- Oat is a viable cash crop that also helps manage the weed seed bank.
- Grain quality is as important as yield.
- Plant certified seed.
- Follow nitrogen, phosphorus and potassium application rate recommendations.
- Underseeding legumes with oat is a good way to incorporate green manure into an organic rotation.
Why should you consider oats in organic production?
Organic agriculture is the practice of producing food, for human and/or animal consumption where most synthetic pesticides and fertilizers are replaced with inputs that are permissible under the USDA guidelines for organic production and/or independent organic certification agencies. For example, urea and anhydrous ammonia are replaced with animal manure and manure composts.
Currently there are over 25,000 certified organic farmers and organic businesses in the US that generate well over $35 billion dollars in retail (USDA, 2012). In Minnesota, the Department of Agriculture (MDA) helps famers transition into or expand organic production.
While a corn soybean rotation is the most common crop rotation across the Corn Belt, organic producers generally deploy a much wider crop rotation that includes small grains and both annual and perennial legumes.
It is safe to say that crop rotation is one of the most critical practices to assure the success of any organic farm. Inclusion of cover crops and green manure crops further expand the usefulness of crop rotation as a means to control weed, insects, and disease problems and manage soil fertility in organic production.
Oat (Avena sativa L.) is a spring-sown cereal well adapted to much of the Corn Belt as it matures early enough to produce grain of acceptable quality. Oat is a cool season grass and as such is very competitive with most annual broadleaf and grassy weeds. Including oat in an organic crop rotation will help deplete the seed bank of a number of important weeds over time:
- Common and giant ragweed
- Warm season grasses such as green and yellow foxtail
This depletion advantage is especially true when combined with tillage immediately following harvest. Thus, the primary roles of oat in an organic crop rotation are that of a viable cash crop and that of a weed control tool to manage the weed seed bank.
Oat is also the most common nurse crop for small-seeded legume establishment like alfalfa. The straw is absorbent and a desirable source of bedding. To produce oat of acceptable quality fertility management and variety selection are two key factors for success.
Field selection and fertility management
Oat performs better when grown in soils that ranging from moderately well-drained to well-drained and with a pH ranging from 5.5 to 7.0. After selecting the area to be planted to oat, soil samples should be collected and sent out to lab analysis to determine the nutrient needs for the oat crop.
Nitrogen (N) requirement will depend on the previous crop grown, N credits from legume crops planted prior to the oat crop, and soil organic matter concentration in the top six inches (Tables 1 and 2). In the eastern part of Minnesota, soil test currently is not used in the N guidelines for oat production. The University of Minnesota guidelines do not differentiate between organic and conventional production practices. Selecting an appropriate yield goal, however, for either production system, is more important than the difference between sources of nitrogen or the production system itself.
Table 1. Suggested nitrogen application rates for oat grown in Minnesota by yield goal when soil nitrate test is not used and soil organic matter is low.
|Crop grown previous year||N Credit||40-60 bu/A||61-80 bu/a||81-100 bu/a||101-120 bu/a||121+ bu/a|
|Alfalfa (4+plants/ft2, Non-harvested sweet clover||104 lb/a||0 lb N/a||0 lb N/a||0 lb N/a||0 lb N/a||0 lb N/a|
|Soybeans||45 lb/a||0 lb N/a||20 lb N/a||40 lb N/a||60 lb N/a||80 lb N/a|
|Edible beans, field peas, harvested sweet clover||45 lb/a||0 lb N/a||20 lb N/a||40 lb N/a||60 lb N/a||80 lb N/a|
|Other legume crops e.g. clover, birdsfoot trefoil||65-80 lb/a||0 lb N/a||0 lb N/a||0 lb N/a||25 lb N/a||45 lb N/a|
|Non-legume crops e.g. canola, potato, wheat, corn||0 lb/a||40 lb N/a||60 lb N/a||80 lb N/a||100 lb N/a||120 lb N/a|
Table 2. Suggested nitrogen application rates for oat grown in Minnesota by yield goal when soil nitrate test is not used and soil organic matter is medium or high.
