Micronutrients status of Florida soils under citrus production
ABSTRACT Micronutrient nutrition plays an important role in citrus production. Soil extraction techniques to measure the status of bio‐available micronutrients are extremely valuable in the diagnosis of deficient or toxic levels of micronutrients. Mehlich 3 (M3), Mehlich 1 (M1), ammonium bicarbonate‐DTPA (ABDTPA), and ammonium acetate, pH 7.0 (AA), extractants were evaluated for their ability to extract Cu, Fe, Mn, and Zn using 45 citrus grove soils, representing 20 soil series with widely varying physical and chemical characteristics and production practices. The mean concentrations of M3 extractable Fe, Mn, Cu, and Zn were 5.5‐, 2.2‐, 1.6‐, and 1.2‐fold greater, respectively, than those extracted by M1. ABDTPA was more efficient in the extraction of Fe, Cu, and Zn, as compared to the M1 extradant, by 3.3‐, 3.0‐, and 1.4‐fold, respectively. Among the four extractants, AA was extremely inefficient in extraction of all the four micronutrients. Evaluation of the data from all 45 citrus grove soils revealed significant pH effects on extractable Zn by M3, Ml, and ABDTPA extractants and Fe by M1 and ABDTPA extracts only. However, evaluation of the data from pH x Cu experiment on a Candler fine sand (0–15 cm depth soil; pH ranging from 4.5–6.9) showed a negative relationship between the Fe extracted by M3, Ml, and ABDTPA extradants and soil pH. Both extractable Mn and Zn were positively correlated to soil pH except for Mn extractable by ABDTPA. Good correlations (r > 0.52) were observed between M3 vs. Ml extractable Cu, Fe, Mn, and Zn and M3 vs. ABDTPA extractable Cu and Zn. Good correlations were generally found between M3 and AA extractable Cu, Mn, and Zn. However, poor extractability of all micronutrients by AA indicated that it is not a suitable extractant for micronutrient analysis of the soil studied. The results suggest that M3 is a suitable extractant for micronutrient analysis on sandy soils under Florida citrus production.
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ABSTRACT: Many tropical plant species originated in areas with acidic soils and do not grow well in calcareous (high pH) soils. It is impossible to acidify soils that have high contents of calcium carbonate in south Florida. Replacing calcareous soils with acidic soils obtained from distant regions is an alternative. Unfortunately, such introduced acidic soils may eventually be neutralized by irrigation and ground water that is saturated with calcium carbonate. The objective of this investigation was to examine the acidity changes and buffering capacities of three types of acidic soils (silica sand soil, red loamy sand soil, and a mixed soil) used to establish tropical plants in a rainforest exhibition at Fairchild Tropical Garden, Miami, FL. The three areas were excavated to remove native calcareous soil, limestone bedrock, and filled with acidic soils. Various rainforest plants were planted. Soil samples were collected in contiguous 10 cm‐deep segments from the soil surface to the bedrock shortly after deposition of the soils and one year later. Soil pH, EC, particle distribution, buffering capacity were determined. Results showed that both silica sand and mixed soils had been neutralized and the soil pH values had risen over 7 in all soil depths after one year. However, less than 10 cm of the surface and bottom soil layers of red loamy sand had been neutralized and the soil pH in the middle of soil profile remained unchanged due to its higher buffering capacity. A column leaching study showed that the acidity in the red loamy sand soil would be neutralized by irrigation water and by capillary movement of groundwater with a high concentration of calcium bicarbonate. Buffering curves indicate that it is easier to maintain acidity in sandy soil than of loamy sand and mixed soils with acidified irrigation water. Indeed it is difficult to acidify the mixed soils with high organic matter content after these soils have been neutralized.Journal of Plant Nutrition - J PLANT NUTR. 01/2003; 26(7):1513-1526.
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ABSTRACT: The proportion of copper (Cu) that can be extracted by soil test extractants varied with the soil matrix. The plant‐available forms of Cu and the efficiency of various soil test extractants [(0.01 M Ca(NO3)2, 0.1 M NaNO3, 0.01 M CaCl2, 1.0 M NH4NO3, 0.1 M HCl, 0.02 M SrCl2, Mehlich‐1 (M1), Mehlich‐3 (M3), and TEA‐DTPA.)] to predict the availability of Cu for two contrasting pasture soils were treated with two sources of Cu fertilizers (CuSO4 and CuO). The efficiency of various chemical reagents in extracting the Cu from the soil followed this order: TEA‐DTPA>Mehlich‐3>Mehlich‐1>0.02 M SrCl2>0.1 M HCl>1.0 M NH4NO3>0.01 M CaCl2>0.1 M NaNO3>0.01 M Ca(NO3)2. The ratios of exchangeable: organic: oxide bound: residual forms of Cu in M1, M3, and TEA‐DTPA for the Manawatu soil are 1:20:25:4, 1:14:8:2, and 1:56:35:8, respectively, and for the Ngamoka soil are 1:14:6:4, 1:9:5:2, and 1:55:26:17, respectively. The ratios of different forms of Cu suggest that the Cu is residing mainly in the organic form, and it decreases in the order: organic>oxide>residual>exchangeable. There was a highly significant relationship between the concentrations of Cu extracted by the three soil test extractants. The determination of the coefficients obtained from the regression relationship between the amounts of Cu extracted by M1, M3, and TEA‐DTPA reagents suggests that the behavior of extractants was similar. But M3 demonstrated a greater increase of Cu from the exchangeable form and organic complexes due to the dual activity of EDTA and acids for the different fractions and is best suited for predicting the available Cu in pasture soils.Communications in Soil Science and Plant Analysis - COMMUN SOIL SCI PLANT ANAL. 01/2005; 36:2601-2624.
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ABSTRACT: Fresh topsoil samples of an alfisol (Oxic Tropudalf) were moistened to 70% field capacity with CuSO4 solution to give varying concentrations of Cu; 0, 87, 174, 348 and 676 mg kg. The treated samples and the untreated controls were incubated at 30°C in a static microcosm for 8 weeks. The microbial respiration, and N and P mineralization were determined fortnightly. At the end of the experiment, total microbial counts, extractable Cu, pH, short-term nitrifier (SNA) and urease (UA) activities were also determined. Copper sulphate treatments significantly acidified the soil and reduced bacterial counts, microbial respiration, N and P mineralization, SNA and UA. Fungal counts, on the other hand, were significantly increased at the highest rates. The ratio of bacterial to fungal populations decreased from 2352:1 in the control to 2.5:1 in soil that received the highest concentration of Cu. Hence, fungi exhibited greater tolerance of high extractable Cu contents than bacteria. Nitrifier activity was significantly reduced by a lower Cu content than was UA. This study shows that repeated applications of CuSO4 could have detrimental effects on ecosystem functioning in terms of microbial numbers and composition, and nutrient cycling.Biological Agriculture & Horticulture - BIOL AGRIC HORTIC. 01/2001; 19(1):1-8.