Phosphorus Fertilizer Calibration for Sugarcane on Everglades Histosols

A calibrated soil test for phosphorus (P) fertilizer application to sugarcane (Saccharum spp.) grown on organic soils in southern Florida is an important best-management practice for minimizing P loads in water draining to the Everglades. The current calibration uses water as the soil extractant, which has the limitations of being very sensitive to pH and being most applicable to short-season crops. Phosphorus fertilizer rate studies at six locations (20 total crop years) were analyzed to develop an updated soil-test P calibration for sugarcane on organic soils. Phosphorus extracted with water, acetic acid, and Bray 2 did not consistently relate well to crop response. A new P soil-test calibration for sugarcane is proposed based on Mehlich 3 soil extraction, with a maximum rate of 36 kg P ha^?1 with ≤ 10 g P m^?3 in preplant soil samples and no P recommended with >30 g P m^?3.     

Comparison of Mehlich-3 and Ammonium Bicarbonate-DTPA for the Extraction of Phosphorus and Potassium in Calcareous Soils from Florida

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate Mehlich-3 (M-3) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) and potassium (K) and to determinate the relationships between extractable P and K and their uptakes by crop in calcareous soils. M-3 and AB-DTPA were compared by using two approaches. In the first approach, the amounts of extracted P and K were compared by analyzing soil samples collected from agricultural production areas; in the second approach, snap beans (Phaseolus vulgaris) were grown in pot to determine the P and K uptakes by crop. There were significant correlations between M-3 and AB-DTPA for both soil test P and K based on soils collected from the agricultural field and the pot study. Soil test P and K by both extractants were significantly correlated with their uptakes by snap bean. The critical value of M-3-P regarding snap bean uptake was 47 mg kg^?1 and was higher than that (18 mg kg^?1) for AB-DTPA-P, whereas critical soil test K levels were similar between M-3 and AB-DTPA. M-3 was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Yield response of soybeans to P and K fertilization as correlated with soil extractable and tissue nutritional levels

Abstract

Bragg soybeans [Glycine max. (L. ) Merill] were grown under field conditions near Sanford, Florida on a tile‐drained Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquod). The objectives were: 1) to assess the K and P fertilizer requirements of soybeans grown in central Florida 2) to correlate soil and tissue nutritional levels with extractable soil nutrients and 3) to assess the influence of K application time on yield.

Experimental treatments were four K rates (0, 50, 100, and 200 kg K/ha), three P rates (0, 25, and 50 kg P/ha), and two sidedress K rates (0 and 50 kg K/ha) at early bloom. Treatments were arranged in a randomized complete block design and replicated four times.

Yield increased with each increase in applied K. Statistical maximum yield was obtained on plots which contained 103 ppm double‐acid extractable K during the pod‐filling stage of growth. Tissue K at early bloom exceeded 2.85% at maximum statistical yield. Potassium applied broadcast at early bloom did not significantly influence yield.

This soil contained approximately 390 ppm double‐acid extractable P prior to P application. No significant yield response to applied P was observed, indicating that the original extractable P content of the soil was adequate for the yield level obtained.

The quadratic regression of the ratio equivalents of double‐acid extractable K:Ca + Mg on the same ratio for the plant tissue is highly significant. This expression was a good predictor of tissue accumulation of these nutrients in that the coefficient for determination was 0.68.     

Comparison of Multi-element to Single‐Element Extractants for Macro‐ and Micronutrients in Acid Soils from Spain

Abstract

Different chemical reagents are used to assess plant‐available nutrients from soils with similar properties. The use of different extractants is a serious limitation when comparing results between different soil‐testing laboratories, often leading to large differences in fertilizer recommendations for similar crops.

In this study, 80 samples from acid soils from Galicia (Spain) were used to compare several soil nutrient extractants. Traditional and tested extractants for acid soil such as Bray 2 and ammonium acetate were used to evaluate multielement extractants such as ethylenediaminetetraacetic acid–ammonium acetate (EDTA‐aa), ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB‐DTPA), and Mehlich 3.

