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

iSDAsoil dataset soil total organic Nitrogen (N) log-transformed 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_log.n_tot_mehlich3_m_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil total N mean value,
• sol_log.n_tot_mehlich3_md_30m_*..*cm_2001..2017_v0.13_wgs84.tif = predicted soil total N 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: log.n_tot_ncs 
R-square: 0.732 
Fitted values sd: 0.326 
RMSE: 0.197 

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

Residuals:
     Min       1Q   Median       3Q      Max 
-1.87298 -0.09584 -0.00985  0.07613  3.14728 

Coefficients:
               Estimate Std. Error t value Pr(>|t|)    
(Intercept)    0.267429   0.493235   0.542    0.588    
regr.ranger    1.128208   0.005766 195.669  < 2e-16 ***
regr.xgboost  -0.048780   0.006108  -7.987  1.4e-15 ***
regr.cubist    0.143954   0.004424  32.539  < 2e-16 ***
regr.nnet     -0.482261   0.797938  -0.604    0.546    
regr.cvglmnet -0.170889   0.004955 -34.489  < 2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 0.1972 on 99249 degrees of freedom
Multiple R-squared:  0.7319,	Adjusted R-squared:  0.7319 
F-statistic: 5.419e+04 on 5 and 99249 DF,  p-value: < 2.2e-16

To back-transform values (y) to g/kg use the following formula:

g/kg = expm1( y / 100 )

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