Document Type

Thesis - Open Access

Award Date

2024

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

A. Joshua Leffler

Second Advisor

Krista Ehlert

Abstract

Rangeland forage nutrition and biomass production are integral components of sustainable livestock grazing systems and are controlled by soil quality and precipitation. I examined the effects of precipitation on growth and nutrition of three forage species in four different soils that span the longitudinal moisture gradient in South Dakota. I grew little bluestem (Schizachyrum scoparium), western wheatgrass (Pascopyrum smithii), and smooth brome (Bromus inermis) in soils representing the eastern tallgrass/mid-grass prairie (Brookings, 700 mm avg. precipitation.), an eastern mid-grass prairie (Highmore, 550 mm avg. precipitation.), a western mid-grass prairie (Cottonwood, 450 mm avg. precipitation.), and a western mid-grass/short-grass prairie (Sturgis, 400 mm avg. precipitation.). Brookings and Highmore soils have coarser texture than Cottonwood and Sturgis and are higher in NO3-, but lower in organic matter (OM). Conversely, Cottonwood and Sturgis soils have a heavy clay texture high in OM but are nutritionally deficient compared to their counterparts from the east side of the state. Plants were grown in two experiments. First, soils were maintained between 20-45% volumetric water content to simulate spring growth with adequate moisture. Subsequently, plants were harvested and allowed to re-grow in four precipitation regimes ranging from drought to record rainfall. During the spring experiment, the Highmore soil produced significantly more biomass of smooth brome and western wheatgrass; however, little bluestem biomass did not differ among soils. During the moisture limited experiment, biomass, crude protein, and digestibility of smooth brome and western wheatgrass were greatest at higher precipitation and particularly in the coarser-textured soils (Highmore, Brookings), which hold less water. Our findings suggests that the balance between precipitation, soil water holding capacity, and the tension at which water is held within the soil is a primary driver of forage production, digestibility, and nutrition; with greater influence observed on C3 species than their C4 counterparts. These results have broad implications for both researchers and producers, aiding land managers to better understand the resources in their care and providing a foundation for future research to explore soil as a predictive factor of forage resource quality and quantity.

Publisher

South Dakota State University

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Rights Statement

In Copyright