Vincent A. Haby

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. I. Boron‐Treated Soil Incubation and Efficiency of Extraction

Abstract Serious challenges associated with hot water extraction, the standard extraction method for water‐soluble boron (B), limit its use in commercial soil‐testing laboratories. Several alternatives to make B testing more practical have been proposed and studied; none of the alternatives have readily replaced the hot water method. Two relatively new, promising B extraction methods are pressurized hot water and DTPA‐Sorbitol. Very little reported work compares B extraction values obtained from the standard hot water extraction method and these two alternative methods. This study was conducted to complete an initial step in validating new procedures—extracting the designated nutrient from fertilized, incubated soils by using standard and alternative extraction methods and comparing the resulting values. The three extraction methods were used to extract B from samples of calcareous sand and silt loam soils and limed, loamy fine sand, all which had been treated with 10 levels of B (0–8 mg kg−1) and incubated for 7 and 28 days. The amount of B extracted increased as the rate of B application increased with all three soil‐extraction methods. High correlations (r 0.977–0.999) were observed between extractable B and rate of B application with all three procedures. Correlations between the amount of extractable B using hot water extraction and the value obtained with an alternative extraction method were similar for both methods (r=0.89). Hot water generally extracted the least and pressurized hot water the most B regardless of soil type, rate of application, or duration of incubation. This study suggests the more easily used methods of pressurized hot water and DTPA‐Sorbitol could be recommended as replacements to the cumbersome hot water extraction.

Effect of sample pretreatment on extractable soil potassium

Abstract Effect of soil sample treatment on potassium (K) release characteristics of Northern Great Plains soils was studied. Samples of agricultural soils were extracted with neutral normal ammonium acetate for K after selected pretreatment. Field‐moist sub‐soil samples with approximately 100 mg/kg extractable K release nearly double this amount after they were air on oven‐dried prior to analysis. The percentage increase in extractable K in dried soils decreased as the K level in the field‐moist soils increased. At 420 and 500 mg/kg, the extractable K content of air‐dried and oven‐dried soils, respectively, equaled the extractable K content of field‐moist samples. Above these concentrations, drying decreased extractable K. Oven‐drying (60 C) affected extractable K more severely than did air‐drying the soils. Drying and grinding the 15‐ to 30‐cm depth samples significantly increased exchangeable K compared to field‐moist samples. Rehydration of oven‐dried soils to 40% water did not affect extractable K. H...

LIMESTONE QUALITY AND EFFECTIVENESS FOR NEUTRALIZING SOIL ACIDITY

Slow reactivity of coarse-grade ag-lime surface applied on soils established to perennial grasses led us to study the effectiveness of finer-ground limestone. Legume production and soil pH were used to evaluate treatments in a glasshouse experiment that included soil-incorporated and surface-applied limestone at increasing rates and effective calcium carbonate equivalence (ECCE) percentages that can be converted to kilograms of effective liming material (ELM) Mg−1. Excessive rates of limestone and the highest ECCE percentage materials decreased clover yield when applied and left on the soil surface. Comparison of ECCE 62% limestone with ECCE 100% limestone verified the initially greater efficiency of the finer lime for forage production. Four to seven years after application, annual ryegrass yields were similar for the ECCE 62% and 100% limestone materials. Seven years after the final limestone treatment, ECCE 100% limestone maintained soil pH 0.3 unit higher than pH due to the same rate of ECCE 62%. At this same time, pH of soil treated with 6.72 kg of ECCE 100% limestone was only 0.2 lower than pH in soil treated with double that rate of ECCE 62% limestone. Calculation of ELM, a term introduced to describe the weight of limestone Mg−1 that effectively neutralizes soil acidity, will enable consumers to realize the number of kilograms of effective lime in each ton, and to calculate the mass of limestone Mg−1 that will be relatively ineffective for neutralizing soil acidity. Ten times ECCE% equals ELM in kg Mg−1 as calculated in equation 1. Limestone with an ECCE of 62% has 620 kg of ELM Mg−1 and 380 kg of ineffective limestone Mg−1. Pounds of ELM per short ton of limestone also can be calculated using 2,000 lb per ton.

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. II. Correlation of Soil Extraction to Responses of Boron‐Fertilized Alfalfa

Abstract Pressurized hot water and DTPA‐Sorbitol are two relatively new, proposed alternative soil boron (B) extraction methods for which no data on yield or plant nutrient uptake have been reported for validation. Both methods initially have shown significant correlation with the hot water extraction method in untreated soils as well as soils incubated with various levels of B. The objective of the research was to extract samples of B‐treated soils by using all three extraction methods and correlate the B values obtained to yield, B tissue concentration, and total B removal of alfalfa (Medicago sativa). Greenhouse and field experiments on alkaline and limed acid soils naturally low in hot water‐extractable B were conducted to test alfalfa response to B fertilizer. In the greenhouse, highly significant relationships exist between plant uptake and extractable B with all three methods at varying levels of applied B, but no alfalfa yield response was observed. All three methods result in accurate predictions of plant B tissue concentrations and total B removal. The field experiment exhibited a significant positive relationship between total alfalfa yield and extractable B using hot water and pressurized hot water extractions. Extractable B using DTPA‐Sorbitol was not related to total alfalfa yield in the field experiment. This work, coupled with the earlier incubation studies, supports the pressurized hot water extraction method as an improvement over hot water in diverse soil types. The lack of relationship in the acid soil supports DTPA‐Sorbitol as an improvement over hot water in alkaline soils.

