In our northern climates we have a relatively short season (about 120 days) to grow a crop. I don’t need to spend any time on the fact that the longer the growing season generally the better the yields. The sooner we can get the crop up and growing the longer it will have to fill and make yield. Proper spring establishment starts with good residue management the previous fall.
SPRING CROP ESTABLISHMENT
Proper spring establishment is crucial to setting things up for a great crop and begins with proper residue management the previous year regardless of the crop or tillage system. If we look at popular crops like corn and wheat which have been studied extensively, there is a strong correlation between crop establishment and final yields. Key to crop establishment is proper seed population, spacing and depth with the final goal being as even germination as possible. Research suggests that corn stands with uneven emergence occurring over a seven-to 10-day period result in a five to 10 per cent yield reduction when compared to even emergence.
If you doubt the importance of proper crop establishment, consider the fact that wheat sets its
maximum yield potential by the six-leaf stage. After that, everything we do for the crop is protecting that yield potential. It should be noted that some crops like canola and soybeans are more flexible than cereals and can make up yield later in the season if conditions are right.
Crop establishment and residue management starts with crop rotation. Longer-season crops that push the limit of heat units and frost-free days need to get established earlier. These longer-season crops also require more available water so depending on which area of the Prairies you call home, residue management can take on two very different approaches.
In drier areas, the more stub- ble height and residue you can leave on the surface, the better the snow catch and moisture retention for later use. In wetter areas, generally the darker we can leave the soil in fall the quicker it warms up and the sooner crops get growing in the spring. Growing high-residue crops in these areas can result in delayed seeding due to the soil being protected from the drying and warming effects of wind and sun.
Another consideration with long-season crops that tend to use more water is that they can also deplete soil water reserves for next year’s crop. If you are in an excess-moisture situation this tends to be a good thing.
MANAGE HEAVY RESIDUE AT HARVEST
Proper distribution of residue at harvest is important regardless if you zero till or incorporate the straw. Uneven distribution of straw will cause varying levels of soil warming in the spring which leads to uneven emergence.
Another aspect that is often overlooked with residue management is nutrient distribution. If we take soybean straw for example, there can be up to 20 pounds of nitrogen in the residue. If it is not properly distributed there can be areas that receive 40 lbs. of N and areas with none which adds to variability. Similarly, residues with a high carbon to nitrogen ratio can tie up some nitrogen during decomposition that was meant for the crop.
See the attached sidebar for some tips on how to get better performance out of your harvester when it comes to residue management.
SEEDING INTO HEAVY RESIDUES
Seeding into heavy residues presents its’ own challenges. Heavy residues keep soils moist and cold in the spring which can delay seeding and decrease early nutrient availability. Uneven distribution will worsen these effects where residue is the heaviest. Heavy residue that is improperly sized can also cause hair pinning when using disc drills or planters and cause bunching or plugging with hoe-type openers.
REMOVAL VS. INCORPORATION
In areas of excess moisture and higher residues there is a continuing debate over whether it’s better to incorporate heavy residues or get rid of them by burning or baling. In my opinion when looking at short term effect, baling or burning wins. The darker the soil in spring the quicker the crop gets growing and a yield advantage is often realized. If we look at long-term effects, by burning or removing the straw we are not only losing valuable nutrients but we are also removing organic matter which aids in nutrient availability and building good soil tilth. Removing these organic materials can contribute to increased compaction in wet years and lower moisture-holding capacities in drier years.
I believe that properly sizing and incorporating the straw will minimize the effects of cool, wet soils in the spring and minimize any drag on yield which will pay off in the long run with soils that are more adaptable to weather extremes.
Along with straw choppers, another popular residue management tool on the Prairies is the heavy harrow often used to distribute residue after harvest. With good clearance and the ability to provide some down pressure, on a hot, dry day it can do a decent job of sizing and distributing straw across a field. But in my experience it does not match the performance of a properly set, fine-cut, straw chopper. Heavy harrows can also work well in the spring to spread residue and dry out fields prior to seeding.
Vertical tillage is a relatively new option gaining popularity across the Prairies in the last few years. Toolbars with wavy coulters set parallel or at a slight angle to the direction of travel help chop and incorporate residue at a relatively shallow one-to two-inch depth. Because the coulters are lifting the soil and mixing it, they still leave a good percentage of residue on the surface. As producers learn the ins and outs of using this tool it may prove to be a good residue management option finding a niche somewhere between conventional and zero till.
Proper crop establishment is critical to achieving high yields and proper crop establishment begins with good residue management the previous fall. Proper combine performance can make residue management a lot easier. As long as high residue levels result in high yields, it’s generally a welcome problem to deal with.
BrunelSabourinisalocationagronomist withCargillAgHorizonsandbasedoutof Morris,Man.Contacthim204-746-4743or [email protected]
If you doubt the importance of proper crop establishment, consider the fact that wheat sets its maximum yield potential by the six-leaf stage