Search

The Solvita Soil Labile Amino-Nitrogen (SLAN) and Soil CO2-Burst (SSCB) tests are used in soil health assessments. Field experiments were conducted from 2014–2016 in Connecticut, USA to: (1) determ...

The Illinois soil nitrogen (N) test (ISNT) and the Solvita Labile Amino-Nitrogen (SLAN) test are chemical analyses that estimate the concentrations of soil labile N. The SLAN uses the same reagent as the ISNT but is a relatively new test with limited field data available. This study was conducted across 6 yr (2008–2013) to determine if concentrations of SLAN–N and ISNT–N are correlated in soils under predominantly Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] lawn turf and to compare the response of SLAN–N and ISNT–N concentrations in relation to varying organic fertilizer rates. Separate randomized complete block field experiments were established in Connecticut on the two species with varying rates of an organic fertilizer to create a wide range of labile soil N concentrations. Soil samples were collected in the spring of each year and analyzed for concentrations of ISNT–N and SLAN–N. For all years and each species, and for pooled years and species, SLAN–N concentrations were positively and significantly (P 0.80) at Year 6 of the study. Furthermore, SLAN–N and ISNT–N concentrations increased linearly (P < 0.05) in response to organic fertilizer rate, but the rate of change was greater for ISNT–N. The data suggest that the SLAN test is generally well correlated with the ISNT and may offer an easy and rapid soil analysis to guide N fertilization.

BACKGROUND: Demand for clinical laboratory services in our institution has increased by 7% each year in the past 5 years, while the amount budgeted for services has remained fixed. To address the issue, we conducted a pilot study to curb inappropriate demand by implementing a minimum retest interval (time-based restrictions on the ordering certain tests) and thus reduce costs. OBJECTIVE: Explore the impact (financial and work volume) of restricting overuse of laboratory tests that add to costs but provide no additional clinical value. DESIGN: Pilot study of means to reduce costs and workload. SETTING: Clinical laboratory that provides diagnostic support to a tertiary care center specializing in transplantation and oncology. METHODS: With the engagement of clinical colleagues, we selected 13 tests characterized by high volume, high cost, or a perception of overuse that adds no clinical value. The selection was also based on established lock-out frequencies identified in a literature review. Data was captured on test numbers before and after initiating computer-based lock-outs along with the reference laboratory cost of these tests for the first 6 months of 2016 and 2017. MAIN OUTCOME MEASURES: Alterations in testing patterns (mimimum retest intervals) and frequencies for tests. RESULTS: The number of tests ordered during the 6-month period in 2017 were reduced by an average of 6.6% versus the same period for 2016, saving 2.03 million Saudi Arabian Riyals (SAR). Given a 7% annual growth in the preceding 5 years, the volume was reduced by 13% in real terms. The percentage reduction in number of tests ranged from as little as 0.2% for PT to 70.3% for an enzyme immunoassay. Savings were 1.4 million SAR in hematology and 0.36 million SAR in microbiology over the 6-month period. CONCLUSION: Minimum retest intervals using computer-based rules are effective in supporting strategies to manage demand. LIMITATIONS: This approach may not be applicable to all laboratory tests; however, the success of this pilot study would encourage more widespread use of this approach. CONFLICT OF INTEREST: None.

