New Cover Crops for California
Fred Thomas
CERUS Consulting, Richvale CA
Introduction
Cover cropping in California has grown increasingly popular with many farmers and ranchers. Most cover crop species and mixtures currently planted have been taken from the forage industry where the plant species have been bred or selected for maximum biomass production. In addition to biomass the other normally selected traits include grain or pulse yield, disease resistance, lodging, shattering, pest tolerance, seed yield, persistence, and other agronomic traits related to yield. With the development of cover cropping as a significant sales category for seed companies, the search for plant species that will be selected for their desired cover crop characteristics has begun to be explored by local, national, and international seed breeders and production companies.
Additionally, some new forage species have been developed that may be used for cover cropping while conferring the benefits of new disease or insect resistance. A list of these newer grains, forages, legumes, and annual clovers are included to explain their place in the palate of available choices for use in cover cropping systems. To ensure that reliable scientific information is developed, California researchers should include newer varieties along with older material in their research.
New Materials
'Trios 102' Triticale: A dormant triticale that was developed for upper Midwest forage. When planted in California in the fall, Trios 102 grows an extensive root system while top growth remains prostrate and dark green. Advantages are that the growth remains low through the winter while making a strong turf for winter orchard operations.
'Weedcheck' Mustard: A nematicidal mustard from Australia available for 1999.
'Nemafix' Mustard: A nematicidal mustard from Australia available for 1999.
'Carpet' Medic: A very prostrate M. polymorpha that only gets 4 inches tall and creates a dense, weed suppressive carpet.
'Overton R- 18' Rose Clover: A very high hardseeded (80%) rose clover selected for hardseededness and cold tolerance by Dr. Ray Smith, Texas Tech. The cold tolerance is to -10° F for use in upper Texas and lower Oklahoma. It is taller and later than Wilton and has very few watermarks compared to Hykon. West coast seed production fields have allowed this product to be used in California cover crops for the past 4 years.
'Nitro' Persian Clover: This clover has been made available from the Australian clover industry for the past two years and has been recommended in the improved BIOS mixtures. It flowers early with Hykon and in 1998 trials continued flowering into June with moisture available. The clover is small seeded with about 600,000 seeds per pound compared to rose clover at 180,000 seeds per pound. The flowers are very aromatic and perhaps good for beneficial insects.
'Bolta' Balansa Clover: An improvement on a previous Balansa clover marketed by the Australian industry. It too is very small seeded at about 500,000 seeds/lb. It is highly productive and reputed to like wet soil conditions. In Kamprath Seed Co. trials in California both Balansa and Persian Clover outyielded the subclovers.
Subterranean Clovers: There are a number of new releases of subterranean clovers which are PVP proprietary products compared to the older public varieties. These new varieties are being tested in California at this time with promising results, however long term replicated trials for persistence will require several years. The new varieties in order of maturity are:
| New | Replacement For |
| Losa | Dalkeith |
| Gosse | Trikkala |
| York | Seaton Park |
| Antas | Clare |
| Limbara | Woogenellup |
| Riverina | Junee |
| Denmark | Karridale/Mt. Barker |
Older Materials
'Juan' Triticale: This UC released Triticale cultivar has been in the marketplace as a grain and green forage product but only recently used as a cover crop. Compared to barley where it has been used on hillside vineyards for erosion, the advantages are that it is faster growing, more cold tolerant, and resistant to barley stripe rust which has decimated many cover crop stands of barley planted in monoculture.
Oilseed Radish: Marketed by specialty cover crop companies, this cover crop is especially active against cyst and sting nematodes. From observational trials at CSU Chico Farm the oilseed radish was equal to phacelia in early vigor and produced exceptional biomass.
Lablab: The two varieties of lablab, Hyworth and Rongal, have been used and marketed in California for 6 years with small amounts of Rongai seed arriving from Brownsville, Texas and a supply imported from Australia of Hyworth 6 years ago. Despite the superiority of this legume as a cover crop over cowpea and considerable testing by Steve Temple and Mark Van Horn at UC Davis; there is still no readily available seed supply.
Future Needs and Availability
The following products should join the above products which are entering the market from local and overseas seed producers. This would encourage both the planting and testing of these cover crops:
Lablab: A decade of solid work has shown the superiority of lablab, yet a supply is not available.
'Hubam' White Sweet Clover~ The previous seed source in Texas has been unable to supply clean seed for sale in California for five years and there are very few production fields left in the South.
Sour Clover: This very common cover crop of 60 years ago for both citrus and almonds has disappeared from the marketplace despite the efforts of Dr. Robert Bugg to encourage seed companies to provide a supply. Resident stands are scattered throughout non-farmed areas in California. Despite the reference in the UC SAREP Cover Crops database this excellent product remains unavailable to California farmers.
Conclusions
The market for cover crop specific seed products is sufficiently developed to encourage breeders and seed marketers to provide new plant materials. The continued expansion of cover crop products that are allelopathic, nematicidal, dwarf, or crop compatible represents a new and increased market venue for cover crop merchants.
Return to the index for the
Cover Crop Research and Education Summaries