Management of postharvest residue, including stubble and straw, is an important practice in grass seed production. Crop residues are managed for pest control, to stimulate seed yield of grasses, to remove large volumes of straw and stubble that might interfere with crop management operations, for income from straw sales, and to recycle nutrients to fields.
Traditional straw management changed rapidly beginning in the mid-1980s as the practice of open-field burning was legislatively reduced in Western Oregon. Previously, this practice was the predominant residue management method, but since 2007 it has been used on less than 10% of the grass seed crop acreage (Figure 4). This reduction has taken place even as the acreage of grass seed crops has reached record levels.
When the discussion on banning open-field burning began, the initial perception was that maximum grass seed yields could not be achieved if substantial straw residue was left on the surface. Subsequent research, coupled with grower input, resulted in the development of management practices that can achieve comparable grass seed yields without residue removal.
Postharvest residue management varies around the world. For example, producers in New Zealand, Washington state and England routinely remove straw for use as feed in dairies and other animal production enterprises. In Argentina, annual and perennial ryegrass straw is usually baled, but it sometimes is chopped before direct seeding the next crop. Danish growers usually bale after the first two years of grass seed production. After the last harvest in a rotation, if they are not able to sell the straw for animal feed or biofuel, it is chopped. In Denmark, use of some fungicides and growth regulators prevent straw use as animal feed.
No “right or wrong” residue management system exists; rather, management choices and costs influence decisions. The choice to bale or chop straw is not always straightforward, and the best option can differ among fields and with stand age. Factors such as economics (straw price, as well as fertilizer, fuel and labor cost), crop rotation, weed problems and stand age interact with grower preferences to determine whether straw should be removed or remain in the field.
Seed yield and quality
With careful and timely management, little difference in grass seed yield is measured regardless of whether straw is baled or remains in the field.
Light penetration to the growing point of the grass plant is critical to the success of either approach. Straw must be removed from the plant crown for adequate sunlight to be received. Timing is critical. Remove straw as soon as possible after harvest, preferably within a week.
Where straw is returned to the field, spread it across the field as uniformly as possible during threshing and subsequent chopping operations. Although finely chopped straw more easily settles between rows than coarsely chopped straw, uniform spreading of all straw is important for adequate light penetration.
When swathing is clean and uniform, and straw is baled in a neat and timely fashion, expending an additional $10–$15 per acre to chop the remaining stubble is not economically prudent (Figure 8).
Comparisons between chopping the full straw load and baling cannot be reduced to a simple statement that seed yield increases or decreases with use of either system. In addition to interacting with straw management, seed yield changes with stand age. This concept is shown for a perennial ryegrass field in Figure 9.
Seed yield also varies annually. Thus, to compare the effect of straw management, Figure 9 uses an index, or relative yield, for each year. Each year, the “bale” treatment was the standard, or 100%. The full straw load treatment yield was slightly less in all years. In general, yield differences between bale or full straw load management are not large, but even a slightly lower yield is a concern for producers.
Perennial ryegrass seed yield under various straw management options was compared in 25 situations during a five-year period. The average seed yield was 8% less when the full straw load was chopped onto the field, compared to removal with baling. For a 1,500 pounds per acre yield, the average reduction would be approximately 120 pounds per acre.
A similar number of comparisons have been made for tall fescue seed yield. The seed yield was comparable for both straw management options. For example, in two second-year tall fescue seed fields, average seed yield when chopping the full straw load was 99% of the seed yield with complete straw removal treatment. Partial straw removal produced a similar seed yield — 101% compared to complete straw removal treatment.
In addition to seed yield, the influence of straw management on seed quality is a consideration. Fortunately, returning straw to fields of perennial ryegrass or tall fescue does not reduce seed purity and germination (Table 1). Seed quality is comparable for both straw management options.
|
Grass species/ Residue management |
Pure seed purity (%) |
Other crop purity (%) |
Inert matter purity (%) |
Weed seed purity (%) |
Germination (%) |
|---|---|---|---|---|---|
|
Tall fescue |
|||||
|
Chop |
95.9 | 0.4 | 3.7 | 0.1 | 91.4 |
|
Bale |
96.1 | 0.3 | 3.5 | 0.1 | 91.4 |
|
Perennial ryegrass |
|||||
|
Chop |
93.8 | 2.0 | 3.9 | 0.1 | 91.6 |
|
Bale |
94.2 | 1.9 | 3.8 | 0.1 | 92.4 |
Nutrient management considerations
This section examines nutrient management topics for different residue management systems in grass seed production. Recommendations apply to perennial ryegrass, tall fescue and annual ryegrass produced for seed in Western Oregon.
Nutrient removal and cycling
Removal of all above-ground biomass (seed and vegetative matter) is the standard practice for several crops commonly grown in western Oregon. Peppermint, silage corn, alfalfa, grass hay and Christmas trees are examples. Nutrient removal is substantial in these situations, but varies among crops (Table 2). Nutrient removal is part of the production cost for these crops. Likewise, this cost should be considered in grass seed production when baling straw (Figure 10).
When only a portion of the crop is harvested, such as pods of green beans or rhubarb stalks, nutrient removal is lower (Table 3). For a crop grown for seed, such as wheat, most of the N is removed with the grain, but most of the K remains in the straw (Table 3).
