Soil Organic Matter Management: The Roles of Residue Quality in C Sequestration and N Supply - Sustainable Management of Soil Organic Matter - page 196

At two of the sites (Dhamrai and Daulatpur), total C was significantly
greater in the ecological fields than in conventional fields, but this was not
so in the two other sites. Indeed, at Gabtali it was significantly lower in the
ecological fields (Table 3.13.2). Total soil C and N change slowly and are
less sensitive than light fractions to management practices (Christensen,
1987). The free organic matter would be expected to be most sensitive
because it turns over most rapidly. However, it will, by its nature, be
affected by sampling time, whereas intra-aggregate material, whilst still
sensitive, is less susceptible to seasonal fluctuations (S.P. Sohi, personal
communication, 1999). Significantly greater amounts of free ( P = 0.05)
and intra-aggregate ( P = 0.001) material were recovered in the ecological
fields at Dhamrai and Daulutpur, whereas lower amounts of free ( P = 0.05)
and intra-aggregate ( P = 0.001) material were recovered at Gabtali and
Shibganj. These findings are in line with the differences in soil total C
(Table 3.13.2). Dhamrai has a difference of 2072 kg C ha −1

for the

Table 3.13.2. Parameters of 'soil fertility'.

Management Soil fertility parameter Dhamrai Daulatpur Gabtali Shibganj

Total C (kg ha − 1 ) Conventional 29,241 ** 30,177 ** 30,373 ** 33,661 **

Ecological Total C (kg ha − 1 ) 30,737 * * 42,129 * * 27,234 * * 33,294 **

Conventional Free organic matter C

(kg ha − 1 )

11, 981 ** 1,364 ** 1,760 ** 1,469 **

Ecological Free organic matter C

(kg ha − 1 )

1,500 * * 1,715 * * 1,370 * * 1,500 **

Conventional Intra-aggregate C

(kg ha − 1 )

1,161 ** 1,119 ** 1,119 ** 2,216 **

Ecological Intra-aggregate C

(kg ha − 1 )

3,233 ** 1,816 ** 1,056 ** 1,925 **

Conventional Microbial biomass C

(kg ha − 1 )

11, 210 ** 11, 226 ** 11, 333 ** 11, 377 **

Ecological Microbial biomass C

(kg ha − 1 )

39, 253 ** 11, 323 ** 11, 150 ** 11, 404 **

Conventional Basal respiration

(kg C ha − 1 h − 1 )

30,78 2.89 30,78 89 1.98 ** 30,89 2.41 308 ,789 1.68 **

Ecological Basal respiration

(kg C ha − 1 h − 1 )

30,788 2.42 * 30,8 789 2.97 ** 30,89 1.25 30,8 789 2.36 * *

Conventional Pot. available N

(kg N ha − 1 h − 1 )

30,7 8 9.98 30,78 89 3.17 ** 38,79 6.66 30,8 789 2.52 **

Ecological Pot. available N

(kg N ha − 1 h − 1 )

30 ,78 9.95 30,788 9 8.56 * * 30,89 7.76 30,8 789 5.20 * *

* Significant at the 5% level; ** significant at the 1% level.