sulfur in these 

 compounds, the groover can figure the approximate amount of lime it will take to 

 neutralize the acidifying effect of the sulfur. 



In addition to sulfur, several of the common nitrogenous fertilizers produce 

 residual acidity. Ammonium sulfate produces the most residual acidity of the 

 common nitrogen fertilizers. It take 110 pounds of limestone to neutralize the 

 acidity developed by the use of 100 pounds of this compound. Ammonium nitrate and 

 urea, also, have an acidifying effect on the soil. 



Effect of Lime on the Orchard Soil 



Chemically , lime brings about many complex changes in an acid soil. If added 

 in sufficient amounts, limestone corrects soil acidity and eliminates aluminum, 

 iron and manganese toxic conditions, Overliraing may create iron, boron and man- 

 ganese deficiency. These deficiences, hovrever, would probably occur only if the 

 soils were limed above the neutral point (pH 7,0), By decreasing iron and aluminum, 

 phosphorus becomes more available. In addition, liming soils increases the calcium 

 and magnesium (v;hen magnesium-containing lime is used) content of the soil. 



Biologically , lime influences soil organisms thereby increasing the activity 

 of the soil organic matter and nitrogen. The rate of turnover of these constituents 

 is more important than the actual amounts present. Decay and ammonification are 

 markedly speeded up by limng an acid soil. Nitrogen-fixation bacteria are stim- 

 ulated and nitrification, the change of ammonia nitrogen to nitrate nitrogen, 

 proceeds more rapidly. 



Physically , lime may improve the physical structure of soils. 



Testing Soils For Acidity 



Soil tests are useful for the determination of lime needs in orchards. With- 

 out a standarized sampling procedure, however, and careful adlierence to this pro- 

 cedure, the value of the soil sample is negligible. 