Nutrient abbreviations
- B: Boron
- Ca: Calcium
- Cu: Copper
- K: Potassium
- KCl: Potassium chloride (muriate of potash)
- K2O: An oxide expression of K used on fertilizer packaging
- Mg: Magnesium
- N: Nitrogen
- P: Phosphorus
- P2O5: An oxide expression of P used on fertilizer packaging
- S: Sulfur
- Zn: Zinc
|
Nutrient removal (lb/a) |
||||||
|---|---|---|---|---|---|---|
|
Crop |
N |
P |
K |
Ca |
Mg |
S |
|
Alfalfa |
500 | 45 | 500 | 220 | 50 | 50 |
|
Corn silage |
175 | 16 | 125 | 35 | 25 | 12 |
|
Grass hay |
120 | 20 | 150 | 20 | 10 | 12 |
|
Peppermint |
200 | 35 | 275 | 90 | 30 | 20 |
aAssumes a yield of 90 pounds oil per acre for peppermint, 25 tons per acre for corn silage, 3 tons per acre for grass hay, and 8 tons per acre for alfalfa. Elemental phosphorus and potassium removal are used rather than oxide forms, P2O5 or K2O.
|
Nutrient removal (lb/a) |
||||||
|---|---|---|---|---|---|---|
|
Crop |
N |
P |
K |
Ca |
Mg |
S |
|
Rhubarb |
65 | 10 | 130 | 65 | 5 | 3 |
|
Green breans |
35 | 5 | 25 | 6 | 3 | 2 |
|
Wheat grain |
90 | 20 | 28 | 5 | 10 | 7 |
|
Wheat straw |
16 | 3 | 80 | 55 | 40 | 30 |
aAssumes a yield of 8 tons per acre for rhubarb, 100 bushels per acre for wheat grain, 3 tons per acre for wheat straw, and 6 tons per acre for green beans. Elemental phosphorus and potassium are used rather than oxide forms, P2O5 or K2O.
|
Grass species/Component |
Weight |
N |
P |
K |
Ca |
Mg |
S |
|---|---|---|---|---|---|---|---|
|
Annual ryegrass |
|||||||
|
Seed |
2,000 | 40 | 8 | 15 | 3 | 3 | 1 |
|
Straw |
4,000 | 40 | 8 | 40 | 17 | 4 | 8 |
|
Total |
— | 80 | 16 | 55 | 20 | 7 | 9 |
|
Perennial ryegrass |
|||||||
|
Seed |
1,500 | 30 | 5 | 7 | 3 | 3 | 1 |
|
Straw |
4,500 | 55 | 6 | 93 | 11 | 7 | 7 |
|
Total |
— | 85 | 11 | 100 | 14 | 10 | 8 |
|
Tall fescue |
|||||||
|
Seed |
1,400 | 30 | 5 | 7 | 3 | 3 | 1 |
|
Straw |
5,000 | 55 | 6 | 103 | 17 | 10 | 8 |
|
Total |
— | 85 | 11 | 110 | 20 | 13 | 9 |
|
Nutrient (%) |
|||||
|---|---|---|---|---|---|
|
Grass species |
N |
P |
K |
Ca |
Mg |
|
Perennial ryegrass |
|||||
|
Range |
0.75–1.75 | 0.05–0.2 | 0.3–2.5 | 0.25–0.5 | 0.1–0.2 |
|
Average |
1.0 | 0.1 | 2.0 | 0.35 | 0.12 |
|
Tall fescue |
|||||
|
Range |
0.7–2.0 | 0.05–0.2 | 0.5–3.0 | 0.2–0.5 | 0.1–0.3 |
|
Average |
1.0 | 0.1 | 2.0 | 0.3 | 0.18 |
When straw remains in the field, nutrient removal in grass seed crops is small, compared to crops such as peppermint, alfalfa or grass hay, where the entire above-ground biomass is removed (Tables 2 and 4). Reduced nutrient removal is one reason given for chopping rather than baling straw.
Nutrient management recommendation: No seed yield increase from added nutrient supply has been attributed to chopping straw when soil test levels are adequate.
Nutrient removal is driven by two factors — the amount of straw removed and the concentration of nutrients in straw. Chopping returns 3–4 tons straw per acre. Baling removes 70–80% of this amount. Baling contractors associated with the Agricultural Fiber Association (a nonprofit association of Oregon straw merchants) estimate that 4,500 pounds straw per acre is removed from perennial ryegrass fields and 5,000 pounds per acre from tall fescue fields. If the amount of straw removed is relatively constant, then tissue nutrient concentration determines differences in nutrient removal. Table 5 shows ranges of nutrient concentrations for perennial ryegrass and tall fescue.
Because straw nutrient concentration varies (Table 5), keep in mind that the nutrient removal data in Table 4 should be used only as an example and not for management decisions. When straw nutrient concentration will be used to make management decisions, annual analyses for individual fields are necessary.
Micronutrient removal is also a concern of growers. Compared to N, P and K, the amount of boron (B) and zinc (Zn) in grass straw is very small (table 6). Even so, growers frequently ask whether micronutrient addition is needed. Research in the past 20 years has not demonstrated the need for micronutrient addition (see Appendix A). For example, B application did not increase seed yield 90% of the time in Western Oregon field studies.
|
|
Micronutrient (oz/a) |
|||
|---|---|---|---|---|
|
Grass species |
Weight (lb/a) |
B |
Cu |
Zn |
|
Tall fescue |
||||
|
Straw |
5,000 | 0.6 | 0.2 | 1.0 |
|
Seed |
1,400 | 0.1 | 0.2 | 0.9 |
|
Total |
— | 0.7 | 0.4 | 1.9 |
|
Perennial ryegrass |
||||
|
Straw |
4,500 | 0.6 | 0.2 | 0.9 |
|
Seed |
1,500 | 0.1 | 0.2 | 1.0 |
|
Total |
— | 0.7 | 0.4 | 1.9 |
Nitrogen (N)
Nutrient management recommendation: Since N supply differences are small regardless of residue management practice, and no research has evaluated whether N rate can be reduced when straw is returned, use the same rate of N regardless of straw management.
One concern with addition of organic residue such as straw is immobilization or preferential use of N by microbes as they decompose the organic material. Immobilization can decrease plant growth when the plant-available N supply is low or when plant demand is high.