Mehlich 3 Extraction of Boron in Boron Treated Soils as Compared to Other Extractants

Abstract Hot water extraction (HW) is time‐consuming, highly variable, and losing popularity as the standard method for estimating plant‐available boron (B) in soil. Proposed alternatives are not widely used and guesstimation is replacing assessment at many soil test facilities. Mehlich 3 is increasingly promoted as a universal extractant, and diethylenetriaminepentaacetic acid (DTPA)–sorbitol and pressurized hot water (PHW) are effective and comparable to hot water extraction but also simpler and easier. Mehlich 3 B extraction has been compared mainly to hot water extraction. Because Mehlich 3 usage would be limited to neutral to acid soils, this study used a limed acid Darco loamy fine sand (loamy, siliceous, semiactive, thermic Grossarenic Paleudult) from eastern Texas to which 10 rates of B were applied followed by either incubation without plants or planting to alfalfa in greenhouse pots. Mehlich 3 extraction of soils obtained from a long‐term experiment on Darco soil from which alfalfa yield response has already been related to hot water, DTPA–sorbitol, and PHW is reported. The purpose was to determine the efficiency of Mehlich 3 B extraction compared to hot water, PHW, and DTPA–sorbitol in these B‐fertilized soils. Mehlich 3–extractable B significantly correlated with the rate of B application to incubation, greenhouse, and field soils and with B concentration and total B uptake in alfalfa in a greenhouse experiment. However, yield responses to B application were not observed in the greenhouse study. In the field where B response to B application was observed, Mehlich 3–extractable B did not correlate with alfalfa yield, whereas hot water and pressurized hot water did. In considering Mehlich 3 for B extraction, be aware that some older inductively coupled plasma (ICP) models may have significant drift when B is measured in Mehlich 3 extractant. In the current study, this problem was overcome with a new model instrument. Although effective in estimating B levels imposed on soils by fertilizer application, Mehlich 3 could not predict yield and thus cannot currently be recommended as a “universal” extractant to include B.

SOIL FERTILITY AND MANAGEMENT OF ACID COASTAL PLAIN SOILS FOR CROP PRODUCTION

Soil acidity and fertility management are critical for crop production on Coastal Plain soils of the southern and southeastern USA. Grasses and legumes are the primary crops grown on these soils. Hybrid bermudagrass (Cynodon dactylon (L.) Pers.) and bahiagrass (Paspalum notatum) are the major warm-season grasses while annual ryegrass (Lolium multiflorum Lam.) is the dominant cool-season grass. Bahiagrass tolerates acidity and low soil fertility. Bermudagrasses tolerate moderate soil acidity levels and readily respond to N, P, and K fertilization. Annual ryegrasses are highly responsive to limestone, N, and P. High rates of ammonium N applied for grass production rapidly increase acidity due to nitrification in these low-buffer-capacity soils. Liming these soils to increase pH improves P use efficiency and forage production. Fertilizer P increased soil test P 38% as soil pH was raised from 4.5 to 6.2 in a Lilbert loamy fine sand (thermic Arenic Plinthic Paleudult). Forage legume crops respond favorably to applied P, K, and B on limed Ultisols. Limestone applied to strongly acid soils increased alfalfa yields greater than 6.2 Mg ha−1. The critical 0- to 15-cm-depth, soil test P level is 20 mg kg−1 for alfalfa (Medicago sativa L.) using the pH 4.2 NH4OAc–EDTA extractant on limed Coastal Plain soils. Alfalfa response to applied B was 3.9 Mg ha−1 and was economical to 4.2 kg ha−1. Regression analysis predicted that raising the level of hot-water soluble B from 0.3 to 0.7 mg kg−1 in the 5- to 15-cm depth increased alfalfa dry matter yield 9 Mg ha−1. The level of hot-water soluble B in the 0- to 5-cm and in the 0- to 15-cm depths did not correlate with yield.

Nitrogen source effects on rabbiteye blueberry plant‐soil interactions

Abstract The acidity of alfisols and ultisols may be unfavorably increased for blueberry production by the use of specific nitrogen (N) fertilizers. Several ammonium containing fertilizers were evaluated for their effects on rabbiteye blueberries (Vaccinium ashei Reade). Rooted ‘Tifblue’ cuttings were grown in a 1: 1 peat: Lilbert loamy fine sand mix for 90 days. After establishment, plants were moved into the glasshouse and fertilized four times at 90‐day intervals with one of six N sources at one of four rates. Nitrogen sources were (NH4)2SO4 (AS), NH4NO3 (AN), urea, urea‐NH4NO3 (UAN), Nitro‐form (NF) and sulfur coated urea (SCU). Rates of N per application were equivalent to 0, 112, 224, or 336 kg/ha. The application of the high rate of each N source reduced plant growth. The 112 and 224 kg/ha N treatments increased growth compared to no nitrogen treatments. When comparing N sources, SCU treatments produced the greatest plant growth and AS treatments the lowest. Sulfur coated urea had less effect on so...

