Temporal Dynamics of Soil Water Among Delineated Management Zones.

Soil and crop processes vary in farmers’ fields in space and time. It remains a challenge to manage fields site-specifically for maximizing biomass production efficiency and environmental benefit. The objective of this study is to delineate management zones with different approaches and evaluate differences in soil water dynamics. A set of direct and indirect measurements that included soil texture, electrical conductivity (EC), soil chemical properties (pH, organic matter, N, P, K, Ca, Mg and Zn), NDVI, topographic variables, were compared with corn yield on a silty loam soil in Princeton, Kentucky. Variables were measured at 96 locations across a 50-m grid. Maps were developed using kriging, and cokriging. A set of variables was selected by using Principal Component Analysis. Two cluster methods (FANNY and CLARA) with selected variables were applied to identify management zones. Optimal scenarios were achieved with dividing the entire field into 2 or 3 areas, depending on what variables were selected. Spatial variability in the field is strongly influenced by topography and soil texture. To compare differences in soil moisture status among management zones, soil matric potential was measured at three depths (20, 40 and 60 cm) using watermarks during spring season of 2016. A continuous wavelet transform and wavelet coherence were applied to evaluate temporal dynamics. Temporal variations in soil water are driven mainly by precipitation but the behavior is different among management zones. The zone with higher clay content tends to dry out faster between rainfall events and reveals higher fluctuations even at greater depth. The other zones are more stable at the lower depth and share more similarities in their cyclic patterns. Results demonstrate the ability to derive potential management zones and how these zones reflect the variability pattern of soil water status. This information helps to manage irrigation water and other resources site-specifically.