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.
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.
Minimizing production problems by developing management practices that are adapted to the area was the goal of the project.
Subsurface drip irrigation (SDI) is new to the Baca County area and most of the management practices being used came from other areas.
Because of this need to develop better management for SDI in this region, the following three practices were demonstrated at this site.
a. Tillage methods for preparing the beds are a problem. These beds need to remain in the same location because of the buried driplines, even though the lines were installed with the use of a GPS system. Disking was done with a specially designed disk to remake beds in the same location.
b. With dripIines installed approximately eight (8) inches below the soil surface and 30 inches apart on the 80-inch beds, ways are needed to get moisture to the seed fix germination. AgriBlend, a combination of HYDROGEL, a water-absorbing cross-linked molecular structure polyacrylamide, and Zeolite, a water-transporting volcanic material was used to help get water to the seeds and hold the moisture around the seed and seedling. The HYDROGEL used in this project is similar to that used with seedling trees.
c. Cover crops are needed to prevent wind damage to the emerging and young plants. The high winds in the area can severely affect crops in the seedling stage. Small grains, planted in late winter or early spring, were selected because of cost and availability of chemicals to kill the crop without injuring the seedling onion crop.
There are 27 zones in the drip irrigation system, each connected to a mainline water delivery pipe, and each of these zones is 6.3 acres (170.1 acres). The 6.3 acres in a zone
are irrigated with equal amounts of water that are applied to the zone from the main line. Depending on the crop acreage, two or more zones can be irrigated at the same time.
In the fall of 2004, the 80-inch beds were disked twice with the specially-made Arizona Drip Wide Bed Disk to prepare the beds for the 2005 cropping season. The beds were then worked four to five times with a culti-packer.
AgriBlend was applied at the rate of 30 pounds per acre in 2004 on beds to be planted to cantaloupe, which was not planted because weather delayed planting beyond an acceptable planting date. Then on February 15, two rows of oats were planted in the
middle of the bed and two rows of oats were planted in the bottom of the furrow. The oats were planted in an effort to reduce sand blowing and damage to the seedling onions.
On March 15, Commeta white onions were planted at the rate of 135,000 seed per acre or about 3- to 4-inch spacing. Three rows, spaced 7 inches apart, were planted over the top of the driplines on each side of the 80-inch bed, about 12 to 14 inches from the center of
The onions were fertilized with 120 pounds of nitrogen per acre as 32% liquid nitrogen and 70 pounds of P205 as 52% phosphoric acid. SELECT herbicide was sprayed at the rate of 10 ounces per acre to kill the oats when the plant height was 6 to 8 inches and for
weed and grass control.
The crop was irrigated to maintain good soil moisture throughout the season and a total of 13.6 inches was applied. The onions plants received a severe hail on June 12 while still in the vegetative stage of grovvth and left jus t tips showing. Since the plants were still in the vegetative stage, the onions were able to recover with some thinning of stands. Blowing winds caused many of the furrows to be filled with sand and also caused some
thinning of stands. The dead oat stubble did offer some protection from the blowing sand while the plants were still small.
Four replications were taken throughout the field in both the AgriBlend treated zone and the untreated zone, selecting locations with uniform stands on September 1. Total field harvest was done on September 12-14.
In 2005, yields calculated from the test plots taken from the AgriBlend treated zone averaged 986 bags per acre (50 pounds per bag), while the untreated zone averaged 944 bags per acre.
There was no significant difference at the 10% level based on these results. These yields include only Jumbo, Medium and Pre-pack grades as culls and doubles were very minimal.
Percentage of onion grade also had little or no variation due to the addition of AgriBlend as both zones averaged approximately 62% Jumbos, 36% Mediums and 2% Pre-packs. Visually there appeared to be better stands in the AgriBlend treated zone than in the untreated zone.
Yields from field harvesting averaged 812 bags per acre (50 pounds per bag) with 94% rated acceptable and 6% discarded as culls. Unfortunately, production yields from the two demonstration zones were not kept separately.