However, to decompose straw, microbes require moisture and moderate temperatures. These environmental factors are not achieved until late April or early May in Western Oregon. Straw remains relatively undecomposed until this time, and then disappears rapidly. Meanwhile, plant demand for N is typically highest in mid-April, just before rapid decomposition (and potential immobilization) occur.
Chopping all the straw onto a field does not immobilize significant amounts of N. Evidence to support this statement is found in the difference between N uptake in treatments that were baled and those where all of the straw was chopped (Figure 11). The difference in N uptake was small, about 15 pounds per acre, and changed with stand age. In the second year of the stand, tall fescue receiving the full straw load contained slightly less N than did the grass where straw was baled. The situation was reversed in a fourth-year field. Similar results are expected in most fields as no adjustment in N rate is necessary when straw is chopped.
Phosphorus (P)
Nutrient management recommendation: Soil test P does not decline when straw is chopped, and its decline is small and gradual when straw is baled. Monitor soil P by regular soil analysis, apply P as recommended in OSU nutrient management or fertilizer guides, and use the same rate of P regardless of straw management.
A similar amount of P is found in grass seed and grass straw. Even though baling straw doubles P removal, P use is small compared to N and K use by grass seed crops (Table 4).
Soil test P declines 1 part per million or less each year with straw removal. This small quantity of P removed with straw will not be detected in a P soil test, especially when soil test P is more than 40 parts per million .
Phosphorus soil tests from two sample depths for bale and chopped straw management were compared on two annual ryegrass fields for three years (Table 7). Phosphorus in the surface 2 inches was likely influenced more by annual fertilizer application than by straw management. In the second sampling depth (2–8 inches), soil test P was 1–2 parts per million lower in the area where straw was baled compared to the chopped area. This rate of decline is minimal and is not a reason to change the P application rate.
|
Soil test P (ppm) |
||
|---|---|---|
|
Straw management |
Depth: 0–2 inches |
Depth: 2–8 inches |
|
Moderate soil test P |
||
|
Bale |
20 | 15 |
|
Chop |
20 | 16 |
|
High soil test P |
||
|
Bale |
48 | 47 |
|
Chop |
47 | 49 |
Soil test P also decreased slightly in the surface inch of soil in a tall fescue grass seed field when straw was baled. After three years of baling straw, soil test P from the surface inch of soil was 4 parts per million less than in soil where straw had been chopped. The soil test values below the surface inch were the same (Figure 12).
A similar decline has been measured in perennial ryegrass (Figure 13). When no P fertilizer was topdressed and straw was removed from a perennial ryegrass seed field, the P soil test declined 1 part per million per year. Over three years, soil test P declined from 17 to 14 parts per million in the surface inch of a Bashaw soil (Figure 13). Slow and slight changes in P soil test values are expected for this soil series, as it is well “buffered."
In contrast to the buffered Bashaw soil, a very sandy golf putting green has little buffering capacity, and rapid soil test change is expected with clipping removal. Figure 14 shows the decline in soil test P for 15 years from a bentgrass putting green with clippings removed and no P fertilizer added. Maximum P soil test decline is expected in this situation. Even so, the rate of decline was slow, only 3 parts per million per year.
These examples illustrate that straw removal changes soil test P slowly, despite doubling P removal. Soil with more than 35 parts per million soil test P can adequately supply P to grass seed crops even when straw is baled for many years, as long as a decade.
Potassium (K)
Nutrient management recommendations: When straw is chopped and the preplant soil test for K is above 150 parts per million, K is adequate for the life of the stand. You do not need to soil test for K or add K for the life of a perennial ryegrass stand or for three to four years for other grass species. When straw is baled, monitor soil test K annually or every two years and apply K using rates provided in Table 8.
Vegetative plant material contains a substantial amount of K (Tables 2 and 4). Removal of 75% or more of the vegetative plant material by baling straw removes 10 times more K than does chopping the straw. Table 4 shows that in some grass species grown for seed less than 10 pounds K per acre is removed in grass seed and approximately 100 pounds K per acre is removed with straw.
Potassium concentration of most perennial ryegrass straw is 1–2%, but it can be higher (Table 5). Potassium removed in 4,500 pounds perennial ryegrass straw ranges from 45 pounds per acre to 90 pounds per acre. The extent of this range emphasizes the need for monitoring soil test K when straw is baled.
The large amount of K removed when straw is baled causes soil test K to decline for all grass species. The decline in soil test K depends on the amount of straw removed, K concentration in the straw, and buffering capacity or clay content of the soil.
Soil test K values higher than 400 parts per million are likely to decline faster than soil test values below 200 parts per million. When soil test K exceeds 400 parts per million, soluble and easily exchangeable K is a larger proportion of the total available K than when soil test K is 200 parts per million. Stopping K application while removing straw under these conditions can cause an initial rapid decrease in soil test K as the easily exchangeable and soluble K is removed by plants. These statements are relevant for Western Oregon soils with moderate clay content and are not applicable to soils with high clay content.
Unlike P, soil test K decline is variable. The surface 1–2 inches of soil can change quickly, sometimes as much as 50 parts per million per year or as little as 5 parts per million per year (Figure 16). The rapid decrease in soil test K in the surface inch stems from high soil test values near the surface, limited soil volume, and the amount of fine grass roots present to efficiently use K.
Soil test K in the surface 2 inches is often two to four times greater than soil test K at a depth of 5 or 6 inches (Figure 17). Since K is not mobile in soil, and grass seed fields are not tilled for several years, K accumulates near the surface from top-dressed fertilizer and recycled crop residue.
Potassium recycling from crop residue is also shown in Figure 17. Potassium is readily leached from dry plant material. As little as ¼ inch of rain will leach K from wheat straw. The same principle applies to grass straw. Soil samples were collected immediately after harvest from a field where the full straw load was chopped. After rain fell, a second soil sample was collected. Soil test K was about 150 parts per million higher in the surface inch of soil after the rain compared to the sample collected at harvest.
