What impact do crop residues on the soil surface have on crop emergence and crop development in the Black soil zone of North West Saskatchewan? To answer this question, a three year Canada-Saskatchewan Farm-Based Green Plan project was undertaken in the Lloydminster ADD District.
The project started in 1994. The objective of the project was to compare the establishment and the rate of crop development under three treatments. These treatments were:
Seven cooperators were selected for the project. An additional location was established at the 1996 SSCA Direct Seeding Field Day site at Wilkie.
Each cooperator was asked to select a field where spring wheat was to be sown into standing wheat or canola stubble. The farmers cultivated an area in the field prior to seeding. Also, an area 40 feet by 40 feet was mowed and all crop residue was raked and removed from the field. The cooperator then direct seeded the entire field to spring wheat.
Data collected from the sites included soil temperature, seeding depth, plant emergence, and crop development. Crop development was assessed using the Haun stage. To explain the Haun stage, a plant with a Haun stage of 3.5 is in the three and one-half leaf stage.
Fields were also observed as the crop approached maturity to see if there were any visual differences between treatments.
What are the results? First of all, let's look at crop emergence. The treatments that did not involve tillage had slightly higher plant numbers than the pre-tilled treatment (Table 1). Therefore, the presence of crop residues on the soil surface did not have a negative impact on the number of plants that emerged.
What about seeding depth? The treatments that did not involve
tillage tended to be seeded slightly shallower than those
treatments that had pre-seeding cultivation (Table 2).
|
Pre-Till |
Mowed |
Direct Seed |
|
|
1994 |
151 |
171 |
163 |
|
1995 |
162 |
161 |
176 |
|
1996 |
201 |
204 |
209 |
|
3 year average |
171 |
178 |
183 |
Table 1: Plant emergence (plants/m2) under 3
different crop residue management treatments
|
Pre-Till |
Mowed |
Direct Seed |
|
| 3 year average |
1.9 |
1.6 |
1.7 |
Table 2: Average seed depths (inches) under 3 different
crop residue management treatments
If one looks at the three year average, there was no
difference between crop development over all the treatments
(Table 3). However, in 1994 there was a slight difference with
the direct seeded plots being about 1/4 to 1/3 of a leaf stage
behind the mowed and pre-tilled treatments. It takes about a week
for a plant to grow a leaf, so in 1994 the direct seeded crop was
2 to 3 days behind the pre-tilled or mowed treatment. There were
no differences in crop development in 1995 and 1996.
|
Pre-Till |
Mowed |
Direct Seed |
|
|
1994 |
4.9 |
4.8 |
4.6 |
|
1995 |
2.5 |
2.7 |
2.7 |
|
1996 |
4.3 |
4.4 |
4.4 |
|
3 year average |
4.0 |
4.0 |
3.9 |
Table 3: Average Haun stage of wheat plants under
different crop residue management systems
If crop residue is not spread evenly, it can cause uneven crop emergence. We looked at seeding depths and crop development under areas of heavy crop residue and areas of low crop residue in the same field. The plants in the heavy residue area were seeded three-quarters of an inch deeper and were one-half of a leaf stage behind the area with low residue. This illustrates the importance of spreading crop residues evenly throughout the field.
To sum up, crop emergence was not reduced when spring wheat was seeded into standing stubble. Direct seeding did not affect the rate of crop development or crop maturity the majority of the time. In a few instances, the direct seeded crop was slightly behind the crop in the mowed and tilled plots.
To ensure that crop development is not retarded under direct seeding, farmers should do the following: