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��Sustainable Agriculture Green Manure Crops Aug. 2002, SA-GM-5 Common Oats Hector Valenzuela1 and Jody Smith2 Departments of 1Tropical Plant and Soil Sciences and 2Natural Resources and Environmental Management ommon oats (Avena sativa), a cool-season annual Ccereal, has gained popularity in Hawaii because of Benefits provided by common oats its ability to provide quick soil cover, suppress weeds, EXCELLENT for suppressing weeds due to rapid and increase soil organic matter at a very modest cost. growth and establishment Its tropical relative, the Black Oats variety, will soon be released in the southern USA under the name VERY GOOD as a catch crop for taking up and SoilSaver and already has a prominent place in some storing excess N and providing erosion control no-till systems and other sustainable agriculture systems GOOD for in Brazil. increasing soil organic matter Characteristics content to Common oats is an upright, annual grass that reaches a improve soil height of 2 5 ft (0.6 1.5 m). It has a fibrous root sys- structure, for tem. In Hawaii its growing cycle is approximately 60 animal grazing days. Its seed is inexpensive and there are many region- systems, and for ally adapted varieties. Consult a seed distributor to providing lasting choose a disease-resistant type. residues for a following crop Environmental requirements Oats thrives in cool, moist climates on well drained soils, TOLERATES low fertility soils but this crop is adapted to many soil types. It tolerates USE IN annual production systems with vegetables, soil pH levels from 5.5 to 7.0, but some varieties can herbs, cut flowers, other ornamentals, and root tolerate soil pH as low as 4.5. It has a wider pH adapt- crops such as dryland taro ability than wheat or barley, and it has a low lime re- quirement. In Hawaii, common oats can be grown year- round at elevations ranging from sea level to 4000 ft, according to the USDA Natural Resources Conserva- tion Service (NRCS). The crop tolerates wet soils better and Lanai suggest that Walken and Coker are prom- than barley. It requires more moisture than other small- ising in terms of vigorous growth, rapid soil cover, weed grain crops. suppression, low plant height, and lack of flowering. CTAHR Cooperative Extension Service agents report Cultivars using the rust-resistant cultivar Coker 234 successfully Common oats cultivars commonly recommended by the on Lanai. Cayuse oats grew well at CTAHR s low- Hawaii NRCS include Newdak , Steele , Swan , and elevation Waimanalo Research Station on Oahu. Stud- Valley. CTAHR oats variety trials on Hawaii, Molokai, ies conducted with sugarcane in central Oahu also Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii without regard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status. CTAHR publications can be found on the Web site <http://www2.ctahr.hawaii.edu> or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu. SA-GM-5 Green Manure Crops: Common Oats CTAHR Aug. 2002 showed that oats interplanted with sugarcane rows pro- of N for each ton of dry matter at plow-down. The addi- vided rapid soil cover and good weed control. Initial tion of this N fertilizer will promote microbial activity growth of the cover crop was much faster than the sug- and will also prevent the decomposing plant material arcane growth, so the cover crop provided early soil pro- from tying up nitrogen needed by the following crop. tection from erosion. Forage oats were also used suc- Alternatively, a mixed cover crop stand of oats and a cessfully for the protection of soils in abandoned pine- legume can minimize potential problems of N immobi- apple fields in Lanai, where a planting of 1000 acres of lization after cover crop plow-down. To allow time for oats showed that the crop can be successfully established residue decomposition, allow 2 3 weeks after cover crop with the winter rains, providing rapid and adequate incorporation before planting the cash crop. ground cover by 30 days after seeding. Incorporating oats into the soil also improves the soil health by improving the soil structure and tilth, Establishment which improves water infiltration. Most of this soil im- Broadcast 110 140 lb pure live seed per acre (3.5 4.5 provement will occur in the top soil layer. As the resi- bu/acre), or drill 80 110 lb pure live seed per acre (2.5 dues decompose, the organic matter additions also en- 3.5 bu/acre). Broadcast and cover or drill to a depth of courage the formation of a rich, beneficial microbial soil 1 D 2 2 inches and disk lightly. If the soil is sufficiently food web. moist, shallow seeding promotes rapid seedling emer- When planted at low densities, oats can also be used gence with reduced root rot disease. as a nurse crop for establishing slower growing legume cover crops. If it grows too vigorously, the oats crop can Uses be mowed to allow better growth of the legume inter- Weed control crop. The CTAHR research with oats on Lanai demon- Common oats