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Fluid Journal : Winter 2015
11 The Fluid Journal Winter 2015 Tissue testing is a well-established science that has a growing data base. Interpretation of tissue testing results is based on and referenced to historical results (chemical concentrations) from studies where crops were considered to have an adequate supply of all nutrients. Information about weather (temperature and water) and soils (pH, CEC, etc.) is lost when tissue concentration data are extracted from the various reports. Compiled reference concentrations for a given nutrient and crop, result in a range of adequacy values that is typically based on relative yield for a given study. For example, tissue concentrations that result in 95 to 100 percent of maximum yield are typically considered “sufficient” or adequate. Yields that are 80 to 95 percent of maximum yield are considered “low.” Yields that are <80 percent of maximum are considered “deficient.” Nutrient concentrations that are considerably greater than the “sufficient” range are considered “high” and could be toxic or result in other problems because of nutrient interactions within plants. Objectives The objective of this research was to: • Begin assessing if and how tissue concentrations in modern high-yielding corn hybrids might have changed over time • See if existing reference The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Winter 2015 • Vol. 23, No. 1, Issue #87 Dr. James Schepers Make sure ear-leaf N concentrations are adequate in corn leaf tissues. Summary: From preliminary observations when evaluating tissue testing data, make sure the ear-leaf nitrogen (N) concentrations are adequate before drawing conclusions about the adequacy of other nutrients. concentrations are still appropriate • See how sufficiency ranges change with growth stage, hybrid, and geographical location (basically, origin of top soil). Methodology Irrigated corn hybrid demonstration plots at Shelton and York, Nebraska were used in the second year of this study. The Shelton study (14 hybrids) was managed by a local Pioneer Hi-Bred representative and the York study (16 hybrids) was managed by the Pioneer staff at the York Research Station. Three additional studies at Johnston, IA , and Bloomington, IL (both rain-fed) and York, NE (irrigated) involved two hybrids that were fertilized at five N rates (0, 50%, 70%, 100% and 130% of recommended). Studies in Iowa and Illinois involved four replications. All plots were sampled at silking (VT growth stage) by removing the ear leaf from 12 representative leaves. Samples were dried and ground before sending to A&L Great Plains Lab for analyses. Results Even though there was considerable variability in nutrient concentrations across hybrids at Shelton (i.e.: B, Mn, and Cu), Mg was the only nutrient found to be potentially low (mean 0.14%, range 0.12to0.20%)atVTwithaCVof16 percent across hybrids. Ear-leaf Mg concentrations across hybrids at York also had a CV of 16 percent, but none of the samples were deemed deficient according to industry guidelines (equal to or greater than 0.13%). Figure 1 illustrates the variability in ear-leaf Mg concentrations at the Shelton location. Even though some of the ear-leaf Mg concentrations were considered to be “low,” the average yield was 259 bu/A (range from 241 Nutrient Concentrations And Balance Important ▼ DOWNLOAD