- Author: Michelle Leinfelder-Miles
- Author: Mick Canevari
A land manager recently contacted me with questions about overseeding alfalfa. Her alfalfa stand is diminishing but not to the point of giving up on it. Rachael Long, Yolo County farm advisor, Dan Putnam, UC Davis alfalfa specialist, and Mick Canevari, San Joaquin County farm advisor emeritus, presented on this topic at the Alfalfa and Forage Symposium a few years back and wrote up a proceedings paper on this topic. Additionally, there is a production manual which is available through the UC ANR catalog.
The table below names seeding rates for various annual and perennial species that could be overseeded into alfalfa. The rates have a range (e.g. 4-8 lbs/acre). First, consider the field conditions and the alfalfa stand in order to pinpoint a rate in that range. For example, if the alfalfa is sparse, 2, then perhaps aim on the high end of that range.
Table. Seeding dates and rates for crops overseeded into alfalfa for the Sacramento and San Joaquin Valleys. In the Intermountain Region (Northern California) annual grasses are planted February to April; perennial grasses are planted August to September or March to April. (Table courtesy Long, Putnam, and Canevari, 2003)
If two overseeded species are desired (e.g. one grass and one legume), then the seeding rate could be reduced by 25-30% for both species. So, for example, if orchardgrass and red clover are to be planted over a sparse alfalfa field, then instead of planting the high rates of both, 8 and 12 lbs/acre, respectively, the rates could be reduce 25% to 6 and 9 lbs/acre, respectively, when planting both species.
The reason it is not recommended to overseed with more than two species is because some of the species will outcompete others. The ryegrasses (annual and Italian) are very vigorous and could outcompete red clover, for example. Orchardgrass or tall fescue are best paired with red clover. Berseem clover and a ryegrass, however, could work well together because they have similar vigor and growth timing.
Overseeding should take place in the fall, and ground preparation is important. Scratch up the soil with a harrow; then broadcast the seed, and roll it to slightly cover the seed. Keep in mind that with broadcasting equipment, if seed size is different, the heavy seed may settle to the bottom, and it may not result in a uniform planting of both species. Ensure that seed is mixed well before broadcasting, or use a grain drill. If substantial rain isn't on the forecast, it is best to irrigate the newly overseeded crop to ensure a good stand.
With proper considerations, overseeding could extend the life of an alfalfa field by 2-3 years.
- Author: Michelle Leinfelder-Miles
Please mark your calendar with the following fall outreach events.
Dry Bean Field Day
August 25, 2016
10:00am-12:00pm
UC Davis Agronomy Field Headquarters, Hutchison Drive, UC Davis
Rice Experiment Station Annual Field Day
August 31, 2016
7:30am-12pm (lunch included)
Rice Experiment Station, 955 Butte City Hwy, Biggs, CA 95917
For more information, visit the Rice Experiment Station website.
Alfalfa and Forage Field Day
September 14, 2016
7:30-12:30pm (lunch included)
Kearney Agricultural Research and Extension Center, 9240 S. Riverbend Ave., Parlier, CA
For more information, see the attached flyer.
UC Soil and Water Short Course
November 17, 2016
7:30am to 4:30pm
Buehler Alumni Center, UC Davis
For more information, please visit the registration website.
California Alfalfa and Forage Symposium
November 29-December 1, 2016
Peppermill Hotel, Reno, NV
For more information, please visit the CAFA website.
Alfalfa and Forage Field Day Flyer
- Author: Michelle Leinfelder-Miles
I recently visited a bean field in the southern part of the county with a PCA. From a distance, the beans in certain areas of the field appeared to be drying up and dying. A closer look showed that the leaf margins were drying up first before the whole plants declined. Pulling up plants by the roots, they appeared to show some reddish root lesions. Soil moisture was good – it seemed neither too wet nor too dry, but there was white crusting on the soil surface of the furrows.
As I was thinking about what could be happening with the beans, a couple things were running through my mind. The patchiness of the problem in the field and the reddish roots made me think that Fusarium root rot (Figure 1) may be a problem. The PCA believed that there had been tomatoes in the field the previous year but that there may have been beans in the field just two years ago. I wondered whether the white crusting on the soil was due to salt. The PCA said that he thought the field was irrigated with groundwater.