Currently, there is no soil-based N test used to guide N fertilizer recommendations for turfgrass. This study was conducted across 3 yr in Connecticut to determine if frequent measurement of soil nitrate–N (No3–N) could be used to estimate color, density, clippings yield, clippings total N concentration, and clippings N uptake in Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns. randomized complete block field experiments were set out on the two species with nine N rates. Soil cores and clippings were collected at 2-wk intervals from May through october and analyzed for concentrations of No3–N and total N, respectively. Turfgrass color was measured with chlorophyll and normalized difference vegetative index meters, and shoot count density was measured after the last sampling. Significant (p < 0.001) Cate-Nelson, linear-plateau, and quadratic-plateau models were observed for all relative measures of turfgrass growth and quality as a function of soil No3–N concentrations. The critical soil No3–N concentrations for the three models that indicated the beginning of a plateau response or marked the Cate-Nelson change point between likely or unlikely response ranged from 3.7 and 18.0 mg kg-1 for Kentucky bluegrass and from 2.5 and 10.1 mg kg-1 for tall fescue. probability plots indicated a high likelihood of acceptable turfgrass responses at the lower range of the critical concentrations suggested by the Cate-Nelson model. These results suggest that frequent measurement of soil No3–N may help to guide N fertilization of Kentucky bluegrass and tall fescue when managed as lawns. Dep. of Plant Science and Landscape Architecture, Univ. of Connecticut, 1376 Storrs Road, Unit 4067, Storrs, CT 06269-4067. Received 5 Mar. 2013. *Corresponding author (karl.guillard@uconn.edu). Abbreviations: AEM, anion-exchange membrane; AIC, Akaike information criterion; C-N, Cate-Nelson; CL, critical level; CNUP, clippings total N uptake; CTN, clippings total N concentration; DMY, clippings dry matter yield; LRP, linear-response plateau; NDVI, normalized difference vegetative index; PSNT, pre-sidedress nitrate test; QRP, quadratic-response plateau. Published in Crop Sci. 54:366–382 (2014). doi: 10.2135/cropsci2013.03.0145 Freely available online through the author-supported open-access option. © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Published November 12, 2013

Plant growth and lead (Pb) uptake by seven willow varieties were investigated in pot and field experiments to assess the suitability of willows for phytoremediation of Pb at heavily contaminated sites such as skeet ranges. Differences in uptake and translocation of Pb in Salix were observed between pot and field experiments. In the pot experiment, willows grown in Pb-contaminated field soil for 6 months showed tolerance to very high soil Pb concentration (21,360 mg kg(-1)), and with the addition of EDTA were able to take up and translocate more than 1000 mg kg(-1) Pb into above-ground tissues. In the field experiment, all willow varieties showed tolerance to heterogeneously high soil Pb concentrations. Plants were also able to take up and translocate Pb into above-ground tissues. However, after 4.5 months, the lead concentration in the above-ground tissues of willows grown in soil amended with EDTA was less than 200 mg kg(-1). The results from the pot experiment suggest that Salix varieties have the potential to take up and translocate significant amounts of Pb into above-ground tissues using EDTA. However, to verify the phytoextraction abilities of Salix in the field, additional research is needed.

Th is study estimated changes in costs of manure handling, costs of the fertilizer replacement value of manure, and expected changes in net revenues associated with the implementation of manure nutrient management plans (NMPs) based on the agronomic critical concentration for P using a partial budget analysis. Th e net revenue from manure management practices traditionally used by farmers in a baseline year was compared with the expected net revenue from practices recommended in NMPs for four dairy farms over 4 or 5 yr in Connecticut. Yields were not measured across the 2862 fi eld-years. Compared with the baseline year, the average annual estimated change in net revenue associated with manure applications based on the NMPs was a negative $2,900 for one large farm and a positive $17,600 for the other large farm, while the net revenue change was a positive $200 and $1,400 for the two medium-sized farms. In years aft er the baseline the average annual estimated change in net revenue for manure management practices for the NMPs compared with the practices reported by farmers was a negative $2,200 for one large farm and a positive $19,300 for the other large farm; the net revenue change was a positive $2,500 and $1,300 for the medium-sized farms. Th e net revenue changes from the NMPs were determined largely by the existing soil test P and K values. Th e complexity of implementing the NMPs made it diffi cult to obtain the expected net revenue changes.

