Final Report for SW02-002
This research project found that delaying the final alfalfa cutting until growth ceases increases subsequent first-cutting yield in a four-cutting, but not three-cutting system. First-cutting growth was impacted by cutting schedule and alfalfa varieties in the four-cutting system. In the three-cutting system, yield was influenced only by variety. Modification of late-season cutting schedule will not be beneficial if the final cutting is not utilized. However, if a non-traditional use is developed, alteration of cutting schedule can increase profits. The experiments will be continued to determine the effect of late-season harvest management on long-term stand life.
1) Determine if modification of present late-season alfalfa harvest practices will affect stand persistence.
2) Determine relationships and interactions between late-season harvest management practices and alfalfa varieties on non-structural carbohydrates, alfalfa stem nematodes, and root and crown rot diseases of alfalfa.
3) Conduct an economic analysis of traditional and modified late-season harvest practices to determine how long-term profitability is affected by management changes.
1) Demonstrate to growers the effectiveness and economics of modification of late-season harvest management practices in maintaining alfalfa stands.
Alfalfa hay is the most important crop grown in the intermountain region of Colorado and Utah, both in acreage and gross financial return (http://www.nass.usda.gov). It is marketed locally, nationally, and internationally. Acreage has remained relatively constant for many years. The life span of alfalfa fields ranges from three to ten or more years depending on location and cultural practices. Some growers plant alfalfa with the intention of keeping it in production for three years and then rotating to other crops, while other growers plant with the intention of keeping it in as long as possible. For growers who wish to keep alfalfa stands productive as long as possible, profitability and sustainability are directly related to stand longevity. Many growers now are concerned that stands are tending to decline much quicker than they did in the past. The reasons for this are not completely clear, but changes in harvest practices and the presence of pests such as alfalfa stem nematode, Ditylenchus dipsaci, and diseases such as Verticillium wilt and crown and root rots play a role in stand decline. Changes in harvest practices have occurred over the past twenty or so years, and are in part the result of a shift to production of higher quality alfalfa, which necessitates more frequent harvesting.
Irrigated alfalfa is typically harvested four times a year in the lower altitude irrigated valleys and two or three times in the higher elevations of the Intermountain West. The final harvest in each area is usually taken in late September or early October. Stands tend to decline after the third production year, and much of the decline has been attributed to alfalfa stem nematode. Alfalfa stem nematode damage symptoms typically increase in the third production year. Symptoms in spring growth include stunting, swollen nodes, shortened internodes, irregular growth, and plant death. Fields with stem nematode damage in first cutting tend to recover and produce regrowth that is relatively free of symptoms in second, third, and fourth cuttings. Some growers recover some of the first cutting production loss in stem nematode affected fields with an early season application of carbofuran, but performance of this insecticide/nematicide has not always been predictable (Hammon, 1999). Diseases such as Verticillium and Fusarium wilts and other crown and root rots are present over most of the Intermountain West, although their impact on yield and stand persistence has not been well quantified.
We hypothesize that much of the stand decline that is currently blamed on stem nematode and diseases are actually the result of plants stressed by lack of sufficient carbohydrate reserves. This lack of carbohydrates allows stem nematodes and root diseases to damage the alfalfa plant to a greater degree than would have been possible if it had not been under nutrient stress. There is little doubt that stem nematode is responsible for much of the poor first-cutting growth and plant death. Perhaps the solution to the stem nematode /stand decline problems may not lie with controlling the nematodes, but rather by managing the plant environment to minimize their damage. Investigation of the impact of an apparently simple change in harvest management practices is the aim of this project. An understanding of the interactions between harvest management, stored non-structural carbohydrates, alfalfa stem nematodes, and plant pathogenic fungi is necessary to fully implement any changes in the way alfalfa is managed.
The climate of the Intermountain West varies significantly. This variation of altitude and precipitation affects the number of cuttings, variety choice, and irrigation management. Site-specific research is needed in different environments to fully understand the interactions between the alfalfa plant, plant pests and pathogens, and field management systems.
Alteration of late-season harvest management will necessitate changes in how final cutting hay is handled. Field climate is marginal at best in late October for curing of traditional hay, and alfalfa that has been frosted must be properly handled to avoid bloat and other health problems with livestock. A grower who now produces four cuttings of high quality hay would have to switch to three traditional cuttings, and one non-traditional cutting. One who currently produces three cuttings would have to switch to two traditional and one non-traditional. This non-traditional cutting will have to be utilized by growers by grazing either standing or windrowed hay, chopping as silage, or taking a chance on field curing and baling hay. An alternative use would be to use the residue as fuel for field burning to reduce dependency on herbicides and insecticide for first-cutting pests.
