----- Original Message ----- From: tachung_h <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, October 12, 2002 3:41 AM Subject: RE: Nutrient blockers
> Hi Lyoyd: Thank you for the kind assistance and explanations. It is very > helpful. > > What does it mean when people say that long term usage of inorganic > fertilizer will cause the soil to become acidic? > Is it because the > fertilizer itself is acidic? There are some fertilisers that are acidic but the main cause of soil acidity seems to be from chemical reactions involved in the nitrogen cycle and breakdown of organic matter There are several mechanisms involved 1. The actual chemistry of the fertiliser applied - when ammonium NH4 is converted to Nitrate NO3 there is excess hydrogen into the soil solution - these fertilisers need about 2kg of lime per kg of Nitrogen to neutralise the released hydrogen. 2. Leaching of Nitrate leaves excess hydrogen 3. Excess application of nitrogen fertiliser burns up soil organic matter leading to further excess of nitrate and leaching (this can happen with excessive animal manures too) Good healthy microbial activity will prevent much of this from happening by buffering the negative effects, by locking up applied nitrogen and releasing it slowly as plants require it. > Or is it because the calcium is bonded with > other ions and leached away? Soils low in calcium (unbalanced) require higher inputs (overdosing)of salt fertilisers to get a satisfactory yield - the plants are watery, brix readings low, and the plants more susceptible to drought stress, diseases and insect attack. There is much more to this than I have written here L Charles > > Regards > TaChung Huang >