Baling straw requires monitoring soil test K. We recommend collecting a soil sample (6- to 7-inch depth) every other year if the initial K soil test result is above 250 parts per million and every year if the soil test result is less than 250 parts per million.
Apply K fertilizer using soil test values in Table 8.
|
Bale |
Chop |
|
|---|---|---|
|
Soil test K (ppm) |
Apply this amount of K2O (lb/a) |
|
| 0–50 | 150–200 | 100–150 |
| 50–100 | 75–150 | 50–100 |
| 100–150 | 0–75 | 0–50 |
| above 150 | 0 | 0 |
Additional soil characteristics
Soil pH and organic matter
Straw management choices result in small changes in soil organic matter and pH. Straw removal decreases soil pH 0.1 unit during the course of three years. This amount is small enough to be within the error of normal sampling and laboratory techniques. From a field management point of view, baling straw does not change soil pH for three to five years, the maximum stand life of many grass seed crops.
Similar to soil pH, organic matter changes slowly. It increases with a change from baling to chopping the full straw load. However, the increase is small (0.1–0.2%), and usually is limited to the surface 1–2 inches of soil.
Calcium and magnesium (Ca and Mg)
Calcium, Mg and K are cation bases, part of the soil system regulating soil pH. Between 15 and 35 pounds per acre of Ca and Mg combined are removed annually with straw. When Ca and Mg removal is combined with K removal, 1 ton of lime is required every four to six years to replace the equivalent of the basic cations removed when grass straw is continuously baled.
Sulfur (S)
Soil testing for S is not recommended. When straw is chopped, a spring application is prudent in the first year to offset S use by microorganisms during decomposition of straw. Applying 10–15 pounds S per acre should be adequate. Application in subsequent years is not usually needed.
Sulfur is also needed when straw is baled. A rate of 10–15 pounds S per acre can be applied annually or 20–25 pounds S per acre every other year. Sulfur can be applied in the spring or fall, but spring application (with the first N application) is recommended.
Economic comparison
Growers often ask for an economic comparison of straw management systems. This task is not simple, as management systems vary among producers, and situations change as stand age increases. Although the economics vary and are complicated, analyzing these costs annually is important when making residue management decisions. Keep in mind that each farm, and sometimes each field, will have its own production costs.
Potassium is the nutrient cost of greatest importance, as it is the only nutrient that is managed differently for the two straw management systems. The per-acre value of K in straw is about 10% of the cost of a ton of K fertilizer. Table 9 provides values for 100 pounds K, an average amount removed per acre when straw is baled, with increasing cost of potassium chloride (KCl) or muriate of potash (0-0-60). See tables 4 and 5 for information about the amount of straw removed and the K content in straw.
This approach can be considered a “short-term” or single-rotation view. Crop residue return usually provides only slight changes in soil properties even after a decade of residue return. Although growers often observe signs of increased organic matter with residue return, such as increased earthworm populations, translating residue return into economic terms is not straightforward.
|
KCl price ($/ton) |
K value in grass straw ($/a) |
|---|---|
| 450 | 45 |
| 500 | 50 |
| 550 | 55 |
| 600 | 60 |
| 650 | 65 |
| 700 | 70 |
| 750 | 75 |
| 800 | 80 |
| 850 | 85 |
| 900 | 90 |
| 950 | 95 |
| 1,000 | 100 |
Conversely, long-term straw baling removes small or moderate amounts of nutrients. Even a small amount of nutrient removal for a long time creates a need for monitoring and possibly for addition of nutrients. For example, our estimate is that 1 ton of lime will be required every four to six years to replace the equivalent of the basic cations removed with continuous grass straw baling.
Conclusion
Each postharvest residue management option has benefits and disadvantages that are summarized in Table 10. The choice to bale or chop differs, depending on straw price, fertilizer and fuel cost, labor cost, crop rotation, field condition, weed pressure, stand age, and grower outlook. An economic comparison of systems is complicated and varies yearly, as fuel and fertilizer prices are volatile. An additional variable is the straw price received by growers, as it varied from 0 to $30 per acre over the past 10 years.
With good management, most grass seed species can be produced under a full straw load or baling system. Growers should consider their economic situation and make a decision that best suits their farm.
|
Bale |
Bale |
Chop full straw load |
Chop full straw load |
|---|---|---|---|
|
Benefit |
Disadvantage |
Benefit |
Disadvantage |
|
About 5% more seed tield than chop Improved weed control Possibly better slug and vole control Income from sale of straw Save cost of chopping straw |
Cost to replace nutrients removed Slightly accellerates soil pH decline |
Carbon to build or maintain soil organic matter Recycles nutrients, especially K Poa annua suppression |
Seed yield reduced about 5% Labor, fuel and equipment cost Possible increased cost of slug and vole control Possible Poa trivialis density increase Reduced efficacy of soil-applied herbicides |
For more information
OSU Extension Publications
- Annual ryegrass nutrient management guide for Western Oregon, EM 8854
- Evaluating soil nutrients and pH by depth in situations of limited or no tillage in Western Oregon, EM 9014
- Fertilizer guide: Fine fescue seed (Western Oregon — west of the Cascades), FG 6
- Perennial ryegrass grown for seed (Western Oregon) nutrient management guide, EM 9086
- Tall fescue grown for seed: A nutrient management guide for Western Oregon, EM 9099
- PNW Weed Management Handbook, grass seed crops chapter
- Weed management in grass seed production, EM 8788
References
Alderman, S.C., W.C. Young III, M.E. Mellbye, and R.L. Spinney. 1993. Effect of post-harvest management treatments on germination of ergot sclerotia. In: W.C. Young III (ed.), 1992 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 93.
Alderman, S.C., S.G. Elias, and A.G. Hulting. 2011. Occurrence and trends of weed seed contaminants in fine fescue seed lots in Oregon. Seed Tech. 33(1):7–21.
