Approximately 65% of the residual mineral N in the soil profile at harvest in the unfertilised control treatment (218 kg N/ha) was at depths [greater than or equal to]60 cm.
Trial 1 results suggested small amounts of N recovery in plant biomass and negligible residual mineral N in the soil profile (Fig.
The amount of N remaining in mineral N form varied from 93 kg/ha (1NLBAR AE) to 750 kg/ha (4.5NLBAR AN), with almost all the residual mineral
N located in the top 0.60-0.90 m of the soil profile (Fig.
The nozzles of trackside dispensers were also getting blocked by the residual mineral
content of the grease.
The effectiveness of a winter cover crop to intercept or trap residual mineral
N that might otherwise be lost through leaching has been reported to range from 12 to 91 kg N |ha.sup.-1~ (11 to 81 lbs N |ac.sup.-1~) |16~.
In the case of mining, the residual minerals
in mine waste can act as food for microbial communities.
The only significant residual minerals
were intimately associated with impermeable clays, shales and organic debris.
These fractions are those most likely to represent trace elements retained by surface reactions such as ion exchange or chemisorption, and therefore the highest proportions of elements are not in these fractions, but present in mineral structures (Fe or Mn oxides, or residual minerals
such as silicates).