Carrie A. M. Laboski

Soil strength and water content influences on corn root distribution in a sandy soil

Initial field observations revealed a shallow corn (Zea mays L.) root system on a Zimmerman fine sand in a corn/soybean (Glycine max L.) rotation. Since root distribution influences crop water and nutrient absorption, it is essential to identify factors limiting root growth. The objective of this study was to determine the factor(s) limiting corn rooting depth on an irrigated fine sand soil. Bulk density, saturated hydraulic conductivity, and soil water retention were measured on undisturbed soil cores. Corn root distribution assessed at tasseling over a 3-yr period showed an average of 94% of total root length within the upper 0.60 m of soil with 85% in the upper 0.30 m of soil. Mechanical impedance was estimated with a cone penetrometer on two dates with differing water contents. Cone penetrometer measurements greater than 3 MPa indicated mechanical impedance in soil layers extending from 0.15 to 0.35 m deep. Penetration resistance decreased as soil water content increased. However, soil water contents greater than field capacity were required to decrease penetration resistance below the 3 MPa threshold. Such water saturated conditions only occurred for short periods immediately after precipitation or irrigation events, thus roots usually encountered restrictive soil strengths. The soil layer from 0.15 to 0.60 m had high bulk density, 1.57 Mg m-3. This compacted soil layer, with slower saturated hydraulic conductivities (121 to 138 mm hr-1), held more water than the soil above or below it and reduced water movement through the soil profile. Crop water use occurred to a depth of approximately 0.75 m. In conclusion, a compacted soil layer confined roots almost entirely to the top 0.60 m of soil because it had high soil strength and bulk density. The compacted layer, in turn, retained more water for crop use.

Investigation of the inorganic and organic phosphorus forms in animal manure.

The most viable way to beneficially use animal manure on most farms is land application. Over the past few decades, repeated manure application has shown adverse effects on environmental quality due to phosphorus (P) runoff with rainwater, leading to eutrophication of aquatic ecosystems. Improved understanding of manure P chemistry may reduce this risk. In this research, 42 manure samples from seven animal species (beef and dairy cattle, swine, chicken, turkey, dairy goat, horse, and sheep) were sequentially fractionated with water, NaHCO₃, NaOH, and HCl. Inorganic (P(i)), organic (P(o)), enzymatic hydrolyzable (P(e); monoester-, DNA-, and phytate-like P), and nonhydrolyzable P were measured in each fraction. Total dry ash P (P(t)) was measured in all manures. Total fractionated P (P(ft)) and total P(i) (P(it)) showed a strong linear relationship with P(t). However, the ratios between P(ft)/P(t) and P(it)/P(t) varied from 59 to 117% and from 28 to 96%, respectively. Water and NaHCO₃ extracted most of the P(i) in manure from ruminant+horse, whereas in nonruminant species a large fraction of manure P was extracted in the HCl fraction. Manure P(e) summed over all fractions (P(et)) accounted for 41 to 69% of total P(0) and 4 to 29% of P(t). The hydrolyzable pool in the majority of the manures was dominated by phytate- and DNA-like P in water, monoester- and DNA-like P in NaHCO₃, and monoester- and phytate-like P in NaOH and HCl fractions. In conclusion, if one assumes that the P(et) and P(it) from the fractionation can become bioavailable, then from 34 to 100% of P(t) in animal manure would be bioavailable. This suggests the need for frequent monitoring of manure P for better manure management practices.

Effect of Fertilizer Nitrogen on Weed Emergence and Growth

Abstract The timing of nitrogen (N) fertilizer application may influence germination, emergence, and competitiveness of weeds. Research was conducted to determine the influence of total inorganic soil N (Nit) on the germination, emergence, and growth of five weed species. In a greenhouse experiment, seed of five weed species were exposed to four levels of N, and seed germination was measured. In the field, urea ammonium nitrate (UAN 28%) was applied at multiple rates at three spring timings, and Nit, weed emergence, and growth were measured for 21 to 35 d after application (DAA). Germination of the four dicotyledonous and single grass species was not stimulated by 450 ppmw of N compared with the untreated control. In the field, Nit of 112 or 168 kg N ha−1, measured at 7 and 21 DAA, was always greater than Nit in the untreated control. The duration of the available N pulse in the upper 8 cm of soil was dependent on N application rate and timing. At 8 to 16 cm of soil depth, Nit was greater when 168 kg N ha−1 was applied compared with no N at 21 and 35 DAA in 2004. Emergence of common lambsquarters increased as N application rate increased for each application date in 2003, but not in 2004. Emergence of ladysthumb increased with N application rate for the April 15, 2003, date; emergence of giant foxtail increased with N application rate for the April 6, 2004, date. Weed biomass was always greater when 168 kg N ha−1 was applied compared with no N, and at four of six N application dates, when 112 kg N ha−1 was applied. This research shows that spring N fertilizer applications increase Nit and weed growth, but the influence of N on weed emergence is dependent on the weed species, seed source, and environmental conditions. Nomenclature: Common lambsquarters, Chenopodium album L. CHEAL; ladysthumb, Polygonum persicaria L. POLPE.

