Rising plate meter mystery

[gellis888]

Hi all, I've started using a rising plate meter since September this year to make feed budgets and try improve pasture use (outdoor wintering ewes).
I've been measuring every week. Since the wetter weather and a couple of frosts I've found the plate meter is reading lower DM/ha in some of the fields. I assume the DM is still there because it hasn't been grazed?
I'm using the standard x 140 + 500 formula - should I have been using different formulas? Or is this just what happens going into winter?

 

[Woolless]

My swardstick gives different amounts of available fodder for the same height in cm depending on the time of year. Do you have a 'smart' plate meter?

 

[gellis888]

My swardstick gives different amounts of available fodder for the same height in cm depending on the time of year. Do you have a 'smart' plate meter?

I see, that must be the same kind of thing then. I've got a plate meter that takes an average of the field and tells you digitally. But I guess it's only as 'smart' as its operator!

 

[Woolless]

I see, that must be the same kind of thing then. I've got a plate meter that takes an average of the field and tells you digitally. But I guess it's only as 'smart' as its operator!

Maybe it's just gone back a bit with the cold weather? You need someone that does this properly to let you know.

 

[MrA.G.]

I think you are supposed to change the formula as the season changes to reflect the change in DM etc. As far as I know the jenquip meter I have came with suggested formula. I just use the same formula but only really measure from March until September

 

[shields kaiser]

The 140 part in your equation or the "multiplier" reflects the Dry Matter so 140 = 14%. In wetter weather I'd imagine you'd have grass dry matter at nearer 12 or 10%., so your multiplier would change to 120 or 100 in this scenario.

As a side job, it would be a good idea to test some yourself so that you know what Dry matter is at certain points of the year. Cut 100g of grass and heat overnight in the oven until the sample doesnt get any lighter - the end weight is the dry matter of your grass at that point - e.g. 10grams was 10% DM.

The "adder" (500 figure) wont be far away at 500 or 600 and I dont think it needs to alter much, but 'i'd find out further as cant remember what it is as a number, minimum volume of DM that you cant measure possibly.

However in answer to your question, using your same formula (14%) and if grass is growing, I'd exepct to see the overall DM increase week on week, its strange that it is decreasing as you say, but possibly because the very wetter grass has less strength to hold up the plate and therefore even with more bulk there actually is less of it as Dry Matter.
I've also been told in the past that you shouldnt measure in frosty weather as it gives a false reading too.

Possibly someone else on here will be able to explain better though?

 

[NZDan]

We lose cover here to wind and frost. If its been quote wet and then we get a run of frosts then covers will drop. Like wise in the summer it is common for covers to get lower due to wind damage.

 

[gellis888]

The 140 part in your equation or the "multiplier" reflects the Dry Matter so 140 = 14%. In wetter weather I'd imagine you'd have grass dry matter at nearer 12 or 10%., so your multiplier would change to 120 or 100 in this scenario.

As a side job, it would be a good idea to test some yourself so that you know what Dry matter is at certain points of the year. Cut 100g of grass and heat overnight in the oven until the sample doesnt get any lighter - the end weight is the dry matter of your grass at that point - e.g. 10grams was 10% DM...

Thanks. That's really helpful, it's definitely easier when you understand how the formula is made!

 

[gellis888]

We lose cover here to wind and frost. If its been quote wet and then we get a run of frosts then covers will drop. Like wise in the summer it is common for covers to get lower due to wind damage.

Interesting you mention wind. Presumably the grass dries out more, proportion of dry matter increases but covers decrease? Correct me if I'm wrong but unless the frost kills the leaves and they decay, actual dry matter shouldn't be being decreasing but fresh weight will? I'm confused as to whether I should assume I still have the same dry matter per hectare or whether I am actually losing kilos of feed energy.

 

[multi power]

Interesting you mention wind. Presumably the grass dries out more, proportion of dry matter increases but covers decrease? Correct me if I'm wrong but unless the frost kills the leaves and they decay, actual dry matter shouldn't be being decreasing but fresh weight will? I'm confused as to whether I should assume I still have the same dry matter per hectare or whether I am actually losing kilos of feed energy.

You will probably loose some feed, the dry matter will also be increasing over winter

 

[NZDan]

Interesting you mention wind. Presumably the grass dries out more, proportion of dry matter increases but covers decrease? Correct me if I'm wrong but unless the frost kills the leaves and they decay, actual dry matter shouldn't be being decreasing but fresh weight will? I'm confused as to whether I should assume I still have the same dry matter per hectare or whether I am actually losing kilos of feed energy.

Here wind just batters the grass till the leaves etc fall apart, we can have high 20 degree days and 50-70km winds. The grass literally blows away.