Pre Mowing: Recreational diesel use?

Cows tucking in to premown grass back in 2012

Today's post is all about the "sexy" topic of premowing grass for grazing. Just from my own conversations with fellow grazers, it seems the majority have dabbled with premowing at some point, with a range of success. My own opinion is that it's an important tool to help manage grass quality heading into the summer. Others are slightly more sceptical. With this in mind I thought I'd share my tips and thoughts on the practice.

Five years ago we sold our topper and instead bought a mower. This was not to cut silage with, but to specifically premow grass. Topping worked OK, but in some situations the dead grass would lie on the ground and prevent the regrowth shooting through. Here was our justification for the change:

Despite the best management in the world cows will not hit 1500kgDM residuals every time, for a range of reasons, some within our control, others not. Over allocation, inclement weather or just plain bad luck! The decision then is to either try and correct the residual mechanically or hope the cows will graze better 'next time'. The problem is the deck is stacked against us if we use the 'next time' approach. Grazing to 1800kgDM for example, shifts the 'growth point' up to this height, with everything below, low quality, unpalatable stem. At this point we saw premowing as a simple correctional tool to reset the paddock. But what if there were other benefits we hadn't considered?

We soon noticed that when the grass was mown, cows were finishing grazing quicker and lying down full. Then there was the jump in milksolids. Cows went from 1.8 to 1.94kgMS almost overnight. During our surplus months we could now allocate more grass to the cows, knowing they could hoover it up, expending less energy walking the paddock pulling the grass themselves. Capturing the benefits of more feed for less effort.

Costing the exercise is a lot harder. Fuel, labour, repairs and depreciation all have a cost. However, the cost of doing nothing, we have seen time and again, as milk output declined every summer. To this day we now take an aggressive approach to residuals. Any paddock which doesn't meet the standard is put on a list and, weather permitting, will be premown in the next round.

Here are my Dos and Don'ts for those wishing to try it out:

• Don't mow in a deficit. Mowing slows regrowth, especially when mowing higher covers.
• Don't mow covers over 3700kgDM. Grass above this cover has lost a lot of its quality and palatability.
• Don't mow more than 24 hours in advance during dry weather. Grass will overwilt.
• Do mow 12-24 hours in front of cows. Some wilting will increase the dry matter of grass without losing quality. In very dry weather, the cows can go in straight after mowing.
• Do mow early in the year. The sooner you can start mowing, the sooner you can stop grass pushing towards heading.
• Do mow high quality lush grass. The better the grass, the more profound the impact from increased intakes.
• Do mow low. Use a plate meter to measure your mowed residual, the closer to 1500kgDM the more effective it is.

I hope these helped. Ultimately whether you use a mower, topper, or a second mob of stock to tidy paddocks doesn't matter. The important thing is to recognise poor residuals and remedy them before it's too late!

Reseeding 101

Here's a post with a guide to reseeding grass to grass!

Sprayed and drilled pasture at the runoff block.

1. Identify why a paddock needs to be reseeded.

Here, good pasture growth records are vital. 

Paddocks ranked according to TDM/Ha 2014

As we can see in the table, my best paddocks grew over 18T whereas my worst barely grew 10T. With this information I can put my efforts into improving these worst paddocks, for maximum return.

The first thing you can do is asses the condition of the sward. If a paddock contains less than 50% perennial ryegrass then it will likely need a reseed. To identify these grasses pluck some grass and check for the distinctive red colour at the base of the stem. These grasses have the highest performance, both in growth, quality and economic response to fertiliser.

Next I'll consult a recent soil sample. Grants in Wales have enabled us to soil test the entire farm every 3 seasons, at minimal cost. Once the status of the paddock is known I can start correcting any deficiencies in PH, P and K indices.

Now I've decided to reseed I can move onto step 2.

2. Choose an appropriate cultivar: My rant against the seed industry!

There are a myriad of different mixes and grass seed houses selling their wares in the UK. Unfortunately, despite having some of the best cultivar research in the world (IBERS, Aberystwyth), farmers have been badly served by the seed industry. 

Mixes often contain upwards of 6 different varieties, with different characteristics and heading dates. These mixes are a nightmare to manage, with grass heading at different times of year. Worse still the high levels of competition in the sward will mean after the initial establishment year, the more competitive grasses will simply kill off any others. This means your 6 variety mix will end up as a 4 variety ley, with the extra seed a waste of money. 

So why are seed houses pushing these mixes? The answer is to shift old stock. One or two of the varieties may be the latest and greatest seed, but the rest will be bulked out with older, lower performance stock.

My advice is to specify your own mixture, you may be surprised to find it no more expensive than buying off the shelf mixes!

Tetraploid vs Diploid

Tetraploids are more open, erect grasses, that are darker in colour. 

Pros: 

-Higher sugars, with some evidence suggesting they support higher animal performance.

-More open making them more clover friendly

-More palatable leading to lower residuals

-Bigger seeds establish faster in adverse conditions

Cons:  

-Less persistent

-Easier to poach in wet weather

-Easier to overgraze in a drought

Diploids are denser growing, more prostrate grasses, paler than tetraploids.

Pros:

-Denser swards

-More tolerant to poaching

-More tolerant to overgrazing

Cons:

-Less clover friendly

-Slightly less palatable

-Smaller seeds, slower establishment in adverse conditions

Remember tetraploids are more competitive in a sward. If you sow 30% Tet. and 50% Dip., after 3 years the sward will be 50-50.

If this all sounds a bit complicated, sow mainly diploids in wetter areas and mainly tetraploids in drought safe, drier areas. Choose 1-3 varieties with 1-2kg/acre of clover (if you want it). Sow at 14kg/acre for Dip. swards and 17kg/acre for Tet.

The new Irish Pasture Profit Index will help you create your own mix:

http://www.agresearch.teagasc.ie/moorepark/PastureProfitIndex/ppts/TeagascPastureProfitIndex2015.pdf

3. Choose a reseeding method.

In NZ it is common to spray off the old ley, then direct drill with the new. This simple system can be very cost effective, roughly a third of the cost of cultivating, harrowing and rolling the paddock. It also has benefits in preserving the soil structure (good for worms!) and avoiding plough pans and associated problems. However some caution must be taken before using this technique.

If there is a high level of root mat, common in old permanent pastures, then the old sward will create an acidic environment when it dies off. This can stop germination, resulting in failure. To get round this you can apply lime before drilling. However in some cases it won't be enough. In this case some sort of cultivation is required to break up the mat before sowing.

Grass emerging in the drill rows.

This year we've taken the risk and sprayed off the old permanent pasture, limed and drilled, with no cultivation. As you can see in the image above the seeds have germinated OK, coming much quicker in the open parts of the paddock where the old mat isn't shading the seedlings. I'm crossing my fingers it will work, but am already regretting not running a harrow over the field to open the sward more before drilling. If I feel brave I'll post another picture in a months time so you can see our success/failure!

I hope this has helped, establishing grass can seem very complicated and often a bit of luck can make all the difference!