Many direct seeders in the northeast are using aggressive harrowing in their production systems. Some would argue that this isn't direct seeding but just changing the primary tillage tool from a cultivator to heavy harrow. However, there are many good conservation minded farmers who still see the need for this type of light soil disturbance.
Justifying the use of a heavy harrow in a soil conserving direct seeding system depends largely on how much residue you produce and the length of your growing season. If the amount of residue mat on your field is going to delay the final day of your seeding operations then you can probably justify some form of aggressive harrowing.
Another circumstance where heavy harrowing has a good fit is when heavy residue is spread poorly enough to cause uneven soil moisture across a field. The wider the swath width at harvesting time the more difficult it is to get that residue spread evenly back out across the field. Some direct seeders will harrow in this circumstance to get an even distribution of moisture across the field. Although we get much greater harvest efficiency out of big combines when we double swath to 50-ft. it is almost impossible to get residue spread back out to 25-ft. on each side of the combine!
For those direct seeding with a seeding machine that has lower residue clearing abilities it is essential to get good even spread of heavy residues and break up the residue some. An aggressive harrowing with a heavy harrow will really reduce the chance of plugging on a seeding tool like the IH 7200. Some direct seeders with difficult to work soil will use the heavy harrow to create a dust mulch to seal in moisture on fields which have low surface residues and will be seeded later in the spring. They can also be used to create better soil flow and seed row closing.
Disturbance creates weed growth but there are some who want to promote weed growth which will be eradicated with winter frosts or the next herbicide application. They are arguing that with our higher moisture conditions in the northeast a percentage of the weeds and volunteers will grow anyway so let's promote that growth before the pre-seed burn-off.
The best fit for heavy harrowing to break up residue is to go as fast as you can on as hot a day as you can find as soon as possible after the combine has left the field. Harrowing in the fall is definitely preferred over waiting to spring. In the spring the straw is so rotten that most of it breaks off and you have more loose straw to contend with. Also, you have missed the opportunity for weed killing frosts.
A heavy harrow with lots of on the go adjustments has been used to redistribute residue from high straw producing areas to areas where it is more beneficial such as knolls. Those producers who farm very variable land also comment that on the go adjustments are important. Peaty areas need to be treated differently than gray clay areas nearby.
For those who are concerned about field finish the heavy harrow can be used to level off fields once a year. I certainly do not recommend harrowing after seeding as you destroy and fill in the perfect little trench you have created at just the right depth over the seed. Cosmetics alone are probably not a good enough reason to harrow but if pull type swathers and sprayers are part of your operation even the leveling you give the field in the fall my help hold them together.
Heavy harrow owners often purchase a granular application kit and use it to surface apply granular herbicides. This is one of the extras of having a harrow in the system.
If you are direct seeding successfully now without aggressive harrowing you should not think about incorporating it into your production system. However, if you grow a lot of residue and can't see how a one soil disturbance per year system could work for you using heavy harrows might help smooth the transition into direct seeding and somewhere in the future you may or may not decide to leave them parked!