pure culturepyroclasticspyrophosphatepyrophyllitepzncqquantity intensity ratioquasicutanquick clayquicksandrr layersr selectedrainfall erosion indexrainfall erosivity indexrainfall interceptionraised bedreaction soilrecessional morainerecoveryrecyclingred desert soilred earthred yellow podzolic soilsredistribution of waterredoxredox concentrationsredox depletionsredox potentialredoximorphic featuresreduced matrixreduced tillagereducing environmentreference electrodereflectanceregolithregosolsregurrelated distribution patternrelative yieldreliefremote sensingrendollsrendzinarenewable natural resourcesresidual fertilityresidual materialresidual shrinkageresidual soilresidue processing