Limestone efficiency and boron effects on forage yield and soil properties

Limestones ranging from 49 to 100% effective calcium carbonate equivalence (ECCE) are applied to acid soils in the southern Coastal Plains states of the USA. Because of the slow reactivity of low ECCE limestone, we evaluated the effects of finer-ground limestone for surface application on soils producing perennial forages. Limestones with ECCE percentages of 62 and 100 were applied at rates of 0, 2.24 and 4.48 t ha-1 to a Darco loamy fine sand (loamy, siliceous, thermic Grossarenic Paleudult). Boron (B) was applied preplant each year at rates equivalent to 0, 1.12, and 2.24 kg ha-1 to study its effect on plant growth and interaction with limestone. Factorial treatments were arranged in a randomised, complete-block design. An experimental line (RD-3) of rose clover (Trifolium hirtum All.) was overseeded into ‘Coastal’ bermudagrass (Cynodon dactylon (L.) Pers.) sod each fall for 3 years. Limestone treatment generally increased clover dry matter yield 3.58t ha-1 over 3 years. Boron and the interaction of B with the finer limestone increased clover yields in 1989 and 1991. Finer limestone increased clover yields at all B rates in 1990. Limestone and B treatments did not affect yield of bermudagrass. Soil pH at 0’5 cm in the lime check plots was lowered from 6.0 in 1989, to 4.8 in 1990 by nitrogen (N) applied to the bermudagrass. During this time, soil pH at 0’5 cm was maintained at 6.2 by ECCE 100 limestone compared to a decline to 5.4 with ECCE 62 limestone. Soil B retention increased as soil pH was elevated. This study indicates that B becomes a crucial consideration when fine limestone is applied to Coastal Plains Ultisols for clover production.

Metabolic Responses Induced by Serial Harvesting of Alfalfa Pasture Established on Amended Acid Soil

Abstract Alfalfa pasture has not been sustainable on the coastal plain of the United States because of its intolerance to soil acidity. This study examined the responses of alfalfa metabolism to differential amendments of acid soil and to serial harvesting. The soil was spatially amended with different quantities of flue gas desulfurization sludge and gypsum after liming to pH 7. The serial harvests oscillated the RNA synthetic activity of glutamate dehydrogenase (GDH) from an oxidized to a reduced state irrespective of the soil amendments. The amplitudes of the redox cycles changed from one harvest to the next, thus demonstrating improved regrowth persistence. The chlorophyll, hexose, nucleotide, and protein contents, and the fructose‐1, 6‐bisphosphatase activity, decreased and fluctuated inconsistently in the successive cuttings. Consideration of the metabolic responses per harvest showed that the alfalfa had optimized saccharide metabolism in the first harvest, optimized RNA metabolism in the second harvest, optimized saccharide and RNA metabolism in the third harvest, and depressed saccharide metabolism in the fourth harvest, thereby optimizing the regrowth potential of the alfalfa pasture. Sustainability of the pasture was conferred by the coordinate compensatory regulation of metabolism in response to the synergistic interaction between the differential amendments and the nitrogen (N) nutrient excreted by the alfalfa into the soil.

Sustainable Alfalfa Production on Coastal Plain Soils of the United States

Abstract Alfalfa (Medicago sativa L.) is rarely grown on the Coastal Plain of southern United States. Production problems include infertile acid soils, inadequate pest control, and high humidity with frequent rainfall events that preclude adequate alfalfa hay drying conditions in spring. Research to overcome soil fertility problems included evaluation of nitrogen (N) rates over alfalfa row spacings and limestone and boron rates in split plot studies; phosphorus (P) rates using a randomized complete block design on eight soil series; and potassium (K), magnesium (Mg), and sulfur (S) rates and zinc (Zn), copper (Cu), and molybdenum (Mo) rates in central composite, rotatable design studies. Field‐scale demonstrations were conducted to verify data from small plot research. Results indicate little need for N fertilization of alfalfa on Coastal Plain soils except possibly under cool or dry surface soil conditions. Increasing the between‐row planting distance from 23 to 69 cm lowered alfalfa dry matter yield by 2.1 Mg ha−1 the seedling year. Alfalfa yielded 11 Mg ha−1 at all row spacings in the drought‐affected third year. Dry matter yield was maximized at 49–73 kg applied P ha−1 on soils testing below 19 mg P kg−1 by the NH4OAc‐EDTA extraction method. The alfalfa stand was lost after one season on plots not fertilized with K. Applied Mg, S, Zn, Mo, and Cu had no significant effect on alfalfa yield. Dry matter increased >5 Mg ha−1 as pH was increased from 6.0 to 7.5. Boron applied at 3.4 kg ha−1 increased alfalfa yields 3.9 Mg ha−1. With improved methods for site selection and adequate fertility, sustainable economic production of alfalfa is possible with rain‐fed conditions on selected, limed Coastal Plain soils.