Much of the alfalfa pest management research in the Intermountain West has focused on stem nematode, disease, or insects, while ignoring the potential interaction of management practices such as late-season harvest management. Late-season harvest management effects on alfalfa stand longevity have been studied in many locations, and literature dates back as far as the 1920s and mid 1930s (Grandfield, 1935; Silkett et al., 1937). Several studies have determined that cutting alfalfa during a critical harvest period of 2 to 6 weeks prior to the first killing frost increases the probability of winter injury (Scheaffer et al., 1988; Horrocks & Zaifnejad, 1997; Welty et al, 1988). Other recent work suggests that the concept of the critical period is not always valid, particularly when winter-dormant, disease-resistant varieties were used under conditions of high soil fertility (Tesar & Yager, 1985). Studies in many areas of the United States, Canada, and other areas of the world have produced mixed results regarding the effects of fall cutting schedules.
Cutting schedules affect the amount of non-structural carbohydrates that are accumulated in the fall. Several studies have confirmed the relationship between carbohydrate concentration in the crowns and roots of alfalfa and stand longevity and yield (Grandfield, 1935; Tesar & Yager, 1985; Schaeffer et al. 1986). Griffin (1991) showed that fall harvest practices and stem nematode feeding affected the accumulation of non-structural carbohydrates in the fall, which in turn affected stand persistence in Utah. Stem nematode damage to plants was increased, and carbohydrate accumulation was less in plants that had been harvested during the critical fall period. Boelter et al. (1985) recorded similar results from experiments in Wyoming where they found that stored carbohydrate levels in stem nematode infected plants were significantly lower than in non infected plants, and winter mortality of alfalfa plants followed the same trend.
Recent work in central Utah showed that cutting during the critical 6-week period before killing frost had detrimental effects on subsequent first-cutting yields and stand persistence at a site near Spanish Fork UT (Horrocks and Zaifnejad, 1997). Their results closely match observed performance of western Colorado alfalfa stands over time.
The effect of late-season harvest management on alfalfa stand persistence was studied with two types of experiments, each performed in multiple locations. Long-term experiments investigating the interactions between alfalfa varieties of different dormancy and pest resistance ratings with traditional and modified late-season harvest management regimes were conducted at the Western Colorado Research Center at Fruita, CO and the Southwestern Colorado Research Center at Yellow Jacket, CO. These experiments addressed Research Objectives 1 and 2. Experimental and demonstration plots investigating the impact of late-season harvest management during a single season were done with grower cooperators and extension agents at several locations in western Colorado. These experiments addressed Research Objective 1, and Education/Outreach Objective 1 in part.
Long-term investigations at research centers:
Experimental plots were planted at the Western Colorado Research Center (Fruita, Mesa County) in August 2002 and Southwestern Colorado Research Center (Yellow Jacket, Montezuma County) in May 2003. The Fruita site is located at an elevation of about 4,500 ft, is furrow irrigated, and traditionally on a four-cutting schedule. The Yellow Jacket site is approximately 7,000 ft in elevation, sprinkler irrigated and traditionally on a three-cutting schedule. The experiments were designed as randomized complete block, split plots, with final harvest timing arranged as main plot and alfalfa variety arranged as sub plots. Two alfalfa varieties with dormancy ratings of 2, 4, and 6 were planted. Within each dormancy rating, one variety with an stem nematode rating of highly resistant and one variety with stem nematode resistance rating of less than highly resistant were used. The main plot (final harvest schedule) treatments consisted of the traditional harvest schedule with the final cutting taken in early October, or a modified schedule. which delayed the final harvest until after the first killing frost and cessation of alfalfa growth.
Plots at Fruita were harvested with a John Deere 2280 equipped with a scale system to record plot weight. Those at Yellow Jacket were harvested with a Carter forage plot harvester with electronic scales on board. A moisture sample was taken from each plot, and weights were adjusted to an air dry basis. All data were subjected to analysis of variance using MSTAT-C.
Each plot was sampled in late fall of 2003, early spring of 2004 and again in the fall of 2004 for non-structural carbohydrate concentration. Crowns were randomly chosen from each plot for analysis using the methods described by Silveira et al. (1978). The carbohydrate analyses were done in the laboratory of Dr. R.D. Horrocks, Brigham Young University, Provo UT. Plant crown and root samples were cultured and fungal pathogens identified during the spring of 2005. The goal was to determine which pathogens were present. Plant pathology samples were collected, cultured and pathogens identified by Dr Curtis Swift (CSU Cooperative Extension, Grand Junction).
