Posts Tagged: alfalfa
Across the globe, scientists have shown that birds can be farmer allies. Insectivorous birds feed on damaging insect pests in many crops including coffee, cacao, oil palm, corn, cabbage and apples. Raptors, including hawks and barn owls, feed on rodents, including gophers, voles and mice (see blog, Barn owls help clean up rodents naturally).
Despite this deep historic knowledge that birds are important predators of crop pests, over time the perception of birds as natural enemies of pests has been generally replaced with the idea that birds are often major crop pests themselves. Indeed, some bird species — like some types of insects — can cause trouble for farmers, but many others — especially those that eat insects and rodents — can be beneficial.
Do birds control insect pests on farms in California's Central Valley?
They do! Recent studies by Dr. Sacha Heath, UC Davis, and Rachael Long, field crops and pest management advisor, UC Cooperative Extension, showed that birds help control insect pests in walnut orchards. Dr. Sara Kross (UC Davis postdoctoral alumnus, now with Columbia University) showed that birds help control alfalfa insect pests.
Birds are voracious predators of codling moth pests in walnuts
Codling moth is a major worm-like pest that infests walnuts, apples and pears. The larvae go dormant during winter, living in cocoons in crevices in trees. Adult moths emerge in the spring, lay eggs and infest crops.
We evaluated bird predation of codling moth using “sentinel prey” and exclosure cages. We glued codling moth cocoons to walnut trunks and covered them with cages, allowing insects and spiders to access the cocoons, but not bird predators. This allowed us to count how many larvae were eaten inside and outside of the cages to estimate pest reduction by birds.
What did we find?
Natural enemies, like parasitic wasps and lacewings, alone reduced codling moth larval numbers by 11%; adding birds into the pest control system reduced them by 46%! Nuttall's woodpeckers and white-breasted nuthatches did a lot of the work; these birds travel up and down the trunks of trees, searching for insects.
Above, a white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. Video by Sacha Heath.
Alfalfa weevils are no match for insectivorous birds
Alfalfa weevils are key pests of alfalfa, reducing yields and hay quality if left uncontrolled. Dr. Sara Kross looked at bird predation of this pest by excluding birds from alfalfa plants via cages, and counting the number of weevils inside and outside the cages. She found that birds reduced the number of weevils by more than 30%, showing their importance in helping to protect alfalfa from this serious pest.
Does field edge habitat, like hedgerows, help attract beneficial birds?
Yes! Hedgerows are important habitat for beneficial birds, serving as nesting, foraging and roosting sites. In a study in the Sacramento Valley, crop margins with hedgerows, tree lines and riparian buffers harbored up to six times more birds and up to three times more bird species than bare or weedy margins.
Walnut orchards adjacent to hedgerows and riparian areas had higher numbers of beneficial birds along with more species. In alfalfa, there were more beneficial birds in fields when at least two tall trees were present along the field edges. More beneficial birds were associated with better pest control, that is, fewer codling moth cocoons and alfalfa weevils.
Birds have large territories, fly long distances, and are influenced by what happens on the farm as well as by what happens in the landscape around the farm. For example, we found that codling moth predation by birds greatly increased in walnut orchards as the amount of habitat in the landscape around the orchards increased (including hedgerows, tree lines, riparian and oak woodlands, and grasslands).
Will hedgerows increase the numbers of pest birds?
Pest birds are present on farms regardless of field edge habitat (such as weedy vegetation or hedgerows). Cases will be different, depending on the crop, but in the fields and orchards of Yolo County, researcher Hillary White (formerly with UCCE and now with U.S. Fish and Wildlife) found that three of the most common avian crop pests (American crow, red-winged blackbird and Brewer's blackbird), were up to 10 times more abundant in agricultural fields with bare or weedy margins than in fields with hedgerows.
What can I do to attract beneficial birds to my farm?
Our avian research team has been quantifying the conditions under which birds are helpful or harmful to growers. We are looking for ways to help farmers create bird habitat on their farms to harness the beneficial pest control services birds can provide, while also protecting crops from the damaging effects of some bird species. This information is available in the new publication “Supporting Beneficial Birds and Managing Pest Birds,” co-authored by the Wild Farm Alliance and Drs. Kross and Heath, and technically advised by UC Cooperative Extension and several farmers. This is a user-friendly guide for farmers and conservation practitioners, with the goal of co-managing farmlands for biodiversity and farming.
A white-breasted nuthatch preys on a codling moth larva “sentinel cocoon” on a walnut tree. (Video still: Sacha Heath)
Because periodic droughts will always be a part of life in California, the UC California Institute for Water Resources (CIWR) produced a series of videos to maintain drought awareness and planning, even in years when water is more abundant.
The final video of the three-part series, which focuses on drought strategies for citrus, was launched April 6 on the UCTV Sustainable California channel. The first episode, which centered on alfalfa production, premiered Feb. 2 on the UCTV Sustainable California channel. The second video, on almonds, was launched March 2 on Sustainable California. A trailer with clips from all three episodes is here.
The videos are inspired by a collection of 19 drought tips produced by CIWR in collaboration with UC Agriculture and Natural Resources researchers during the drought of 2010-16. The tips cover a broad spectrum of California crops, from alfalfa to walnuts. Topics also include salt management, use of graywater in urban landscapes, and the use of shallow groundwater for crop production.
The drought tips collection and the drought tip videos were sponsored by the California Department of Water Resources. Following are links to each of the videos:
The CIWR drought tip series opens with Cannon Michael of Bowles Farming in Los Banos. The alfalfa grower works with UCCE specialist Dan Putnam. “There's a lot of misunderstanding about alfalfa as a crop,” Michael said. “It does take water to grow it, as with anything, but you get multiple harvests of it every year.”
The second episode features almond producer Raj of Meena farms. He works with David Doll, UCCE advisor in Merced County. “One positive of this drought,” Meena said, “is that it has forced us all to be more efficient in how we use our water.”
The series finale features Lisa Brenneis of Churchill-Brenneis Orchard in the Ojai Valley of Ventura County. She worked with UCCE advisor Ben Faber to install a new water-efficient irrigation system. “Irrigation is the only job we really have to do,” Brenneis said, “and we have to get it as right as we can.”
For a complete list of drought tips, see http://ucanr.edu/drought-tips.
“In general, a reduced lignin trait in alfalfa is very welcome,” said Dan Putnam, UC Cooperative Extension specialist in the Department of Plant Sciences at UC Davis. “The low-lignin trait has some interesting potential implications for dairy cows and other ruminants, as well as for yield, agronomic efficiency, and even energy and water use efficiency.”
The new variety, called KK179, was developed by Forage Genetics International, Monsanto and the Nobel Foundation. Some of the field testing took place at UC Davis and the UC Intermountain Research and Extension Center in Tulelake, Calif.
KK179 differs from most other GMO agricultural crops in that the modification improves the plant quality. Other common modifications, such as glyphosate resistance and addition of a Bt gene, were designed to help with pest control.
Another difference is the source of the modified gene, Putnam said. In glyphosate-resistant (Roundup Ready) alfalfa, for example, the plant was modified by inserting a bacteria gene. Gene segments reducing lignin were derived from alfalfa itself.
Lignin is a fibrous part of cell walls in plants. It strengthens stems, helping the plant grow upright. However, its concentration in alfalfa is high compared to other forages, a drawback for what is considered the premiere forage of dairy cows.
“Farmers often try to cut early to reduce lignin,” Putnam said. “Unfortunately, yields are decreased by early cutting, often by many tons per acre. If growers were able to harvest later and still obtain good quality, yields would improve.”
That leads to the potential energy- and water-conserving aspects of the KK179 alfalfa.
“If growers reduce harvests by one each year and increase yields with no quality penalty, energy use would decline,” Putnam said. “Also, the amount of milk produced per unit of water used to grow the feed may be increased.”
KK179 won't be for everybody, Putnam cautions. Some export markets reject GMO technology, so growers should check whether their markets will accept alfalfa with the low-lignin trait. Another concern is the possibility of gene flow for farmers who grow alfalfa seed for organic production or export.
“Further research and experience by farmers and researchers are needed to fully understand the importance and implications of reduced-lignin alfalfa on farms,” Putnam said, “but this trait holds some very exciting possibilities.”
An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025
But in addition to its over $1 billion value to the state of California, alfalfa provides a host of environmental benefits that are frequently overlooked. What are these benefits?
Benefits to the soil. In addition to being an important cash crop for growers, alfalfa is good for our soil. Alfalfa is a perennial flowering plant in the pea family that is planted in the fall and remains in a field for four to six years. The crop requires few inputs, as the plants fix their own nitrogen from Rhizobia bacteria colonizing the roots, with 90 percent coming from atmospheric nitrogen. Free fertilizer from nature! The long alfalfa stand life also gives the soil a chance to rest from frequent field crop rotations, helps provide nitrogen for subsequent crops and improves soil tilth.
