Management Practices for Drip Irrigation in Baca County, Colorado

The Ag Professional + Producer project was designed to help establish management practices for drip irrigation on onions in Baca County, Colorado that would improve germination, emergence and stands with resulting increase in yield, quality and returns.
Due to a declining water table with diminishing pumping volumes, agricultural producers are looking for ways to improve irrigation efficiency, lower labor and production costs while maintaining and/or increasing yields and returns.

Three major problems confront agricultural producers, (1) tillage methods to maintain beds over subsurface driplines in the same location, (2) a means of protecting the small emerging onion plants from blowing sands in an area with high average winds, and (3) ways to improve movement of water from subsurface driplines to the shallow planted onion seed for adequate germination and emergence.

A specially designed disk was purchased and used to maintain the beds as close as possible to the same location each year because of the subsurface driplines under the beds. Tillage also had to be shallow enough to prevent disking the subsurface driplines.
This disk is an Arizona Drip Wide Bed Disk.

In the spring of 2005, oats were planted on the middle of the bed and in the furrow, and then in the spring of 2006, a mix of oats, triticale and wheat were planted in the middle of the bed combined with roughing of the furrows. Both of these practices substantially reduced damage irom blowing sand resulted in excellent stands of onions from seed.

AgriBlend, a combination of HYDROGEL, a water-absorbing polyacrylamide, and Zeolite, a water-tansporting volcanic material, was incorporated in the bed in an attempt to improve gennination of the small, shallow planted onion seed. With well-timed rains
in 2005 and 2006, germination in the treated and untreated areas produces similar stands. In 2005, the AgriBlend treated area and the untreated area produced similar yields of 986 and 944 50-1b bags of onions per acre, respectively. However, in 2006, the AgriBlend
produced a significantly higher yield of 955 50-lb. bags per acre compared to 843 bags harvested from the untreated area. The AgriBlend area also produced a significantly higher number of jumbo-sized onions, 628 compared to 510 50-lb. bags per acre.
Unfortunately, a bacterial soft rot infected the onions in 2006 and prevented commercial harvest.

Introduction

The Baca Conservation District teamed up with the Natural Resource Conservation Service (NRCS) to offer irrigators an opportunity to install subsurface drp irrigation (SOl) systems with a 75% cost-share incentive of $900 per acre because of their concern for the rapid dewatering of the groundwater aquifer in southeast Colorado. The dewatering of the aquifer is resulting in lower yields and financial returns from crops such as corn, gnlin sorghum, sunflowers and wheat.

The Ogallala Aquifer has been dewatered in many areas and the remaining areas are being rapidly dewatered. The underlying Dakota Aquifer is a sandstone lurmation where amounts of water are aflected by the size of the crevices in the limestone and precipitation. The region averages 15 inches of precipitation annually and about 75% occurs between March and September. Rainfall during the growing season is very erratic
and unpredictable, varying from as little as 8 inches to as high as 30 inches. Because of the unreliability of amount and timing of rainian, crops need to be supplemented with ground water for optimum crop production and fmancial returns.

Driven by the need to use the remaining groundwater more efficiently and by the high cost of pumping, producers are looking for a more efficient and profitable irrigation system for producing these crops as well as some high-value crops, such as cantaloupe, onions, squash and other vegetables.

SDI applies water to crops in small amounts with little waste when managed properly. Water can be applied in amounts to match the crops' water-use rates and can be as efficient as 98%. This is because the water is emitted below the ground surtace and not
subject to surface runoff and has limited evaporation. Most of the water lost by SDI is due to over-irrigation.

Furrow irrigation is used on most of the land, but recently, more center pivot sprinkler
systems have been installed in an effort to use the groundwater more efficiently. Furrow
irrigation is about 50% efficient as excessive winds in the region results in high levels of
evaporation. The same winds can severely affect patterns of the center pivot irrigation
systems and reduce irrigation efficiency. Both of these methods of irrigation require
larger amounts of pumped water because of the inefficiencies of the systems under these
environmental conditions when compared to SDI.

With an average elevation of approximately 4,000 feet, the area is subject to high winds. Because of these high winds, wind generators with three (113 foot) blades have been installed on several hundred acres. These winds cause blowing of the predominately loam soils and can quickly destroy young crops.

Subsurface drip irrigation (SD1) is a means of conserving the ground water supply that some of the more innovative producers began installing in 2003 with the help of the cost­share incentive. Even with the cost-share incentive, SDI is a costly and new method of irrigation to all of the producers in the area. As a result, many producers are reluctant to make the investment in SDI without knowing more about management of these systems.

Because of the high cost of installation, producers are looking at high-value, high-risk crops such as onions, cantaloupe and other vegetables as a means of increasing returns from the land. And, because most of these crops are hand-harvested, the labor coming in for the halvest can help to improve tbe local economy through increased economic activity.