Spatial variability of aggregates and organic carbon under three different uses of indian black earth in southern Amazonas

Abstract

Indian Black Earths (IBEs) are distributed throughout the Amazon. They are characterized by their high chemical fertility and agricultural potential. IBEs have high organic carbon, favouring the improvement of soil structure. This work aimed to evaluate the aggregates and organic carbon (OC) spatial variability in different IBEs in southern Amazonas. We evaluated the organic carbon spatial variability, mean weight diameter (MWD), soil bulk density (ρ b ) and aggregate classes under three uses of soil: pasture, cocoa, and coffee. We collected 528 soil samples in a point grid according to its use at two depths: 0.0-0.05 m and 0.10-0.20 m. Results were subjected to variance, descriptive, and geostatistical analyses. We concluded that the soil use influenced the IBEs physical attributes soil behavior, concentrating the higher values of CO, aggregates > 2.00 mm, and MWD at 0.0-0.05 m in relation to ρ b and aggregates < 2.00 mm where the higher values were the ones at 0.10-0.20 m. Aggregates < 2.00 mm (0.10-0.20 m) and OC (0.0-0.05 m) did not show spatial dependence, while the class of aggregates > 2.00 mm was the only attribute which represented to be a natural characteristic of the soil, with a strong spatial dependence, independently the land use and depth. There was no spatial relationship between the attributes studied and the geomorphic diversity.

Multivariate analysis in the evaluation of soil attributes in areas under different uses in the region of Humaitá, AM

“…A similar thing occurred with GMD in soils under grassland, motivated by the extensive development of the grass root system, considered the main particle aggregation agent in tropical soils, both by the release of exudates and by interlacing small clods and, consequently, forming larger structures (Salton and Tomazi et al, 2014). This result corroborates those of Gomes et al (2017) when assessing spatial variability of aggregates and organic carbon in different land uses in southern Amazonia. According to Campos et al (2013), there is a highly significant correlation between the increase in organic matter content and the increase in aggregate stability; however, Alho et al (2014) points out that a high WMD aggregate does not always have adequate pore-size distribution in the interior.…”

“…Soil penetration resistance (SPR) presented high values of ≥ 2.00 kPa in forest and grassland soils in the 0.0-0.10 m layers, with decreases of 44.92% and 70%, respectively on the 0.10-0.20 m depth (Table 1). In fact, the highest SPR value found on the soil surface under grassland was due to animal trampling, which produces in the area in contact with hull a force greater than the soil can withstand (Gomes et al, 2017;Debiasi and Franchini; (Table 1), which is consistent with the high values of BD (>1.50 Mg m-3), lower MaP (0.06 m 3 m -3 ) and TP (0.44 cm 3 cm -3 ). For Giarola et al (2007), the reduction of TP in the grassland areas is due to the reduction of the MaP, since the MiP is little influenced by the soil management, as was verified in the present study.…”

“…Problems that directly affect the preservation of natural resources, the soil attributes being the main physical and chemical indicators of these changes (Oliveira et al, 2015). Studying the influence of different land uses in the southern Amazon, Gomes et al (2017) reported that the use of grassland soil increased bulk density with reduction of total pore space and aggregate stability when compared to soil management with cocoa and coffee. In this same alignment, Aquino et al (2014) found that conversion of forest areas to grassland increased soil resistance to penetration.…”

Variability and spatial correlation of aggregates and organic carbon in indian dark earth in Apuí region, AM

“…It can be due to the intrinsic pedogenic factors and processes of soil formation and its interactions with the landscape, as well associated to the management (MARQUES JÚNIOR et al, 2008). Soil revolving by practices such as plowing, and gradation change the variability of the organic matter of the soil and properties influenced by it, as soil density and resistance to penetration, porous space and soil water movement can change the variability of organic matter and soils (SOARES et al 2016;Gomes et al, 2006Gomes et al, ) et al, 2017. In his investigation Corá et al (2004) conclude that soil management altered the spatial dependence of chemical attributes and soil clay content on the surface layer to decrease the spatial variability of the attributes in relation to the deeper layer.…”

Spatial and temporal variability of soil and plant attributes after application of cellulose residue

“…Evaluating changes in the soil productive capacity and associating them to eucalyptus plant development constitute processes which require precision silviculture using geostatistics as a tool to assess the spatial variability of production and its subjacent factors (Hegde et al, 2015). Spatial dependence analysis of georeferenced data requires its adjustment to semivariograms as a function of the distance between samples subsequently compiling kriging maps for each soil and plant attribute in question, leading to the achievement of specific soil management zones for the given attribute (Gomes et al, 2017).…”