Are cracks in the soil a replacement for sub-soiling?

[Feldspar]

Speaking to a soil expert not so long ago he opined that the following claim is a myth: When soil cracks due to dry weather Nature has sub-soiled for you.

IIRC his reasoning was that between the cracks the same structural problems continue to exist and are almost worsened by the cracking because the soil shrinks compounding the problem of tight soil. So, if you had a tight structureless soil with a plough pan which needed restructuring, have those cracks not really solved the problem?

 

[rob1]

Speaking to a soil expert not so long ago he opined that the following claim is a myth: When soil cracks due to dry weather Nature has sub-soiled for you.

IIRC his reasoning was that between the cracks the same structural problems continue to exist and are almost worsened by the cracking because the soil shrinks compounding the problem of tight soil. So, if you had a tight structureless soil with a plough pan which needed restructuring, have those cracks not really solved the problem?

We all know the definition of an expert

 

[JonL]

imo cracking helps soil structure at depths below that which we can fix with flatlift/subsoiler, but is no substitute in the top 10-16"

 

[Feldspar]

We all know the definition of an expert

So, what's wrong with the argument? I did some digging the other day and between the cracks the soil is like a boulder - i.e. almost impenetrable.

 

[rob1]

So, what's wrong with the argument? I did some digging the other day a-nd between the cracks the soil is like a boulder - i.e. almost impenetrable.

Guess it depends on how far apart the cracks are, and why you want to loosen the soil, I think it was JB who quoted somewhere that OSR has a root force of 300psi, think that would go through most soil, it is a lazy rooter tho so the soil needs to be compacted to the same degree or it will go sideways as soon as it meets something a bit tighter. I want cracks to help drainage and allow air into the soil. Without getting into a DD is better than other types of cultivation debate I believe that worms and OM are the most important things in soil health and and subsoiingl does not help that, IMO of course. The worse compaction is that close to the surface caused by traffic or stock and surely cracking from droughts must relieve that. I think most agree that crops grow better in consolidated soil( within reason of course) than in loose soil

 

[Baling Hay]

Guess it depends on how far apart the cracks are, and why you want to loosen the soil, I think it was JB who quoted somewhere that OSR has a root force of 300psi, think that would go through most soil, it is a lazy rooter tho so the soil needs to be compacted to the same degree or it will go sideways as soon as it meets something a bit tighter. I want cracks to help drainage and allow air into the soil. Without getting into a DD is better than other types of cultivation debate I believe that worms and OM are the most important things in soil health and and subsoiingl does not help that, IMO of course. The worse compaction is that close to the surface caused by traffic or stock and surely cracking from droughts must relieve that. I think most agree that crops grow better in consolidated soil( within reason of course) than in loose soil

Why does subsoiling not help OM or worms?

 

[Feldspar]

Guess it depends on how far apart the cracks are, and why you want to loosen the soil, I think it was JB who quoted somewhere that OSR has a root force of 300psi, think that would go through most soil, it is a lazy rooter tho so the soil needs to be compacted to the same degree or it will go sideways as soon as it meets something a bit tighter. I want cracks to help drainage and allow air into the soil. Without getting into a DD is better than other types of cultivation debate I believe that worms and OM are the most important things in soil health and and subsoiingl does not help that, IMO of course. The worse compaction is that close to the surface caused by traffic or stock and surely cracking from droughts must relieve that. I think most agree that crops grow better in consolidated soil( within reason of course) than in loose soil

I think the drainage side of things may well work to stop flooding on the macro scale - cracks here and there act like plug holes in bath and let rainfall through the profile. I still worry that between the cracks (which are 30cms apart say) there is still a structural problem which means that at the micro level roots can still be operating in anaerobic conditions due to too much water and too little air and still have a plough pan to break through (with the sideways rooting problems you describe) in their local environment; a crack every foot doesn't obviously help the majority of plants deal with a plough pan. I think JonL's view probably fits with my personal challenge which is the need to deal with structural problems in the top 8 inches as well as deeper structural issues. Long term I hope that OM and worms will do the work but in the short term some steel might be needed to allow a rape crop to perform this next year.

 

[Lincsman]

I think it will end up just as tight when it swells, a subsoiler makes craks that wont fit together again so the soil retains some pockets of air.

 

[Steevo]

Surely it's bound to help. It may not solve the problem straight away, but surely each time the ground cracks (i.e. this summer, next summer, the summer after etc) the cracks appear in different places. They don't follow the same channels each year do they...?

 

[Feldspar]

Surely it's bound to help. It may not solve the problem straight away, but surely each time the ground cracks (i.e. this summer, next summer, the summer after etc) the cracks appear in different places. They don't follow the same channels each year do they...?

I agree it must have some effect. Whether it is a net positive effect I'm not so sure. Obviously when the soil cracks it rips apart quite a bit of the nearby plant's rooting system which can't be good, it also lets moisture out of the soil which again can't be good in this sort of weather. Long term no-till soils don't seem to crack in the same way which probably indicates better structure.

 

[Chalky]

We have grass margins on heavy soil & they crack massively as there is something always growing on them. When we have on occasion been doing some drainage work, I would say that the crumb structure beneath the sod is magnitudes better than that under the annual cultivation, so I'm not sure that soils which don't crack are better structured. Up north we had soil so heavy that even in the 2003 drought, soil 2 inches down was like plasticine- no cracks- just sh!t! More 'normal' clays cracked as you would expect.

Agree with one of the other posts, the natural cracks will seal up again with the addition of water, and falling finer materials from above may make them even tighter along the former fissure line than they were prior to cracking. One good thing though, at least you know that if its cracked, the subsoiler/flatlift etc will do a good job when in the field.

 

[Feldspar]

We have grass margins on heavy soil & they crack massively as there is something always growing on them. When we have on occasion been doing some drainage work, I would say that the crumb structure beneath the sod is magnitudes better than that under the annual cultivation, so I'm not sure that soils which don't crack are better structured. Up north we had soil so heavy that even in the 2003 drought, soil 2 inches down was like plasticine- no cracks- just sh!t! More 'normal' clays cracked as you would expect.

Agree with one of the other posts, the natural cracks will seal up again with the addition of water, and falling finer materials from above may make them even tighter along the former fissure line than they were prior to cracking. One good thing though, at least you know that if its cracked, the subsoiler/flatlift etc will do a good job when in the field.

Just thinking aloud, could it be that no-till soils which have higher OM hold more water and so dry out as much?

 

[Godber]

If our heavy soils dry, as they are now, then we have a soaking before ploughing it turns over far nicer than if moisture remained throughout the summer. Which may suggest its in better order for the earlier cracking.

 

[rob1]

When ground is ploughed and left rough it dries out and becomes like concrete, well mine does, then if it gets some rain it falls apart easily , so cant see why undisturbed ground would not do something similar as opposed to becoming even tighter, ti what depth would depend on soil type and length of dry spell i would think

 

[Jamin]

I think the question I would be asking myself is how does the crop look? If it looks well and yields and is dry at harvest I will definitely not be going in with a subsoiler wearing metal, burning diesel and bringing up boulders for the sake of justifying all those horses I have strapped to the front.

I will be thanking Mother Nature for the help and using all the time i shall save not doing deep cultivations in making sure the next crop goes into a nice tilth in good time. Can't see any point ripping land up to have it bake out like concrete that u then can't get a nice seed bed on without burning even more diesel. Just my opinion and stand to be proved wrong.

 

[Rob Holmes]

Speaking to a soil expert not so long ago he opined that the following claim is a myth: When soil cracks due to dry weather Nature has sub-soiled for you.

IIRC his reasoning was that between the cracks the same structural problems continue to exist and are almost worsened by the cracking because the soil shrinks compounding the problem of tight soil. So, if you had a tight structureless soil with a plough pan which needed restructuring, have those cracks not really solved the problem?

I was told that too, went to an Agrii 'Smart' farm event and the bloke from Glenside said exactly the same as you

 

[rob1]

may be a bit thick but cant seen why a plough that goes through soil at say six to eight inches in a year like this when it is dry will create a pan by smearing the soil but a subsoiler with wings to create lift going through my clay subsoil which is always damp wont smear and create its own pan

 

[Rob Holmes]

may be a bit thick but cant seen why a plough that goes through soil at say six to eight inches in a year like this when it is dry will create a pan by smearing the soil but a subsoiler with wings to create lift going through my clay subsoil which is always damp wont smear and create its own pan

It does! Thats why you should sub soil when bone dry, not many people do this and recreationally subsoil,
we're on heavy clay (red in parts) and have not subsoiled since we grew maize over 10 years ago and have not suffered a yield loss

 

[rob1]

It does! Thats why you should sub soil when bone dry, not many people do this and recreationally subsoil,
we're on heavy clay (red in parts) and have not subsoiled since we grew maize over 10 years ago and have not suffered a yield loss

Totally agree, so cant see what good going through ground lifting up those blocks is going to do, using a slitter to crack the blocks vertically would be better, going to have a trial this year on some of my heavy ground to see if any benefit.

Interestingly where the claydon front leg has gone through the tramline there are large cracks but none where the crop is

 

[Lincsman]

A plough in hard cracked clay soil does not pan it actually loosens below it... walk behind and watch.

Cracked soil not moved but the cracks filled up with fine soil will self compact when it wets and swells.. bale sledges used to be the worst for this.