Assessing Spatial Break-even Variability in Fields with Two or More Management Zones

Abstract

Farmers are interested in knowing whether applying inputs at variable rates across a field is economically viable. The answer depends on the crop, the input. their prices, the cost of variable rate technology (VRT) versus uniform rate technology (URT). and the spatial and yield response variability within each tield. Methods were investigated for determining the range of spatial variability over which the rctum t o VRT covers its additional cost compared with URT in fields with rnultiple management zones. Models developed in this article, or variants thereof, could be uscd to hclp farmers make the VRT adoption decision. : nrrrncigrincnt :one.\. riitrogctz. prc~c.isioi1 , f i r r n~i n~, site,-.s/):l,c~cijic. Key Words mcrrzagerncJiz/, .spc~/iul hrc~cik-ei~cv~ c.crriahility propol.rior~.s, spatir/l vcrrinhility, vcrrinhlp rci/c7 teclznology. vic~l(l rrsponsc ~~c~ricrhiliry.Agricultural fields consist of numerous areas that differ from one another with respect to the factors that condition crop growth (Can-' t (11.; Hannah, Harlan, and Lewis; Hibbard c,t a/.; Malzer ct ~1 1 . ; Sawyer; Spratt and Mclver). Precision farming uses a set of technologics to gather information about the heterogeneous makeup of a farm field and uses that information to make management decisions that address site-specific crop nceds within the field (Swinton and Lowenber-DeBoer). Its component technologies en-Burton C. English is a professor, S.B. Mah:~jjanashetti

Perceived importance of precision farming technologies in improving phosphorus and potassium efficiency in cotton production

“…Cotton is a high-value, high-input crop requiring large applications of P and K in general. English et al (2001) suggested that VR applications of fertilizer could lead to increased yields and/or lower levels of fertilizer use compared to uniform-rate applications.…”

Changes in Producers' Perceptions of Within-Field Yield Variability after Adoption of Cotton Yield Monitors

“…In the absence of spatial yield monitor information, it is possible that farmer overconfidence (i.e., underestimating within-field yield variability) could influence the decision to adopt variable rate application technologies. Without yield monitor information, the farmer would perceive more spatially homogenous yields and be less likely to use variable rate input application techniques (English, Mahajanashetti, and Roberts, 2001;Larson and Roberts, 2004).…”

“…Thus, this particular farmer may decide not to invest in VR technology to apply inputs at variable rates across different sections of the field. As English, Mahajanashetti, and Roberts (2001) have shown, the economic viability of VR input application depends critically on the degree of the spatial variability of the farmer's fields; higher spatial variability results in higher returns from the use of VR application technologies. However, if the farmer's prior perception of spatial yield variability is lower than the true spatial yield variability, an error could be made in the grower's decision-making about whether or not to adopt VR technology.…”

Delineation of Management Units for Site-Specific Irrigation

“…Roberts et al (2000) developed a general framework to evaluate the returns of variable rate nitrogen application. English et al (2001) extended the framework for use in a field with multiple management zones. They concluded that the final decision of whether to use variable rate (site-specific) over uniform rate varies from field to field, depending on the spatial variability of the soil and the yield response variability among the management zones.…”