To put something behind my hunch, I sent plant samples up to the disease diagnostics lab at UC Davis. Tests confirmed that both Fusarium and Rhizoctonia inoculum were present on the plant roots and that the Fusarium inoculum was particularly high. Fusarium spores can survive in the soil for several years, and UC IPM guidelines suggest rotating out of beans for at least three years in Fusarium-affected fields. Unfortunately, Fusarium spores will live in the soil even when bean hosts are not present.
Stress conditions in the field can worsen Fusarium infection, particularly conditions of too much or too little water, compaction, and salinity. We tested the soil salinity at this site and found the electrical conductivity (EC) of the surface soil to be around 5.0 decisiemens per meter (dS/m). Beans are very sensitive to salinity, and yield declines are expected when rootzone soil salinity is as low as 1.0 decisiemens/meter. It would appear that salinity could be stressing the beans and causing them to be more susceptible to the Fusarium inoculum in the soil. Because this grower is irrigating with groundwater, I would recommend that he get his water tested for salinity. If the water salinity is acceptable, then he should consider how he will leach the field this winter, perhaps augmenting rainwater with irrigation water (assuming normal-to-low precipitation this winter). If his groundwater is high in salts, then he should consider using a different water source for irrigating and leaching (if available) and rotate to more salt-tolerant crops, like small grains, for at least three years.
- Author: Michelle Leinfelder-Miles
- Author: Michelle Leinfelder-Miles
I was recently contacted by a PCA who was observing armyworm feeding in Delta rice fields. Over the last two years, both locally and in the Sacramento Valley, armyworms have been striking rice fields earlier in the season and in greater numbers. This has been described by farm advisors in the UC Rice Blog. Armyworms are generally a summer pest of rice, spending spring and early summer months on other plants, but over the last two years, armyworm feeding has been detected in June. Armyworms generally only have one generation in rice later in the season, but last year, earlier infestations caused concern for there to be two generations. This was not generally observed, but PCAs should keep this in mind again this year as they scout throughout the summer.
Armyworm defoliation is most deleterious during stem elongation and grain formation and is observed as angular cut-outs from the leaves (Figure 1). UC IPM guidelines state that yield may be affected if defoliation is greater than 25 percent of the plant at two to three weeks before heading, and they provide the following monitoring instructions.
To sample, choose a part of the field where you have observed injury. Select a plant at random and pull it up or move all the surrounding foliage away and check for defoliation. Check the plant from the top of the leaves to the base of the plant and the water surface for armyworms. Determine if 25% or more of the foliage has been removed by armyworms; also note if you find armyworms on neighboring weeds or rice plants. Record your observations on a monitoring form. Repeat this procedure every 5 to 10 feet across a transect until 10 plants have been examined. Move to a different part of the field where feeding is evident and examine 10 more plants in the same manner. Repeat this procedure at several areas of the field until you are confident that you have an estimate of the average field condition.
It is important to monitor throughout the season in order to detect damage severity, and thus, know when to treat. Later in the season, damage may also occur on the panicle rachis. UC IPM guidelines recommend treatment when, in the vegetative stage, at least half of the plants sampled have at least 25 percent defoliation and armyworms are present. When the panicle has formed, UC IPM guidelines recommend treatment if 10 percent of the sampled panicles are damaged and armyworms are present. Armyworms are generally more apparent at night or in the cooler morning hours; thus, monitoring should occur when worms are active and apparent.
Early season management of armyworms includes weed management around the perimeter of fields. Registered chemicals are limited but include certain pyrethroids, which have not always proven efficacious, and carbaryl, which cannot be used within two weeks of a propanil application. The carbaryl label also includes precautionary language regarding bees, so it would not be recommended when rice is neighbored by insect-pollinated crops, like melons.
This year, the California Department of Pesticide Regulation has issued a crisis exemption under the US EPA Section 18 to allow for the use of Intrepid 2F (methoxyfenozide) on armyworms in certain rice growing counties, including San Joaquin County. The emergency exemption is valid until September 30, 2016. Please contact the county Agricultural Commissioner's office for more details.