Fall cutting date studies, 2003-2005
Experiments designed to determine the impact of different fall cutting dates on subsequent first-cutting yield were conducted at the Western Colorado Research Center at Orchard Mesa during the 2003/04 and 2004/05 growing seasons. The final cutting was taken on six different cutting dates: September 29, October 6, 13, 20, & 27, and October 1, 8, 15, 21, & 29 in 2004. There was an uncut control plot in each year. First cutting was taken on May 21, 2004 May 19, 2005.
Plots were harvested using a self-propelled sickle bar mower. Plant material was transferred onto a tarp to be weighed using a hanging spring scale. Moisture samples were collected and yield adjusted to an air dry moisture. Non-structural carbohydrate samples were taken on November 13, 2003, and again on March 9, 2004. The 2004/05 experiment was sampled on November 18, 2004. Samples were collected and analyzed using the same methods outlined in the previous section.
Carbohydrate levels during regrowth
A sampling scheme was designed to determine the pattern of carbohydrate use and production by the alfalfa plant during regrowth after a cutting. Two alfalfa fields at WCRC@FR were sampled for non-structural carbohydrates nine times after third cutting in 2004. The samples were taken weekly from a newly planted and an established alfalfa field. The samples were analyzed using the methods described above.
On-farm trials with grower/cooperators:
On-farm trials were conducted in 13 trial strips with seven grower cooperators in 2003 and 2004. These trials were designed to meet the needs, interests. and equipment of individual grower/cooperators. All were designed to compare traditional late-season harvest schedules to a modified schedule where the final harvest is not taken until after killing frost. Cooperators simply left a small strip of alfalfa unharvested during their final cutting. Final-cutting yield was estimated by weighing the hay in a measured distance of windrow. The unharvested plots were marked so they could be found the following spring. Subsequent first-cutting yield in the fall harvested and unharvested plots was measured by cutting a measured area within each plot with a small sickle bar mower, weighing the hay and adjusting to air dry moisture based on a sub sample.
Long-term investigations at research centers:
Delaying the final harvest until growth had ceased significantly increased subsequent first-cutting yield in the four-cutting system at Fruita (P=0.054), but not in the three-cutting system at Yellow Jacket. There was an apparent increase in total yield of 1 ton per acre over the three years the treatments were applied at Fruita, although there was no statistical significance. If the final cutting was not taken, yield was decreased by 4.5 tons per acre at Yellow Jacket (P=0.0034) and 2.1 tons per acre at Fruita (P=0.625).
Dormancy 4 and 6 cultivars yielded more hay than dormancy 2 cultivars at Fruita (P=0.0003). Dormancy 2 and 4 cultivars had greater yield than dormancy 6 at Yellow Jacket ((P=0.0548). There was a yield benefit to stem nematode resistant varieties at both sites. The resistant cultivars had a 1.13 ton/acre greater yield than susceptible varieties at Yellow Jacket (P=0.0059) and 3.6 ton per acre at Fruita (P<0.0001) over the four years that data were collected.
Fall cutting date studies, 2003-2005
The results of the harvest date studies in 2003 and 2004 confirm reports in the literature that harvest between two and six weeks before the time growth ceases are detrimental to subsequent first-cutting growth (Scheaffer et al., 1988; Horrocks & Zaifnejad, 1997; Welty et al, 1988), at least in four-cutting systems. There was strong correlation (r2= 0.97 in 2004 and 0.87 in 2005) between final cutting date and subsequent first-cutting yield, with later cutting dates yielding more hay than earlier cutting dates. In 2004 first-cutting plots that were cut after October 20 had 0.25 ton per acre greater yield than plots cut September 29. The first-cutting 2005 plots that were harvested after October 22 had 0.4 ton per acre greater yield than those cut October 1.
On-farm trials with grower/cooperators:
Thirteen trials with grower cooperators were conducted, of which ten were in 2002/03 and three in 2003/04. Eleven trials were conducted in four-cutting systems, with the remainder in three-cutting systems. In four-cutting trials, there was 30% greater first-cutting yield in unharvested strips than in those in traditional harvest strips. There was no difference in yield in the harvest strips in the three-cutting systems. Alfalfa stem nematodes were present in all fields, and nematode damage symptoms of stunting, swollen nodes, and irregular growth were more prevalent in the traditional cutting systems. In late fall samples, total non-structural carbohydrate levels were greater in all fields in which the final cutting was skipped. This trend did not carry over to spring samples, when there were no differences in non-structural carbohydrate levels.