Influence of fertilizer management and soil fertility on tuber specific gravity: a review

Tuber specific gravity is a measure of potato internal quality and is used by the potato processing industry for assessing crop acceptability. Potato growers, therefore, have an interest in understanding how nutrient management practices influence specific gravity. This paper provides a review of research on fertilizer and soil fertility influences on specific gravity. Excessive application rates of nitrogen and potassium, along with excessive soil levels of either nutrient, may reduce tuber solids. Phosphorus applications may improve specific gravity when soil test phosphorus levels are low. Fertilizer materials with higher salt indices will decrease specific gravity more than fertilizer materials with lower salt indices.ResumenLa gravedad específica del tubérculo es un indicador de la calidad interna de la papa y es usado por la industria de procesamiento para evaluar la aceptabilidad del cultivo. Por lo tanto, los productores de papa tienen interes en comprender cómo es que las practicas de manejo influyen en la gravedad especifica. Este articulo proporciona una revision de la investigacion sobre la influencia que tienen el fertilizante y la fertilidad del suelo sobre la gravedad especifica. La aplicacion excesiva de nitrogeno y potasio junto con niveles excesivos en el suelo de cualquiera de los dos nutrientes puede reducir los solidos en el tuberculo. Las aplicaciones de fósforo pueden mejorar la gravedad específica cuando las pruebas de fósforo arrojan niveles bajos. Los fertilizantes con índices altos de sales reducirán la gravedad específica más que aquellos que tienen índices bajos de sales.

Impact of manure application on soil phosphorus sorption characteristics and subsequent water quality implications

For nutrient management purposes, it is important to understand the impact of manure application on soil phosphorus (P) sorption characteristics and what it means with regard to potential environmental problems. The objectives of this study were (i) to determine whether previous manure applications impact P sorption capacity and strength; (ii) to characterize the relationship between water soluble-P (WSP) and degree of P saturation (DPS); and (iii) to characterize the relationship between WSP and P sorption capacity and strength. Phosphorus sorption isotherms were constructed for seven pairs of soils with and without a history of manure application. Within a soil series, P sorption isotherms were compared to determine the effects of manure application. Manure application increased sorption capacity significantly in the Nicollet soil series. Phosphorus sorption capacity was unchanged by manure application in the Waukegan soil series. Manure application reduced P sorption capacity in the Port Byron, Sanburn, Verndale, Ves, and Barnes soils. Phosphorus sorption strength decreased in five of the seven soil series after manure application. The degree of P saturation and soil test P were strongly linearly correlated to WSP. Water soluble-P was less than 1 mg L−1 when DPS was less than 21.7%. When manure application increased DPS to more than 26%, sorption strength was reduced; P was bound less tightly to the soil on low strength sorption sites, such that P was more readily available. Sorption strength was used to determine the soil test P level above which there is increased risk to water quality because of reduced sorption strength and subsequent increases in WSP; this occurred when Bray-P was greater than 60 mg kg−1. Phosphorus sorption strength seems to be the sorption property that is most sensitive to applications of P.

FIELD PERFORMANCE OF A LOW-DISTURBANCE, ROLLING-TINE, DRIBBLE-BAR MANURE APPLICATOR

A need exists for tillage and manure management options that allow farm managers and consultants to address specific environmental risks and agronomic needs. A low-disturbance, rolling-tine aerator coupled with a dribble-bar manure slurry distribution system was evaluated for effects on crop residue cover, manure surface exposure, post-application manure nutrient uniformity, and concentration of total suspended solids in runoff from wheat stubble on a Capac sandy loam soil. The aeration process decreased soil bulk density and increased the initial water infiltration rate with little loss of crop residue cover. Aeration tillage increased surface roughness and created depressions at regular intervals in the tine path that accumulated manure slurry and reduced overland flow. The greatest soil phosphorus concentration was in the surface to 7.6-cm soil layer at the point of tillage tine entry, and little of the manure slurry moved below that depth within 48 h of application. The concentration of total suspended solids in the runoff increased as tillage intensity increased.

Manure composition and incorporation effects on phosphorus in runoff following corn biomass removal.

