A beel thicky infested with water hyacinth

Available soil nitrogen squs represents the easily oxidisahle form of total
nitrogen in the soil and its level is influend largely by the organic matter content of
the soil. Available nitrogen followed the trend of organic carbon and its values ranged
from 145 to 410 mg/l. It was ratha low in the bxls of both the Brahmaputra valley and
the Barak valley from a fisheries point of view The low available nibogen of soils is
mainly due to reduced microbial activities rn d slow rate of decomposition of soil
organic matter on account of the prevailing atidic reaction of the soil. Beels of the
Brahmaputra valley had higher mean value of a\ ailable nitrogen compared to the Barak
valley. Beels of Central Assarn showed high. st mean value of available nitrogen.
followed by Lower and Upper Assam.
Ava~lable soil phosphorus, important in nfluencing the aquatlc product~\,ity.
\*.as rather poor in most of the heels and the valu: -an@ between 0.8 and 27.0 mg kg:l
Such lo& level of available so11 phosphoru is attributable to the prcscnrc of
macrophytes, especially the rooted ones wh~ch ,pidly use up most of the ava~lahle
phosphorus. Becls of the Brahmaputra valley ha h~gher level of available phosphorus
(14.5 mg ;kg) compared to the Barak valley (8.: rng/kg). Beels of Central Assam had
the highest mean value of ava~lable-P followed I y Lower and Upper Assam Calc~um
carbonate content ranged from 4.5 to 67.0 gkg u !h the mean value of 23.0 gkg. Hcels
of Barak \alley had sl~ghtly h~gher mean value I f CaCO, than beels of Rrahnlaputra
valley uhilc same mean value was recorded in 111. beck of Lower. Central and llppcr
Assani.
Loamy soil contain~ng all the three fracl,.lns almost in equal proponions IS
cons~dered to be conduccve to product~vity. Houever, most of the beels studled by
CIFRl had poor soil texture. Beels of Karimgwj t,~strict of Barak valley and Sihsagar
d~str~ct of Upper Assarn had better soil texture coml ared to other districts. It 1s ohserved
that thc soil of the heels of Brahmaputra valley arc more productive than that of Barak
valley beels. Among the distncts of Brahmaputra isalley, beels of Central Assani arc
more conduc~ve to biological productiv~ty In resp .ct of organlc carbon and nutnent
status of the so~l. Soil qual~ty in beels of d~ffere~: regions of Assam is depicted In
Table 7.