Linear regression analyses were performed to relate the amount of each nutrient obtained by traditional soil extractants to the amount obtained by multielement extractants. Strong correlation was found between extractable Bray 2 P and Mehlich 3 P (r²=0.97, slope=0.87, and intercept=?0.48). The slope of the regression line between EDTA‐aa‐extractable calcium (Ca) and that from ammonium acetate (Aa) approached 1∶1 (r²=0.86). Similar results were obtained for magnesium (Mg) (r²=0.99). Soil zinc (Zn) concentrations extracted by Mehlich 3 and EDTA‐aa were similar; slope of the regression line was 0.95 (r²=0.88). With regard to copper (Cu), Mehlich 3 extracted approximately 20% more Cu than EDTA‐aa.

The results showed that Mehlich 3 and EDTA‐aa are suitable for assessment of plant available phosphorus (P), potassium (K), Ca, Mg, Cu, Zn, and iron (Fe) in acid soils.     

Leaf Phosphorus Diagnosis of Sugarcane on Organic Soils

ABSTRACT

Most of the sugarcane (interspecific hybrids of Saccharum sp.) production in Florida is on organic soils. Supplemental phosphorus (P) fertilizer is often applied for optimum yields, but producers are required to reduce P levels in farm drainage waters. The objectives of this study were to relate optimum leaf P tissue concentration with yield in organic soil, and to determine optimum leaf sampling dates during the summer. Eight genotypes were planted at two locations, eight additional genotypes were planted at a third location, and eight more genotypes were planted at a fourth location. Crops were grown for three years. Measurements of leaf P concentration were repeated during growth seasons and over crop years for a total of six sampling dates at each location. Three fertilizer P treatments (0, 24, and 48 kg ha^?1 yr?1) were applied to all genotypes at each location. Leaf samples were partitioned into early-, mid-, and late-summer dates. Early-leaf samples had the widest range in leaf P concentrations compared with mid- and late-season leaf samples. Correlation analyses of yield vs. leaf P concentration across all treatments in early- and mid-summer were statistically significant (P < 0.05), but coefficients were low (r = 0.14 and 0.26, respectively). No consistent relationship across locations described the effect of leaf P tissue concentration on yield. Leaf P concentrations could not provide accurate P fertilization rates that will give maximum sugarcane yields and prevent over-fertilization of P. The highest potential for relating leaf P concentrations with yield appears to be from early leaf samples.     

Divergent Relationships of Phosphorus Soil Tests in Temperate Grassland Soils

Abstract

Various soil tests are used to estimate phosphorus (P) availability for both crop uptake and potential loss to water. Conversion equations may provide a basis for comparison between different tests and regions, although the extent to which information can be interchanged is uncertain. The objective was to determine and quantify relationships between specific soil test extractants for samples taken annually in October and February over 4 years from four sites in each of eight soil series under grassland. The extractants comprised Mehlich‐3, Morgan, Olsen, Bray‐1, lactate–acetate, CaCl₂ (1∶2 and 1∶10 soil–solution ratios), and resin. The results showed distinct relationships for each soil series, for which individual lines regression models (different intercepts and slopes) were superior to a single conversion equation across all soils. The ensuing difference between soils was large and ranged from 1.9 to 8.0 and 9.2 to 15.6 mg kg^?1 P for Morgan and Olsen, respectively, at 20 mg kg^?1 Mehlich‐3 P. Generally, the environmentally oriented tests CaCl₂ and resin correlated best with Morgan. Some soil‐specific limitations were also observed. CaCl₂ was less efficient than Morgan, and Morgan less efficient than Mehlich‐3 on a high Fe–P soil derived from Ordovician‐shale diamicton, compared with the general trend for other soils. This finding suggests that further disparity may arise where evaluation of critical, or other, limits across regions involves even a limited sequence of tests.     