provides several alternative methods of strated its many potential uses as a forage, soil conser- weed control, reducing the need for chemical weed con- vation alternative, and nurse crop to establish tropical trol. Oats germinate very quickly and are able to smother grass pastures (with rainfed alfalfa) and hay fields (with out emerging weed species. In addition, oats release al- green panic). lelopathic compounds, plant-made chemicals that hinder weed growth for several weeks. However, these same Management cautions compounds can hinder the growth of subsequent crops The allelopathic compounds that make oats an ideal crop such as lettuce, watercress, rice, wheat, and peas, so this for suppressing weeds may stunt the growth of a subse- allelopathic trait should be taken into consideration when quent cash crop. Avoid planting lettuce, cress, or peas planning the timing and sequence of a crop-rotation pro- immediately after incorporating oats. Allow 3 weeks for gram on the farm. The allelopathic compounds tend to the allelopathic compounds to decompose. break down in about three weeks. Pest problems Soil improvement When grown for grain or forage, oats tends to have more Common oats produces about 2 tons/acre dry matter and insect problems (such as armyworms, grain aphids and takes up about 16 lb of nitrogen in each ton of dry mat- mites, wireworms, cutworms, thrips, leafhoppers, grubs, ter (NRCS). Summer (June planting) fresh weight bio- and billbugs). Cultivars resistant to rust, smut, and blight mass yield at the Waimanalo Research Station were about have been developed; consult seed dealers for the latest 3700 lb/ac at 6 weeks after planting, harvested when information. Rust resistance may be a useful consider- the plants were 14 inches tall. A later planting (Sept.) in ation in some areas of Hawaii. Waimanalo with a 3-month growing cycle resulted in fresh weight biomass yields of 5400 lb/ac with plants Red and black oats harvested when 13 inches tall. Red oats (Avena bysantina) is recommended by NRCS The tissue N content of oats is about 1.2%. For an as a non-legume green manure. Establishment informa- optimal rate of oats residue decomposition, apply 20 lb tion and management features are very similar to com- 2 SA-GM-5 Green Manure Crops: Common Oats CTAHR Aug. 2002 mon oats. Red oats have grown very well at the Wai- For assistance: manalo Research Station. Contact your nearest Cooperative Extension Service of- Black oats (Avena strigosa) is a tropical and sub- fice for additional assistance in selecting appropriate tropical annual cereal enjoying enormous popularity as cover crops and green manures for your farm and crop- a cover crop in conservation-tilled soybean in Brazil. ping situation. Help can also be obtained from the USDA Black oats produces large amounts of biomass, has al- Natural Resources Conservation Service field offices lo- lelopathic properties similar to common oats (can sup- cated on each island. press weeds and crops for a few weeks), is somewhat Visit CTAHR s Sustainable Agriculture for Hawaii resistant to root-knot nematode (Meloidogyne javanica), Program Website at <http://www.ctahr.hawaii.edu/ and is very rust resistant. It can also serve as a forage sustainag> to find additional information about green crop. Low-elevation field plantings in Waimanalo (both manure and cover crops. The site also includes refer- broadcast and drilled in rows) showed excellent crop ences and links to other useful on-line resources. uniformity and stand establishment, vigorous growth, and local adaptability. The only cultivar currently avail- able in the USA is SoilSaver , which is a joint release between Auburn University and IAPAR (Institute of Agronomy of Parana, Brazil). Sustainable Agriculture in Hawaii . . . . . . integrates three main goals environmental health, economic profitability, and social and eco- nomic equity. Sustainable farms differ from con- ventional ones in that they rely more on manage- ment practices such as crop diversification and crop rotation, agroforestry, integrated pest management, rotational grazing, and innovative marketing strat- egies. For further information on Sustainable Agri- culture in Hawaii, contact: Dr. Richard Bowen, Hawaii SARE Program Coordinator phone (808) 956-8708 e-mail: <rbowen@hawaii.edu> <http://www.ctahr.hawaii.edu/sustainag/> This material is based on work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, and the Agricultural Experiment Station, Utah State University, under Cooperative Agreement 98-ESAG-1-0340. Portions of this text were adapted from the USDA Natural Resources Conservation Service Hawaii Field Office Technical Guide, Section IV, Code 340, Cover and Green Manure Crop May 1992. Plant drawing reprinted from Managing Cover Crops Profitably, 2nd edition, published by USDA s Sustainable Agriculture Network (SAN), original illustration by Marianne Sarrantonio and Elayne Sears. Logo drawing courtesy of Deitrich Varez. 3

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