Barker, R.E., G.W. Mueller-Warrant, W.C. Young III, and R.L. Cook. 1995. Seedling contamination in perennial ryegrass when changing from one cultivar to another. In: W.C. Young III (ed.), 1994 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 102.
Chastain, T.G., W.C. Young III, C.J. Garbacik, B.M. Quebbeman, G.A. Gingrich, M.E. Mellbye, and S. Aldrich-Markham. 1996. Residue management options for Willamette Valley grass seed crops. In: W.C. Young III (ed.), 1995 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 106.
Chastain, T.G., W.C. Young III, G.L. Kiemnec, C.J. Garbacik, B.M. Quebbeman, G.A. Gingrich, M.E. Mellbye, and G.H. Cook. 1996. Intensive management of grass seed crop straw and stubble.
In: W.C. Young III (ed.), 1995 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 106.
Chastain, T.G., W.C. Young III, C.J. Garbacik, T.B. Silberstein, and M.E. Mellbye. 1997. Full straw management: Effect of species, stand age, technique, and location on grass seed crop performance. In: W.C. Young III (ed.), 1996 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 110.
Chastain, T.G., W.C. Young III, G.L. Kiemnec, C.J. Garbacik, T.B. Silberstein, G.A. Gingrich, and G.H. Cook. 1997. Stubble management for creeping red fescue and Kentucky bluegrass seed crops. In: W.C. Young III (ed.), 1996 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 110.
Chastain, T.G., T.M. Velloza, W.C. Young III, M.E. Mellbye, C.J. Garbacik, and T.B. Silberstein. 1999. Dieback of perennial ryegrass does not reduce seed yield. In: W.C. Young III (ed.), 1998 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 112.
Chastain, T.G., W.C. Young III, C.J. Garbacik, P.D. Meints, and T.B. Silberstein. 1999. Residue management and stand age does not affect seed quality in grass seed crops. In: W.C. Young III (ed.), 1998 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 112.
Chastain, T.G. and W.C. Young III. 1999. Post-harvest residue management: Species, stand age, and technique affects grass seed yield. In: Proc. 4th International Herbage Seed Conference, 4:152–156.
Chastain, T.G., W.C. Young III, C.J. Garbacik, P.D. Meints, and T.B. Silberstein. 2000. Alternative residue management and stand age effects on seed quality in cool-season perennial grasses. Seed Tech. 22:34–42.
Fisher, G.C., J.T. DeFrancesco, and R.N. Horton. 1997. Slug populations in grasses grown for seed. In: W.C. Young III (ed.), 1996 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 110.
Gavin, W.E., G.M. Banowetz, J.J. Steiner, S.M. Griffith, and G.W. Mueller-Warrant. 2006. Fast and accurate method for estimating slug densities. In: W.C. Young III (ed.), 2005 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 125.
Gervais, J.A. 2006. Voles in the valley. In: W.C. Young III (ed.), 2005 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 125.
Gingrich, G.A., T.B. Silberstein, and W.C. Young III. 2002. Effect of spring nitrogen rates and Palisade applications on seed yields in red fescue. In: W.C. Young III (ed.), 2001 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 121.
Hardison, J.R. 1980. Role of fire for disease control in grass seed production. Plant Disease 64:641–645.
Horneck, D. and J.M. Hart. 1989. A survey of nutrient uptake and soil test values in perennial ryegrass and turf type tall fescue fields in the Willamette Valley. In: H.W. Youngberg and J. Burcham (eds.), 1988 Seed Production Research at Oregon State University, Department of Crop Science, Ext/CrS 74.
Horneck, D.A. and J.M. Hart. 1992. Third-year response of tall fescue and perennial ryegrass to lime and phosphorous during a four year study. In: W.C. Young III (ed.), 1991 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 89.
Horneck, D.A., J.M. Hart, and W.C. Young III. 1994. Effect of soil K on perennial ryegrass and tall fescue. In: W.C. Young III (ed.), 1993 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 98.
Horneck, D.A. 1995. Nutrient management and cycling in grass seed crops. Doctor of Philosophy Dissertation. Oregon State University.
Meints, P.D., T.G. Chastain, W.C. Young III, G.M. Banowetz, and C.J. Garbacik. 1997. Physiological responses of creeping red fescue to stubble management and plant growth regulators. In: W.C. Young III (ed.), 1996 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 110.
Mellbye, M.E., W.C. Young III, T.B. Silberstein, and G.W. Mueller-Warrant. 1992. Annual bluegrass and rattail fescue control under non-burning systems of residue management. In: W.C. Young III (ed.), 1991 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 89.
Mellbye, M.E., W.C. Young III, T.G. Chastain, T.B. Silberstein, and C.J. Garbacik. 1998. The effect of straw removal and different establishment systems on soil fertility levels in annual ryegrass seed fields. In: W.C. Young III (ed.), 1997 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 111.
Mellbye, M.E., W.C. Young III, and C.J. Garbacik. 2012. Long-term evaluation of annual ryegrass cropping systems for seed production—Year 6. In: W.C. Young III (ed.), 2011 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 136.
Mueller-Warrant, G.W., W.C. Young III, and M.E. Mellbye. 1992. Perennial ryegrass response to crop residue removal methods and herbicide treatments. In: W.C. Young III (ed.), 1991 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 89.
Mueller-Warrant, G.W., W.C. Young III, and M.E. Mellbye. 1992. Tall fescue response to crop residue removal methods and herbicide treatments. In: W.C. Young III (ed.), 1991 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 89.
Quershi, M.H. 1995. Tall fescue growth and nitrogen uptake as influenced by non-thermal residue management. M.S. thesis. Oregon State University.
Schumacher, D.D., T.G. Chastain, C.J. Garbacik, and W.C. Young III. 2005. Response of fine fescue seed crop cultivars to residue management practices in the Willamette Valley. In: W.C. Young III (ed.), 2004 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 124.