Sugarcane yield response to calcium silicate on Florida mineral soils

Abstract

Silicon (Si) is a beneficial nutrient for sugarcane (Saccharum spp.) and yield responses to Si amendment have been determined on soils with low soluble Si. Because a soil test Si calibration has not been published for sugarcane grown on Florida mineral soils, the objectives were to determine sugarcane yield response to silicon soil amendment on two mineral soils (Entisol and Spodosol) and to relate sucrose yield to soil-extractable Si. Calcium silicate application rates were 0, 3.4, and 6.7?Mg ha^?1 (Site 1) and 0, 2.2, 4.5, and 6.7?Mg ha^?1 (Site 2) in small-plot (120 m² plot^?1) experiments, with Si application resulting in significant increases in biomass and sucrose ha^?1. Calcium silicate requirements of 6.7 and 4.3?Mg ha^?1 were determined with initial acetic acid-extractable Si of 21 and 46?g m^?3, respectively. Nonlinear models indicated that Si amendments will be required with acetic acid-extractable Si <105?g m^?3.     

Development of a New Soil Extractant for Simultaneous Phosphorus,Ammonium, and Nitrate Analysis

Abstract

A new soil extractant (H³A) with the ability to extract NH₄, NO₃, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H³A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH₄ and NO₂/NO₃. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH₄ or NO₂/NO₃. H³A was highly correlated with soil‐extractable inorganic N (NH₄, NO₂/NO₃) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.     

Comparison of EDTA and ammonium Bicarbonate-DTPA for the extraction of phosphorus in calcareous soils from Kerman,Iran

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate sodium ethylene diamine tetra acetic acid (Na₂-EDTA) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) to determinate the relationships between extractable P and its uptake by crop in calcareous soils. Na₂-EDTA and AB-DTPA was compared by the amounts of extracted P by analyzing soil samples collected from agricultural production areas. There were significant correlations between Na₂-EDTA and AB-DTPA for soil test P based on soils collected from the agricultural field. Soil test P by both extractants was significantly correlated with plant P concentration. Na₂-EDTA was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Evaluation of soil extractants for silicon availability for sugarcane

Adequate evaluation and interpretation of silicon (Si) phytoavailability in soil is a key to fertilizer recommendation. This study was conducted to determine the effect of soil texture on the choice of Si extractant, and provide baseline data on the relationship between extractable Si and sugarcane Si accumulation. The effects of soil texture and extractant solutions of Si were investigated on soil of nine areas of sugarcane cultivation. Si contents in clayey soils were higher than in sandy soils only in the extraction with standard calcium chloride, acetic acid, potassium chloride (KCl), and sodium acetate buffer. Other extractants failed to reveal differences in the Si availability among the three soil textures. The choice of the extractant should consider soil texture for the determination of adequate Si contents in soils planted with sugarcane, and the extractants that proved to be more efficient in the three soil textures was acetic acid and KCl.     

Impacts of flooding,nitrogen-fertilization,and soil-depth on sugarcane nutrients grown on Histosols

Abstract

Sustainable production in the Everglades Agricultural Area (EAA) is confounded by decreasing soil depth and high annual rainfall. Formerly a sawgrass marsh, Histosols predominate much of the EAA and these soils have frequently flooded following their drainage in the early 20th century. Subsidence has increased inundation frequency as soil depth has decreased to less than 25?cm in many locations. A 2-year lysimeter study was conducted to examine alternative management practices for improved agricultural sustainability given frequent flooding and reduced oxidation rates on Histosols. Specific management factors examined included water-table, soil depth, and nitrogen (N) fertilizer effects on sugarcane leaf nutrient concentrations and soil nutrient cycling. The trial utilized soil depths of 13 and 25?cm, water tables of constant and periodically flooded, and N fertilizer rates of 0 and 168?kg ha^?1?year^?1. Periodic flooding increased plant uptake of manganese (Mn), silicon (Si), and boron (B). Yield increases associated with additional N indicate a potential need to develop fertilizer rate recommendations for shallow Histosols. Soil depth impacted sugarcane nutrient uptake with 25?cm of soil depth significantly affecting examined leaf nutrient concentrations except iron (Fe). Sugarcane yield may benefit if additional N and potassium (K) are added at rates specific to soil depth. Proximity to bedrock led to excessive calcium (Ca) uptake and low K and Fe DRIS (Diagnosis and Recommendation Integrated System) values were below recommendations. Data from this study can assist development of precision agricultural practices in the EAA that utilize soil depth.     

