Agronomy Library > Annual Weeds

Planning for Peas Starts in Your Stubble
Author: Rick Taillieu, Reduced Tillage LINKAGES
Date Created: July 22, 2002
Last Reviewed: February 03, 2009
Crop rotations and residue management are two corner stones of successful reduced tillage cropping systems. Pulse crops are now widely grown in Alberta, and for direct seeders they are a critical component of their crop rotation. Field peas are well adapted to reduced tillage systems and the increase of pea acres in Alberta over the past decade has coincided with the rapid adoption of direct seeding. Field peas help increase diversity in a crop rotation, which is essential for producers looking to achieve the economic and conservation benefits of reduced tillage. The planning and management required to grow peas makes them a perfect fit for direct seeding.       Field pea nodules fixing nitrogen Benefits of Direct Seeded Peas Standing stubble catches more snow and conserves moisture, which enables shallower seeding into moisture. Peas that emerge quickly are more competitive with annual weeds. Anchored stubble dramatically reduces the risk of soil erosion and potential crop damage. Standing stubble also reduces the wind's drying effect on seedbed moisture. Erosion risks related to pre-emergent rolling are virtually eliminated in a low disturbance direct seeding system. Selecting Your Stubble Regardless of your seeding system, avoid planting peas in fields that have heavy perennial weed pressure, dangerous herbicide residues, high residual nitrogen levels or increased disease risks related to short crop rotations and susceptible varieties. Perennial weed control in field peas is best achieved with pre-harvest glyphosate the year prior to peas.  A post harvest application may be more effective for dandelion control. Managing Your Stubble Successful direct seeding begins in the fall with good residue management. Taking the time to properly manage straw and chaff at harvest time is the key factor in how smooth seeding will be the following year and will improve crop emergence and maturity. Generally, when harvesting remember that the stubble left behind should be shorter than shank spacing of the drill. This will improve the flow of residue and reduce plugging problems during seeding. Anchored, undisturbed stubble is easier to seed directly into. Chaff must be managed during harvest. The combine must spread the chaff that is not being collected for removal. Ideally chaff should be spread over the entire cutting width. Chaff that is not spread will contribute to cooler soil temperatures and nitrogen tie up, often visible as stripes in spring fields. Post harvest harrowing is very ineffective at redistributing chaff. Spreading, baling, and harrowing are the three basic choices in terms of straw management. Chopping & Spreading Residue For true no-tillers the combine is the one chance to manage the straw that they have produced. The finer the straw is chopped - the better it can be spread. The more evenly it is spread, the easier seeding will be next spring. Straight cutting and leaving tall stubble will increase combine efficiency and reduce the workload of your chopper and spreader. Selecting shorter varieties will further reduce the volume of cereal straw produced. Maintenance of the straw chopper's knives or hammers will ensure performance. The condition of the straw plays a key role in managing crop residue, as chopping of dry straw is much easier. Combines should be unloaded on the go, or operators should pull out of the swath to unload. This will limit the number of straw piles that can affect seeding operations and crop emergence. Baling to remove straw is another option in direct seeding systems. Baling excess straw is more economical that tillage. Baling straw does also remove nutrients, which must be considered when placing a value on the straw. The removal of straw limits snow catch potential and may also increase the potential for soil erosion. Harrowing the Stubble Heavy-harrowing after harvest will further break down straw and help distribute straw evenly over the field. Harrowing will not spread chaff unless the harrow is 'full' of straw. Heavy harrowing is best done in the fall under warm and dry conditions. While increasing harrowing speed will further aid the spreading action, it also increases the risks associated with knocking down and dislodging the stubble. Spring winds may result in blowing straw on harrowed fields, which can reverse the positive distribution effects. Loose straw will concentrate in low spots and along field margins. Harrowing will stimulate germinate of weeds and volunteer crops.. This can be of benefit to producers if the weeds are managed appropriately. Heavy harrows and rotary harrows can also be used to incorporate granular herbicides in the fall. Scouting in the Stubble Scouting for weeds in standing stubble at any time of the year requires getting down on your hands and knees and really looking in the residue. Weed seedlings are often present in higher numbers than are apparent from the road. Winter annual weeds should be closely monitored following harvest. Late fall applications of 2,4-D and MCPA will provide the best control. A pre-seeding application of glyphosate will provide your peas with a clean start in the spring. The relationship between peas and reduced tillage is mutually beneficial. Peas are more tolerant of cooler soil temperatures associated with direct seeding, and allow for earlier seeding. The first step in reducing your nitrogen costs is to grow a nitrogen fixing crop like field peas. The earlier harvest date helps spread out the fall workload. The long term success of a direct seeding system requires a diverse rotation. All that leaves me out standing in your stubble asking two questions, "why isn't every direct seeder growing peas?" and "why isn't every pulse grower direct seeding?"