Greater demand for corn ( L.) stover for bioenergy use may lead to increased corn production acreage with minimal surface residue cover, resulting in greater risk for soil erosion and phosphorus (P) losses in runoff. A rainfall simulation study was conducted to determine the effects of spring-applied dairy cow () manure (none, in-barn composted, and exterior walled-enclosure pit) with >200 g kg organic solids content following fall corn biomass removal with and without incorporation (chisel plow [CP] and no-till [NT]) on sediment and P in runoff. Runoff was collected from a 0.83-m area for 60 min following the onset of rainfall simulation (76 mm h), once in spring and once in fall. Runoff dissolved reactive P (DRP) and dissolved organic P (DOP) concentrations were positively correlated with manure P rate and were higher in NT compared with CP. Conversely, sediment and particulate P (PP) concentrations in runoff were inversely correlated with manure P rate (and manure solids) and were higher in CP compared with NT. Runoff volume where no manure was applied was higher in NT than in CP in spring but similar in fall. The addition of manure reduced runoff volumes by an average of 82% in NT and 42% in CP over spring and fall. Results from this study indicate that surface application of dairy manure with relatively high solids content may reduce sediment and PP losses in runoff without increasing the risk of increased DRP and DOP losses in the year of application where corn biomass is harvested.

Manure-Induced Soil-Water Repellency

This laboratory study was conducted to evaluate the potential of nine manure samples from dairy (n = 7), beef (n = 1), and swine (n = 1) to cause water repellency (WR) in six soils; in addition, the duration of WR in two soils was assessed in an incubation study. Manures were applied to supply 40 mg phosphorus (P) kg−1 to each soil. Sand content in the soils ranged from 179 to 909 g kg−1. Water repellency was assessed with the water drop penetration time (WDPT) and the degree of repellency with the soil wetted area (SWA) methods. The potential for animal manure to induce WR measured with the WDPT method was dependent on the manure type and soil series. Swine manure did not increase the WDPT of any soil; beef manure increased WDPT in three of the six soils, whereas dairy manure had the greatest effect on WDPT. Results of the SWA method were similar to those with the WDPT; however, there were additional soil-water behavioral patterns identified by the SWA. For example, dairy manure 5 increased WDPT of a soil from 1 to 9 sec, whereas the SWA showed a decrease in the drop area from 120 mm2 in the control to 26 mm2 after manure addition. Incubating manure-treated soils for 1 and 2 weeks decreased the induced WR in the Antigo soil, but had little effect on the Rosholt. Field studies should be conducted to assess these phenomena under natural climatic conditions.

Field performance of a low-disturbance, rolling-tine manure slurry injector

There is a need for tillage and manure management options that allow farm managers and consultants to address specific environmental risks and agronomic needs. A low-disturbance, rolling-tine aerator coupled with a dribblebar manure slurry distribution system was evaluated for effects on crop residue cover, soil bulk density, manure surface exposure, manure nutrient placement and post-application uniformity, and concentration of total suspended solids in runoff from wheat stubble on a Capac sandy loam soil. The aeration process decreased dry bulk density and increased the initial water infiltration rate with little loss of crop residue cover. Aeration increased surface roughness and created depressions at regular intervals in the tine path that reduced overland flow and accumulated manure slurry. The greatest soil phosphorus concentration was in the surface-to-7.6 cm soil layer at the point of tillage tine entry, and little of the manure slurry moved below that depth within 24 h of application. Generally, the concentration of total suspended solids in the runoff increased with tillage intensity.

Evaluation of the Haney Soil Health Tool for corn nitrogen recommendations across eight Midwest states

Use and development of soil biological tests for estimating soil nitrogen (N) availability and subsequently corn (Zea mays L.) fertilizer N recommendations is garnering considerable interest. The objective of this research was to evaluate relationships between the Haney Soil Health Test (HSHT), also known as the Soil Health Tool or Haney test, and the economically optimum N rate (EONR) for corn grain yield at 17 sites in eight Midwest US states in 2016. Trials were conducted with a standard set of protocols that included a nonfertilized control plus six N rates applied at planting or as a split between planting and sidedress, soil samples for the HSHT prior to planting, and grain harvest at physiological maturity, and determination of EONR for each N application timing. Results indicated that HSHT recommendations with expected yield accounted for ≤28% of the variation in EONR among sites and N timings. Two components of the HSHT not directly used in the HSHT N recommendation for corn, the soil health calculation, or soil health score, and the Solvita carbon dioxide (CO2)-Burst lab test, accounted for the most variation in EONR. These two components were moderately related (R2 = 0.29 to 0.39) to soil organic matter (OM), highly related (R2 = 0.98) with each other, and subsequently both accounted for over one-half (R2 = 0.55) of the variation in EONR for N applied at planting or as a split. With additional research, these two components may help improve N recommendations for corn in the Midwest, especially Solvita CO2-Burst because it costs less to determine than the soil health calculation.