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Options of rational managemet of high N-NH4 soils (fwd)





---------- Forwarded message ----------
Date: Thu, 31 Jul 1997 07:42:30 -0700
From: "Ricardo M. Braga" <rmbraga@200.238.230.34>
To: sustag@beta.tricity.wsu.edu
Subject: Options of rational managemet of high N-NH4 soils

Subject:Dear Sustag friends,

        I just finish a data compilation of soil Nmineral (NH4 e NO3)in a
organic produce field (Rio de Janeiro - Brazil) and I found that N-NH4 is 
predominant in the field.
        N-NO3 is very low and goes dow, close to 1 ppm, at time of
vegetable N uptake.The peack of NO3 in soil is 15 ppm but only at the end
of our studies, 200 days after set-out.
         N-NH4 goes up to 50 ppm. The data appears well, but somehow
nitrification holdup.I`ve tried to explain it by soil ph . It was 5.2 at
starting and 6.1 at work tail-end where the soil nitrate peack was found.
A mesofauna study comes up with high collembola soil population, another
point to sum acids soil.
The soil moisture was also high, helping slowing dow nitrification. The
soil is a podzol.A positive correlation was found between N-NH4 and soil 
moisture.

        My discussion questions are about rational field management. I`m
not sure if this single situation is going to be observe again, but if
does, how could be the management options for a produce (vegetables) 
field.
        I`ve thought in irrigation management, that means lower
soil moisture - higher nitrification. Another way would be split manure
aplication to get less nh3 loss.
        Is not this situation very different of temperate soil?
        Any add or tip please send to the lis or my email that I`ll give
a feed back to the list.

Thanks



--
Ricardo M. Braga
MS student of Agroecology
CAIXA POSTAL 74591
AGENCIA SEROPEDICA - UFRRJ - ITAGUAI
RIO DE JANEIRO - BRAZIL
CEP : 23851-970
Email : rmbraga@xnet.pegasus.com.br
        rmbraga@ufrrj.br




--
Ricardo M. Braga
CAIXA POSTAL 74591
AGENCIA SEROPEDICA - UFRRJ - ITAGUAI
RIO DE JANEIRO - BRAZIL
CEP : 23851-970
Email : rmbraga@xnet.pegasus.com.br
        rmbraga@ufrrj.br