Alternatives Using Windbreaks and Other Vegetative Plantings: Sub-Irrigation Tree Tube Trial

Introduction

The establishment of trees in eastern Montana is a challenge. Many techniques have been tried and only a few have been developed that actually show a benefit.

The sub-irrigation tree tube trial was designed to provide private agricultural landowners an alternative for establishing and managing trees. This technique was developed at the USDA Plant Materials Center in Los Lunis, New Mexico, to improve establishment and tree survival in the more arid parts of New Mexico.

The original technique has special requirements that were not readily available, so for the purpose of this demonstration trial the following concepts were implemented. Water was placed below the herbaceous competitive zone in order to maintain and/or increase tree establishment and survival, and to minimize maintenance intensity, as required by present day methodologies.

Objectives

One objective of this demonstration project was to explore a new technique for establishing trees in a dryland environment. The demonstration project also provided a means to make a comparison between this new, sub-irrigation technique and standard methods using a variety of shrub and tree species. Another objective of the project was to develop a method to enhance tree survival and establishment in remote areas that do not lend themselves to traditional maintenance methods, i.e. living livestock shelters, living snow fences, and wildlife clump plantings.

Study Area

As many different locations as possible will be pursued, the following sites have been identified:

1. Glendive: Standard clean, tilled windbreak planting
2. Baker: Living livestock shelter, Living Snow fence; and Wildlife Clump Planting; (planted into domestic and native sod)
3. PMC
1. Circle District field trial
2. Bridger PMC

Methods

Thin-walled PVC tubes, which were four inches in diameter and 36 inches tall, were placed in the soil adjacent to the planted tree using a post auger (Gidding’s soil auger). These tubes had slits on one side starting at 18 inches and progressing down the tube to the bottom. Depending on the soil type, modifications were needed to the slits and capping of the PVC pipe. In heavier soils, the slits were made bigger. In heavier and coarse soils, the bottom of the PVC pipe was capped. These pipes were installed and compared to the standard method of windbreak establishment using standard weed barrier and clean till methods. The comparison required surface watering an equal number of conventionally planted trees as trees watered using the sub-irrigation tubes. The conventionally planted trees were surface watered using the same amount of water at the same time as the sub-irrigated trees. The two planting techniques were compared in living livestock shelters, living snow fences, and wildlife clump plantings.

The standard comparison was made between trees that receive no supplemental water and trees that receive supplemental water. Supplemental water was administered on the surface and to an equivalent number of trees that received tubes. The trees received two gallons of water through the PVC pipes, twice a year. The trees also received a surface application of two gallons of water, twice a year. Replications of this technique required at least five trees per treatment.

The thin-walled PVC pipe was used in order to place water at a depth of at least 18 inches below the surface of the soil in late spring (June, before summer drought) and late fall before soil freeze up (October to avoid sending plants into the winter dry).

Soil assessments and descriptions were made at each site and were noted during the evaluation portion of this trial.

NRCS Windbreak/Shelterbelt Guidelines, Practice Code 380, were followed for site preparation. The management practices will be carried out for the life of the project which is approximately 20 years.

Tillage comparisons were also recorded between those rows which received tillage between and within rows and with watering pipes and those rows receiving no tillage and without watering tubes.

Results

Data is being collected and evaluated. Further results are expected within three years.

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Sub-Irrigation Tubes for Semi-Arid Environments (PDF; 111 KB) Plant Materials Today January 2007 Newsletter

Contact Information

Robert Kilian
NRCS Range Management Specialist
Miles City, Montana
(406) 234-7905 ext 114

Joe Scianna
NRCS Horticulturalist
Bridger Plant Materials Center
Bridger, Montana
(406) 662-3579