Critical trifoliolate leaf and petiole potassium concentrations during the reproductive stages of soybean

Document Type

Article

Publication Date

11-1-2016

Abstract

The critical K concentration in soybean [Glycine max (L.) Merr.] has been determined only for leaf tissue at the R2 (full bloom) stage. Our research objective was to develop critical K concentrations in soybean for both leaves and petioles across reproductive stages. Fifteen fully-expanded, uppermost trifoliolate leaves with petioles plot–1 were collected 7 to 12 times from the V5 to R7 stages in five research trials that evaluated multiple fertilizer-K rates and/or cultivars from different maturity groups (MGs). Both leaf- and petiole-K concentrations, regardless of site-year, cultivar, and fertilizer-K rate, peaked around R2 stage and declined linearly with time at average rates of –0.198 g K kg–1 d–1 for leaves and –0.559 g K kg–1 d–1 for petioles. The leaf- and petiole-K concentrations at the R2 to R6 stages explained 48 to 80% and 41 to 85%, respectively, of the variation in relative yield (RY). Petiole-K concentration was a better predictor of RY than leaf-K at the R2 stage where the predicted critical range (CR) concentrations were 14.6 to 19.0 g leaf-K kg–1 and 30.1 to 38.3 g petiole-K kg–1. The wider CR of petiole-K at the R2 stage followed by a greater linear decline rate across reproductive stages indicates that growth stage as well as deficiency and sufficiency thresholds for petiole-K could be more easily categorized than for leaves. Overall, the ability to interpret the K nutritional status in soybean tissues at numerous reproductive growth stages will improve K management.

Publication Source (Journal or Book title)

Agronomy Journal

First Page

2502

Last Page

2518

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