Natural Resources, School of


First Advisor

Dr. Daniel Snow

Second Advisor

Dr. Xin Qiao

Third Advisor

Dr. Matteo D'Alessio

Date of this Version

Summer 7-27-2020


Dissanayake, D. M. P. B. (2020). Beneficial Effect of Injected Air into Subsurface Drip Irrigation (SDI) on Plant Growth Using Runoff from a Feedlot


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In partial Fulfillment of Requirements For the degree of Master of Science, Major: Natural Resource Sciences, Under the supervision of Professor Daniel D. Snow. Lincoln, Nebraska: July 2020

Copyright 2020 Padmasankha Dissanayake


Due to water scarcity and increasing food demand, nonconventional water sources (e.g., human and animal wastewater) represent a valuable alternative to traditional water resources for agricultural use. Among these alternatives, treated animal wastewater, particularly feedlot runoff may represent a valuable solution in states like Nebraska due to its abundance. Subsurface drip irrigation (SDI) is a low-pressure micro-irrigation system that delivers water to the crop root zone through buried drip tapes with embedded emitters at fixed intervals. Despite multiple advantages (great water application uniformity, high water use efficiency, and improve fertilizer application), SDI can lead to poor aeration in the rhizosphere while applying water as drops. Therefore, to prevent these low levels of oxygen, injected air into SDI has been applied during the past twenty years. Aerated SDI has also been used to increase the crop yield, its quality, weight, and dimensions, as well as the dimensions of the roots. However, to the best of my knowledge, no other studies have been conducted using treated wastewater (e.g., feedlot runoff) to grow crops in the presence of SDI coupled with air-injection.

This study evaluated the effect of irrigation with feedlot runoff into air-injected SDI on 1) soil properties (e.g., water content, oxygen, etc.) and 2) corn (Zea mays) and sugar beets (Beta vulgaris) production.

The soil oxygen increased with air injection and the soil moisture content increased during the multiple irrigation events. Injected air significantly increased soil oxygen. The aerated zone at 45 cm contained the same and/or even greater amount of soil oxygen that non-aerated zone at 25 cm depth. The soil moisture content was lower in the aerated zones compared to the non-aerated zones. The impact of injected air on the growth of the two crops was no statistically significant. This may be related to the limited number of crops manually harvested and investigated. Injected air enhanced the yield of the two crops. Corn yields were 7.7 ± 0.9 Mg/ha and 7.3 ± 1.0 Mg/ha with and without air injection respectively. A 5.50 % yield increase was achieved using injected air. Sugar beet yields were 54.23 ± 11.21 Mg/ha and 50.33 ± 11.65 Mg/ha with and without air injection, respectively with a 7.75 % yield increase. Sugar yield increased by 8.0 % in the presence of air injection (7.82 ± 1.61 Mg/ha with air and 7.24 ± 1.72 Mg/ha without air). Two hailstorms toward the end of the study damage the two fields and consequently negatively affected the study. These results are encouraging considering the expected increased yield after the first year.

Advisor: Daniel D. Snow