Boelter, R.H., F.A. Gray, and R.H. Delaney. 1985. Effect of Ditylenchus dipsaci on alfalfa mortality, winterkill and yield. J. of Nematology 17(2):140-144.
a Silveira, A.J., F.F. Feitosa Teles and J.W. Stull. 1978. A rapid technique for total nonstructural carbohydrate determination of plant tissue. J. Agric. Food Chem. 26:770-772.
Grandfield, C.O., 1935. The trend of organic food reserves in alfalfa roots as affected by cutting practices. J. Agron. Res. 50:697-709.
Griffin, G.D. 1991. Relationship of Ditylenchus dipsaci and harvest practices to the persistence of alfalfa. J. of Nematology. 23(3):306-315.
Hammon, R. 1999. Management of alfalfa stem nematode and alfalfa weevil with Furadan 4F. In:
Hammon, R.W and S.M. Max (ed). 1999. Western Colorado Research Center 1998 Research Report. Colo. Agric. Exp. Sta. Tech. Rpt. TR99-12:6-7.
Horrocks, R.D. and M. Zaifnejad. 1997. Late-season management of alfalfa in irrigated valleys of the Intermountain West. J. Prod. Agric. 10:96-101.
Sheaffer, C.C., J.V. Wiersma, D.D. Warnes, D.L. Rabas, W.E. Lueschen, and J.H. Ford. 1986. Fall harvesting and alfalfa yield, persistence and quality. Can. J. Plant Sci. 66:329-338.
Scheaffer, C.C., G.D. Lacefield, and V.L. Marble. 1988. Cutting schedules and stands. P. 411-437 In A.A. Hansen et al. (Ed.) Alfalfa and Alfalfa Improvement. Agron. Monogr. ASA, CSSA, and SSSA, Madison WI.
Silkett, V.W., C.R. Megee, and H.C. Rother. 1937. The effect of late summer and early fall cutting on crown bud formation and winter hardiness of alfalfa. J. Am. Soc. Agron. 29:53-62.
Tesar, M.B. and J.L. Yager. 1985. Fall cutting of alfalfa in the North Central USA. Agron. J. 77:774-778.
Welty, L.E., R.L. Ditterline, and L.S. Prestbye. 1988. Fall management of alfalfa. Montana Agric. Res. 5(2):16-19
Impacts from this project, while present, are minimal at this point. This is because the project was designed as long term, and extension efforts are in the early stages. Data collection from the fourth year has just been finalized, and it is our intention to continue collecting data from the experiments at Fruita and possible Yellow Jacket into the future for as long as the alfalfa stand is acceptable. Extension efforts have not been high priority because of the lack of hard data to support our ideas. That data now exists to the point that some initial recommendations can be made.
One grower who had an on-farm trial, Fry Farms, has skipped the final cutting on several fields, then used the residue as fuel to burn the stubble in the spring and skipped the traditional herbicide treatment for winter annual mustards and insecticide treatment for alfalfa weevil. This cost savings for pesticides coupled with yield increase from skipping the final cutting paid for the lost cutting.
Fall rains in two of the past four years have made October cutting difficult, and many growers have skipped their final cutting. The decision not to cut was made by several growers after discussion of this project. They observed the impact of their decision on spring growth, and these on-farm observations are valuable in shaping grower opinions.
During the spring of 2005, a stem boring weevil was found in many western Colorado alfalfa fields. The weevil was discovered by a local field man monitoring for alfalfa stem nematode. This insect is unknown in the literature and had significant impact in many fields. Its discovery was indirectly related to the project, and it is the focus of ongoing research. None were found in 2006, and its identification is still unknown.
Education and Outreach
Field Days and Workshops:
Feb 18, 2004 Ute Mountain Ute Farm & Ranch Ag Clinic, Towoac (25)
March, 18 2004 Cortez Agriculture Workshop (40)
May 19, 2004 KAFM interview, Paonia
July14, 2004 Uncompahgre Valley Agricultural Field Day, Olathe (30)
Feb 24, 2005 Ag Production workshop, Delta (25)
March 8 & 9, 2005 Small Acreage Forage Workshop, Grand Junction, Montrose (35)
Education and Outreach Outcomes
Areas needing additional study
The long-term impacts of altering final harvest dates need to be studied over the long term. This project has collected data for four years in two fields. We intend to keep collecting data from the plots at Fruita and Yellow Jacket for as long as possible. We will self fund the costs associated with this project.
Demonstration projects need to be conducted in other geographic regions. The results from this study do not follow what the literature suggests regarding the impact of modified harvest schedule in three cutting systems in southwestern Colorado. Impacts from modification of final harvest vary with region and with individual grower management.