James R. Brown

SOIL PHOSPHORUS DISTRIBUTION AND CONCENTRATION FROM REPEATED STARTER PHOSPHORUS BAND APPLICATION

Soil sampling to determine soil phosphorus (P) availability is complicated by the presence of residual P bands that have not been disturbed by tillage. This study investigated the soil P distribution and longevity of P bands applied in no-tillage culture on a Mollic Endoaqualf soil (fine, montmorillonitic, mesic). Starter band P treatments of 0, 5, 10, and 20 kg P ha−1 were applied to corn (Zea mays L.) in a no-till corn-soybean [Glycine max. (L.) Merr.] rotation from 1990 through 1996. Treatments were rerandomized with each application, such that differing starter band histories were established, which served as treatments for soil and plant sampling. In 1996 the 10 and 20 kg P ha−1 bands were marked with monofilament line in the soil during the application process. In April 1997, contiguous 2.0 cm wide, 15 cm deep soil cores (30 per row) were taken across the 1996 corn rows. Soil core Bray-1 P concentrations that were 52 to 54 mg kg−1 greater than adjacent cores clearly indicated the presence of one and presumed three year old residual bands of 20 kg P ha−1 treatments. Cross-sectional soil samples of these bands (1.61 cm2 samples) had P concentrations that were 35 times that of non-band affected soil, and band widths were 8 to 10 cm. When sampled by 2.0 cm diameter cores these bands were evident in only two adjoining core samples. Older greatly decayed bands were also evident by core P concentrations that were 2 to 7 mg kg−1 greater than adjacent cores. Cross-section samples showed the bands had P concentrations that were 2 to 3 times greater than non-band affected soil. These bands were presumed to be five and seven years old. Based on the standard deviation of the 30 core sets of samples, an impractical number of samples would be required for random sampling to achieve a precision level better than 4 mg P kg−1. Pooling all the soil across a row (a slice sample) reduced variability enough to achieve 2 mg kg−1 precision with 95% confidence with no more than 9 slices per composite sample, and P concentrations would be increased 2 to 2.9 mg kg−1 relative to soil without bands. In 1997 oat (Avena sativa L.) growing directly over 10 kg ha−1 bands and non-band affected soil had similar whole plant P contents at Feekes growth stage 10. Yet the oat had incrementally greater plant P contents in response to 1997 broadcast P amounts of 0, 15, 30, and 44 kg ha−1. Soil sampling strategies that variably weight band-affected soil relative to soil outside the band only slightly influence soil P recommendations. The choice of a sampling strategy should be based on the need for accuracy and the bias desired (inclusion or exclusion of bands). Despite the ability to measure residual soil band P to various levels of precision with sampling strategies that variably weight band affected soil in the sample, soil extractable P from bands may not well represent P actually available to plants.

Tolerance of forage legumes to lime-stabilized sludge

Abstract Lime‐stabilized sludge (LSS) from dairy processing waste‐water treatment plants is a desirable product for land application. The material contains lime, which neutralizes soil acidity, and P, which is useful as a plant nutrient. The fineness of the lime and the solubility of P make LSS especially desirable in establishing forage legumes. This greenhouse study had two objectives: to determine a reasonable quantity of LSS for establishing forage legumes such as alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) and to prevent adverse effects on seedlings. Sludge was applied at 0, 2.5, 5.0, 7.5 g kg‐1 to an acid, low P soil in pots, and alfalfa and red clover seeds were sown. All treatments received 123 μg g‐1 potassium as KCl. A completely randomized design with four replications was used. Each species was handled as a separate study. Dry matter production was measured at one‐tenth bloom stage. Plant samples were analyzed for P, K, Ca, and Mg content. Soil samples taken at the end ...

Effects of sulfur application on yield and composition of soybeans and soil sulfur 1

Abstract Soybeans (Wayne cultivar) were grown on Mexico silt loam at four soil applied S levels over 4 years. The innate sulfur level of this soil appeared to be adequate for optimum grain yield. The additional sulfur had no effect on grain yield, oil concentration, essential amino acids and sulfur concentration in the seed. Sulfur extraction from profile cores after the study indicated movement of sulfur from the Ap into the upper B horizon over the course of the study. The soil sulfur test was improved when pHs was included in an expression for the Ap horizon.

Lime stabilized sludge treatment of acid soils relative to soil acidity minimums for sludge application

Abstract Lime stabilized sludge (LSS) from wastewater treatment plants contains lime, which may neutralize soil acidity, and P, an essential plant nutrient. Guidelines for use of land application of secondary sludges call for the soil pH to be at 6.5 or above prior to application. This greenhouse study was initiated to determine the effects of placement of LSS from two sources on soil and plant parameters of three test species grown on two soils each limed and unlimed. Test crops were radish (Raphanus sativus L), tall fescue (Festuca arundinacea Shred), and red clover (Trifollum pratense L.). An objective was to determine the need for a pH ≥ 6.5 prior to application of LSS. Aliquots of two acid soils were limed and left unlimed. The soils were potted after receiving the equivalent of 57,000 kg ha‐1 of either dairy or municipal LSS placed in the 2,500 g of potted soil. One crop of radish and two cuttings of the forages were taken. Placement did not affect dry matter yields but the municipal sludge treated ...

Soil nitrate measurements for prediction of n response by corn in a udollic ochraqualf

Abstract A three year continuous corn experiment was conducted to evaluate the use of soil nitrate nitrogen determination as a means of modifying nitrogen recommendations for corn. Three rates of nitrogen (84, 168, 252 kg/ha) were used. Nitrate nitrogen contents of the soil profile to 60 cm depth were determined several times over the three year period. The rainfall distribution and crop demand for N appeared to have the greatest effect on soil nitrate levels at any given sampling. Quantity of nitrate nitrogen in the soil profile near planting of corn had no significant effect on corn grain yields. The analyses of samples showed seasonal and treatment changes. There were some significant carryover effects on corn yields but these effects were not measurable using only soil nitrate analysis. Coefficients of variation for the nitrate measurements went as high as 100% and were not due to laboratory procedures. The sample variability, difficulty of sampling and lack of relationship of results to corn yields m...

The influence op soil treatments on elemental composition of corn and on zinc soil tests on two Missouri soils 1

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.

Micronutrient topdressing of alfalfa (medicago sativa L.) on a udollic albaqualf 1

Abstract An established stand of alfalfa (Medicago sativa L.) was topdressed with two rates each of borax, zinc sulfate, and copper sulfate at two levels of applied P and K. Yields and plant composition were determined at five harvests over two seasons. Treatments were not effective in increasing yields but topdressing with B and Zn increased the concentration of these elements in the plant tissue. The Cu concentration in alfalfa tissue was not affected by topdressing with copper sulfate. Phosphorus application rates of about four times removal rates were needed to maintain the Bray 2 soil test level of the soil.