Doctoral Dissertations

Date of Award

8-2002

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

Donald D. Tyler

Committee Members

Michael D. Mullen, Allan E. Houston, John D. Joslin, Donald G. Hodges

Abstract

It is not known if a short-rotation woody crop (SRWC), grown on an agricultural site, will affect subsequent row crops if the site is returned to agricultural production after harvest of the SRWC. In this study, a woody biomass crop was integrated with an annual row crop system in a row crop-woody crop-row crop rotation. The objectives were to: i) document the post-harvest effects of a woody crop rotation on soil C, N, and aggregate stability, ii) determine the woody crop's impact on future row crop production and N fertilization efficacy, and iii) measure changes in C and N fluxes due to the woody crop rotation. The study was in southwestem TN on a Memphis-Loring silt loam intergrade (Typic Hapludalfs - Oxyaquic Fragiudalfs). Soybean [Glycine max (L.) Merr.] was followed by four-year (SY4C) and five-year (SY5C) rotations of American sycamore (Platanus occidentalis L.), followed by no-till corn (Zea mays L.). Continuous row crops (soybean converted to corn) served as a control (SBC). Four rates of broadcast NH2NO3 were applied to corn (0, 73, 146, and 219 kg N ha-1).

Four- and five-year sycamore rotations significantly affected soil properties and post-sycamore corn grain production. During three years of com production immediately following sycamore harvest, increases in total soil C and N concentrations below a 2.5 cm depth were attributed to the sycamore rotation, specifically to sycamore roots. Soil inorganic N concentrations were higher in the SBC than the SY4C system at a depth of 0 to 2.5 cm. Soil aggregate stability, at depths from 2.5 to 15 cm, was greater in the SY4C than the SBC system. No mechanical problems were encountered when planting no-till corn over sycamore stumps. Significant increases in N were observed in decomposing sycamore roots and stumps. Microbial immobilization of soil inorganic N during decomposition of woody sycamore residues was suspected to have reduced the amount of N available to corn plants during the first two years following sycamore harvest. First and second-year com after sycamore harvest required a 50% higher rate of N fertilization to maximize yield than com in the SBC system.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS