Selection of a suitable crop rotation can provide many benefits for producers. Unfortunately, we have seen producers move to shorter rotations consisting of spring annual crops solely due to cash flow considerations. Shorter rotations, often involving canola followed by a cereal crop then canola again, can lead to problems with pest and disease outbreaks. As we shorten the period between similar crops we can create the opportunity for problems to occur.
As farming operations become larger and more intense in scope, the pressure to get the crop into the ground in the shortest possible time becomes greater. Often producers are forced to look after farming activities while ignoring other aspects of their lives. Crop rotations can provide producers with the opportunity to spread out their work load, reduce their crop investment risk and diversify the ecological environment of their land base.
Inclusion of a legume crop, such as a clover or alfalfa, in crop rotations can pay significant benefits through their ability to fix atmospheric nitrogen. Increasing the use of legume crops will help to extend the supply of traditional fertilizer sources manufactured from natural gas.
Table 1 shows estimates of yearly nitrogen fixation by perennial legumes. Compared to the annual legumes, perennial legumes have higher levels of nitrogen fixation when averaged over the life of the stand. A portion of this fixed nitrogen is removed as hay and does not remain in the soil. But what is left as root exudates, decaying roots and above-ground stubble is significant and helps to maintain soil fertility.
Field studies have shown that between 10 and 20 per cent of the total nitrogen added to the soil by green manure crop is used by the subsequent annual crop. An additional 64 per cent of the legume nitrogen can be found in the top 1.2 metres (four ft.) of soil, 14 months after a green manure crop. This nitrogen becomes available as plant residues continue to decompose.
The timing of legume incorporation should maximize top-growth and nitrogen fixation while minimizing soil moisture depletion. The present recommendation is incorporation at full bloom. After full bloom the plant material becomes tougher and will take longer to decompose and release plant nutrients for subsequent crops. Very young plant material, on the other hand, may decompose quickly after incorporation, leaving the released nitrogen vulnerable to leaching and volatilization.
It’s important for producers evaluating legume crops in rotation to consider how different legumes vary in terms of both their ability to fix nitrogen and how soon they can do this in the growing season. For example, with red and alsike clover the differences can be dramatic and worth considering. AAFC Beaverlodge trials (Rice and Hoyt) compared alsike and red clover both for their ability to fix nitrogen (Table 2) and how rapidly this is accomplished. In the case of alsike clover, by the end of July it has fixed 85 per cent of its potential yearly total. Red clover, on the other had, has only managed to fix 73 per cent of its potential yearly total by the end of July. It would appear that when selecting from these two legume crops, producers should opt for alsike clover for its ability to fix more nitrogen and to do so sooner in the growing season than red clover.
Winter crops such as fall rye or winter wheat involve field operations that are potentially less busy than the spring, by moving the seeding and harvesting operations from May and October to August. Winter crops begin growing much earlier in the spring and can usually be vigorously growing prior to most annual weeds. It is not uncommon for producers who grow winter wheat to report that there is no need for a grassy weed herbicide due to the competitive nature of the winter wheat choking out the wild oats.
CLOVER’S IMPACT ON SOIL N
The objective of this trial was to compare the economics of under-seeding different species of clover on subsequent crop production.
2005 Trial Site
A field-scale, replicated trial was set up at Central Peace Conservation Society’s NEWPRO Agronomy Research Center located two miles west of Wanham, Alta. CPCS would like to extend its thanks to Richard Norton and NEWPRO for their generous support of our research program by providing this site for our use.
The zero-to six-in. soil test revealed the following information:
Nitrogen: 38 lb./ac. deficient.
Phosphorus: 20 lb./ac. deficient.
Potassium: 451 lb./ac. optimum.
Sulphur: 26 lb./ac., marginal.
EC: 0.26, good.
Organic Matter: 8.1 per cent.
The target yield of 35 bu./ac. of canola called for:
72 lb. N, 35 lb. P205,0 lb K2O
and 21 lb. S per acre. A pre-seeding burn-off herbicide consisting of 0.33 litres per acre of Roundup WeatherMax in five gallons of water was applied on May 5. The major weeds noted were dandelion and Canada thistle. The previous crop was wheat.
Nexera 822 Clearfield canola, provided by Dow AgroSciences for this trial, was seeded at a rate of 6.7 pounds per acre on May 9 at a depth of 0.5 in. using a Haybuster 8000 zero-till hoe drill with 10 in. spacing and three-in. paired rows. Clearfield canola was utilized in this trial as it allows the herbicide Odyssey or Pursuit to be used for weed control. Odyssey and Pursuit can also be sprayed on the clover seedlings that were to be under seeded. Both red and alsike clover were mixed with the canola seed prior to the seeding operation. The red clover was seeded at a rate of 7.3 pounds per acre and the alsike clover at a rate of four pounds per acre.
There were three treatments:
*Nitrogen fixation estimates include nitrogen in the total plant
Source: Rice and Hoyt.
*means followed by the same letter are not significantly different at P=0.05 #1 Canola @ $5.50/bu.
common alsike and red clover seed @ 1$/lb.
*calculated using Roundup WeatherMax @ $127/ jug, 2,4-D Ester 700 @ $95/jug, Curtail M @ $110/jug, conventional sprayer @ $2.95/ac. and weed wiper sprayer @ $5/ac.
1. Check –Nexera 822 alone.
2. Red clover and Nexera 822 together.
3. Alsike clover and Nexera 822 together.
The plan for 2006 was to allow the under seeded clover to grow until August when it will be sprayed out with a combination of Roundup and Lontrel. The check treatment will be chemfallowed for most of 2006. All three treatments will be seeded to winter wheat in late August/early September 2006 and reseeded to canola in 2007 to look for residual nitrogen benefits from the clovers. An economic analysis will be performed to see which of the treatments, in the long term, produced the best profit margin.
The fertility program consisted of 73-24-12-12 that was deep-banded one-in. below the middle of the three-in. paired seed row at the time of seeding. Moisture was considered to be very good and there were no problems encountered with the seeding operation.
An in-crop herbicide was applied June 8 consisting of the recommended rates of Pursuit Ultra applied using a water volume of five gallons per acre. The canola crop was at the one-to three-leaf stage. Both alsike and red clover were at the cotyledon to two-leaf stage. The major weeds were Canada thistle, dandelion and volunteer wheat. The Canada thistle was especially heavy on the western portion of the plot area. Unfortunately there are no herbicide options for effective control of this weed when clover is underseeded. Producers need to ensure that adequate perennial weed control is performed the previous year. Pre-harvest Roundup is a good option to consider as any tank mixes containing clopyralid used in the year previous would result in a carry-over that would damage the clover seedlings.
The plot was swathed on August 31. There were no problems that were encountered during the swathing operation. After the swathing operation we were able to see that both the alsike and red clover were well established.
The plots were combined on September 19.
The strips were weighed with a weigh wagon and samples were retained to determine per cent dockage, per cent moisture and grade. The results are given in Table 3.
YEAR TWO, 2006
During 2006 the red and alsike clover was allowed to grow. The only field activities were to conduct herbicide applications for weed control purposes.
We were (and are) still learning to use the weed wiper. The application rate we ended up using appears to be significantly higher than we ought to be capable of achieving. Thus the costs attributed to it are probably higher than we would expect once we have greater experience with using the weed wiper. Having said that, it certainly works remarkably well and gave us exceptional control of the Canada thistle that we used it on.
The major weeds noted in the chemfallow strips were Canada thistle, dandelion and volunteer canola. In the clover, the major weed was Canada thistle. The total cost for herbicide application on the clovers was $53.98 per acre and the cost for chemfallow herbicide applications was $38.64 per acre during the 2006 season. The August 11 application was made, as we had concerns as to how rapidly the clovers were drying down. We hoped to have them desiccated completely to allow for an easier seeding operation. At the same time there were some Canada thistle growing on the chemfallow that we decided to take advantage of the spraying operations to achieve further control of this weed. Herbicide applications were made as follows in Table 4:
Winter wheat, provided by Bernie Schoorlemmer for this trial, was seeded at a rate of 150 pounds per acre on August 25 at a depth of 0.5 in. using a Haybuster 8000 zero till hoe drill with 10 in. spacing and three-in. paired rows. There was no fertilizer applied with the seed in order to allow us to fully evaluate the N-supplying capabilities of the different treatments.
IMPORTANT NOTE:Although I have seeded through some very heavy residue conditions with the Haybuster 8000 in the past, thanks to its coulters, I have yet to encounter a situation that I could not seed though. However, the drill met its match at this trial. The alsike clover was less difficult to seed through but seeding into the red clover strips led to many plugging problems. Producers should consider taking action to deal with this issue. Solutions that could be tried are:
1. Baling clover for hay.
2. Mowing clover.
3. Combining clover stands for seed.
One of the additional benefits from seeding a crop like winter wheat can be its competitiveness with annual weeds like wild oat. Producer experience has been that the winter wheat crop shows such an aggressive growth habit that grassy weed herbicide applications are frequently unnecessary. Less expensive, broadleaf applications can still be useful for controlling weeds such as stinkweed, narrow-leaved hawk’s beard, shepherd’s purse and wild buckwheat.
Soil samples were obtained from the plot area from each treatment/ replicate prior to the seeding operation. The results are given in Table 5.
Observations that were made one week after seeding found that the winter wheat seeded into the chemfallow had germinated. In comparison, the winter wheat seeded into the red and alsike clover areas did not show signs of significant crop germination. The entire plot area was affected by the significantly drier growing season that was experienced during the late-June to August period. It also serves as a reminder that the chemfallow areas had sufficiently higher moisture, allowing the winter wheat to germinate.
CPCS wishes to extend its thanks to Calvin Yoder, Sandra Burton, The Peace Region Forage Seed Association and Bernie Schoorlemmer for their support and assistance with this project.
Tune in next issue for years three and four of this project.
GarryRopchanisresearchco-ordinatorfor theCentralPeaceConservationSocietyand alongwithhissonAidan,operatesagrain farmnearGrimshaw,Alta.Contacthimat [email protected]
TABLE 1 ESTIMATED ANNUAL NITROGEN FIXATION (LB./AC.) BY PERENNIAL LEGUMES FROM AGRICULTURE CANADA RESEARCH STATION, BEAVERLODGE, ALTA.
TABLE 2 ANNUAL NITROGEN FIXATION BY ALSIKE AND RED CLOVER GROWN ON A GREY LUVISOL SOIL
Average In Grey Soil, lb./ac.*
Alsike Clover lb/ac.
Red Clover lb/ac.
Treatment Yield bu./ac.* % Moist.* % Dock.* % Green* Treatment Cost $/ac. Cont. Margin $/ac.
TABLE 4 HERBICIDE APPLICATIONS, 2006
August 11 Product
0.33 l/ac. Roundup WeatherMax
0.67 l/ac. Roundup WeatherMax and 200 ml/ac. 2,4-D
Roundup WeatherMax with Weed Wiper sprayer
Curtail M and 0.33 l/ac. Roundup WeatherMax
Curtail M and 0.33 l/ac. Roundup WeatherMax Cost $/ac.*
TABLE 5 SOIL SAMPLE RESULTS, 2006