Phosphorus Buffering Capacity Indices as Related to Soil Properties and Plant Uptake

ABSTRACT

Evaluation of the plant-available phosphorus (P) in calcareous soils is commonly performed by removing a portion of solid phase P using chemical extractants. Critical soil test values, however, may be affected by variation in sorption and buffering behavior of different soils. The objective of this study was to evaluate the importance of buffering capacity indices to predict P uptake by wheat (Triticum aestivum). Eleven surface soil samples were assayed for a number of P intensity (CaCl₂-P) and quantity (Olsen-P, Colwell-P, and Resin-P) factors. Some phosphorus buffering indices were obtained from P sorption equations. A single-point index of buffering was also determined experimentally. In a greenhouse experiment, wheat was grown for 35 and 70 days on the same soils and P uptake was determined. Nonlinear and linear equations described the P sorption data (P < 0.001). Buffering indices derived from these equations were highly correlated with single-point index of capacity. Clay content was the most important soil property affecting the buffering capacity factor. The phosphorus intensity index (CaCl₂-P) was weakly related to P uptake (P < 0.05). Among the quantity factors only Resin-P was significantly correlated with P uptake. Buffering indices showed significant but inverse relationships with P uptake only at 70 days harvest (r = ?0.69 to ?0.71; P < 0.05). Combination of intensity or quantity factors with buffering capacity indices, such as intensity/capacity or quantity/capacity indicators, improved considerably the ability to account for variations in P uptake by wheat.     

Predicting Plant Phosphorus Requirements for Hawaii Soils using a Combination of Phosphorus Sorption Isotherms and Chemical Extraction Methods

Phosphorus (P) is an essential nutrient for plant growth and reproduction. One of the tasks of soil testing is to identify whether the soil P level is sufficient to meet crop requirements, and if not, to provide an estimate of the quantity of P that must be added for good growth of a given crop. Data for 12 soils (11 series) from Hawaii were used to develop correlations between critical P concentrations in soil solution derived from P sorption isotherms with P extracted with Mehlich 3, Olsen, or modified Truog solutions. Extractable P, in turn, was correlated with P fertilizer requirements. Critical P levels in soil solution reported in the literature for various crops ranged from 0.005 mg L^?1 for cassava (Manihot esculenta) to 0.30 for lettuce (Lactuca sativa) and to 1.6 for nonmycorrhizal onions (Allium cepa). The P buffer coefficient, defined as the ratio of fertilizer P added to extractable P, averaged 2.2, 4.2, and 8.6 for the modified Truog, Olsen, and Mehlich 3, respectively. Phosphorus requirements for certain crops could be estimated by the following steps: (i) obtaining (possibly one time only) soil solution P levels via P sorption isotherm for a given soil (series or family), (ii) identifying the critical soil solution P for a given crop from the literature, (iii) regressing soil solution P against extractable P, and (iv) establishing relationships between extractable P and fertilizer P.     

Use of adsorption and buffer capacity in soil testing for phosphorus

Abstract

The methods used to predict phosphorus (P) fertilizer requirements use extractable P levels. The inclusion of soil P buffer capacity with extractable P levels to improve fertilizer P prediction accuracy should be further investigated for Mediterranean soils. The objectives of this study, were to characterize the P adsorption properties of selected soils and to compare different soil P buffering capacity indices to determine their contribution to predict P fertilizer requirement. Twenty‐one soils were collected and P adsorption isotherms determined. On 11 soils wheat was grown in the greenhouse and P requirement determined. The Langmuir adsorption isotherm described the P adsorption of all soils. The prediction of crop P requirement was improved by the inclusion of a soil P buffer capacity index in the prediction equation. The index proposed by Salmon is easy to determine under routine soil analyses and does not require special analytical equipment. However, clay content can be used to predict the Salmon buffer index for similar soils.     

The influence op soil treatments on elemental composition of corn and on zinc soil tests on two Missouri soils

Abstract

Corn (Zea mays L) was grown at three locations on soil treated with Zn at two levels of soil fertility. Corn leaves were sampled at 2 stages of growth and analyzed for several elements. Yields were measured and soils were analyzed for O.lN HCl and DTPA extractable Zn and by standard testing methods for other components.

Zinc at 10 and 20 lb/A did not affect corn grain yields. The Zn treatments significantly increased leaf Zn concentrations. The influence of leaf sampling time differed between locations. The DTPA and O.lN HCl extractable soil Zn both reflected the Zn soil treatments. The DTPA appeared to extract a more soluble component of soil Zn which became more un‐extractable with time. In general, the extractable soil Zn was poorly correlated with Zn concentrations in the corn leaves. Under the conditions of the experiment the soil Zn levels as measured by the 2 extractants were a poor predictor of plant Zn when soil Zn levels were adequate.     

A quantitative study of native soil phosphorus supply to plants

Abstract

Rhodes grass (Chloris gayana Kunth ) plants were grown on various soil types In order to study the relationships between the available and hardly available soil P fractions. Results indicate that when plants are grown intensively in soils for long periods without additional P fertilization, recharge rate of the available fraction of soil P becomes a limiting factor. An approach to determine the recharge rate, using data on plant uptake and changes in sodium bicarbonate extractable soil P content are suggested.     

Soil‐Test Methods for Florida Sands Treated with an Aluminum–Water Treatment Residual and Various Phosphorus Sources

Use of aluminum (Al)–rich water treatment residuals (Al‐WTR) has been suggested as a practice to immobilize excessive phosphorus (P) in Florida soils that could represent an environmental hazard. Fertilizer P requirements can differ in WTR‐amended and unamended soil, so careful selection of soil‐testing methodology is necessary. Acidic extractants can dissolve WTR sorbed P and overestimate plant‐available P. We evaluated the suitability of the Mehlich 1 P (M‐1P) and other agronomic soil‐test procedures in an Al‐WTR‐treated Florida soil. Bahiagrass (paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a Florida topsoil amended with four sources of P at 44 kg P ha^?1 (P‐based rates) and 179 kg PAN ha^?1 [nitrogen (N)–based rates] and three WTR rates (0, 10, and 25 g kg^?1 oven‐dry basis). Both water‐extractable P (WEP) and iron (Fe) strip P (ISP), but not M‐1P, values of soil sampled at planting of each grass were greater in the absence than in the presence of WTR. Total plant P uptake correlated with WEP (r² = 0.82^***) and ISP (r² = 0.75^***), but not M‐1P (r² = 0.34^***). Correlations of the dry‐matter yield, P concentration, and P uptake of the first bahiagrass were also better with WEP and ISP than with M‐1P values. However, regression of plant responses with M‐1P improved after the first crop of bahiagrass. Both WEP and ISP values were better predictors of available soil P than M‐1P in a field study with same four P sources surface applied to established bahiagrass at the same two P rates, with and without WTR. Both WEP and ISP are recommended as predictors of P adequacy in soils treated with WTR, especially for soils recently (< 5 months) treated with Al‐WTR.     

