Date of Award:

5-2021

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Soils and Climate

Committee Chair(s)

Matt Yost

Committee

Matt Yost

Committee

Niel Allen

Committee

J. Earl Creech

Abstract

Two approaches to water optimization in agriculture are to increase soil water retention and improve the efficiency of irrigation. A soil amendment that has received attention for its ability to increase soil water retention is biochar, the remaining biomass after high C materials have been pyrolyzed (burned with limited oxygen and heat). Two studies were conducted at a total of 10 site-years in Utah from 2018 to 2020 to evaluate how wood biochar influences the productivity and crop quality of irrigated alfalfa (Medicago Sativa L.), corn (Zea mays L.), and wheat (Triticum L.), along with soil water tension. One study included a single biochar rate of 22 Mg ha-1 at two irrigation levels (full vs. partial), where soil-incorporated biochar increased silage corn yield by 12% in 2018 and reduced yield by 10% in 2019. Top-dressed biochar had no impact on alfalfa yield from 2018-2020, in either irrigation rate. The other trial had six to seven biochar rates (0 – 67 Mg ha-1), plus the addition of wood chips at a single rate (22 Mg ha-1) at one site. This trial displayed a yield decrease of 0.01 Mg ha-1 of wheat grain for each additional Mg ha-1 of biochar applied, however there were no impacts on silage corn production. Data obtained over ten site years showed minimal impacts from biochar on crop yield, quality, or soil water tension, leading us to conclude that wood biochar was not an effective tool for enhancing crop production or conserving irrigation water in arid agriculture.

Most pivot sprinkler package in the Intermountain West are classified as mid-elevation sprinkler application (MESA). Several studies of low elevation spray application (LESA), low energy precision application (LEPA), and mobile drip irrigation (MDI) have demonstrated greater efficiency than MESA, due to less loss between the time that the irrigation water leaves the nozzle and enters the rootzone. However, these advanced sprinkler packages have rarely been tested at a reduced application rate. Eight site-years of data were collected at four Utah farms from 2018 to 2020, to evaluate crop yield and quality responses to full and reduced rates of each system in alfalfa, corn, and small grains. Soil water tension was also measured. Data showed that the advanced systems were sometimes able to maintain yield and quality while applying 15 to 25% less water, yet there were situations where MESA outperformed the advanced systems. This led us to conclude that there is not one style that will have the best results all the time, but that tailoring the package to the field characteristics is where the optimization with these packages can occur. Therefore, this chapter is being published as an Extension Guidebook for farmers.

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