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Limited-irrigation annual forage research

Rex Kirksey Published on 30 May 2011

Farmers in the Tucumcari area of eastern New Mexico have received limited amounts of water or no water at all for irrigation since 2002.

For most of the past decade, irrigation quantity and seasonal availability has been severely limited.

Consequently, farmers must plan for the summer growing season without knowing how much water – if any – will be available for irrigation.

Still, even when there is limited or no water in early spring, there is a good chance that spring and summer rains will provide sufficient inflow to provide at least some late-season irrigation.

A project to evaluate late-planted, short-season annual forage crops for adaptability and yield potential in the Southern High Plains was initiated in 2010 at New Mexico State University’s Agricultural Science Center at Tucumcari.

The criteria for selecting crops for inclusion in the trial included the following: selected crops would be annual forages; they have demonstrated potential to produce marketable yield in 100 days or less; they should have some level of heat and drought tolerance; they need to be productive with limited irrigation but capable of responding to increased water availability; they must be capable of being grown with relatively limited management and labor inputs; they must be compatible with the equipment base currently used by local farmers; and a marketing outlet must be available within 100 miles.

The decision to evaluate late-planted crops was made with the purpose of allowing growers an opportunity to delay cropping decisions as late in the season as reasonably possible.

Planning for crop establishment in late June or early July provides an opportunity for increased water storage and allows for the accumulation of soil moisture following early summer rainfall events. Late-season crops also offer potential for growers to produce an alternate crop following early season losses that may have occurred due to wind or hail.

The decision to delay crop establishment until as late as the first week of July necessitates the use of crops that have a high likelihood of rendering a harvestable product within 100 days after planting. Based on a July 1 planting date, a 100-day growing season would extend until October 9. The average first freezing temperature (32ºF) at Tucumcari occurs on October 23.

A number of crops are capable of producing a harvestable yield within 100 days or less, but this project chose to focus on forages.

Most farms in the local area have combinations of crops and beef cattle, and there are a number of dairies in the surrounding areas of eastern New Mexico and west Texas, which purchase large quantities of forages. Most local producers have the equipment necessary to grow and harvest forages. Additionally, forages can be harvested prior to physiological maturity, lessening the risk of losses associated with an early killing frost.

Millets and sorghums comprised the majority of the forage entries selected for the test. Seed for all entries was commercially available and varieties were selected based on potential adaptation to the environment and cultural management of the trial.

Due to varietal diversity in sorghum forage types, the test included two different forage sorghum genotypes: a brown mid-rib (BMR), photoperiod-sensitive variety and a non-BMR, non-photoperiod-sensitive variety. Forage sorghums were planted in rows (30-inch centers) and also drilled on a 10-inch spacing, since there is a lack of information as to which planting method is most advantageous for hay production.

All other entries were drilled. A photoperiod-sensitive sorghum x sudangrass entry was also included. Oats, the only cool-season species in the trial, were included to see if they would produce an adequate quantity of high-quality forage in fall from an early summer planting.

Teff was included as potential horse-quality grass hay. Annual legumes that had shown potential for use, based on previous research at the science center (cowpea, lablab and soybean), and Korean lespedeza were sown with pearl millet to assess the effects of adding a legume on forage quantity and quality. Buckwheat, the only broadleaf non-legume in the trial, was included for its potential to break the cycle of continuous grass production.

The study was planted on July 1, 2010. Split applications of fertilizer totaled 120 pounds per acre nitrogen, 50 pounds per acre phosphorus and 16 pounds per acre sulfur and applied water (15.6 inches irrigation + 5.5 inches precipitation), totaled 21.1 inches.

The entire test was swathed on October 6 – 97 days after planting – as a single-cut hay harvest and baling took place, by species, based on curing time. Bales were weighed by plot and hay core samples were collected, oven-dried and analyzed for nutritive quality by near infrared reflectance spectroscopy (NIRS).

All differences have a high degree of statistical significance (99.99 percent certainty that differences existed).

Sorghum x sudangrass was the most productive entry; however, its yield was similar to the forage sorghums and pearl millet when planted as a monoculture or with Korean lespedeza or lablab. All other entries had significantly lower yield than the sorghums and pearl millet as a group. There was no difference in yield of the sorghum forages, whether planted in rows or drilled.

Yields for pearl millet were comparable, whether planted as a monoculture or when planted with legumes, except yields were significantly reduced when it was planted with soybean.

Nutritive value of all entries was within the expected range for warm-season annual forage grasses. Many of the lower-yielding entries had greater nutritive value than the higher-yielding entries, but the reduced economic return from the lower yields would likely not be offset by the increased economic value that should result from the higher nutritive value.

Establishing pearl millet with legumes did not significantly increase nutritive value. While pearl millet did not produce the highest dry forage yield or the highest forage quality, it did produce the best combination of yield and high quality. Planting legumes with pearl millet did not increase nutritive value, presumably due to the relatively low proportion of legume in the overall mixture, based on observations.

Study results indicate multiple annual forage crops offer potential for producing hay in late-planted, water-limited situations in the Southern Great Plains. Sorghum x sudangrass and forage sorghums, which are the traditional crops for hay production, were among the most productive entries. However, pearl millet, which is not widely grown in the region, provided the best combination of forage yield and quality, when grown either as a monoculture or in combination with selected annual legumes.  FG

Rex Kirksey is a superintendent and college professor at New Mexico State University Agricultural Science Center at Tucumcari. Other collaborators on this project were: Leonard Lauriault; Mark Marsalis; Sangu Angadi; Bryan Niece; Aaron Scott; and Jason Box.

PHOTO:
Results indicate multiple annual forages offer potential for producing hay in late-planted, water-limited situations. Photo courtesy of Rex Kirksey.

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Rex Kirksey
Science Center Superintendent
New Mexico State University

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