Biological control agents like Bacillus subtilis offer an alternative and supplement to synthetic pesticides. Antibiotic production by biocontrol strains of B. subtilis can play a major role in plant disease suppression. Our current understanding of B. subtilis antibiosis comes from culture media measurements of antibiotic production and in vitro suppression of pathogens. Quantifying the antibiotic metabolite chemistry of B. subtilis biofilms growing on root surfaces provides a more accurate understanding of in vivo antibiotic production. An analytical method based on solid-phase extraction (SPE) with high-performance liquid chromatography (HPLC) and mass spectroscopy (MS) has been developed to quantify antibiotics produced by B. subtilis growing on plant roots. Cucumber ( Cucumis sativus ) was grown in composted soil and potting media inoculated with B. subtilis strain QST 713 (AgraQuest, USA). Two important B. subtilis antibiotics, surfactin and iturin A, were extracted from root and rhizosphere soil using acidified organic solvents followed by cleaning and concentration using SPE. HPLC and HPLC-MS were used to measure surfactin and iturin A. Rhizosphere concentrations of both antibiotics increased with plant age. For plants grown in peat-based potting media, surfactin concentrations increased from 9 μg g −1 root fresh weight (RFW) at 15 d to 30 μg g −1 RFW at 43 d. Iturin concentrations were 7 μg g −1 RFW at 15 d and 180 μg g −1 RFW at 43 d. In an initial field trial in a composted fine sandy loam, we demonstrated rhizosphere production of surfactin and iturin under competition and predation by the myriad macro- and microfauna existing in a fertile high-organic soil, with mature B. subtilis -inoculated cucumber roots yielding 33 μg g −1 RFW surfactin and 630 μg g −1 RFW iturin at 78 d.

Successful precision agriculture requires an understanding of spatial variability of soil properties, crop growth, and their interactions. The objectives of this study were 1) to examine the spatial variability of soil properties, cotton lint yield, and fiber quality and 2) to evaluate the spatial variability within mapping units at a production‐field scale. This research was conducted on an irrigated 49‐ha cotton field in Texas from 1998 through 2000. Samples were collected from regular 1‐ha grids, triangular, and random points. Results indicated that soil properties had stronger spatial dependence than did cotton lint yields and fiber quality. Soil properties, except nitrate (NO3 −) nitrogen (N) and Olsen phosphorus (P), were strongly spatially dependent, whereas lint yield was moderately to strongly spatially dependent. Fiber quality was moderately spatially dependent. Spatial appearance of higher yield in drier years was associated with the distribution of soil properties favoring cotton grow...

Discussions of N fertilizer needs for corn (Zea mays L.) usually are based on the assumption that economic optimum rates (EORs) of N provide the best benchmark to indicate the rates most likely to maximize profits for producers. We describe methods for calculating some additional benchmarks and illustrate how efforts to improve N management could be advanced by recognizing several alternative benchmarks simultaneously. We analyzed data from 54 small-plot trials with a new procedure that disaggregates problems associated with systematic model bias and variability in crop yield responses to fertilizer N. We compared the commonly used method for calculating EORs to a method that is described as discrete marginal analysis at near-optimal rates of N fertilization. We described methods for calculating the incremental break-even rate, the incremental rate that gives no crop response, and the incremental rate of N that gives the desired level of profit. Discussions of the relative merits of each benchmark suggest that problems associated with calculating and using the concept of EORs can be avoided by presenting the alternative benchmarks as proposed in this paper.

Efforts to calculate economic optimum rates (EORs) of N fertilization for corn (Zea mays L.) have been hampered by a lack of methods for disaggregating problems caused by model bias and variability in crop responses to N. We illustrate how the concepts of ex post and ex ante analyses can be used in a multistep procedure to disaggregate these problems when calculating ex post EORs when large amounts of data are available. Five models were used to describe yield responses from a collection of 54 small-plot trials that included seven rates of N. The multistep procedure included steps to reduce model bias and steps to reduce unexplained variability by forming categories based on information available at the time of fertilization. The concepts of ex post and ex ante analyses were used to clarify what information is important at each stage of the procedure and to ensure that information generated in early steps is used effectively in later steps. Analyses illustrate that calculated values for EORs should be expected to vary with the amounts of information available and that the new procedure can be described as a systematic search for the best EOR that can be calculated with existing information. Although this procedure may have little practical use when data are collected in traditional small-plot trials, illustration of this method by using data collected in such trials revealed the problems of model bias and variability in yield response as well as the potential for solving these problems in production systems where advances in technology make it practical to collect unprecedented amounts of data.

The consensus of soil fertility specialists working in the northeast USA was that soil testing and recommendation systems for P needed to be reexamined because of recent changes in soil testing methodology in the laboratory and corn (Zea mays L.) production technology in the field. Soil tests (M-COL, MM-COL, B-ICP, M1-ICP, and M3-ICP) were performed by either colorimetry or inductively coupled plasma (ICP) emission spectroscopy on samples from soil test calibration studies conducted during 1998 to 1999 at 51 experimental sites chosen to represent a range of soils, including Ultisols, Spodosols, and Alfisols, in northeastern states (Connecticut, Delaware, Massachusetts, Maryland, Maine, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and West Virginia). The mean P measured by M-COL, MM-COL, B-ICP, Ml-ICP, and M3-ICP was 8.3, 6.6, 148, 66, and 121 mg P kg -1 , respectively. Production practices followed local state extension recommendations at each site and included P fertilizer treatments: none, 15 kg P ha -1 banded, or 60 kg P ha -1 broadcast. Combined analysis of variance over sites showed that plant height at 35 d after planting, silk emergence, grain yield, and grain dry down were enhanced by the broadcast P treatment. There were yield increases (P < 0.10) to the band treatment at only four sites and to the broadcast treatment at nine sites. Cate-Nelson statistical analysis of relative yield in relation to soil test P failed to identify soil test P critical levels for any of the soil test methods. The percentage of experimental sites that had soil test P levels below the currently used critical levels in the region ranged from 14 to 65% of the sites. Results showed that 17 to 47% of those sites testing below the critical level exhibited a yield increase (P < 0.10) to broadcast P. Some of the yield responsive sites had soil test P above currently used critical levels. The calibration data obtained from the present study and the relationships examined between soil test P and relative yield do not necessarily validate the currently used soil test P critical levels nor does the data enable much refinement. This study shows that the current critical levels frequently permit both types of errors in soil test prediction; indicating a need for P fertilization when it may not be needed and not indicating a need for P fertilization when it may be needed. The second type of error is usually avoided by recommendations for crop removal rates of P.

The pre-sidedress soil nitrate test (PSNT) was evaluated in 27 fields in New Jersey, 6 in Connecticut, 5 in Delaware, and 2 on Long Island in New York for its ability to predict whether sidedress N is needed to grow fall cabbage (Brassica oleracea var. capitata) as a double crop. Soil NO3-N concentrations measured on 20 field sites on the day of transplanting and 14 days after transplanting indicated that NO3-N concentrations over this time period increased, and that residues from the previous crop were not causing immobilization of soil mineral N. The relationship between soil NO3-N concentration measured 14 days after transplanting and relative yield of marketable cabbage heads was examined using Cate-Nelson analysis to define the PSNT critical level. Soil NO3-N concentrations ≥24 mg·kg-1 were associated with relative yields >92%. The success rate for the PSNT critical concentration was 84% for predicting whether sidedress N was needed. Soil NO3-N concentrations below the PSNT critical level are useful for inversely adjusting sidedress N fertilizer recommendations. The PSNT can reliably determine whether fall cabbage needs sidedress N fertilizer and the practice of soil NO3-N testing may be extendable to other cole crops with similar N requirements.

This paper demonstrates the use of a feed-forward neural network model to quantify the partitioning of phosphate onto water treatment residual (WTR) as a function of pH. Reasonably good results were obtained with a limited amount of experimental data. The neural network models were essentially as good as the specific mechanistic model used. Comparison of the neural network models with simple models obtained from statistical regression shows the neural network models to be superior. Quantification of the distribution of phosphate in this system may allow accurate prediction of available phosphate in a land application scenario. In surface complexation studies where mechanistic models are not available, it is recommended that neural network models be used.

Trapping results indicate that pepper maggot, Zonosemata electa (Say), flies occupy tree canopies adjacent to fields when not on host plants. Several in- and near-field trap positions were used to find a reliable monitoring system for adult pepper maggots. Traps baited with liquid ammonium hydroxide (Stills-style trap), hung in the canopy of trees on the edges of pepper fields, caught significantly more Z. electa flies than when positioned lower along the treeline or in the field. In a second experiment, significantly more pepper maggot flies were captured in sugar maples compared with choke cherry trees, which indicates a pest preference for certain nonhost habitats. The lowest trap height tested (2.1 m) failed to capture Z. electa flies in either tree species when the pest population level was low. These studies demonstrated that pepper maggot flies can be reliably detected with Stills-style traps positioned at approximately 6.4 m height within the canopy of sugar maple trees adjacent to pepper fields. Fruit oviposition scars also are useful site-specific indicators of pepper maggot presence/absence and may aid in determining if insecticide applications are necessary and in timing sprays.

