iSDAsoil: soil fine-earth bulk density for Africa predicted at 30 m resolution at 0-20 and 20-50 cm depths

iSDAsoil dataset soil fine-earth bulk density in 10×kg/m3 predicted at 30 m resolution for 0–20 and 20–50 cm depth intervals. Data has been projected in WGS84 coordinate system and compiled as COG. Predictions have been generated using multi-scale Ensemble Machine Learning with 250 m (MODIS, PROBA-V, climatic variables and similar) and 30 m (DTM derivatives, Landsat, Sentinel-2 and similar) resolution covariates. For model training we use a pan-African compilations of soil samples and profiles (iSDA points, AfSPDB, LandPKS, and other national and regional soil datasets). Cite as:

Hengl, T., Miller, M.A.E., Križan, J. et al. African soil properties and nutrients mapped at 30 m spatial resolution using two-scale ensemble machine learning. Sci Rep 11, 6130 (2021). https://doi.org/10.1038/s41598-021-85639-y

To open the maps in QGIS and/or directly compute with them, please use the Cloud-Optimized GeoTIFF version.

Layer description:

• sol_db_od_m_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil bulk density mean value,
• sol_db_od_md_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil bulk density model (prediction) errors,

Model errors were derived using bootstrapping: md is derived as standard deviation of individual learners from 5-fold cross-validation (using spatial blocking). The model 5-fold cross-validation (mlr::makeStackedLearner) for this variable indicates:

Variable: db_od 
R-square: 0.819 
Fitted values sd: 0.269 
RMSE: 0.126 

Random forest model:
Call:
stats::lm(formula = f, data = d)

Residuals:
     Min       1Q   Median       3Q      Max 
-1.06778 -0.06450  0.00215  0.06585  0.90016 

Coefficients:
              Estimate Std. Error t value Pr(>|t|)    
(Intercept)   -0.05538    0.04860  -1.140  0.25451    
regr.ranger    0.86305    0.01577  54.733  < 2e-16 ***
regr.xgboost   0.15383    0.01651   9.315  < 2e-16 ***
regr.cubist    0.02039    0.01113   1.832  0.06695 .  
regr.nnet      0.03465    0.03710   0.934  0.35036    
regr.cvglmnet -0.03021    0.01032  -2.927  0.00343 ** 
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 0.1263 on 13565 degrees of freedom
Multiple R-squared:  0.8194,	Adjusted R-squared:  0.8193 
F-statistic: 1.231e+04 on 5 and 13565 DF,  p-value: < 2.2e-16

To back-transform values (y) to kg/m-cubic use:

kg/m3 = y * 10

To submit an issue or request support please visit https://isda-africa.com/isdasoil