COMPARISON OF SOIL QUALITY PARAMETERS UNDER DIFFERENT VEGETATIONS

Abstract

A short-term field experiment was conducted to study the effects of differentvegetation covers on the soil fertility status. Soil samples were taken fromseveral fields from Mapalana farm. The treatments were grass x legumemixed sward (T1), grass monoculture (T2), legume monoculture (T3),vegetable (T4), coconut field with natural vegetation (T5), forest land (T6),bare land (T7) and cover crop grown with rubber (T8).

Each field was divided in to 20 x 20 m four blocks and four random samplesfrom each block were taken at 0-10 em depth. Soil samples were passedthrough 0.2 mm sieve and finely ground for subsequent analysis. Sampleswere analysed to determine the pH and organic matter content. Soil nitrogenpercentage was analysed by the Kjeldhal method. Bulk density wasdetermined using the soil core method and oven drying at 105° C until aconstant weight was obtained.

Soil organic matter content ranged from 3.622 % ± 0.819 (grass x legumemixed sward) to 1.433 % ± 0.833 (vegetable). Grass, legume, forest andcoconut land had medium organic matter contents. Vegetable land had theleast organic matter content may be due to chemical fertilizer application.Soil nitrogen percentage was also highest in mixed culture (0.1812 % ±0.0016) followed by the legume crop (0.162 % ± 0.0089) showing thebenefits of nitrogen fixation and transfer in increasing soil organic matter andnitrogen. The nitrogen content of coconut land was also higher (0.1384 % ±0.0157) due to nitrogen recycling via buffalo manure. Similarly nitrogenpercentage of the soil was lowest in vegetable cultivation (0.0571 % ±0.0088).

In contrast, soil bulk density was higher (p<0.05) in coconut land (1.491g/cm ' ± 0.1037). This may be due to the soil compactions occurred by longtermbuffalo grazing. Undisturbed lands such as forest cover, cover crop withrubber plantation etc. had lower bulk densities (1.257 g/crrr' ± 0.369 and1.255 g/crrr' ± 0.033 respectively). Highest value (P<0.05) of pH wasobserved in grass monoculture (6.3933 ± 0.311). Mild acidic conditions of soils were shown in mix culture (4.84 ± 0.29), vegetable (4.59 ± 0.22), bareland (4.89 ± 0.20) with cover crop grown with rubber (5.12 ± 0.25)

The study concluded that the grass x legume mix culture showed benefits ofnitrogen fixation and transfer associated with higher total nitrogen andorganic matter content in soil. Positive impact on soil nitrogen status onbuffalo grazing showed negative impact on soil bulk density. Humanintervention such as chemical fertilizer application etc also affect on soilcharacteristics.