Alfalfa is an insectary. Alfalfa also hosts a diversity of insects, many of which are beneficial, such as lady beetles and parasitoid wasps. These in turn help control other types of insect and mite pests in alfalfa and other crops, potentially saving growers money for pest control. One option to further manage crop pests is by strip cutting the alfalfa, a process that leaves some uncut areas during harvest so that alfalfa serves as a trap crop, holding pests that could infest neighboring crops.
Many of these wildlife benefits have been documented by bird-lovers (For more information, see Farming for birds: Alfalfa and forages as valuable wildlife habitat).
Alfalfa-ice cream in the making! Markets for alfalfa primarily include the dairy industry, with alfalfa being an important part of a cow’s feed ration, as it provides high protein and energy for high milk production. This is economically important (the dairy industry is worth $7 billion per year) but also important for human nutrition. A California alfalfa field can produce 2,400 gallons of milk per acre. So the next time you have pizza (with cheese), milk on your cereal, or ice cream, thank alfalfa.
When you smell the fragrance of newly mown hay, thank the alfalfa grower and the “Queen of Forages” which helps produce milk right here in California. Watch the fields for bird activity and see if you can spot some Swainson’s hawks feeding on rodents and helping alfalfa growers with pest control, or curlews and egrets foraging for prey. But also be grateful for a host of important wildlife and environmental benefits to the landscape that alfalfa provides.
For more information, see the UC alfalfa workgroup website.
You may wonder about this practice of ‘sheeping off’ or grazing alfalfa fields, as sheep are most associated with rangelands in the coastal foothills or the Sierras. Basque sheepherders have historically managed sheep grazing in the Sierra Nevada mountains, which is a legacy that still remains in arborglyphs, or drawings in aspen trees, and in current grazing leases on federal lands. But sheep grazing in alfalfa fields has also been a long-time practice, probably for as long as there’s been alfalfa in our valley.
Alfalfa growers also benefit from sheep grazing in their fields during wintertime when the alfalfa is dormant. Alfalfa is a perennial crop which means that the root system remains alive below ground throughout the year even when the stems and leaves die during winter dormancy. Sheep feed on winter weeds, helping to control them in both seedling as well as established alfalfa stands that may negate the need for an herbicide treatment. Sheep grazing also reduces the alfalfa vegetation that dies back in winter, producing cleaner hay, the following spring. Sheep also help control weevil insect pests by feeding on older alfalfa stems, where the weevils lay eggs. This practice may help reduce weevil pressure and feeding damage to the first alfalfa cutting when weevils are actively feeding, a positive benefit, especially for organic growers.
The correct timing of alfalfa grazing is especially important for sheep producers since incorrect timing can result in a potentially lethal condition in sheep called bloat. Bloat occurs when a ruminant, such as a sheep, consumes too much fresh alfalfa with a high concentration of leaf proteins called saponins. When saponins are digested in the rumen, they create foam that prevents the sheep from burping up gases that are a produced from digestion in their stomach. Grazing too early in the fall or too late in the spring increases the risk of bloat, which is another reason why alfalfa grazing is done during the winter months.
Studies in California have documented economic benefits for both sheep producers and alfalfa growers. Sheep producers benefit from high quality feed during wintertime. Alfalfa growers benefit from weed and weevil control, as well as cleaner hay that can result in higher quality forage compared to non-grazed alfalfa stands.
Next time you come upon an alfalfa field full of sheep, know that they’re there for a purpose, providing feed for sheep and weevil and weed control for the alfalfa, in an environmentally sound manner. And, see if you can get in a game of ‘I Spy’ and find those Great Pyrenees dogs.
For more information, see the articles listed below:
- Bell, C.E. and J.N. Guerrero. 1997. Sheep grazing effectively controls weeds in seedling alfalfa. California Agriculture 51(2):19-23. http://ucce.ucdavis.edu/files/repositoryfiles/ca5102p19-67649.pdf
- Doran, M.P., L. Hazeltine, R.F. Long and D.H. Putnam. 2010. Strategic grazing of alfalfa by sheep in California’s Central Valley. Technical Report. http://cesolano.ucanr.edu/files/63758.pdf
- Pelton, R.E., V.L. Marble, W.E. Wildman and G. Peterson. 1988. Fall grazing by sheep on alfalfa. California Agriculture 42(5): 4-5. http://ucce.ucdavis.edu/files/repositoryfiles/ca4205p4-68804.pdf
'Sheeping off' an alfalfa field.