Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Reddy, K. Raja

Committee Member

Macoon, Bisoondat

Committee Member

Phillips, J. Mike

Committee Member

Shankle, Mark W.

Committee Member

Arancibia, Ramon A.

Date of Degree

5-17-2014

Document Type

Dissertation - Open Access

Major

Agronomy

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Temperature and soil moisture (SM) are the two main environmental factors affecting sweetpotato growth and yield. Quantitative functional algorithms of plant growth and developmental processes under a wide range of above factors are needed for developing tools for modeling. Four experiments were conducted to quantify early and late season SM and temperature effects on sweetpotato growth, development, and physiology. In experiment I, effects of five SM levels were evaluated in a greenhouse using cultivars, Beauregard and Evangeline. Experiment II was conducted to evaluate late-season SM effects with four evapotranspiration (ET) based irrigation. In experiment III, five temperatures were imposed at early season (0-59 days after transplanting (DAT)). Late season temperature effects were evaluated with four day/night temperatures from 17 to 91 DAT, in experiment IV. Experiments II, III, and IV were conducted in soil plant atmosphere research facility using Beauregard. Growth, developmental, and physiological parameters were measured. Rate of storage root (SR) development of both cultivars showed a quadratic decline with decreasing SM. Soil moisture optima for SR initiation were 0.168 and 0.199 m3 m-3, equivalent to 63 and 75% field capacity (FC), for cultivars Beauregard and Evangeline, respectively. Shoot biomass declined more rapidly than root with declining SM. Results revealed that, maintaining SM closer to FC during early season is beneficial for early development of root and shoot. Storage root biomass declined quadratically with declining irrigation. The optimum irrigation was 72% of ET and less biomass was partitioned to SRs above that level. Early season temperature study revealed, SR conversion efficiency increased quadratically and reached optimum at 23.9°C with increasing temperature. Maximum rate of SR initiation was reached at 29.5°C in 16.7 d. Biomass partitioned to roots declined linearly with increasing temperature. The SR production efficiency declined from 0.43 to 0.08 g SR kg-1 total weight, and dropped by 81% relative to optimum temperature. The SR fresh weight at high temperature declined 99% relative to optimum temperature. High temperature during mid- and late-seasons partitioned more biomass to shoots, less to roots lowering SR yield. The functional algorithms developed are vital to make management decisions and to develop crop models.

URI

https://hdl.handle.net/11668/18191

Comments

temperature||storage roots||sweet potato||soil moisture

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