The objective of this laboratory study was to measure the effect of dewatered water treatment residual (WTR) on extractable P and Al in soils with above-optimum P concentrations. A secondary objective was to document the variability of the metal content of WTR during 1 yr. Two soils, a Paxton fine sandy loam (coarse-loamy, mixed, active, mesic Oxyaquic Dystrudept) and an Enfield silt loam (coarse silty over sandy or sandy-skeletal, mixed, active, mesic Typic Dystrudept) with above-optimum Mehlich 3 P concentrations (833 mg kg -1 and 630 mg kg -1 , respectively) were amended with four dewatered WTRs. The WTRs were dewatered using three treatments: (i) WTR dewatered at 40°C in a forced-air oven (DRY), (ii) WTR dewatered by freezing at -4°C and then dried at 40°C in a forced-air oven (FROZEN), and (iii) WTR dewatered to 4.5% solids at 40°C in a forced-air oven (RAW). The WTRs were added to the soils at rates of 20 or 60 g kg -1 and incubated for 21 d. The WTRs in the RAW treatment significantly reduced Mehlich 3 P concentrations compared with the DRY and FROZEN treatments. The RAW treatment reduced soil P concentrations an average of 64% compared with a reduction of 28% for the DRY treatment and 23% for the FROZEN treatment. The results suggest that the method used to dewater WTR will alter its ability to decrease Mehlich 3 P soil concentrations. The secondary objective involved collection of two of the WTRs every 3 wk for 1 yr and subsequent analysis for metal concentrations. The metal concentrations changed little during the year and only Cu, due to its use as an algicide, was elevated.

There is little published data to support current recommended plant populations of 11,500 to 17,500 plants/acre (28,600 to 34,600 plants/ha) for fresh market sweet corn (Zea mays L.) in the northeastern United States. The plant population likely affects marketable yield and recovery of nitrate. Residual soil nitrate is of concern because of the potential for nitrate contamination of water supplies. Our objectives were to determine the effect of plant population on the yield of sweet corn grown for fresh market without irrigation and on the amount of nitrate in the surface 1 ft (30 cm) of soil at harvest. Seven main-season sweet corn varieties were planted in a total of eight experiments in 1995, 1996, and 1997. Seven experiments were in Connecticut and one was in New Hampshire. All but one of the varieties were standard (su) or sugary enhanced (se) varieties. The experimental design was a randomized complete block with four replications, and the treatments consisted of 12,000, 16,000, 20,000, 24,000, and 28,000 plants/acre (29,600, 39,500, 49,400, 59,300, and 69,200 plants/ha). The yield of marketable ears was classified based on the length of the ears. The results suggest that the current recommendations for plant population in the Northeast US may be too low. Populations of 20,000 and 24,000 plants/acre produced consistently greater yields of ears greater than 7.0 inches (178 mm) long. Soil nitrate-N concentrations at harvest were about 8 mg·kg-1 lower with 16,000 plants/acre or greater, compared with 12,000 plants/acre, which suggests that populations of 16,000/acre or greater should decrease the potential for nitrate contamination of water supplies in the fall, winter, and early spring.

The pre-sidedress soil nitrate test (PSNT) is recommended in many states as a best management practice (BMP) for corn (Zea mays L.). A 2-yr study was conducted in Connecticut on a Woodbridge fine sandy loam soil (coarse loamy, mixed, mesic Aquic Dystrochrept) to determine NO 3 -N concentrations and losses in soil water from corn managed with three different N fertilization regimes: (i) PRE, 196 kg N ha -1 applied preplant; (ii) PSNT-1, 90 kg N ha -1 applied at preplant and any remaining N needs estimated by the PSNT (0 kg ha -1 in 1995 and 45 kg ha -1 in 1996); and (iii) PSNT-2, no preplant N and all N needs estimated by the PSNT (34 kg ha -1 in 1995 and 123 kg ha -1 in 1996). Percolate was collected with zero-tension pan lysimeters. Flow-weighted NO 3 -N concentrations from the PRE treatment were 22.3 mg L -1 in 1995 and 17.4 mg L -1 in 1996; the PSNT treatments were 0.05) different among N treatments. These findings suggest that a well calibrated soil N test can reduce excess fertilization and the potential for NO 3 contamination of groundwater.

