Title:	DRIS Analysis Identifies a Common Potassium Imbalance in Sweetgum Plantations
Author(s):	Coleman, Mark D.; Chang, S.X.; Robison, D.J.
Date:	2003
Source:	Communications In Soil Science And Plant Analysis. Vol. 34, Nos. 13 & 14, Pp. 1919–1941
Description:	DRIS (Diagnosis and Recommendation Integrated System) analysis was applied to fast-growing sweetgum (Liquidambar styraciflua L.) plantations in the southeast United States as a tool for nutrient diagnosis and fertilizer recommendations. First, standard foliar nutrient ratios for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were established using high-yield stands from a region-wide sweetgum fertilization study. DRIS indices were then calculated for the low-yield stands in the same study and stands fromfour other studies to evaluate foliar nutritional characteristics. Low-yield stands showed strong negative K imbalance, indicating insufficient K, but also showed strong positive Mg imbalance. Potassium imbalance was also observed in the other four data sets tested. DRIS analysis successfully identified the tendency for K insufficiency to increase from early to late in the growing season, probably due to K foliar leaching and low soil K supply. While insufficient N was common in all the stands tested, the DRIS analysis failed to identify any P imbalance. We recommend that K be applied in N:K ratios less than one to correct K imbalance problems in the studied sweetgum plantations. Supra-optimal Ca and Mg levels are expected to decline once insufficient N and K are corrected. DRIS analysis provides the means for diagnosing nutrient imbalance and a potential basis for prescribing corrective amendments in sweetgum plantations.
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