Date of Award


Degree Name

MS in Environmental Sciences and Management


Natural Resources Management


College of Agriculture, Food, and Environmental Sciences


Nicholas Babin

Advisor 2

Charlotte Decock

Advisor Department

Natural Resources Management

Advisor College

College of Agriculture, Food, and Environmental Sciences


The agricultural industry is one of the main drivers of soil degradation due to conventional crop production methods and overuse of soil which results in accelerated erosion, loss of soil fertility, acidification, and salinization (Lal, 2015). Loss of soil fertility from degradation can be detrimental to crop production as plants grown under nutrient limited conditions show signs of physiological stress and reduced photosynthetic rates leading to reduced yields (Zangani et al., 2021). Organic crop production and fertilizers are viable alternatives to conventional methods as they improve soil fertility and the physiological and biological properties of soil (Ilahi et al., 2021). This research investigates the impacts of soil nutrient conditions from organic fertilizer (No Fertilizer, Medium Fertilizer, High Fertilizer) on physiological stress, photosynthetic rate, and crop development of Salanova lettuce (Lactuca sativa) – a crop of economic importance. A secondary aim of the study was to evaluate the relationship between plant stress, photosynthetic rate, and plant growth in lettuce in order to find an ideal organic fertilizer regime that maximized plant height and yield. Stomatal conductance and chlorophyll fluorescence were measured to evaluate plant stress and photosynthetic rate while leaf area index, plant height, and yield were measured to evaluate crop development. The leaf area index, stomatal conductance, chlorophyll fluorescence, plant height, and yield of lettuce were very similar in each treatment – No Fertilizer, Medium Fertilizer, and High Fertilizer. These results indicate that there was no significant difference between the three organic fertilizer levels on physiological stress, photosynthetic rate, or crop development of Salanova lettuce. Additionally, when evaluating the relationship between stomatal conductance chlorophyll fluorescence and yield in each treatment, stomatal conductance and chlorophyll fluorescence were not found to be significant predictors of plant height or yield in any of the treatment groups. There is a possibility that the No Fertilizer group did not experience the same level of nutrient deficiency as the crops in previous studies which could explain the differing results. Future experiments are recommended to increase the sample size, do a more thorough analysis of soil nutrient conditions prior to planting, and to evaluate more plant growth variables.