The concentration of nitrate in the lower portion of corn stalks 1 to 3 wk after physiological maturity is a reliable tissue test for detecting optimal or above-optimal supplies of available N for corn (Zea mays L.) grown for grain. This test, the end-of-season corn stalk test, has not been evaluated for silage corn. The test would be especially valuable for silage corn because this crop is frequently grown on manured fields where assessing the N status is difficult due to unquantified rates of N application and variable mineralization of organic N. This study reports nitrate concentrations in lower corn stalks shortly before harvest of silage and evaluates their use as an end-of-season corn stalk test for silage corn. Also explored is the possibility of collecting corn stalks up to 24 h after a field is harvested. Lower corn stalk samples were collected from a total of 19 N-response trials on corn fields with a history of manure applications in Connecticut in 1994 and 1995. In 1996, corn stalk samples were collected at harvest and 24 h after harvest from 20 farmers' fields. Three commonly used methods for defining a critical nitrate concentration, the quadratic-plateau model, the linear-plateau model, and the Cate-Nelson method were used to describe the relationship between relative yield and stalk nitrate concentrations. Three different critical concentrations were calculated by the three methods, which suggests that an optimal range of 500 to 1000 ppm nitrate N is appropriate for this test. There was no significant change in the nitrate concentration of stalk samples collected at harvest and 24 h after harvest. These results suggest that the end-of-season corn stalk test can be used as a convenient method to define excess N availability and to improve N fertilizer recommendations for silage corn fields.

Lead tolerance and accumulation in five willow clones were investigated using a nutrient film technique. Plants were exposed to 0, 48, 121, 169, or 241 microM Pb for 14 days. Tolerance indices (TI) and critical toxicity thresholds (EC50) were determined for five willow clones. SX61 had the highest TI values (92%) in the 48 and 121 microM Pb treatments, as well as the highest EC50 threshold values (70.5 microM for roots, 155.9 microM for aboveground tissue), indications of a high degree of tolerance to Pb. This clone also developed the highest biomass of all the clones tested. We found significant variation in willows' lead accumulation. The highest Pb content in roots (24 mg plant(-1)) and aboveground tissue (7.6 mg plant(-1)) was recorded in the 48 microM Pb treatment in SX61. Based on high biomass, TI, ECso, and Pb content in plant tissues, SX61 holds promise for phytoextraction of lead.

Alfalfa (Medicago sativa L.) contributes substantial N to grain crops that follow, but there is uncertainty concerning the amounts. The objective of this study was to determine optimal rates of N fertilization for first-year corn (Zea mays L.) grown after alfalfa. Fertilizer N was applied at seven rates, ranging from 0 to 200 Ib/acre, at 29 trials conducted over 4 yr in northeast Iowa. Concentrations of soil nitrate in late spring and concentration of nitrate in cornstalks at the end of the season were used to help determine optimal N rates. Fertilizer significantly increased yields at six of the 29 trials. The rate of N fertilization most profitable when applied across the 29 fields was mainly determined by cost of fertilization and value of grain. At prices prevailing in the Corn Belt, applications of 0 and 25 Ib N/acre were the most profitable [...]

High nitrate (NO 3 -N) concentrations in Iowa rivers have been linked to areas of intensive row crop production, but they have not been experimentally linked to specific management practices used during row crop production. This study demonstrates how the late-spring test for soil NO 3 -N and the end-of-season test for cornstalk NO 3 -N can be used to measure N sufficiency levels across many fields and how the results can be used to evaluate management practices within a watershed. More than 3200 soil and cornstalk samples were collected over a 12-yr period from fields planted to corn (Zea mays L.) and already fertilized by farmers using their normal practices. Results showed that early-season rainfall and associated N losses were major factors affecting N concentrations in soils and cornstalks. Evidence for NO 3 -N movement from fields to rivers was provided by an inverse relationship between annual means for NO 3 -N concentrations in soils and rivers. Because these losses can be avoided by delaying N applications, the practice of applying N several weeks or months before plants grow was linked to inefficient use of fertilizer and manure N by crops. Results of the study demonstrate how aggregate analyses of soil and cornstalk samples collected across many farms and years make it possible to identify the major factors affecting N management outcomes and, therefore, N management practices that are likely to produce the best outcomes within a watershed or region. This approach seems to have unique potential to interrelate the management practices of farmers, the efficiency of N fertilization, and NO 3 -N concentrations in rivers.

