1998•UA Campus Repository (The University of Arizona)Requires access
Developing Sap Nitrate Tests for Wheat and Barley, Maricopa, 1998
Edgar Alsop Riley, Thomas L. Thompson, Scott A. White, Mike Ottman
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Abstract
The standard procedure for determining nitrogen (N) status in small grains is to sample lower stem tissue for nitrate (NO₃) analysis. The tissues are then submitted to a laboratory for analysis. Sap nitrate (NO₃) can be analyzed in the field, immediately after collecting the sample, using a Cardy meter. Guidelines for sap analysis have not yet been determined. The objectives of this study were to: (i) correlate NO₃-N in dried stem tissue with sap NO₃-N, and (ii) develop sap NO₃ test guidelines for N management in durum and feed barley. In November 1997 one variety of durum (Kronos) and one variety of feed barley (Gustoe) were planted at the Maricopa Agricultural Center. Three N rates (80, 200, and 400 lbs N/acre) were applied in four split applications. Each treatment was replicated five times in a randomized complete block design. Samples were collected from lower stems at the 3-4 leaf 2 node, flag leaf visible, and heading growth stages. Grain yields ranged from 5185 lbs/A to 7156 lbs/A for Kronos and 6314 lbs/A to 7517 lbs/A for Gustoe. Maximum yields were achieved at 200 lbs N/A for both varieties. Correlation coefficients between stem NO₃-N and sap NO₃-N were 0.79 for Kronos and 0.84 for Gustoe. Sap NO₃-N analysis can be used to determine N status during the season for both Kronos and Gustoe.