iSDAsoil: soil pH for Africa predicted at 30 m resolution at 0-20 and 20-50 cm depths

iSDAsoil dataset soil pH (1:1 Soil-Water Suspension) 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, 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_ph_h2o_m_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil pH mean value,
• sol_ph_h2o_md_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil pH 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: ph_h2o 
R-square: 0.818 
Fitted values sd: 0.972 
RMSE: 0.459 

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

Residuals:
    Min      1Q  Median      3Q     Max 
-5.5939 -0.2328 -0.0066  0.2222  4.7477 

Coefficients:
               Estimate Std. Error t value Pr(>|t|)    
(Intercept)    1.113440   1.164473   0.956 0.338986    
regr.ranger    1.032918   0.003138 329.116  < 2e-16 ***
regr.xgboost  -0.014201   0.004185  -3.393 0.000691 ***
regr.cubist    0.049667   0.003709  13.392  < 2e-16 ***
regr.nnet     -0.188570   0.188214  -1.002 0.316398    
regr.cvglmnet -0.059763   0.003636 -16.438  < 2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 0.4591 on 133378 degrees of freedom
Multiple R-squared:  0.8176,	Adjusted R-squared:  0.8176 
F-statistic: 1.195e+05 on 5 and 133378 DF,  p-value: < 2.2e-16

To back-transform values (y) to index use:

index = y / 10

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