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- All Subjects: Ecology
- Creators: College of Integrative Sciences and Arts
- Creators: School of Geographical Sciences and Urban Planning
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
- Resource Type: Text
As the world’s population exponentially grows, more food production is required. This increasing food production currently has led to the un-sustainable production of chemical fertilizers and resultant overuse. A more sustainable option to enhance food production could be the use of fertilizer derived from food waste. To address this, we investigated the possibility of utilizing a fertilizer derived from food waste to grow hydroponic vegetables. Arugula (Eruca sativa) ‘Slow Bolt’ and lettuce (Lactuca sativa) ‘Cherokee’ and ‘Rex’ were cultivated using indoor deep-flow hydroponic systems at 23 ºC under a photosynthetic photon flux density of 170 µmol∙m−2∙s−1 with an 18-hour photoperiod. Plant nutrient solutions were provided by food waste fertilizer or commercial 15:5:20 NPK fertilizer at the identical electrical conductivity (EC) of 2.3 mS·cm–1. At the EC of 2.3 mS·cm–1, chemical fertilizer contained 150 ppm N, 50 ppm P, and 200 ppm K, while food waste fertilizer had 60 ppm N, 26 ppm P, and 119 ppm K. Four weeks after the nutrient treatments were implemented, compared to plants grown with chemical fertilizer, lettuce ‘Rex’ grown with food waste fertilizer had four less leaves, 27.1% shorter leaves, 68.2% and 23.1% less shoot and root fresh weight, respectively. Lettuce ‘Cherokee’ and arugula grown with food waste fertilizer followed a similar trend with fresh shoot weights that were 80.1% and 95.6% less compared to the chemical fertilizer, respectively. In general, the magnitude of reduction in the plant growth was greatest in arugula. These results suggest that both fertilizers were able to successfully grow lettuce and arugula, although the reduced plant growth with the food waste fertilizer in our study is likely from a lower concentration of nutrients when we considered EC as an indicator of nutrient concentration equivalency of the two fertilizer types.
This study examined crayfish diet within varying hydrologic environment in lotic systems using stable isotope analysis of crayfish and basal resources to add depth to previous findings. Crayfish are numerous and are omnivorous, opportunistic feeders, feeding on invertebrates, vegetation and detritus. Arizona streams stand apart from the Eastern and Northwestern aquatic ecosystems of the United States because Arizona has no native crayfish species. Two species have been introduced and become widely established in Arizona (Orconectes virilis and Procambarus clarkii), with concern for further introduction of crayfish species and more information on how these two species impact the native species in the streams is needed. Previous studies have focused on crayfish abundance with hydrologic variation and crayfish diets within a lentic system, but few have focused on how the diet of consumers varies with hydrologic variability. Crayfish are hardy and have a dramatically increasing population within Arizona and therefore inhabit systems with a wide range of hydrologic variability which may contribute to spatial variability. The results show that crayfish diets do show a significant level of seasonal variation in some study locations, in both C source and trophic level. Hydrologic variation was also shown to impact crayfish diet at several study sites, with increasing magnitude of event (both floods and droughts) correlating with a change toward more aquatic C sources and lower trophic position in several of the study sites. In some locations, the correlation was not as strong with variation and diet change and showed less change in C source and rather showed an increase in trophic position.