Soil Quality Assessment Of Natural Rubber Plantation

This thesis paper assesses the quality of soil on rubber plantation with particular emphasis placed on its physical, chemical and biological parameters.For the composition of humic acids, soil and compost of derived humic acids (CHA) were extracted with a slightly HA modified procedure recommended and used by the IHSS to isolate standards of humic acid.Meanwhile, we analyzed for microbial biomass Carbon and Nitrogen. For this purpose, soil samples (0-20 cm depth) were collected from three random sampling quadrants(10 m x 10 cm) at each site.In each quadrant the soil was collected from five points randomly, and mixed into one sample.All statistical work was done using the SPSS 11.5 for Windows.One-way ANOVA was used to analyze means to least significant difference at the 5% level.For the analysis of community structure of fungi and bacteria counts, surface soil (0-10 cm deep) was collected from the O/A horizon at three vegetation zones-grassland, fertilized and non-fertilized soils.Three composite samples were collected in each zone with use of a soil auger (8 cm diameter and 10 cm deep).A mixture of three sampling points formed a composite sample of a given zone.For statistical analysis, data were converted by log transformation before applying ANOVA. Statistically significant differences (p<0.05) between treatments were compared with the use of Duncan's multiple range test (SAS,2001).Regression analysis was used to determine correlations between SIR-calculated fungal biomass and ergosterol fungal biomass levels.Organic matter distribution within 5 separate years (2003,2004,2005,2006 and 2007) was evaluated and the results show that the year 2004 had the highest Total humic acids(147.060g/kg soil);2006 had the second highest Total humic acids value (93.452g/kg soil).It was further indicated by our results that the quantity of Total humic acids in 2003 and 2007 were somewhat close (72.884g/kg and 59.988 g/kg soil) respectively.However, the least Total humic acids concentration was recorded in the year 2005 (23.885g/kg soil).Like Total humic acids, humin concentration was highest in 2004 (98.567g/kg soil) closely followed by 2006 (87.573g/kg soil)while in 2003 and 2007 the concentrations of humin were also close (67.133g/kg and 55.824g/kg soil) respectively.As was the case with THA, the least quantity of humin was observed in 2005(21.358g/kg soil).Meanwhile, as has been observed in cases of THAs and humin, the year in which fulvic acid concentration was seen to be remarkably higher was 2004 (48.493g/kg soil).The distribution trends as seen in the 5 years were similar. This is an indication that time has an effect on organic matter distribution in the soil.The impact of distance away from the fertilizer area on organic matter distribution was evaluated. There were four measured distance made between the fertilizer pit and sample extraction spot. These are 0-10 cm,20-30cm,50-60cm and 80-90cm.The pit from which the soil samples were collected was 40-60cm deep.50-60cm distance had the highest Total humic acids (34.827 g/kg soil) while the lowest Total humic acids was shown in 80-90cm distance(10.593g/kg soil).Equal quantity of Total humic acids was observed in both 20-30cm (27.616g/kg soil) and 0-10cm (27.773 g/kg soil) distances. The least THA was observed in 80-90cm distance category(10.593 g/kg soil).With respect to fulvic acid, its maximum concentration was found in the 50-60 cm distance category (23.808 g/kg soil) as was in the case of THAs. The lowest concentration of fulvic acid was observed in 80-90cm distance (5.967g/kg soil) while in the case of 0-10cm(18.494 g/kg soil) and 20-30 cm(18.185g/kg soil),both had equal amounts of FA concentration, quite the same as THAs.Very much like THA and FA,the highest quantity of humin was shown in 50-60cm distance category(11.020g/kg soil) while its least concentration was seen in 80-90cm distance category (4.626g/kg soil).Distance categories of 0-10cm (9.279g/kg soil) and 20-30cm (9.431g/kg soil) both had equal quantity of humin.The distribution pattern among Total humic acids,fulvic acid and humin within the 4 distance categories had no significant difference. The variation in organic matter distribution relative to soil profile at a distance of 50-60cm away from the fertilizer area was assessed.The highest concentration of THAs was manifested in the 0-20cm profile ranges (47.825g/kg soil) but the THAs concentrations within 20-40cm profile and 40-60cm