Semester of Graduation

Fall, 2021

Degree

Master of Science (MS)

Department

School of Plant, Environmental, and Soil Science

Document Type

Thesis

Abstract

The nursery and greenhouse industries have continued to increase in production and sales over the past two decades. This increase in horticultural production necessitates a greater demand for finite natural resources, specifically water. Sustainable water resource management will be critical to the success and continual growth of the nursery industry. Strategic irrigation scheduling and innovative substrate management practices can improve nursery resource efficiency. Soilless substrates were originally utilized by the industry to increase substrate air-filled porosity, to ensure adequately drained container systems. Thus, the implementation of these soilless substrates can lead to an inefficient use of water and fertilizer. Substrate stratification, the vertical stacking or layering of two different substrates with unique system hydraulics within the container, is a substrate management strategy that demonstrates promising opportunities to augment nursery resource use. In the lower strata, coarse bark particles are utilized to increase air-filled porosity and drainage where a water table is often formed. Layered above are components with an increase in water holding capacities, either fine bark particles or fibrous substrate amendments integrated with conventional pine bark to retain water and nutrients, allowing for more uniform hydraulic gradients and wetting fronts. The research herein involves a three-tier approach to determine and better understand the influence substrate stratification has on crop growth and its water dynamics between and during irrigation applications. Substrate stratification reveals that crop growth, quality, and yield can be improved while reducing water inputs when paired with resourceful irrigation scheduling. Moreover, stratifying substrates can limit the tension fluctuations that inevitably occur in the upper proportion of the substrate profile. These fluctuations were further reduced, when smaller, more frequent irrigations were applied relative to non-stratified systems. Lastly, fallowed stratified substrates hydrated better than non-stratified systems did when irrigated under drier conditions and rooted stratified systems drained more than non-stratified systems. Engineering individual strata layers for added benefits is valuable; however, bark:coir layered above coarse bark proved to be even more advantageous for plant growth and resource use. The research herein concludes innovative substrate engineering in concert with strategic irrigation scheduling may allow for improved nursery sustainability and resource efficiency.

Committee Chair

Fields, Jeb S.

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