|Crop grown previous year||N Credit||Organic matter content||40-60 bu/a||61-80 bu/a||81-100 bu/a||101-120 lb/a||121+ lb/a|
|Alfalfa (4+plants/ft2, Non-harvested sweet clover)||104 lb/a||medium/high||0 lb N/a||0 lb N/a||0 lb N/a||0 lb N/a||0 lb N/a|
|Soybeans||45 lb/a||medium/high||0 lb N/a||10 lb N/a||30 lb N/a||50 lb N/a||70 lb N/a|
|Edible beans, field peas, harvested sweet clover||45 lb/a||medium||0 lb N/a||25 lb N/a||40 lb N/a||55 lb N/a||70 lb N/a|
|Other legume crops e.g. clover, birdsfoot trefoil||65-80||medium||0 lb N/a||0 lb N/a||0 lb N/a||15 lb N/a||35 lb N/a|
|Non-legume crops e.g. canola, corn, potato, wheat||0 lb/a||medium||30 lb N/a||50 lb N/a||70 lb N/a||90 lb N/a||110 lb N/a|
Nitrogen recommendation when using soil nitrate test
For the western part of Minnesota the amount of N needed for optimum oat production can be estimated using the soil analysis and the amount of N recommended can be used according to the following equation:
Nneeded = (1.3)*(Expected Yield (bu / acre)) – STN – Nlegume
Where the Nneeded is the amount of N from Table 1; STN is the amount of nitrate available according to the soil test nitrate levels from 0 to 24 inches, and Nlegume is the credit from the previous crop as indicated in Table 1 N credit column.
Phosphorus (P) and potassium (K) levels in the soil should also be determined so that deficiencies can be corrected. In organic oat production the nutrient sources used to supply any nutrient must follow the recommendations provided by the Organic Materials and Review Institute (OMRI).
In most cases, when N is applied P and K will also be applied. This is because the most commonly used sources of N in organic agriculture are animal manure, animal manure compost, or other green leaf compost, which also have considerable amounts of P and K (Table 3).
Careful examination of nutrient status of the soil should precede any further nutrient addition and will minimize potential environmental problems that can result from over application of nutrients. In addition to macronutrients, manure and compost will also supply micronutrients and organic matter to the soils.
Table 3. Approximate nutrient composition on a total basis of various types of animal manure and compost (all values are on a fresh weight basis).
|Manure Type||Dry Matter||Total N||P2O5||K2O|
|Swine, no bedding||18%||10 lb/ton||9 lb/ton||8 lb/ton|
|Swine, with bedding||18%||6 lb/ton||7 lb/ton||7 lb/ton|
|Beef, no bedding||52%||21 lb/ton||14 lb/ton||23 lb/ton|
|Beef, with bedding||50%||21 lb/ton||18 lb/ton||26 lb/ton|
|Dairy, no bedding||18%||9 lb/ton||4 lb/ton||10 lb/ton|
|Dairy, with bedding||21 lb/ton||9 lb/ton||4 lb/ton||10 lb/ton|
|Sheep, no bedding||28 lb/ton||18 lb/ton||11 lb/ton||26 lb/ton|
|Sheep, with bedding||28 lb/ton||14 lb/ton||9 lb/ton||25 lb/ton|
|Poultry, no litter||45 lb/ton||33 lb/ton||48 lb/ton||34 lb/ton|
|Poultry, with litter||75 lb/ton||56 lb/ton||45 lb/ton||34 lb/ton|
|Turkey, no litter||22 lb/ton||27 lb/ton||20 lb/ton||17 lb/ton|
|Turkey, with litter||29 lb/ton||20 lb/ton||16 lb/ton||13 lb/ton|
|Horse, with bedding||46 lb/ton||14 lb/ton||4 lb/ton||14 lb/ton|
|Poultry compost||45 lb/ton||17 lb/ton||39 lb/ton||23 lb/ton|
|Dairy compost||45 lb/ton||12 lb/ton||12 lb/ton||26 lb/ton|
|Mixed compost: Dairy/Swine/Poultry||43 lb/ton||11 lb/ton||11 lb/ton||10 lb/ton|
Analyze your nutrient source for best results
Table 3 provides an average value of nutrient found in several organic sources; however, the grower should have an analysis of the manure or compost that will be applied to each particular field so that precise nutrient calculations can be done and the correct amount of nutrient can be applied. Follow the recommendations provided by the University of Minnesota guidelines for proper calculation of the correct amount of N to be applied to organic oat when using either manure or compost.