Senseman, S.A. (ed.) 2007. Herbicide Handbook, 9th edition. Published by the Weed Science Society of America, Lawrence, KS.
Silberstein, T.B., T.G. Chastain, and W.C. Young III. 2012. Evaluation of chemical and mechanical methods for maintaining stand productivity in fine fescue seed crop production systems in the absence of open field burning, 2011. In: W.C. Young III (ed.), 2011 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 136.
Steiner, J.J., W.E. Gavin, G.W. Mueller-Warrant, S.M. Griffith, G.W. Whittaker, and G.M. Banowetz. 2006. Cropping system management options for Willamette Valley voles. In: W.C. Young III (ed.), 2005 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 125.
Steiner, J.J., S.M. Griffith, G.W. Mueller-Warrant, W.R. Horwath, L.F. Elliott, D.B. Churchill, S.C. Alderman, R.E. Barker, T.G. Chastain, R.P. Dick, and W.C. Young III. 1995. Nonthermal grass seed production system research status report. In: W.C. Young III (ed.), 1994 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 102.
Young III, W.C., D.O. Chilcote, and H.W. Youngberg. 1984. Post-harvest management alternatives for grass seed production. In: W.C. Young III (ed.), 1983 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 50.
Young III, W.C., H.W. Youngberg, and D.O. Chilcote. 1984. Post-harvest residue management effects on seed yield in perennial grass seed production. I. The long-term effect from non-burning techniques of grass seed residue removal. J. Appl. Seed Prod. 2:36–40.
Young III, W.C., T.B. Silberstein, and J.M. Hart. 1992. Nitrogen fertilizer requirements for grass seed production in non-burn post-harvest residue management systems. In: W.C. Young III (ed.), 1991 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 89.
Young III, W.C., T.B. Silberstein, and D.O. Chilcote. 1993. Evaluation of equipment used by Willamette Valley grass seed growers as a substitute for open-field burning. In: W.C. Young III (ed.), 1992 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 93.
Young III, W.C. and T.B. Silberstein. 1994. Effect of stubble clipping height on perennial ryegrass seed crops. In: W.C. Young III (ed.), 1993 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 98.
Young III, W.C., G.A. Gingrich, and B.M. Quebbeman. 1994. Post-harvest residue management effects on seed yield in fine fescue seed production. In: W.C. Young III (ed.), 1993 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 98.
Young III, W.C., G.A. Gingrich, and B.M. Quebbeman. 1995. Post-harvest residue management effects in Chewings fine fescue seed production. In: W.C. Young III (ed.), 1994 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 102.
Young III, W.C., T.G. Chastain, M.E. Mellbye, T.B. Silberstein, and C.J. Garbacik. 1998. Crop residue management and establishment systems for annual ryegrass seed production. In: W.C. Young III (ed.), 1997 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 111.
Young III, W.C., H.W. Youngberg, and T.B. Silberstein. 1998. Management studies on seed production of turf-type tall fescue: I. Seed yield. Agron. J. 90:474–477.
Young III, W.C., M.E. Mellbye, and T.B. Silberstein. 1999. Residue management of perennial ryegrass and tall fescue seed crops. Agron. J. 91:671–675.
Young III, W.C., M.E. Mellbye, G.A. Gingrich, T.B. Silberstein, S.M. Griffith, T.G. Chastain, and J.M. Hart. 2003. Defining optimum nitrogen fertilization practices for grass seed production systems in the Willamette Valley. In: W.C. Young III (ed.), 2002 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 122.
Young III, W.C., T.B. Silberstein, T.G. Chastain, and C.J. Garbacik. 2004. Fall nitrogen on tall fescue. In: W.C. Young III (ed.), 2003 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 123.
Zapiola, M.L., T.G. Chastain, W.C. Young III, C.J. Garbacik, and T.B. Silberstein. 2005. Palisade and field burning in creeping red fescue in the Willamette Valley. In: W.C. Young III (ed.), 2004 Seed Production Research at Oregon State University, Department of Crop and Soil Science, Ext/CrS 124.
Appendix A. Research on which this publication is based
The 1969 Oregon Legislature gave the Oregon Sanitary Authority (now the Department of Environmental Quality) the power to limit the amount of field burning. A field burning permit fee system was initiated in 1971 to pay the administrative cost of a regulatory smoke management program, and to establish a research and development program to seek alternatives to open-field burning. Thus began a long history of research to quantify the advantages of field burning and to develop practical, nonthermal alternatives.
In the early 1970s, attention was focused on thermal sanitation alternatives to open-field burning in the form of machine sanitizers. In addition, propane flaming of stubble following removal of straw was evaluated. Studies of seed production without thermal sanitation were also initiated. Results were mixed, depending on species and the thoroughness of mechanical residue removal.
Subsequent legislation continued to restrict open-field burning, while research continued to provide growers with guidance in managing seed crops using nonthermal cropping systems. Studies have addressed all aspects of agronomy, including disease, weed, and insect control; crop physiology; and nutrient management. In 2011, only 11,806 acres of grass seed crops were burned — less than 4% of the acres in production in Western Oregon.
- 1989–1991: A long-term investigation to consider the interaction between postharvest residue management, N, and K was established. Research was conducted on two perennial ryegrass and two tall fescue fields. Removal of straw following seed harvest removes significantly more K than that “lost” in the seed crop alone. As a result, soil test K is lower when crop residues are removed. On the other hand, changing to a nonthermal cropping system did not result in a significant loss of N, as grass straw contains only about 1% N.
- 1990–1993: Nonthermal residue management treatments were evaluated in grower-established perennial ryegrass and tall fescue fields at 13 locations. Trials continued for a second year at 10 of the original sites, and six sites were evaluated for a third year. Four nonthermal postharvest techniques were common to most locations. Perennial ryegrass stands were more adversely affected by the presence of greater amounts of postharvest residue than was tall fescue. However, increased weed pressure was observed in both species.
