The accuracy of soil and plant analytical results are occasionally called into question by laboratory clientele. Although laboratories generally conduct internal quality assurance procedures, there are few external performance testing programs for the industry. In 1994, a proficiency testing program was initiated for soil and plant samples for agricultural laboratories in the western United States to provide an external quality control for the lab industry. The program involves the quarterly exchange of soil and plant samples on which soil salinity, soil fertility, and plant nutrition analyses are conducted. One hundred laboratories are annually enrolled in the program from 24 states and Canadian provinces. Results of 3 years of the program indicate soil nitrate, soil pH, extractable potassium, soil and organic matter are reproducible within 10% between laboratories. Soil-extractable phosphorus (by five methods), soil-extractable boron, and soluble chloride were only reproducible within 15% to 20% between laboratories. Plant nitrogen and phosphorus results were consistent across samples, laboratories, and methods. Variability in plant nitrate increased with decreasing tissue concentrations. Overall accuracy and precision of reported results, based on the use of NIST certified reference botanical samples, were excellent for N, P, K, Ca, and Cu. Generally, for any given analysis, the results of ≈10% of the laboratories exceed two standard deviations from the mean. Overall, significant improvement was noted in the laboratory industry proficiency through the course of the program.
Robert O. Miller, Steven E. Newman and Janice Kotuby-Amacher
Mary Lamberts, Teresa Olczyk, Stephen K. O'Hair, Juan Carranza, Herbert H. Bryan, Edward Hanlon and George Hochmuth
A baseline survey was conducted to determine grower fertilizer management practices for five vegetable crops: beans, malanga, potatoes, sweet corn, and squash. This was done in conjunction with a 3-year replicated fertility trial with four vegetable crops (1993–94 through 1995–96) in the Homestead area. Questions included: fertilizer rates and timing, source(s) of fertilizer recommendations, soil and tissue testing, irrigation, changes in practices, summer cover crops, rock plowing, spacing, and type of fertilizer used. Survey results will be presented.
Mary Lamberts, Teresa Olczyk, Stephen K. O'Hair, Juan Carranza, Herbert H. Bryan, George Hochmuth and Edward Hanlon
Replicated fertility trials with four vegetable crops on the limestone soils of Dade County, Fla., have been conducted for 3 years (1993–94 through 1995–96). The purpose was 1) to determine crop nutrient requirements, 2) to calibrate a soil testing model, and 3) to develop additional information for plant sap quick tests. The crops included snap beans, Irish potatoes, sweet corn, and malanga (a.k.a. yautia or tannia, Xanthosoma sagittifolium Schott). Another two field demonstrations using reduced rates of phosphorus on tomatoes were conducted in 1995–96. The involvement of the local fertilizer industry in these trials and grower outreach efforts will be discussed.
Ricky D. Kemery and Michael N. Dana
Fir seedling transplant containers were used as an alternative to conventional plug containers (72 per tray) in a system to grow seedlings of native prairie perennials and install them on a highway site in central Indiana. Plants grown in deep-tube fir-seedling containers exhibited greater fresh and dry weights than conventional plug transplants with no root circling. Results from survival data indicate that plants grown in fir seedling containers offer better chances of success on highway sites with low soil fertility and poor soil structure. A chronology of installation methods, tools, and mechanization possibilities is presented.
Dorm G. Shilling, Joan A. Dusky, Mark A. Mossier and Thomas A. Bewick
Poor emergence of commercially grown lettuce has been observed when planted immediately after the removal of a celery crop. Greenhouse experiments were conducted to evaluate the possible allelopathic effects of celery residue on the emergence and growth of lettuce. The influence of amount and type of celery tissue, growth medium and fertility, incubation time in soil, and amendment of growth medium containing celery residue with activated charcoal was evaluated with respect to the allelopathic potential of celery. Celery root tissue was 1.8 and 1.6 times more toxic to lettuce seedling growth than was celery petiole or lamina tissue, respectively. Lettuce shoot growth was inhibited to a greater extent when grown in sand amended with celery residue rather than either amended vermiculite or potting soil. Incubation of celery root residue in soil for 4 weeks increased phytotoxicity at 1% (v/v) and decreased it at 4% (v/v). Increasing the fertility of pure sand with varying amounts of Hoagland's solution did not reverse the allelopathic effects of celery residue. The addition of activated carbon to the medium increased the growth of lettuce exposed to celery residues. Celery residues possess allelopathic potential to developing lettuce seedlings. Celery tissue type and concentration, soil type, incubation of celery root residue in soil, and addition of activated carbon to the growing medium influenced the magnitude of the observed phytotoxicity.