Grain Yield and Mineral Element Composition of Maize Grown on High Phosphorus Soils Amended with Water Treatment Residual

ABSTRACT

The potential for phosphorus (P) movement from poultry-litter amended soils into surface waters heightens the need to manage elevated P concentrations. Amending high P soils with aluminum (Al) rich drinking water treatment residue in a greenhouse study reduced water extractable P levels and induced P deficiency in container grown wheat. Objectives of the current investigation were to determine the effect of water treatment residue on grain yield, leaf and grain mineral nutrient concentrations in corn (Zea mays L.) grown under field conditions and to examine pH, water and Mehlich 3-extractable P, and 0.01 M calcium chloride extractable Al in the amended soils at two sites. Poultry litter was amended with 0, 5.6, and 11.2 Mg ha^{? 1} of water treatment residual and applied to two sites prior to planting with corn in 1998. Additional rates (16.8 and 33.6 Mg ha^{? 1}) of water treatment residue were applied directly to half of each plot on site I in 1999. Results indicated that water treatment residue application did not adversely affect corn grain yields or alter concentrations of mineral nutrients in leaves and grain. Water and Mehlich 3-extractable P and calcium chloride extractable Al concentrations were unchanged with water treatment residue applications in both years on both sites. Further studies are needed concerning optimal annual dosages and long term loading rates for direct soil application of water treatment residue to reduce soluble phosphorus.     

Relationships between the Ratio of Plant-Available Phosphorus (P-AL) to Total Phosphorus and Soil Properties

Abstract

The relationships between the ratio of plant-available phosphorus (P-AL) to total P and soil properties were examined in 52 samples of mineral soils collected from different parts of Norway. The ratio P-AL/total P in the soils was used as a measurement of a soil's capacity to bind P in sparsely soluble forms and of the possibility for plants to utilize added P. Simple regression analysis showed that the ratio P-AL/total P was correlated with clay (r= ?0.60???, significant at the 0.1% probability level), Tamm acid oxalate extractable Fe (r= ?0.63???), and Tamm acid oxalate extractable Al (r-= ?0.44???), but not with organic C and pH. Variation of Fe, Al and clay content could explain 50% of the variation of the ratio of P-Al/total P. Partial correlation coefficients showed that Fe was the most important factor explaining the variation of the ratio of P-AL/total P.     

Predicting Maize Yield,Nutrient Concentration,and Uptake in Phosphorus- and Potassium-Fertilized Soils: Pressurized Hot Water and Other Alternatives to Mehlich I Extraction in Guatemala Soils

Abstract

Poor accessibility and cost of soil testing reduce effectiveness of fertilizer use on small‐scale subsistence farms, and inadequate funding promotes adoption of soil tests in developing countries with minimal validation. For example, Mehlich I extraction of phosphorus (P) currently used extensively in Guatemala may not be suitable for Guatemala's broad range of soils. At least four alternatives are available but relatively untested [Bray 1, Mehlich III, Olsen, and pressurized hot water (PHW)]. Pressurized hot water is relatively simple and inexpensive but is not yet tested against other extraction methods under variable P or potassium (K) fertilization levels. To determine whether PHW‐extracted nutrients could be used to predict maize yield and nutrient concentration and uptake, soil, plant tissue and grain samples were obtained from a multiple‐site field study, and calibration studies were conducted using five rates of P and three rates of K on soils incubated without plants or cropped with maize in greenhouse and field conditions. In the multiple‐site field study, maize yield related significantly to PHW‐extractable P (r²=0.36) and to leaf P concentration (r²=0.23), but Mehlich I–extractable P did not. In the two soils used in the greenhouse study, maize yield, vegetative P concentration, and total P uptake by maize were predicted by PHW‐extractable P (R²=0.72, 0.75, and 0.90, respectively). In the field experiment, grain yield was not improved by P or K application, but P concentration of maize leaf tissue did relate significantly with PHW‐extracted P (R²=0.40). Mehlich I did not. There were no yield responses to K application in any experiment, but relationships defined between extractable K for all five K‐extraction procedures and soil‐applied K were similarly significant. In comparison, PHW was as good as or better than Olsen whereas Bray 1 and Mehlich III were less consistent. Mehlich I was overall the poorest P extractant. Mehlich I extraction of P should be replaced by one of the four alternatives tested. PHW is the least expensive and, therefore, most viable for use in Guatemala soils.