| | Incorporating Manure Into a Direct Seeding System
One of the questions farmers ask about direct seeding is how to use livestock manure without incorporating it into the soil. Ron Heller, reduced tillage agronomist with RT LINKAGES – Vermilion, responds in this manner:
| 1. | Generally, manure is a disposal problem more than it is a crop nutrient. Of course, it has value as a soil amendment in that manure spreading returns organic matter and nutrients to the field. Two reasons for working manure into the soil are traditionally to reduce odors (mainly ammonia release) and conventional seeding, which requires some tillage anyways. However, it is not uncommon for manure to be spread on pasture and hay fields, although more careful spreading and perhaps even harrowing may also be necessary. The main concern, especially with large quantities of fresh solid or liquid manure, is where and when to competently dispose of it. Manure storage, handling, and application do not come without cost, can be a nuisance, and sometimes the system is environmentally inadequate. Do we really understand the trade-off involved when we also want it to perform as a means of crop fertilization? |
| 2. | Increased soil fertility in the year of manure application is a bonus when it occurs. Another way to look at this is to assume that nutrient loss in manure begins before it is moved to the field. Nitrogen (N), phosphorous (P) and potassium (K) are essential nutrients for crop growth which manure can supply in varying degrees. How much nutrient value a manure source contains (and its availability over time) is important to know but difficult to assess. To what extent nutrient loss will occur between the time manure leaves the animal and is applied in a field is at best a guess. In any case, it remains difficult to place exact values on manure resources based on nutrient content alone. Depending on the state of the manure applied, nutrient capture through tillage can be more perception than reality. How many growers realize that in the long term it is advisable to match P rather than N to crop use? Also, by nature manure is dropped directly on the ground. (Cats bury their business, but I don’t see ranchers training cows to cover up their pies…) Why do we think it needs to be incorporated into the soil with tillage? Here’s a simple chart that reflects a relative sampling of different manure: |
Nutrient value of solid fresh manure [kg/ tonne]
| Manure Type | N | P | K |
| Cattle | 6 | 3 | 6 |
| Pig | 5 | 4 | 5 |
| Chicken | 15 | 9 | 5 |
Source: Sask. Guide to Farm Practice
| 3. | Manure by itself, for the sake of soil health, should not be the sole focus. Organic matter is key in soil quality. Growers who use livestock manure on their fields have the benefit of maintaining and building soil quality beyond those who continually deplete organic matter with tillage and export it as grain, straw, feed and fodder. Even though excess straw and fibre content (organic matter) in raw manure is often a compelling reason for tillage incorporation, this should not remain a major deterrent for reducing tillage. Direct seeding is intended to handle increased crop residue and surface trash (organic matter). With good distribution manure is not a barrier for many operators. |
| 4. | Manure as a soil amendment cannot be over-stated! Increased organic matter improves moisture holding capacity and nutrient release. In a University of Alberta soil quality study near Edmonton, it was found that even after removal of 20 cm of topsoil (scalping) the addition of manure increased water infiltration by 10 - 359% and crop yields by as much as 371% over the non-manure treatments. Here’s what the yield-effect on wheat looked like: |
Wheat Yield (bu/ac)* on plots where topsoil was removed
| Scalping Depth (cm) | Un-amended | Manure-amended |
| 0 | 50 | 70 |
| 10 | 25 | 62 |
| 20 | 7 | 35 |
Source: AAFRD Fact Sheet – Restoring Eroded Soils
*Bu/ac yield figures are approximations as taken from bar graphs
| 5. | Routine manure spreading habits can be changed to accommodate less tillage. Assuming that every acre is not required every season, by rotation, fields can be designated as disposal grounds. If soil incorporation of manure seems essential, then only that portion of the cropland is tilled, leaving the rest of the farm conducive to direct seeding management. With planning, the benefit of manure can be spread over the whole farm and not just on the same nearby fields year after year. Again, depending on the manure type, there are some management methods that are compatible with a change to direct seeding. Low soil disturbance technology for liquid manure injection systems is improving and composting solids is becoming popular. Studies conducted with composted beef manure operations suggest an economic balance exists between any nutrient loss and the cost reductions gained in hauling and spreading. Both injection and compost systems diminish the manure odor concerns normally linked to field spreading. |
| 6. | With Alberta’s new Agricultural Operation Practices Act (AOPA), there are now specific requirements for manure management. Here is where a better understanding of manure composition and nutrient content is pertinent. Determining appropriate rates for manure application must now include more than the practical limitations of hauling, spreading and tillage incorporation. All manure users should become familiar with these regulations. Soil testing, record keeping and restrictions to application rates apply in some cases. Generally stated, manure incorporation within 48 hours is called for, but there is a clear exception for frozen or snow covered ground (?) as well as forage and direct seeded croplands! An important guide for direct seeders is to observe the setback distances from water bodies and slope adjustments to ensure they do not create a risk to the environment when applying manure. This should be seen as common sense. |
In summary, the term incorporate really means to include, merge, integrate or use. So, it makes sense to include something as beneficial as manure to enhance our cropping practice whenever we can. There are gradual and long term advantages for growers to merge direct seeding and manure as a worthwhile way of retaining fresh organic matter to build soil. However, used exclusively as a crop fertilizer program, manure has less immediate value to direct seeders, especially where intensive tillage is required – this tends to disintegrate the usefulness of direct seeding.
Ron Heller
Conservation and Development, Alberta Agriculture and Food, Vermilion, AB
Tel: 780-853-8262
Email: ron.heller@gov.ab.ca |
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