Effects on Soil
Much research has been undertaken around the world on the effects of anhydrous ammonia on microbes in the soil. That research has demonstrated that high concentrations of ammonia alter soil biology and soil pH in the ammonia retention zone.
However, as the conversion of ammonia to nitrate nitrogen occurs in the ammonia retention zone, the toxicity in this zone reduces and soil microbes are able re-populate to levels that previously existed.
The ammonia band affects only about 6% of the top 40 cm of the soil, assuming the nitrogen rate is 180 kg/ha applied at 1 m row spacing and 0.3 mdeep, so a great percentage of the soil and associated soil microbes are unaffected by an application of BIG N.
Soil microbes outside of the ammonia retention zone, such as nitrifying bacteria, initially increase in number and move into the ammonia zone, gaining energy by converting ammonia into nitrates. Populations then decrease to previous levels as the amount of ammonia (energy source) in the soil diminishes.
Comparisons are often made between urea and BIG N on their respective effects on soil biology. In the manufacturing process, urea is made from BIG N and, when applied to the soil, breaks down in the hydrolysis process into ammonia and carbon dioxide. Taken in context with the size of the ammonia retention zone which would apply for urea, it is logical to assume that the effects on soil biology from both urea and BIG N would be similar, because urea can convert to similar ammonia concentrations in soil.
While it is known that the alkalinity of ammonia can solubilise organic matter (as can lime), BIG N’s effects on the soil’s chemistry and physical properties have been found to be localised, short-term and non-cumulative.
Normal agricultural use should not compact your soil, damage organic matter or reduce carbon levels.
Stubble retention practices, maximising water use efficiency through appropriate nitrogen nutrition and organic matter management will have a far greater influence on your soil structure and organic matter levels.
‘Comparing grain yield and protein from pre-plant application of anhydrous ammonia and urea over four cereal crops’ D.W. Lester C.W Dowling, 10th Australian Agronomy Conference.
‘Comparing grain yield and protein from pre-plant and at-sowing N aplication to cereal crops’ D.W. Lester C.W Dowling, 10th Australian Agronomy Conference.
‘Grain yield and protein responses to anhydrous ammonia (as Cold Flo) and urea and their effects on the soil’ GRDC project: CSP 169.