We farm in the "Bear Hills" just south of Biggar in the moist dark brown soil zone. I've often questioned the "moist" part and can clearly recall my brother-in-law wishing he could buy an inch of rain.
To be successful and profitable, water conservation must be foremost when developing a farming strategy. Traditionally, this included summerfallow. maximizing moisture efficiency to reduce risk and enhance productivity, lead me to experiment with zero tillage ten years ago. Our last fallow was in 1991. In our farming area, twenty acres of zero-till in 1987, has grown to 100,000 acres in less than 10 years.
Our farming practice has focused on water efficiencies. We try to make sure as much of the water available will contribute to crop production. This means greater yield and profit potential. Water is lost by evaporation and runoff. Snow must be considered as a source of water. We want to keep it in the fields and out of the ditches, coulees and trees. Properly managed snow can contribute to the water available for crop production.
Residue management is fundamental to water conservation. We straight combine most of our crops, leaving 12-16 inches of standing stubble. We try to spread the chaff and straw from the back of the combine as evenly as possible across the width of cut. This has five positive results:
1. The tall stubble catches snow and there is more potential here than people realize. The stubble fills with snow, packs and refills. A cycle that often repeats.
2. The snow in stubble acts like a blanket and reduces the frost level which enhances the potential for infiltration in the spring. I also suspect that less solar heat is required to warm the soil in the spring.
3. The stubble slows the snow melt reducing quick run-off potential. Several warm, sunny days in early spring will often result in a quick melt and run-off on summerfallow. Remember, water that leaves the field won't contribute to yield.
4. In the spring, the residue on the ground and standing stubble reduces evaporation, which allows successful shallow seeding. This translates into quick emergence and early seedling vigour. The young crop is also protected from winds that can damage or destroy. "Blown out" canola comes to mind.
5. Chaff and straw residues, evenly spread, provide a cover to further reduce evaporation and can have a positive weed control effect.
We also try to disturb the soil as little as possible to reduce water evaporation and incorporate fewer weed seeds. Our only tillage is a 12 foot strip around field margins after harvest to act as a fire guard and to keep grass from encroachment.
One pass at seeding time with a Harmon paired row drill on 12 inch centres, applies all the seed and fertilizer. I'm also convinced that the paired row seed pattern increases crop vigour and reduces weed competition. The less disturbance, the less water is lost and fewer weeds are started. I've read that one pass with a deep tillage cultivator can cost half an inch of rain. Nothing evaporates water more quickly than a tilled black field on a sunny, windy day. Its easy to understand that trapping snow and reducing evaporation can provide more water for the crop.
The last thing I want to address in speaking about water use efficiency, is infiltration and run-off. In the early years of zero-till, I heard about infiltration rates, soil aggregate stability and organic level improvements under a zero-till management system. I'm afraid I treated those claims much like those of a snake oil salesman. I have now become a firm believer in the contribution zero-till makes in improving these soil characteristics.
The information on the following two graphs were compiled from
one of my zero-till fields and a conventional tillage system
across the fence line. 1995 was the fallow year in the
conventional tillage system. This work is some of the first two
years of data in a four year study, headed by Dr. Jane Elliot
from the National Hydrology Research Institute. The purpose of
this study is to analyze how water movement is affected by
tillage systems. To measure water infiltration, cylinders were
placed on the soil, filled with water and the rate the soil
absorbed the water was measured. These graphs were compiled by Al
Efetha.
In all instances, the infiltration was better on zero-till fields. The shoulders on the hill tops are the most dramatic as the zero-till areas will accept twice as much water before run-off occurs than conventional tillage hill tops. Remember, if the water runs off the field, yield potential leaves with the water. Soil nutrients (especially nitrogen), and herbicides also move with the water. This means that on our farm, "gully washer" rains can improve yields rather than be an erosion disaster. This table is also from this study (Table 1).
Table 1: The soil biochemical and physical properties for two management systems in a Rolling Glaciolacustrine Landscape.
|
Zero Tillage
|
Conventional Tillage
|
|||
|
Mean
|
Std. Dev.
|
Mean
|
Std. Dev.
|
|
| Residue Cover (% area) |
93.0
|
9.7
|
10.1
|
6.8
|
| % Organic Carbon |
3.2
|
0.4
|
2.8
|
0.6
|
| Total Nitrogen (mg/kg soil) |
2496
|
399
|
2008
|
635
|
| Carbon:Nitrogen Ratio |
13.0
|
1.1
|
14.4
|
3.0
|
| Total Phosphorus (mg/kg) |
700
|
50
|
653
|
85
|
| `95 Infiltration Rate (mm/hr) |
113.3
|
125.1
|
75.9
|
47.8
|
| `96 Infiltration Rate (mm/hr) |
82.9
|
38.2
|
68.5
|
44.6
|
| `95 Final Infiltration (mm/hr) |
70.9
|
46.5
|
50.5
|
42.5
|
| `96 Final Infiltration (mm/hr) |
75.8
|
43.5
|
51.7
|
42.5
|
| January Snow Depth (mm) |
82.4
|
43.5
|
82.2
|
81.8
|
| February Snow Depth (mm) |
126.5
|
54.0
|
61.8
|
80.0
|
| % Sand |
7.3
|
2.6
|
6.3
|
3.9
|
| % Silt |
63.6
|
14.0
|
66.5
|
12.5
|
| % Clay |
29.6
|
14.0
|
27.9
|
2.8
|
| % Aggregate Stability |
61.4
|
9.9
|
49.5
|
15.4
|
| October 18-95 (% Moisture) |
27.5
|
1.9
|
26.6
|
2.3
|
| October 22-95 (% Moisture) |
24.6
|
3.3
|
27.9
|
2.8
|
| April 30-96 (% Moisture) |
34.0
|
2.9
|
32.7
|
5.5
|
| May 15-96 (% Moisture) |
30.5
|
2.7
|
31.1
|
3.5
|
| Please take special note of residue cover and organic carbon levels. | ||||
The infiltration rates are a summary of the previous graphs. The snow depth differences between January and February could read before and after wind. The last portion on percentage moisture, indicates that even though the conventional system had access to two years of water supply, it had no more water available to grow a crop in 1996 that had been summerfallowed than did the continuously cropped zero-till.
In conclusion, I must acknowledge a bias my perspective. Over the last 10 years, I've become a dedicated zero-till farmer. I take great comfort in knowing my farm is as resistant to soil erosion as possible. This fall was a lovely tenth anniversary as our zero-till wheat across the farm surpassed the best across the farm wheat yield we ever had under a tillage-fallow system. If you can see the relationship between water conservation and potential profit, you should give zero-till serious thought.
I've only discussed practices directly affecting moisture use efficiency. To be successful, you must develop a sound management strategy that incorporates residue management, rotations, weed management, soil fertility, and crop establishment. Zero-till has great potential to increase yield, reduce erosion and restore fertility. In my opinion, its worth the effort. Zero-till is not a forgiving system, so study the system carefully. A sound understanding of the entire no-till system reduces the chance of failure. I'm not aware of any farmer in our area that has gone back to a conventional tillage system after direct seeding.