Potato Yield!?!?

[Paulieb]

Just re-read before posting - I know its long but it is interesting....honest!!

This year I'm being particularly 'over the top' when it comes to documenting my potato planting/harvesting!!

However, I did decide to run a few tests/comparisons to see what might work best, for instance:
How many tubers in a container gives the biggest yield?
Does the size of the tuber make a difference?
How much does the growing media affect yield?
Does rock dust make a difference?

Most of these were planted in 50% last years compost, some new compost, rock dust, potato fertiliser, with a bit of BFB.

To cut a long story short (for now), today I harvested my Lady Balfour's, and from my small comparison it seems 'LESS IS MORE'.

*Having 1 tuber per container, compared to 2 or 3, yielded more potato (15% more). There were less spuds but they were bigger (so easy for most types of preparation).

*Also I compared the yield of 4 buckets with varying sizes of tubers including one that was cut before planting:
120g seed - 1000g yield - 52 potatoes
60g seed - 1000g yield - 42 potatoes
60g seed - (120g cut in half) - 875g yield - 30 potatoes
60g seed - (120g cut in half) - 950g yield - 39 potatoes

****So this suggests to me that the smaller the tuber the less potatoes you will get, however provided the environment is good feed, etc), then you can still get a decent yield.*****

My spreadsheet is rather confusing so will save some info for later in the thread if peeps want more!

Hope that all makes sense!!

[Ger-annie-um]

Crikey, that's some test! We put 3 tubers in a 35 litre tub (vales Emerald) and got 6Lb 9oz out....no idea how that compares, would be grateful if you did the math
As an aside we just dug 2 rows ( 8 tubers per row) of Sante potatoes and got 82LBS

On course for over 500lbs of spuds, curtesy of other half's total inability to say no to anyone who offers 'a couple of seed spuds we have over'. Anyone short of spuds in the Forest of Dean can just pop over to us.....cheaper than the Co-op

[Bill HH]

I think it is brilliant that you did this, we are all told things about gardening yet never really know if they are true, some of these golden rules have been passed down for years yet are without foundation. I hope you continue in this way and let us know the results.

[solway cropper]

How big are the containers?

I put one seed per tub and my best yield from a 10l flower bucket is about 1.5kg. From a 17l polypot I'd expect 2.5 to 3kg.

Over the years I have found that if you are going to put several seed spuds in a container it really does need to be a big one.

[gozsanton]

how many eyes did each seed have?

[Kirk]

My concern is to report the results not what you want.
The 120gm and 60gm seed produced the same yield.
You cannot directly compare a halved 120gm to a whole 60gm as the starting conditions are different.
That would mean tuber size has little or no effect, both having produced 100gm.
Smaller seed potatoes may have the advantage of producing the same yield but on average bigger potatoes for eating. This is more useful to the home grower.

How many were actually usable potatoes, a 1000gm yield of 52 potatoes makes me suspect that a lot were quite small, and in effect of little use. How many were say greater then 50gm in weight, not even sure that 50gm is a usable size, but it is a nice round number.

For others reading the report they may need to be made aware that Lady Balfour is a high yielding variety. So other more common varieties you would not expect to match the yield.

[WendyC]

Beechgrove did a test with putting different amount of seed potatoes in a pot:

To quote "The overall conclusion was that 3 tubers was the
optimum number to be planted in each pot. Four
tubers planted did not produce any extra crop. "

[Paulieb]

Crikey, that's some test! We put 3 tubers in a 35 litre tub (vales Emerald) and got 6Lb 9oz out....no idea how that compares, would be grateful if you did the math
As an aside we just dug 2 rows ( 8 tubers per row) of Sante potatoes and got 82LBS

On course for over 500lbs of spuds, curtesy of other half's total inability to say no to anyone who offers 'a couple of seed spuds we have over'. Anyone short of spuds in the Forest of Dean can just pop over to us.....cheaper than the Co-op

We could probably start our own forest of dean 'co-op' just selling potatoes!

[Paulieb]

How big are the containers?

I put one seed per tub and my best yield from a 10l flower bucket is about 1.5kg. From a 17l polypot I'd expect 2.5 to 3kg.

Over the years I have found that if you are going to put several seed spuds in a container it really does need to be a big one.

The results above refer to a morrisons flower bucket. I did water them quite often, but perhaps missed a few days when they needed water, and also didn't really feed them anywhere near as much as I should have or wanted too.

The tubs with multiple seed potatoes were the black 30 litre potato buckets with handles.

[Paulieb]

how many eyes did each seed have?

I didn't note this, but appreciate now that this could have a considerable bearing on results.

This will have to be included in next years tests!!

[Paulieb]

My concern is to report the results not what you want.
The 120gm and 60gm seed produced the same yield.
You cannot directly compare a halved 120gm to a whole 60gm as the starting conditions are different.
That would mean tuber size has little or no effect, both having produced 100gm.
Smaller seed potatoes may have the advantage of producing the same yield but on average bigger potatoes for eating. This is more useful to the home grower.

How many were actually usable potatoes, a 1000gm yield of 52 potatoes makes me suspect that a lot were quite small, and in effect of little use. How many were say greater then 50gm in weight, not even sure that 50gm is a usable size, but it is a nice round number.

For others reading the report they may need to be made aware that Lady Balfour is a high yielding variety. So other more common varieties you would not expect to match the yield.

Hi Kirk, I agree with what you say and it is difficult to compare the cut potatoes. But in this particular case having cut the potato in half, that potato produced nearly double the yield, albeit from twice the volume container (being in 2 containers).

I also agree that although I've tried to keep conditions equal throughout my test, there are variables that I did not record (for example, number of chits per potato), and also the inevitable bias of me wanting to be able to use half the amount seed potatoes next year. I also think perhaps that a morrisons flower bucket is a bit small for 1 maincrop spud anyway any that by using a small container the yield has been limited (so in the ground for instance the bigger potato may produce more, maybe).

Also there were lots of grape sized potatoes which I won't be using, which I did not count, as this time I was interested in measuring the total yield and finishing in time to go and watch the Arsenal vs Spurs game. Though I am now tempted to measure the weight of each potato next year to be able to do some sort of standard deviation sum to compare that way.

[Paulieb]

Beechgrove did a test with putting different amount of seed potatoes in a pot:

To quote "The overall conclusion was that 3 tubers was the
optimum number to be planted in each pot. Four
tubers planted did not produce any extra crop. "

On the evidence of my results, I really think 1 or 2 seed potatoes is all you need for a 30 litre bucket. By putting in 3 or 4 you're just wasting seed potatoes.

[WendyC]

I don't know the size of container used but seems to back up what you found.

[Paulieb]

I did see that on Beechgrove and they looked similar to my 30 litre containers.

From my own experiments regarding number of seed potatoes (which I mentioned in the first post) here are the results.

Container size=30l
Variety=Lady Balfour
Growing time = ~21 weeks
All grown in same media (New compost, Old compost, BFB, Rockdust, Potato fert).
1 seed potato - Yield 1100grams - 50 potatoes
2 seed potatoes - Yield 950g - 55 potatoes
3 seed potatoes - Yield 930g - 55 potatoes

Clearly having just 1 seed potato yield more potato, which stands to reason, as when you plant most veg they can suffer for being too close together. The diameter of the tub is about 18 inches which is roughly the distance suggested for Maincrop spuds.

Then perhaps more importantly there were less potatoes (meaning that on average they were bigger spuds) meaning they were more useful in the kitchen for things like baked potatoes, mash, etc.

In the 2/3 seed potato tubs there were lots of small tubers (grape size) which would not have grown anymore as the plant had died back, though if I'd been on top of the feeding, maybe they would have.

At the moment next years plan is to generally compare 1 seed vs 2 seeds over my whole crop.

[Kirk]

Your original said:

120g seed - 1000g yield - 52 potatoes
60g seed - 1000g yield - 42 potatoes
60g seed - (120g cut in half) - 875g yield - 30 potatoes
60g seed - (120g cut in half) - 950g yield - 39 potatoes

If we ignore tuber size and instead go by weight.
If I go into Super Garden Centre and find they are selling 600gm bags of absolute clones of your potatoes in the 2 sizes you gave, 120gm and 60gm.

So I buy 2 bags of 120gm seed potatoes, and 1 bag of 60gm seed potatoes.
I then plant them as you did, two lots whole, one lot halved.

Bed A:
120gm whole seed potatoes.
I get 5 plants yielding 1kg per plant so 5 Kg.

Bed B:
60 gm whole seed potatoes.
I get 10 plants yielding 1Kg per plant so 10Kg.

Bed C:
120gm seed potatoes halved.
I get 10 plants yielding for every pair 1.825Kg so 9.125Kg.

On this basis the single large tuber is the worst performing by quite a wide margin for the gardener.

Your original seemed bias towards pointing out the benefit of a nice large tuber, reasonable if you get a fixed number per unit cost, if the purchase unit is weight then a large tuber is possibly the worst you could select, unless sliced in half.