Concerns over compaction from fall tillage

Details

Published on Thursday, November 13, 2014

By Elmer Kaskiw

Farm Production Advisor, MARFD

This fall has seen more producers resort to traditional tillage with sweeps as a means of drying out top soil in preparation for next spring’s seeding.

Certainly, there is no question that fall tillage with sweeps will dry out the top four to six inches of soil and will reduce the amount of standing stubble and consequently, the amount of snow retained and snow melt come next April. The concern with this type of fall tillage is that in most instances, the tillage operation will begin to create a compaction layer once the previous crop’s root system is seared off. Previous crop root systems are critical in maintain soil structure and allowing spring moisture to continue to percolate down into the lower subsoil. 

These fall worked fields are generally able to tolerate or absorb low to moderate spring moisture however, it is under above normal precipitation levels where these fall worked fields become problematic. Once the top four to six inches of topsoil becomes saturated in the spring, there is little movement of moisture down into the lower subsoil, making these worked fields difficult if not impossible to seed using traditional seeding methods. This was certainly evident this past spring where fields that had only minimal disturbance from the previous fall were able to support seeding equipment while extensively worked fields either went unseeded or were not seeded till June. 

Recent research with traditional fall tillage with sweeps has shown that one tillage pass can increase soil density by approximately 75 per cent and can result in a 90 per cent increase in wheel sinkage in subsequent passes with as much compaction damage now occurring in subsequent passes due to the soil now having a much higher soil density. The more dense soil becomes, the more difficult it is for moisture to move through it. Traveling on saturated dense topsoil creates a hydraulic ram affect since water cannot be compressed. This results in surface compaction now getting directly transferred to the subsoil. Once this compaction moves into the subsoil, it becomes very difficult to alleviate. 

A crop’s rooting depth should not be underestimated. This past summer, a soil pit dug in early August saw a spring wheat crop still root to a depth of over four feet, even under the above normal May/June and early July rainfalls. The ideal fall stubble situation is to try and maintain as much of the plant root integrity as possible, while still opening and moving the topsoil slightly to allow better snow melt infiltration and quicker soil warming come next spring. This in many instances is accomplished ideally by the fall banding of ammonia or urea using narrow one inch knives. There are however many producers who have moved to a one pass seeding systems where the fertilizer is applied in the spring at seeding, thereby minimizing nitrogen losses due excess moisture, flooding and unseeded acres. This lack of any fall tillage beyond perhaps a heavy harrow operation has led to the development of a wide array of what are often referred to as “vertical tillage” implements. These implements all have varying degrees of soil disturbance varying from a slight fracturing of the soil surface to virtually complete residue knock down and inversion of the soil surface. Each implement has their own best fit depending upon a producer’s soil type and topography. 

Under coarser soils and or more rolling topography, a lower disturbance implement would be best suited. If soils are heavier and erosion concerns are minimal, then more disturbance can be tolerated, keeping in mind the need to maintain as much root integrity as possible. Being able to adjust the amount of disturbance based upon field conditions would be ideal, especially when it come to working out field ruts and dealing with patches of foxtail barley where more disturbance is desirable.  

MASC Deadlines

Just a quick reminder that the Excess Moisture Insurance Coverage and the Harvested Production Report both need to be in and dealt with by the end of this month. Be sure to contact your local MASC representative for further details.