were approximately equal. According to our research results, the THAs concentration within 20-40cm profile was 36.453g/kg soil;soil profile range of 40-60cm had THAs concentration of 34.827g/kg soil.With regards to humin,its maximum amount of concentration was recorded in the 0-20cm profile range with a quantitative value of 35.558g/kg soil.The least quantity of humin was observed within the 40-60cm profile(11.020g/kg soil).Humin concentration found in 20-40cm profile was 26.578g/kg soil. Additionally, the maximum FA concentration was found within the 40-60cm profile (23.808g/kg soil);0-20cm(12.267g/kg soil) and 20-40cm (9.875g/kg soil) profiles had relatively similar amounts. The distribution pattern among THAs, humin and FA are similar.The variation in organic matter distribution relative to soil profile at the distance range of 0-10cm away from the fertilizer was evaluated (fig 3d.)Data collected vividly showed the maximum concentration of THAs in 20-40cm profile (63.705g/kg soil) closely followed by 0-20cm profile (61.457g/kg soil).However, the least THAs concentration was observed in 40-60cm profile (27.773g/kg soil).Quantitatively, the humin concentration recorded in 20-40cm and 0-20cm profiles were approximately equal.20-40cm and 0-20cm profiles had concentrations of 53.137g/kg soil and 53.120g/kg soil respectively. The least quantity of humin was recorded in 40-60cm profile. With respect to FA,its maximum concentration was found in 40-60cm profile(18.494g/kg soil)while the lowest was seen in 0-20cm profile (8.337g/kg soil).The amount of FA found in 20-40cm profile was 10.569g/kg soil.The distribution trends among THAs, humin and FA are the same.The impact of soil fertility on the quantity of soil actinomyces was assessed.With reference to the maximum count of actinomyces recorded in each fertility level,our data showed that the highest actinomyces count was recorded in the low fertility soil in the 0-20cm surface soil (77 x 102/g soil) and the second highest was observed in the middle fertility soil in the 0-20cm surface soil (41 x 102/g soil), with the least count being observed in the high fertility soil in the 0-20cm surface soil (33 x 102/g soil). Additionally, the following data was obtained:high fertility soil,within the 20-40cm subsoil,it had 23 x10~2actinomyces counts and 18 x 10~2 actinomyces counts in the 40-60cm subsoil as its minimum count while its maximum count was 33 x 102 actinomyces; middle fertility soil had 15 x 102 actinomyces in the 20-40cm subsoil while its minimum actinomyces count was 9 x10~2 with in the 40-60cm subsoil;maximum counts of actinomyces of the middle fertility soil was 41 x 102/g soil with the 0-20cm surface soil;low fertility soil minimum actinomyces count was 23 x 102/g soil within the 40-60cm subsoil while its maximum was 77 x 102 within the 0-20cm surface soil. The 20-40cm subsoil of low fertility soil had 48 x 102/g soil.It is interesting to note that all three fertility levels had their maximum actinomyces counts in the topsoil while their least showed up in the 40-60cm subsoil.The low fertility soil had a considerable count of actinomyces (48 x 102/g soil) far beyond what was observed in the two other fertility levels.The impact of soil fertility level on soil fungi count was evaluated.The maximum concentration of fungi for low fertility soil was 18 x 103/g soil within the 0-20cm surface soil;for middle fertility soil it wasl8 x 10~3/g soil within the 0-20cm surface soil; and 15 x 103/g soil was for high fertility soil within the 0-20 surface soil.The minimum fungi count within each of the three soil fertility levels were as follows: Low fertility soil 5x 103/g soil within the 40-60cm subsoil,middle fertility soil and high fertility soil both had 3 x103/g soil respectively, within the 40-60cm subsoil.Within the 20-40cm subsoil,high fertility and low fertility soils had 7 x 103 fungi count respectively;middle fertility soil had 6 x 103 fungi count. According to our results,the highest counts of fungi for each of the three soil fertility levels were concentrated in the topsoil while their individual least counts were found in the 40-60cm subsoil horizon.The effects of soil fertility on soil bacteria count was assessed as well.The respective maximum bacteria counts found in the 0-20cm surface soil of low, middle and high fertility soils were 48 x103/g soil,62 x 103/g soil and 90 x 103/g soil respectively. The highest bacteria count was recorded in the high fertility soil followed by middle