Tuesday, 5 May 2015

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. 
-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
-Less persistent
-Easier to poach in wet weather
-Easier to overgraze in a drought

Diploids are denser growing, more prostrate grasses, paler than tetraploids.
-Denser swards
-More tolerant to poaching
-More tolerant to overgrazing
-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:

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!

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