The ability to increase pools of soil organic C (SOC) in agricultural ecosystems is of interest both for sequestering atmospheric CO 2 , and for restoring organic matter pools important to soil health. It has been well established that tillage and harvest management regimes can influence SOC in cropland, but long-term, continuous experiments are rare. We investigated the dynamics of relic and new SOC pools using δ 13 C analysis in cornfields (Zea mays L.) established in 1972 at the University of Connecticut Research Farm. The plots have been under no-till (NT) or conventional till (CT) management, with residues returned (+) or residues removed (-) within each tillage treatment. After 28 yr of continuous management, NT increased SOC significantly by 48.3 ± 9.9 g C m -2 yr -1 over CT in treatments with residue returned (i.e., NT+ compared with CT+), and by 60.1 ± 13.8 g C m -2 yr -1 over CT in treatments with residue removed (i.e., NT- compared with CT-). Residue return in NT+ plots did not increase SOC relative to NT- plots (23.0 ± 12.7 g C m -2 yr -1 , N.S.), but residue return to the CT+ plots resulted in a significant increase in SOC of 34.8 ± 11.1 g C m -2 yr -1 over SOC content in CT- plots. The greatest difference in SOC content was found between the CT-and NT+ treatments (83.1 ± 10.7 g C m -2 yr -1 ). Our results indicate that there may be a rapid cycling of the aboveground C4-C back to the atmosphere as CO 2 or lost as dissolved organic C from the soil profile. Such a rapid cycling of returned C4-C suggests that the annual return of aboveground biomass may not increase soil C storage over the long term once soils have reached a steady-state SOC level.

A composting facility in New Milford, Conn. (NMF), utilizes food-processing residuals, including spent tea leaves, coffee grounds, cocoa shell and cleanings, wastewater treatment sludge from a food ingredients manufacturing plant, and past-expiration processed vegetable products. Materials are composted in aerated, frequently turned windrows under cover. The range of inputs, combined with time constraints on the composting process, has resulted in a variable, immature compost product with a high rate of microbial activity. Users have expressed concern about potential phytotoxicity or nutrient immobilization from using NMF compost. Therefore, research was conducted to determine the influence of cured and uncured NMF compost amendments on potentially sensitive crops with high nutrient requirements. Arugula (Eruca vesicaria) and green bibb lettuce (Lactuca sativa) were grown on two Connecticut organic farm research sites in 1998 and 1999. Both sites have soils classified as coarse loamy over sandy or sandy-skeletal, mixed, mesic, typic, Dystraudepts. Farms differed in the length of time under organic farm management. One farm has been an organic farm since 1988 and consequently has high soil fertility, while the other was a first-year organic farm in 1998, and had relatively low soil fertility. Three amendment types were applied: cured compost, uncured compost, and organic fertilizer (5N-3P2O5-4K2O). Amendment application rates were estimated to provide a comparable range of plant-available nutrients for the amendments and a control without fertilizer. Compost application rates were 3.4, 6.8, 20.2, 35.8, and 71.7 Mg·ha-1 (dry-weight basis) in 1998 and 11.2, 22.4, 44.8, and 89.6 Mg·ha-1 (dry-weight basis) in 1999. Organic fertilizer application rates were 1.34, 2.68, 5.36, 10.72, and 21.44 Mg·ha-1 in 1998 and 1.34, 2.68, 5.38, and 10.72 Mg·ha-1 in 1999. Soil organic matter and nutrients increased with amendment application rate at both locations. Crop yields increased with amendment rate at the new, lower-fertility farm, but yields did not respond to amendments at the older, higher-fertility farm. Yield differences were minor between the uncured and cured compost treatments at both locations. This indicates that either cured or uncured NMF food-processing residual compost can be successfully used as an organic soil amendment for salad green production.