C STOCKS AND SPECTROSCOPIC ASSESSMENT OF C STABILITY IN KENYAN SOILS. Aline Segnini 1,2 , Adolfo Posadas * 1,2 , Roberto Quiroz 1 , Lieven Claessens 3 , Carla Gavilán 1 , Débora M.B.P. Milori 2 & Ladislau Martin Neto 2.
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C STOCKS AND SPECTROSCOPIC ASSESSMENT
OF C STABILITY IN KENYAN SOILS
Aline Segnini1,2,Adolfo Posadas*1,2, Roberto Quiroz1, Lieven Claessens3,
Carla Gavilán1, Débora M.B.P. Milori2 & Ladislau Martin Neto2
1International Potato Center (CIP) – Lima, Peru; 2 Brazilian Agricultural Research Corporation (EMBRAPA)/ Embrapa Agricultural Instrumentation - São Carlos-SP, Brazil. 3CIP - Nairobi, Kenya. [email protected]
Soil carbon stocks (CS) and soil carbon stability data are required to make decisions to guarantee sustainable land use in intensively cropped areas. The present study reports the findings of a comparative analysis in different agro-ecologies in Embu – Kenya, where soils under different uses – e.g. native vegetation, forest, tea, coffee, and crops under different rotations - were sampled. Carbon stocks were analyzed in 3 areas for different soil land uses and native vegetation as reference.Whole soil samples were also characterized using the Laser-Induced Fluorescence Spectroscopy (LIFS) to assess the carbon stability
Table 1. Mean characteristics of soil sampling sites (0-30 cm).
# natural vegetation: transition between forest and savanna; * rotation crops: maize, peas, green grams, cow peas, pumpkin; † rotation crops: maize, beans, mango, banana, cassava, papaya, peas, green grams.
Table 2. Soil carbon stocks (kg m-2) bysoillayer and total (0-30 cm). Data from soils sampled in different cropping systems in Embu/Mbeere - Kenya.
#CARBON STOCKS = (C × d × T); C is the carbon content in g kg-1; T the sample layer thickness in meters and d the soil layer bulk density in Mg m-3;
# LIF index estimated as the ratio of area under fluorescence emission (430 - 800 nm) by total organic carbon content.This index is associated with C stability. The stability is highest for the native vegetation and lowest for the forest. Stability also increases with soil depth
Coffee + Eucalyptus
Figure 2. Humification index of whole soils obtained through Laser Induced Fluorescence Spectroscopy (LIFS).
Figure 1. Map from study sites in Embu District - Kenya representing soil sampling in different land uses from a transect of approximately 50 km. Examples of crops and native vegetations.