- 1992–1998: A statewide investigation of nonthermal postharvest residue management in seven seed crop species was launched using field-scale replicated treatments in commercial production fields over a six-year period. Residue management techniques varied among species and locations, but three basic approaches were tested: (1) full straw management (chopped in place; no straw removal), (2) clean, nonthermal management (bale, bale + flail, bale + flail + rake, bale +vacuum sweep), and (3) thermal methods (open-field burn and propane flame stubble after straw removal). Species differed greatly in seed yield performance under clean nonthermal management and full straw load approaches.
- 1998–2002: Large-scale on-farm trials were conducted in perennial ryegrass, tall fescue, fine fescue and annual ryegrass over several seasons to evaluate optimal spring N rate. Applying more than the optimal rates did not ensure increased seed yield. Soil test results at optimal use rates showed little potential for leaching losses, as applied N was efficiently used by the crop.
Appendix B. Voles and slugs
Growers comment that increased populations of some pests, such as voles and slugs, occur when straw is left on the field. A logical assumption is that straw provides increased habitat and food sources. However, comparisons of no-till production (residue is left on the field) and conventional tillage (no residue is left) indicate that for slug populations, tillage is more important than the amount of straw left on the field. Tillage likely destroys and disrupts pest habitat.
Voles
The gray-tailed vole is native to Willamette Valley prairie grasslands that are now dominated by agriculture, including substantial acreage of grass grown for seed. Voles construct networks of surface runways and burrows. Grazing damage to grass seed crops by voles varies annually and tends to peak in four- to six-year patterns. When such peaks occur, grazing and tunneling can cause substantial economic losses (Figure 20).
Two crop management factors influence vole activity: the method of crop establishment and the crops grown immediately preceding the grass crop. Established perennial grass seed stands provide a stable habitat for vole populations compared to annual crops such as crimson clover, meadowfoam or cereal crops. In addition, establishment of crops using direct seeding maintains undisturbed habitat for voles, whereas tillage disrupts pathways and burrows, reduces available food supply and likely causes vole mortality.
Rotating perennial grass seed crops with crops such as wheat, meadowfoam, vegetables or annual clovers reduces vole populations, even when direct seeding is used. This phenomenon may occur because annual crops provide less cover during winter and early spring than do established perennial grass seed stands. Also, with many annual crops, relatively little cover remains after summer harvest.
Elimination of field burning to dispose of perennial grass straw after harvest raises questions about whether voles are more numerous when straw is removed by baling or when the full straw load is returned. Studies in the Willamette Valley show that full straw chop-back compared to bale/flail management practices do not change short-term vole activity in perennial grass seed fields. Both straw management practices provide sufficient cover to maintain vole populations. In addition to cover provided by residue and crown regrowth, seed left in the field after harvest and roots from remaining plants result in a sufficient food supply to sustain vole activity.
Baiting with zinc phosphide can reduce vole populations in some circumstances. However, baiting poses a risk to nontarget species, and little information is known about timing, rate per hole, or number of holes to treat. Currently, zinc phosphide bait is registered for use on a SLN Section 24(c) label in Oregon. If you are considering a zinc phosphide application, determine whether a current registration exists and which product(s) are allowed. Follow all guidelines from the Oregon Department of Agriculture.
Slugs
Historically, tillage and open-field burning helped reduce slug and other pest populations to manageable levels in Western Oregon perennial grass seed systems. In the absence of such practices, substantial pest pressure can cause crop loss (Figure 21). Chopping the full straw load increases the quantity of surface residue, creating the food, habitat, and moisture essential for increasing slug populations.
A laboratory study found that as straw residue and biomass increase, optimal environments for slug egg laying and juvenile survival in late winter also increase (Table 11). Conversely, a field study conducted on annual ryegrass showed no significant difference in adult slug populations due to residue management practices.
Regardless of the amount of residue left in a field, reducing slug populations to a manageable level with chemical control can be difficult and costly. Surface residue can make bait “discovery” difficult, reducing control. Thus, multiple applications of baits, sprays, or granules are typically needed to reduce slug populations, especially where surface residue is high.
Currently (2012), metaldehyde, iron phosphate and iron EDTA are registered for use on grass seed crops in Oregon. Apply baits and other products in the fall, before mid-November. Apply to moist soil when nighttime temperatures are above 45° F and wind speed is less than 10 miles per hour. Baits may be applied again in the spring when temperatures rise. Success of applications will vary.
|
Residue |
Straw biomass (g/ft2) |
Egg density (ft2 |
|---|---|---|
|
High |
784 | 33 |
|
Low |
36 | 3 |
In conclusion, established perennial grass seed stands provide a stable medium for vole and slug populations compared to annual crops. In addition, establishment of crops using direct seeding maintains undisturbed habitat for voles and slugs, whereas tillage disrupts pathways and burrows, reduces available food supply, and likely causes mortality for these pests.
Appendix C. Weed management
The presence of weeds in perennial grass seed fields negatively affects grass seed yield and quality. Weed management also increases production costs (including herbicide and application costs), and the presence of weed seeds in harvested grass seed increases seed cleaning costs. Weeds may also have indirect production costs; for example, the life of perennial grass stands may be reduced, and growers are sometimes forced to rotate to less profitable crops in an effort to manage problem weed populations. Management of both grass and broadleaf weeds is critical for achieving consistently high grass seed yield and quality. In general, grass weed species reduce grass seed yield and quality more than do broadleaf weeds. Unfortunately, grass weed species are often more difficult to manage in grass seed crops than are broadleaf species.
Some grass weed species, including annual bluegrass; roughstalk bluegrass; various brome species, such as California brome and downy brome; bentgrass species; and rattail fescue can be especially difficult to manage because their life cycles are similar to those of grass seed crops. Some of these species have also developed herbicide-resistant biotypes. In some cases, there simply is a lack of effective selective herbicides to manage these grass weed species in grass seed crops.
