Date of Award

Spring 1998

Project Type

Dissertation

Program or Major

Plant Biology

Degree Name

Doctor of Philosophy

First Advisor

George O Estes

Abstract

Field, greenhouse and laboratory studies were conducted to investigate the effects of soil-incorporated organic wastes on nitrogen release patterns, groundwater nitrate-nitrogen levels, nutrient/metal uptake, and plant yield.

Three field studies with corn (Zea mays L.) were conducted during 1993 to 1997 at three locations in New Hampshire using a randomized complete block design with three or four replications, two or three waste materials as main plots, and various application rates as subplots. Compared to dairy manure, Concord biosolids showed a slower release rate measured as soil NO$\sb3$-N concentrations in early season but higher post-harvest levels of soil NO$\sb3$-N.

Groundwater NO$\sb3$-N levels often exceeded the public health standard below fields amended with organic wastes. Significant variability, particularly in N content, was observed with aerobically digested, compared to anaerobically digested biosolids.

Lime-stabilized biosolids supplied abundant Ca. Trace metal contributions to land from biosolids will be minimal; Cu and Zn were the dominant metals in the biosolids studied.

Yield response varied from year-to-year and site-to-site. Analysis of variance for yield at Site I showed a significant year-to-year difference but no significant between treatments difference. At Site II, corn yield was more responsive to treatments in 1994 than in 1993 or 1995. At Site III the agronomically optimum application rate of available N was 112 kg/ha for Hanover biosolids while that for Suncook biosolids was 84 kg/ha.

Two greenhouse experiments conducted from 1994 to 1996 evaluated the effects of soil temperature on N release from three organic wastes and its uptake by corn, and bioavailability of heavy metals across a range of soil pH's to three vegetable plants. The concentration of NO$\sb3$-N in soil amended with biosolids was about twice as high as that with manure, and six times as high as that with compost. Nitrogen uptake efficiency by corn increased with increasing soil temperature at the low and intermediate application rate of biosolids. All vegetable species--bean, lettuce and radish--showed poor growth at low soil pH ($<$5.3). Concentrations of Zn and Cu in the edible portion of plant tissue were slightly elevated with decreased soil pH.

In laboratory incubations which used soils amended with lime-stabilized biosolids or biosolids compost, clay content of soil exhibited a significant influence on NH$\sb4$-N production.

An advanced integrated monitoring systems (AIMS) was developed to track N transformations. The AIMS incorporated four components--PSNT samples derived from the root zone, soil pore moisture collected below the root zone, deep soil cores (120 cm) and groundwater samples. Results from the AIMS showed that (1) a seasonally-delayed, quantitatively-high bioavailability of N existed in biosolids-amended soils compared to manured soils, (2) acid-extractable levels of Zn and Cu in biosolids-amended soils were highest among the six metals studied, (3) high leachability of NO$\sb3$-N through the vadose zone to groundwater occurred post-harvest following preplant application of high rates of organic wastes, and (4) use of a 50% nitrogen mineralization rate (NMR) for aerobically digested biosolids, and 30% for anaerobically digested biosolids appears justified in order to minimize nitrogen pollution in groundwater. (Abstract shortened by UMI.).

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