Soil management determines sampling density/spatial dependence of dynamic soil properties

Sampling designs are needed to characterize spatial variation in 'dynamic' soil properties - those which change with time. The objectives were to: (1) identify spatial scales of dynamic soil properties; and (2) relate spatial structure to surface conservation practices. Twelve continuous and discontinuous no-tillage fields in the Choptank basin, Delmarva Peninsula, USA were sampled at 0-5 and 5-10 cm for soil organic matter (SOM) and at 0-5 cm for aggregate size distribution (mean weight diameter-MWD). Management influenced property magnitude and spatial dependence. MWD was greater with continuous no-till and spatial variation rose more quickly with increased sampling density than with discontinuous no-tillage. Discontinuous no-tillage captured 60% of MWD spatial variation at small scales (10 m sampling lag/100 m maximum distance); 12% was determined at the 50 m lag/500 m maximum distance and 6% was captured at 100 m lag/1000 m and 400 m lag/4,000 m. Continuous no-tillage increased MWD spatial dependence capture to 80% at the smallest scale, but no spatial variation was determined at larger scales. SOM was smaller with continuous no-till, but more SOM spatial variation was captured at the smallest scale with discontinuous no-tillage. Dynamic soil property sampling density and map resolution need to be accounted for when assessing model outcomes.