Monday, November 5, 2007
103-2

Spatial Patterns of Physical Properties in Heterogeneous Citrus Soils of Florida.

Kirandeep Mann1, Arnold Schumann1, Thomas Obreza1, Willie Harris1, Jerry B. Sartain2, Sanjay Shukla1, and Max Teplitski3. (1) Newell Hall, University of Florida, Soil and Water Science Department, Gainesville, FL 32611, (2) Univ. of Florida, 414 Newell Hall PO box 110510, Gainesville, FL 32611, (3) ufl, gainesville, FL 32611

Spatial yield reduction and soil heterogeneity were studied in a Florida citrus grove (10 ha) located near Wauchula in Hardee County, Florida to identify soil physical properties responsible for differentiating soil productivity. Tree canopy volumes were measured using an ultrasonic array and DGPS receiver in order to quantify productivity. Fruit yield was mapped from harvester trucks equipped with DGPS receivers and data loggers. The grove was classified into five productivity zones as representative of very good, good, medium, poor and very poor growth areas on the basis of canopy volume. Soil samples were collected at 30 representative locations at 4 profile depths up to 60 cm and were analyzed for texture, sand particle size, soil organic matter (SOM), soil color, bulk density, hydraulic conductivity and water content at permanent wilting point (PWP). Among the soil properties SOM content showed a continuous decrease along the productivity gradient and depth in all the productivity zones, but soil physical properties behaved differently with the depth in different productivity zones. Sand content also decreased (r=-0.65) along productivity gradient. In color, the parameter of lightness “L” decreased with the productivity and increased with the depth and was highly negatively correlated (r= -0.74) to the canopy volume. The parameter of red-green scale “A” increased with productivity and was positively correlated (r=0.49) to the canopy volume. Soil bulk density did not show a particular trend along the productivity gradient. The volumetric water content at PWP increased with the productivity, whereas hydraulic conductivity decreased. Organic matter (r=0.71) and water content at PWP (r= 0.80) were highly positively correlated to the canopy volume. The regression analysis of soil properties averaged across the profile showed that SOM, lightness of soil color and water content at PWP explained 50, 55 and 64 % of spatial variation in canopy volume respectively.

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