J.L. Walworth, D.E. Carling and G.J. Michaelson
3 Research Associate. 1 Assistant Professor of Soil Fertility/Horticulture. 2 Professor of Horticulture. The authors wish to acknowledge Peter Rissi for his technical assistance with these studies. The cost of publishing this paper was
Tina Gray Teague and Gail S. Lee
Soil fertility studies conducted in commercial vegetable fields to examine alternative uses of mid-south agricultural wastes as soil amendments included work with poultry litter, cotton gin trash, and rice hulls. Poultry litter applications ranging from 0.3 to 0.9 Mg·ha–1 resulted in significant increases in spinach, cabbage, turnip greens, and collard yields grown in soils damaged by precision leveling or in sandy soils with low organic matter; however, positive yield response to litter applied to undamaged soils was variable. Raw rice hulls applied at rates ranging from 2 to 44 Mg·ha–1 resulted in reduced cabbage yield. Trials with cotton gin trash and cover crops on yield of cabbage, broccoli, southern pea, snap bean, and cucumber indicate significant problems with weeds following use of raw gin trash. Composting alleviated most weed problems, but no yield response was apparent at composted gin trash rates ≤9.6 Mg·ha–1. High rates (60 Mg·ha–1) of composted gin trash on damaged soil significantly improved cabbage yield. There were increases in soil pH and Ca levels. Research was supported by a SAREIACE grant.
Laura K. Paine and Helen Harrison
Since the domestication of the first crop species, farmers have dealt with the problem of soil depletion and declining crop yields. Fallowing of land was the first approach to restoring soil fertility, and is still the most commonly used method among indigenous farmers. Alternatives to fallow, such as crop rotation and green manures, developed in a number of areas. The earliest record of their use is in Chinese writings from ca. 500 B.C. Discussion of these practices is found in European agricultural publications dating from the 16th century. While these ancient techniques have proven value for soil conservation, their use in modern agriculture is quite limited. Renewed interest within the agriculture community in recent decades has resulted in a greater research effort in the areas of green manures, cover crops, and living-mulch cropping systems.
Christopher Worden, George Elliott, Bernard Bible, Karl Guillard and Thomas Morris
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.
R. Terry Jones and David C. Ditsch
Tomato fertility trials (1992–94) showed no yield response to fertigation N rates between 101–393 kg·ha–1. In 1995, soil Cardy NO3-N readings taken just prior to fertigation showed 53 kg NO3-N/ha in the top 30 cm. Laboratory test on the same sample showed 72.4 kg/ha (NO3 + NH4-N). Forty percent of the available nitrogen was NH4-N, which is not detected by Cardy meters. Soil mineral N levels were measured at fourth injection, second harvest, and 9 days after last harvest. On these dates the 0 kg N/ha treatment had 28, 24, and 8 mg N/kg available in the top 15 cm of soil, similar to the N fertigation treatments. As the growing season progressed, soil mineral N levels decreased, and 9 days after the last harvest residual soil N levels were close to those seen initially. Tomato petiole sap Cardy NO3-N readingsshowed a significant difference between the 0 kg·ha–1 treatment and those (84, 168, and 252 kg·ha–1) receiving N (512 ppm vs. 915, 1028, and 955 ppm NO3-N, respectively). Treatments receiving fertigation N gave petiole sap NO3-N readings higher than those listed by Hochmuth as sufficient for tomatoes. While the data showed a clear separation between the three N treatments and 0 N rate, no significant difference in yield of US #1 or US #2 large fruit occurred. This suggests that adequate N fertility was provided from O.M. mineralization. The highest N rate also had significantly more US #1 small and cull tomatoes than the other treatments. Some Kentucky soils have adequate residual N capable of producing commercial fresh-market tomato crops with little or no additional N. In addition to potential ground water pollution, overfertilization of tomatoes may decrease fruit size and reduce fruit quality by causing NH4-K + ion competition, as well as increase the risk of certain fungal and bacterial diseases.