The reduction in yield of field harvest as compared to yields from the plots indicate that yields were severely affected by stand and that total zone yields need to be taken to compare the AgriBlend treated zone to the untreated zone. Separate zone yields plan to be taken in 2006 as well as plot yields and plot grading.
Educational & Outreach Activities
Two subsurface drip irrigation workshops were held in Springfield, Colorado as part of the demonstration project. The first workshop was held on AugLlst 1, 2004 and followed with a field trip to the SDI installation at the Brent Morris farm. The second workshop was held in Springfield, Colorado on January 8, 2007 presenting results from the 2005 and 2006 crop years.
A poster program was also presented and discussed at the 2006 Bi-annual Field Day at the Colorado State University Arkansas Valley Research Center in Rocky Ford which was attended by some 120 growers, drip irrigation representatives and other interested
This Final Report with information and pictures of the Demonstration Project will be posted on the Web Page of Colorado State University at: www.colostate.edu/~cwis303 or by email upon request at: James.Valliant@ColoState.EDU.
In 2006, the beds were prepared by disking twice with the specially-made Arizona Drip Wide Bed Disk, from Coolidge, AZ. The beds were then worked four to five times with the culti-packer.
AgriBlend was applied at the rate of 30 pounds per acre on beds with Gandy Boxes and incorporated with a culti-packer. Then, on March 10, a combination of oats, triticale and wheat was planted in the middle of the bed. This combination of small grains was planted in an effort to reduce sand blowing and damage to the seedling onions.
On March 8, Granero white onions were planted at the rate of 135,000 seed per acre or about 3- to 4-inch spacing. Three rows, spaced 7 inches apart, were planted over the top of the driplines on each side of the 80-inch bed, about 12 to 14 inches from the center of the bed.
The onions were fertilized with 150 pounds per acre of nitrogen as 32 percent liquid nitrogen and 50 pounds of P205 as 52 percent phosphoric acid through the SDI system. SELECT
herbicide was sprayed at the rate of 10 ounces per acre to kill the small grains when the plant height was 6 to 8 inches and for weed control.
Tbe crop was irrigated to maintain good soil moisture throughout the season and a total of 24 inches was applied.
Winds caused some blowing sand, but the stands of small grains and roughing up of the furrows prevented significant damage. Using both of these practices resulted in excellent stands of seeded onions. Rains and cold weather were received starting September 1 before the onions could be harvested. As a result, a bacterial soft rot infected many of the onion plants. As a result, the crop could not be hatvested for commercial sale.
Six replications were taken throughout the field in both the AgriBlend treated zone and the untreated zone on September 25. These yield samples were taken at the same
locations in the field in the two zones. None of the onions were harvested for production due to disease and the crop was a total loss!
Tilling of the beds with the specially designed wide bed disk appears to be the best way to maintain the beds in the same location above the driplines and to prevent damage to
the subsurface drip lines.
Planting of oats in the middle of the beds between the onions and in the furrows or planting of oats, triticale and whe at in the middle of the beds betvveel1 the onions and
roughing of the furrows did reduce wind damage on the young emerging and seedling onion plants. Planting the small grains in Febnlary or March allowed for sufficient growth to provide a wind barrier, but did not produce too much foliage to prevent killing
ofthe small grains with chemicals.
The results of the addition of AgriBlend, a HYDROGEL/Zeolite combination, to the soil were not conclusive ove r the 2-year study period as significant increases in yield and quality was produced only in 2006. Additional demonstration work, under these conditions, are needed to confirm the results of applying AgriBlend on seeded onions using subsurface drip irrigation (SDI).
Many of the groundwater aquifers in Colorado, Kansas, Texas and throughout the southwest are being rapidly dewatered. With fuel costs increasing, water tables dropping and pumping rates diminishing, pumping less water and being able to produce a comparable or bctter crop with SDI is an economically sound method of irrigation, especially in these windy, arid regions.