CORRECTION OF LIMED-BIOSOLID INDUCED MANGANESE DEFICIENCY ON A LONG-TERM FIELD EXPERIMENT

Land application of lime-stabilized biosolids has been reported to cau se Mn deficiency in wheat (Triticum aestivum L.) and soybean [Glycine max(L.) Merr.]. Deficiencies were observed on a longterm biosolid rese arch experiment in Beltsville, MD, that had been established on a Gale stown sand (sandy, siliceous, mesic Psammentic Hapludult) in 1976 with lime-stabilized biosolids applied at 224 and 418 Mg ha(-1). For the p resent study, a randomized complete block experiment was set up in plo t areas of the original study. Soil amendments included MnO at 50, 100 , and 200 kg ha(-1), and MnSO4 at 200 kg ha(-1). Plots were split with random half plots receiving a foliar application of MnSO4 at 0.5 kg h a(-1) Mn. Soybean and wheat were double cropped for two seasons (1993- 1995). Measured indexes of deficiency included youngest emerged blade (YEB) and grain Mn, plant chlorophyll, and yield. Wheat exhibited seve re Mn deficiency for both seasons in the 224 Mg ha(-1) biosolid plots. Only plants grown in the MnSO4-amended soils were not deficient in Mn . Foliar Mn spray also alleviated Mn deficiency. Although soybean plan ts were not Mn deficient, plants in the MnSO4-treated plots had higher YEE Mn concentrations. Soil extractions to reflect phytoavailable Mn, including Mehlich 1(M1), Mehlich 3 (M3), acid DTPA were conducted on moist soils. Results from M3 and DTPA extractions mirrored plant respo nse. The M1 extraction did not predict plant response indicating that this extraction is not appropriate for predicting Mn deficiency in coa rse textured high pH soils.