fertility soil while the least of the highest was seen in the low fertility soil. Meanwhile, the least bacteria count within each of the fertility levels observed in the 40-60cm subsoil is as follows:low fertility 4 x 103/g soil;middle fertility 8 x103/g soil; and high fertility 10 x 10~3/g soil.20 40cm subsoil had the following bacteria counts in each of the fertility levels:17 x 103/g soil for high fertility soil;14 x 103/g soil for middle fertility soil;and 19 x 103/g soil for low fertility soil.The maximum counts of bacteria within each of the three soil fertility level were observed in the effective surface soil horizon while their least amounts showed up in the 40-60cm subsoil horizon.During our research, we evaluated soil microbial biomass carbon (MBC) within different soil fertility levels.The maximum amounts of MBC of each of the three fertility levels observed in the 0-20cm surface soil are as follow:high fertility soil 255mg/kg soil;middle fertility 238mg/kg soil;and low fertility 135mg/kg soil.Their MBC minimum concentrations shown in the 40-60cm subsoil are also reflected below: low fertility 83mg/kg soil;middle fertility 105mg/kg soil;and high fertility 133mg/kg soil.Within the 20-40cm subsoil the quantity of MBC are as follow:high fertility 185mg/kg soil;middle fertility 143mg/kg soil;and low fertility 112mg/kg soil.It is important to establish that within in each of the three fertility levels, the highest quantity of MBC appeared in the surface soil horizon while their lowest appeared in 40-60cm subsoil horizon.Microbial biomass N distribution within different levels of soil fertility was also analyzed.The highest MBN concentration of each of the three fertility levels concentrated in the 0-20cm surface soil was as follows:high fertility soil 38mg/kg soil; low fertility 28mg/kg soil;and middle fertility 22mg/kg soil.Also, their least concentrations found in the 40-60cm subsoil were as follows:high fertility 31mg/kg soil;middle fertility 18mg/kg soil;and low fertility 24mg/kg soil.20-40cm subsoil had the following MBN data:high fertility soil 35mg/kg soil;middle fertility soil 21mg/kg soil;and low fertility soil 17mg/kg soil.The maximum concentration of MBN in each of the three fertility levels appeared in the surface soil horizon while their least showed up in the 40-60cm subsoil horizon except low fertility soil which had its least MBN concentration in the 20-40cm subsoil horizon.The effects of soil fertility on soil MBC & MBN were assessed in this research.The results revealed that the maximum concentration of MBC was observed in natural vegetation soil (398.80mg/kg soil) followed by non-fertilized soils (398.80mg/kg soil). Further, the least MBC concentration was recorded in the fertilized soil.The highest concentration of MBN was recorded in the fertilized soil (225.23mg/kg soil) while the least was observed in non-fertilized soil (41.05mg/kg soil).Natural vegetation soil had the second highest (52.70mg/kg soil) next to the fertilized soil.The effects of soil fertility on soil bacteria, fungi and actinomyces counts were evaluated.The maximum bacteria counts among the fertility levels was shown in the fertilized soil (237.5475878 x 10~3/g soil)followed by natural vegetation soil (85.36 x 103/g soil).The least bacteria counts were seen in the non-fertilized soil (52.90304818 x 103/g soil).The highest count of fungi was recorded in the fertilized soil (27.37 x 103/g soil) accompanied by natural vegetation soil(16.50 x 103),with the least being observed in the non-fertilized soil (8.67 x 103/g soil).Meanwhile, the actinomyces counts at all fertility levels were nearly equal-fertilized soil had the highest (2.74 x 102/g soil), second highest was in natural vegetation(1.65 x 102/g soil) and the least was in non-fertilized soil (0.87 x 102/g soil).The central objective for this research has been to quintessentially establish which of the three parameters-physical,biological and chemical-can best be used to assess soil quality. Our research has shown that the biological parameter is the best to be used in the assessment of soil quality. Biological and biochemical parameters are quite sensitive to the slightest modifications that the soil can undergo in the presence of any degrading agent whereas physical and physico-chemical parameters get altered only when the soil undergoes a really drastic change.Because of this limitation, physical and chemical parameters can not be considered as the best parameters for soil quality assessment.