For example, Alderman et al. (2011) analyzed data from fine fescue seed lots (chewings, creeping red and hard fescues) submitted to the Oregon State University Seed Laboratory for purity analysis and weed seed contamination analysis from 1986–1995 and 2002–2006. They found that the most common weed seed contaminants were rattail fescue, annual bluegrass and downy brome.
Effects of straw management on weed management: The role of herbicide chemistry
Management of volunteer grass “sprout” and grass weed species in perennial grass seed crops typically occurs through the use of soil-applied herbicides coinciding with the onset of fall rains. Thus, straw management practices immediately following grass seed harvest can influence weed management decisions.
The ultimate goal is to use the most effective herbicides that match the weed species spectrum present in an individual field. At the same time, certain herbicide properties affect weed management efficacy. One important factor is the relationship of the herbicide product to soil organic matter content and crop residues on the soil surface. Growers need to consider this factor in order to select products and application timings that complement straw management strategies.
Soils contain organic matter, clay particles and crop residues. Following herbicide application, these soil materials control herbicide adsorption, or accumulation of the herbicide active ingredient on the surfaces of solids in the soil/water/air interphase near the soil surface. The interaction between crop residues and herbicides, and the resulting impacts on weed control efficacy, are extremely complex. This interaction is further influenced by environment or by management practices (for example, precipitation or irrigation following application of soil-applied herbicides).
One way to characterize soil-applied herbicide products and match them to a straw management system in perennial grass seed crops is to use the Koc value associated with each herbicide. The Koc, or the normalized soil-water partition coefficient for organic compounds, is a measure of the affinity of a particular herbicide to organic material. Herbicides with high affinity to organic materials tend to have high Koc values and vice versa.
Soil-applied herbicides with very high Koc values will bind with crop residues and soil organic matter and are never active in the soil solution. Thus, they provide poor weed control unless they are applied to bare soil or somehow incorporated into the soil solution, for example, through tillage or irrigation. The particular formulation of a given herbicide product plays only a small role in the adsorption and desorption dynamics of the active ingredient in soils and crop residues. The chemistry of the active ingredient itself drives the process.
Soil-active, fall-applied herbicides are those most affected by straw management in grass seed cropping systems. Table 12 lists all of the commonly used, soil-applied herbicides for grass weed management during typical fall application in western Oregon, as well as their associated average Koc values. Note that not all of the herbicides listed in table 12 are registered for use in all perennial grasses grown for seed in western Oregon.
In Table 12 we see that the Koc values for flufenacet are much lower than those for pendimethalin, indicating that pendimethalin has a much higher affinity for organic materials than does flufenacet. Therefore, where the majority of straw residue is returned to the soil surface, a fraction of the applied pendimethalin will be adsorbed to the grass straw residue. Thus, pendimethalin would be expected to have less herbicidal activity on grass weed species, such as annual or roughstalk bluegrass, than would flufenacet. Similar reduced weed management efficacy would be expected in a heavy straw load situation for herbicides that have a high affinity for organic materials (Table 12).
However, products such as pendimethalin or diuron are used successfully in grass seed cropping systems when they are applied to predominantly bare soil. Examples include relatively young perennial grass seed stands (perennial ryegrass in its second crop year or tall fescue in the fall/winter following spring planting) or when grass straw is baled. Also, the herbicide adsorption process to crop residue can be partially overcome with supplemental irrigation immediately following herbicide applications.
Grass seed production practices continue to change. Thus, an understanding of the interactions between herbicide chemistry and straw management systems is critical to successful weed management. Grass seed growers need to utilize the herbicide product, all other management considerations and costs being equal, that best fits with their straw management practices in individual fields.
Specific weed management recommendations in various grass species grown for seed, including herbicide application rates and suggested application timings, are found in the Grass Seed Crops chapter of the PNW Weed Management Handbook.
The herbicide adsorption phenomenon discussed above has led to continual refinement of site-specific application rates in many crops. For some soil-applied herbicides, rates are based on soil type and organic matter content, with the goal of maximizing weed-control efficacy while limiting risk of crop injury. Optimizing the use of these soil-applied herbicides, taking into consideration the strengths and weaknesses of each product, has been the focus of research at Oregon State University beginning in the early 1950s and continuing today. This research was pioneered by Orvid Lee, Arnold Appleby, George Mueller-Warrant, Ron Burr, Bill Brewster and Carol Mallory-Smith, working with others in private industry.
|
Active ingredient |
Trade name |
Average reported Koc values (mL/g)a |
Affinity for organic materials |
|---|---|---|---|
| chlorsulfuron | Glean XP | 40 | Low-moderate |
| dimethenamid-P | Outlook | 55–125 | Moderate |
| diuron | several | 480 | Moderate-high |
| ethofumesate | several | 340 | Moderate |
| flufenacet | component of Axiom | 113–613 | Moderate-high |
| S-metolachlor | several | 21–200 | Low-moderate |
| mesotrione | Callisto | 14–390 | Low-moderate |
| metribuzin | several, component of Axiom | 3–60 | Low |
| oxyfluorfen | Goal | 2,891–32,381 | High |
| pendimethalin | Prowl H20 | 13,000–29,400 | High |
| pronamide | Kerb | 570–2,240 | Moderate-high |
| terbacil | Sinbar | 55 | Low |
| paraquatb | several | 1,000,000 | Extremely high |
aSource of Koc values: Herbicide Handbook, Weed Science Society of America, 9th edition, 2007.
bParaquat is not a soil-applied herbicide, nor is it registered for use in grasses grown for seed, but is included in this table as an example of an herbicide active ingredient with an extremely high Koc value and one that has no soil activity in contrast to the other herbicides listed in the table.
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