The amount of the nutrient available for crop uptake is not necessarily the same as the values listed in Table 3. For P and K, typically about 80% to 100% can be considered available in the first year; however, N that is available is much lower and ranges about 50% of the total in the first year. For the remaining 50% of the N applied, 25% is considered available in the 2nd year and 12% available in the 3rd year. More information on manure nutrient availability can be found on the Manure land application website.
Over application of manure and compost can cause adverse effects not only for the crop but also for the environment. Over application of N can cause the oat crop to stay on a vegetative stage longer than ideal and minimize yield potential.
Proper handling of manure after broadcast application onto the field is required to assure nutrients react with the soil to reduce loss of soluble forms. Nitrogen volatilization when manure is surfaced applied and not incorporated is a major pathway for N loss from manure. When manure or compost is left on the soil surface P can runoff the field with rainfall water, which would minimize the nutritional value of manure and lead to environmental degradation.
The best management strategy to maximize the effectiveness of manure or compost as a nutrient source and minimize environmental problems is to incorporate applied manure or compost within 24 hours after application. Manure or compost should not be applied to frozen soils as significant amounts of nutrient can be transported off the field with snow melt.
Grain yield and quality
While grain yield is an important criterion in variety selection, grain quality is as important as grain yield if the harvested grain is to be marketed. Oat color is an important consideration and it is advisable to talk to potential buyers whether they prefer yellow or white oats.
The second quality factor is test weight and although varieties differ some for test weight, the most important step to maintain test weight is select a variety that matures early enough to escape heat stress during grainfill.
Crown rust resistance
Another selection criterion for variety selection is the level of resistance of the variety to crown rust (Puccinia coronate Corda var. avenae W.P. Fraser Ledingham). Crown rust is the most widespread and damaging disease of oat. Epidemics of crown rust are common in the Upper Midwest, including Minnesota, in part because the alternate host common buckthorn (Rhamnus cathartica L.) is commonly found in woodlands and windbreaks. Only select varieties with the best resistance ratings to crown rust to avoid total crop failures. Consult the field crop trials, published annually by the Minnesota Agricultural Experiment Station, for resistance ratings.
Use certified seed
Only use seed from registered and certified seed classes of known varieties. Certified seed must be sold with an accompanying blue tag that lists the variety name germination, weed seed, and inert matter percentage; seed lot number; and source of production. Avoid seed sold as VNS (variety not stated) because the seed could be a varietal mixture, an unknown variety, old seed that did not sell well, or a disease-susceptible variety.
Seeding dates and rates
Oat should be planted as early as possible to maximize yield and test weight. Grain yields decrease an estimated percent per day when planting past the optimum planting dates as the odds of heat stress later in the growing season will increase. Unlike corn and soybean where organic producers often use delayed planting as a strategy for weed management, organic small grains should be at the same time in early spring as conventional small grains.
Optimal plant populations are important to maximize grain yields. An initial stand of 28 plants per square foot or 1.2 million plants per acre is considered ideal for oat when seeding early. Plant populations below optimum can result in
- Increased weed pressure.
- Excess tillering and uneven maturity.
- Lower grain yield potential.
Above-optimum populations can result in
- Lack of tillering.
- Weaker stems.
- Increased risk of lodging.
