Spatial Variability in Precision Agriculture What is it? What is it? – Precision n. The quality or state of being precise. Used or intended for precise measurement. Used or intended for precise measurement. Made for the least variation from a set standard. (Webster, 1995) Made for the least variation from a set standard. (Webster, 1995) – Precise adj. Capable of, caused by, or designating an action, performance, or process carried out or successively repeated within close specified limits (Webster, 1995). What is it? What is it? – Precision n. The quality or state of being precise. Used or intended for precise measurement. Used or intended for precise measurement. Made for the least variation from a set standard. (Webster, 1995) Made for the least variation from a set standard. (Webster, 1995) – Precise adj. Capable of, caused by, or designating an action, performance, or process carried out or successively repeated within close specified limits (Webster, 1995).

Precision Agriculture What is it? What is it? – Precision in management? – Knowing more precisely the size of fields, size of fields, level of inputs (rates), level of inputs (rates), yields, yields, $ costs, and $ costs, and $ returns? $ returns? What is it? What is it? – Precision in management? – Knowing more precisely the size of fields, size of fields, level of inputs (rates), level of inputs (rates), yields, yields, $ costs, and $ costs, and $ returns? $ returns?

Precision Agriculture What is it? What is it? – Management of production inputs in relation to more precisely delineated needs (Johnson, 1/18/01). Recognizes spatial variability of production needs within a population of production units, where production units are smaller than they used to be. Recognizes spatial variability of production needs within a population of production units, where production units are smaller than they used to be. What is it? What is it? – Management of production inputs in relation to more precisely delineated needs (Johnson, 1/18/01). Recognizes spatial variability of production needs within a population of production units, where production units are smaller than they used to be. Recognizes spatial variability of production needs within a population of production units, where production units are smaller than they used to be.

Spatial variability among production units. What is the size of a production unit? Depends on the enterprise. – Small dairy = single dairy animal. – Wagoner Ranch, TX = 7,000 – 8,000 acre wheat field. Agronomic units = “fields” What is the size of a production unit? Depends on the enterprise. – Small dairy = single dairy animal. – Wagoner Ranch, TX = 7,000 – 8,000 acre wheat field. Agronomic units = “fields”

Spatial variability among production units. What causes field delineation. – Natural boundaries. Rivers Rock out-crops – Political boundaries. Roads Survey units – Land ownership Consolidation What causes field delineation. – Natural boundaries. Rivers Rock out-crops – Political boundaries. Roads Survey units – Land ownership Consolidation

Spatial variability among production units. What causes field delineation. – Soil productivity appropriate to the crop (e.g. bottom land for alfalfa). – Size determined by land use Government acreage restrictions (CRP) Tees, fairways, greens – Size that is “convenient” to the operation for administering production inputs. Cultivation Planting Harvesting (mowing) Fertilizing Irrigation Etc. What causes field delineation. – Soil productivity appropriate to the crop (e.g. bottom land for alfalfa). – Size determined by land use Government acreage restrictions (CRP) Tees, fairways, greens – Size that is “convenient” to the operation for administering production inputs. Cultivation Planting Harvesting (mowing) Fertilizing Irrigation Etc.

Spatial variability (macro) for agronomic land use. Inherent (natural). – Related to soil productivity and soil forming factors Time Parent material Climate Vegetation Slope Inherent (natural). – Related to soil productivity and soil forming factors Time Parent material Climate Vegetation Slope

Soil acidity and Oklahoma rainfall Usually acidic Usually not acidic

Spatial variability (macro) for agronomic land use. Acquired (use induced). Influence of historical crop production on soil properties. –Alfalfa vs. wheat for acidification and soil organic matter. –Fertilizer use and change in soil fertility (Garfield County). Acquired (use induced). Influence of historical crop production on soil properties. –Alfalfa vs. wheat for acidification and soil organic matter. –Fertilizer use and change in soil fertility (Garfield County).

C.V. = 54 Acquired spatial variability (macro).

Garfield Co. Farmer’s Use of Soil Testing and Fertilization PreviousPreviousGrainGrain Normal Fertilization Soil Test Results AcresAcres Soil Test YieldYieldNNPP 22 OO 55 KK 22 OOpHpHNNPPKK SurSurSubSub 86*86* *118* *30* *65* *Savings from no fertilizer to four fields = 299 acres X $24.50/acre, = $7,325 Acquired spatial variability (macro).

Acquired spatial variability (micro). pH=4.9 BI = 6.6 N = 10 P = 93 K = 435 Bottom pH=5.2 BI = 7.0 N = 13 P = 54 K = 354 Terrace 1 pH=5.3 BI = 6.9 N = 10 P = 44 K = 415 Terrace 2 pH=5.7 BI = 6.9 N = 20 P = 23 K = 397 Terrace 3 pH=5.4 BI = 6.8 N = 20 P = 31 K = 522 Terrace 4 pH=5.5 BI = 6.7 N = 12 P = 32 K = 423 Terrace 5 pH=4.6 BI = 6.8 N = 16 P = 65 K = 310 Upland pH=7.3 BI = -- N = 67 P = 22 K = 343 “BadSpot” pH=5.2 BI = 6.8 N = 14 P = 49 K = 408 FieldAveragepH= BI = N = P = K = FieldRange

“Cow Pocks” in wheat pasture Acquired spatial variability (micro).