Degree Type

Dissertation

Date of Award

1981

Degree Name

Doctor of Philosophy

Department

Agronomy

Abstract

A single field experiment was conducted in both 1979 and 1980 to study the effect of tillage and mulch treatments on the early growth of corn plants. The objectives of this research were: (1) to separate and measure the effects of tillage and mulch on early growth of corn, (2) to determine whether observed differences in corn growth represented a response to soil temperature or to other factors associated with the tillage and mulch treatments, and (3) to determine the influence of tillage and mulch on the concentration of nutrients in young corn plants;Two tillage treatments, conventional tillage (CT) and no-tillage (NT), were used in the study. Two ground cover treatments, bare soil and mulch consisting of residue from the previous crop, were superimposed on each tillage treatment. Four planting dates of 3-week intervals were also included to provide a range of soil temperatures;Soil temperature was monitored during the test period, using thermocouples and a multipoint recording system. An accumulated growing degree unit (AGDU) was calcuated from the soil temperature measurements from each plot. Plant emergence rate was recorded. Whole plant samples were collected at leaf stages 4 and 6 to measure plant height and dry weight and to provide plant material for chemical analysis. Plant population and dry matter and grain yields were measured at the end of the growing season;The AGDU values were found to be lower on mulched than on bare soils, but were not significantly influenced by the two tillage systems. These temperature related values appeared to be the dominant factor affecting rate of seedling emergence and early-season plant growth. Seedling emergence was slower on the mulched soil than on bare soil, but the differences were smaller for the later planting dates. Plant growth, as measured by plant height and dry weight, was significantly reduced by mulching at both sampling dates. These growth differences were smaller at the later planting dates. Consequently, the rate of plant development in both years of study seemed to be mainly influenced by the factors having the most control over soil temperature, ground cover and date of planting;The measured early-season growth differences apparently disappeared with time, since the plant population, dry matter yield, and grain yield at harvest time did not differ with any of the imposed treatments;Plant nutrient concentrations were affected by both tillage and ground cover. The concentration of K, Ca, Fe, Mn, and B tended to be lower in plants grown under NT compared to Ct. Manganese, B, Al, and Cu were generally less in plants from mulched as compared to bare soil. Boron was the only element which seemed to be influenced by planting date. The concentration of B was less under NT and mulching at the late planting dates but not at the early one. All of the measured elements were considered to be present in adequate amounts and none of the observed differences in concentration were related to plant growth.

DOI

https://doi.org/10.31274/rtd-180813-5450

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Neal Rueben Hageman

Language

en

Proquest ID

AAI8122519

File Format

application/pdf

File Size

101 pages

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