amount of these bases and therefore these bases must be present in the soil in 

 proportions that v:ill result in the plant absorbing the most desirable amount of 

 each. In acid soils vrhere all of these bases are lov/ the addition of any one of 

 the bases separately as a fertilizer may actually cause a decrease in the absorp- 

 tion of the others by the plmat and the net effect vdll be a decrease . 

 in. ^rield rather than the expected increase, j\nother direct effect of soil 

 acidity is that some plants are actually sensitive to the acidity itself. 

 Obviously this effect can be corrected only by red\icing the acidity. 



Several other effects result from soils becoming extremely acid. Some of 

 these effects are chemical and others are biological. The chemical effects are 

 usually those associated with increased solubility of elements vdiich are toxic 

 to the plant xrhen present in too high concentration in the soil solution. Iron, 

 aluminum, and manganese become more soluble r;hen the acidity is increased and 

 cause a depression of plant grov;th because of tlieir excessive availability. In 

 addition, iron and aluiainum react vriLth phospliates in more acid soils to form 

 insoluble coinpounds caid thus indirectly affect the phosplic.te nutrition of the 

 plant by malcing this essential substance less availa.blc. 



The undesirable biological effects that result from extre.ae acidic condition • 

 of the soil are associated v;ith botli the acidity and the chemical behavior of the 

 elements needed for the nutrition of tiie soil nicroorganisras . The m.ore desirable 

 bacteria are replaced by fungi v;hic]i produce substfuices v/hich are toxic to plants. 

 The beneficial legiuac bacteria v;ill not grow rnd fix nitrogen and the series of 

 bacteria which cooperate to convert organic matter to available nitrates are 

 slowed dovm in their activity, ilaiiy other soil microorganisms that gro-v." vrall and 

 produce desirable substances in neutral soils are limited in their acti-'ri.ty in 

 extremely acid soils. 



Before the orchardist uses fertilizer to increase productivity, it is 

 necessary that he correct the acidity of extremely acid soils with dolomitic 

 limestone or i^ther neutralizing materials, Tlio fertilizer can then perform its 

 functions without being limited by the factors resulting from extreme acid 

 conditions in the soil. 



In summary, neutralizing excessive soil acidity brings about the follov/ing: 



1, Increased supply of available calciiun - calcium and magnesium, if 

 dolomitic limestone is used, 



2, Increased availabilitj'- of phosphates, 



3, Decrease of essential elements v;hich arc toxic if present in too high 

 concentration such as iron and manganese, 



4, Decrease of toxic non-TCSsentials such as aluminum and certain organic 

 toxins, 



5, Substitution of beneficial bacteria for the less desirable fungi, 



— Dale JI, Sieling 



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