E.A. Hanlon

Soil penetrometer resistance and bulk density relationships after long‐term no tillage

Abstract Soil penetrometer resistance (SPR) and bulk density (p) measurements can be used for assessing soil strength or density. Results from this research add to the understanding of residual soil compaction of sandy soils by answering three questions: What are the long term effects of no‐tillage on SPR and p in a double‐cropping rotation? Where in the soil profile are maximum SPR and p values found? How much of the variations in SPR are accounted for by the regression of p? Compaction was evaluated at the end of an 8‐yr oat (Avena sativa L.)/Bragg soybean [Glycine max (L.) Merr.] double‐cropping tillage experiment. The soil was Arredondo fine sand (Grossarenic Paleudults). The four treatments (replicated four times) included no‐tillage (NT), conventional tillage (CT), no‐tillage plus in‐row subsoiling (NTPS), and conventional tillage plus in‐row subsoiling (CTPS). Forty days after planting soybeans the soil was irrigated to field capacity. Readings were taken to a depth of 60 cm at five positions in th...

Initial calibration and correlation of inorganic-phosphorus soil test methods with a bahiagrass field trial

Abstract In recent field studies, bahiagrass (Paspalum notatum L.), a major forage crop in Florida, did not respond to added P fertilizer even though preplant Mehlich‐1 (M‐1) soil test indicated very low extractable P (<10 mg/kg). Selected extractants for soil P were statistically compared to improve the predicted need for P fertilization. A separate field study was used to provide yield and nutrient uptake data. The field experiment was arranged in a randomized complete block design with four replications on a Myakka fine sand (hyperthermic aeric Haplaquod). Plots were fertilized in March of 1989 and 1990 with 0,17, 34, 51, and 68 kgP/ha. Soil samples were taken from the Ap horizon (0 to 15 cm) in January, 1990. Extractants included iron hydroxide impregnated filter paper (Pi), anion exchange resin (trimethyl benzyl ammonium active group), M‐1, Mehlich‐3 (M‐3), and water. There was a high correlation between Pi and the resin procedures (r2 = 0.96). These methods gave higher extractable P values compared ...

Soil nutrient variability and soil sampling in the everglades agricultural area

Abstract The variability of soil nutrients and sampling was investigated in the Everglades Agricultural Area (EAA), on a Lauderhill muck (euic, hyperthennic Lithic Medisaprist), Pahokee muck (euic, hyperthennic Lithic medisaprist), Okeelanta muck (euic, hyperthennic Terric Medisaprist), and Torry muck (euic, hyperthennic Typic Medisaprist). Soils in adjacent fields at the same location under either sugarcane (Saccharum spp.), sweetcorn (Zea mays L.), or sod [Stenotaphrum secundatum (Walt) Kuntze], were sampled. Surface samples were taken across existing canals between two fields at each location using a sampling grid technique. On all samples, soil pH, ash content, and total and extractable P, K, Ca Mg, Mn, Fe, Cu, and Zn were determined. Results showed that selected soil chemical properties from the Histosols from the EAA are spatially dependent. Anisotropic semi‐variograms showed that ditch and road spoils are two of the main factors influencing in‐field soil variability. Block‐kriged contour maps of pr...

Inorganic phosphorus and manure effects on bahiagrass production on a Spodosol

Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.

Optimization of solution:soil, ratio and shaking times of the Mehlich-III soil test on histosols

Abstract The University of Florida Everglades Soil Testing Laboratory has been determining water‐extractable P in organic soils (Histosols) since 1944. The water extractant has consistently provided reliable correlations for vegetable commodities, but not for agronomic crops. Recent research has suggested that the Mehlich‐III soil test has potential for use on Histosols. However, no information indicated if solution: soil ratios (RAs) and shaking times (SHs) used for mineral soils would be appropriate for organic soils, which have appreciably lower soil bulk densities. A laboratory study with SHs ranging from 1 to 29 min and RAs ranging from 8 to 22 (v/v) arranged in a central composite rotatable design (ccd) was conducted using four Florida Histosols. Nine treatment combinations of RAs and SHs were used. Two replications of the ccd were performed with duplicate extractions for each sample. The fitted second‐degree response surface equations for P and K nutrients with surface contour plots were shown for ...

Recent changes in phosphorus and potassium fertilizer recommendations for Tomato, Pepper, Muskmelon, Watermelon, and Snapbean in Florida

Abstract Mehlich‐I soil‐test calibrations and fertilizer recommendations were reviewed in light of the current literature. This review lead to 22 research/demonstration experiments conducted dominantly on cooperators’ fields. Crops included tomatoes (Lycopersicon esculentum Mill.), pepper (Capsicum annuum L.), watermelon (Citrullus lanatus Thunb., Matsum. and Nakai), muskmelons (Cucumis melo L. Reticulatus group), and snapbean (Phaseolus vulgaris L.). Soils selected for these trials included Ultisols, Spodosols, and Entisols. Minimum data collection at all sites included preplant soil tests (0‐ to 15‐cm depth) using the Mehlich‐I extractant, leaf tissue sampling (usually most recently‐matured leaf), and harvest data using USDA grading standards. Typically, four or five rates of P and/or K were used with four or five replications. The growers’ fertilization practices were also included in the trial. Additional yield samples were collected from outside the experimental area to verify yields obtained by the ...

Potassium and magnesium uptake by wheat and soybean roots as influenced by fertilizer rate

Abstract Greenhouse‐pot experiments were conducted to compare wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merrill] in terms of their potassium (K) and magnesium (Mg) uptake. Previously, a field study indicated that various rates of K and Mg fertilization did not produce a significant wheat‐yield response. However, a yield increase with residual K and Mg was measured for the subsequent soybean crop. The 0 to 15 cm layer of Norfolk loamy fine sand (fine loamy, siliceous, thermic Typic Kandiudult) from two different sites was used for the pot experiments. Soil from both sites had a pH of 5.1. Potassium as potassium sulfate (K2SO4) was mixed into the soil from the K‐deficient site and Mg as magnesium sulfate (MgSO4) was mixed into the soil from the Mg‐deficient site. ‘Florida 301’ wheat and ‘Cobb’ soybean were grown in winter and summer, respectively. Soybean and wheat were similar in K uptake/g of roots on the first and second sampling dates. However, by the third sampling date, K uptake/g of ...

Mehlich‐I soil‐test calibration for watermelon: Cu, Zn, and Mn

Abstract Predictive soil tests were used to detect possible need for Cu, Zn, and Mn fertilizers for the optimum production of watermelons (Citrullus lanatus (Thumb.) Masf.) in north and central Florida. Predictive Mehlich‐I soil testing indicated a possible response to additions of Mn and Cu but not to additions of Zn at three locations: Gainesville, Dunnellon, and Live Oak. Results showed no total marketable yield response to selected Cu, Zn, and Mn treatments at any of the three sites. Yields for the Gainesville, Dunnellon, and Live Oak sites were 41.5, 29.0, and 38.0 Mg/ha, respectively, well above the state average watermelon yield of 19.0 Mg/ha. Tissue analyses at the Gainesville and Live Oak sites showed Cu, Zn, and Mn levels within or above suggested sufficiency ranges. This study indicates that current University of Florida interpretations for the Mehlich‐I extractant can identify sites with adequate extractable Cu, Zn, and Mn levels, thus avoiding unnecessary fertilization. At no time were Univer...