When seeding is delayed
Seeding rates should be adjusted by about 40,000 plants per acre per week of delay and up to 1.6 million seeds per acre when planting is delayed past the optimum planting date. This will compensate for reduced yields that occur due to reduced tillering in late plantings.
Legume companion crops
Oat can be underseeded with red clover or alfalfa. Red clover tends to be less competitive with oat and is more easily terminated, while alfalfa can be used as an acceptable alternative. Red clover can be underseeded at six to ten pounds per acre, while alfalfa can be underseeded at eight to ten pounds per acre. Underseeding these legumes is an excellent, low-risk way to incorporate green manures into an organic crop rotation.
Organic oat research at the Southwest Research and Outreach Center (SWROC)
The SWROC at Lamberton, MN has been conducting replicated field trials on certified organic ground since 2014 to provide Minnesota organic growers with data to maximize crop profitability and production of organic oat.
- Previous years’ crop was soybean in 2013, 2014, and 2015.
- The nutrient sources used in this research were beef manure and beef manure compost.
- Each source of nutrient was applied at 0, 45, 90, and 135 lbs N/Ac and replicated four times.
- The treatments were broadcast and then incorporated soon after application to assure no N would volatilize prior to incorporation.
- This study also investigated varieties with different maturity and different seeding rates:
- In 2014, the varieties tested were ‘Shelby’ (medium season), ‘Tack’ (early season), and ‘Hi-Fi’ (late season).
- In 2015 the varieties tested were ‘Shelby’, ‘Tack’, and ‘Deon’ (late season).
- In 2016 the varieties tested were ‘Shelby’, ‘Deon’, and ‘Saber’ (early season).
The best N rate used varied by variety and year. Soybean can provide a significant amount of N for the crop planted after soybean harvest regardless of whether a crop is conventionally or organically grown. From Tables 1 and 2, the required N rates for optimum oat yield after soybean ranged from 0 to 80 lbs N/ac.
The best yield for the 2014 was around 80 (Shelbi and Tack) to 100 (Hi-Fi) bushels/ac. From Tables 1 and 2, the required N rate to add after a soybean crop would be 50 lbs of N/ac, matching our results for organic oat production being fertilized with either beef manure of beef manure compost.
In 2015 and 2016, the best yield was around 130 bushels/ac and all three varieties had similar yield. The highest yield was again observed between the rates of 45 and 90 lb N/ac, which also matches the recommended rates from Tables 1 and 2.
In all three years of the research, N rates higher than 90 lb N/ac had decreased yield compared with the lower rates of N. Therefore, when oat is planted after soybean, it is recommended that the N rates be limited to no more than 90 lb N/ac as higher rates will limit organic oat yield.
Seeding rate is the next most important consideration after nutrient management in oat production. Seeding rate is based on the number of bushels of seed per acre to be planted. A seeding rate of 3 bu/ac has been shown to yield as much as 4 bushels under normal conditions.
In trials conducted at the SWROC it was observed that organic oat yield as function of seeding rate was very consistent among the varieties used, though it varied by year.
- In 2014 and 2015 there were no significant differences between the two seeding rates.
- However, in 2016, seeding at the 4 bushel/ac resulted in 103 bushel /ac; while seeding at the 3 bushel/ac resulted in 99 bushel/ac.
In general, seeding at 3 bushel/ac will provide as consistent yield as seeding at 4 bushel/ac, and economically it might make more sense to not exceed the 3 bushel/acre seeding rate.
USDA – Organic Standards:
USDA – What is Organic Agriculture?
MDA – Beginning and Transitioning Farmer Information (including current funding available for improvement or the beginning of a new operation):
University of Minnesota Extension – Fertilizer Recommendations by crop:
Organic Materials Review Institute (OMRI):
University of Minnesota Extension – Using manure and compost as nutrient sources for fruit and vegetable crops:
University of Minnesota Extension – Fertilizer recommendations for oat in Minnesota
University of Minnesota Extension – Manure land application
Reviewed in 2018