When tropical grass seed ain't tropical grass seed

What to look for in your seed

Tablelands Telegraph - December 2021

Phil Cranney, Senior Land Services Officer, Pastures

There are some similarities between tropical and temperate pastures. The cost to establish is the same - $450-$500/Ha. However, in these southern areas, germination to establishment is much riskier for the tropical grass compared to the temperate grass.

Often those establishment issues experienced with tropical grasses start a domino effect on extra costs, such as:

  • Delayed grazing, due to different growth stages of the new plants
  • Poor plant density allows weeds to fill the spaces, which can lead to seed set
  • If those summer grass weeds are allowed to seed, it becomes a lost production and lost quality issues driving your optimal stocking rate down

Tropical grass seed is expensive. Therefore, it is important to give yourself the best chance to establish a decent plant density, usually 10 plants/m2. The top 5 basics you should be looking for from tested seed analysis:

  • Ensure the seed test is from an accredited lab
  • Purity % - be sure to take note of the “other seed” % (weed seed?)
  • Germination % (typically lower for tropical grass, compared to temperate)
  • Take note the 10-day germination %, when working out your sowing rate
  • TZ tests are not that reliable, because it includes abnormal and fresh seeds

The other key point to consider is the seed coating rate. If it is coated at 200%, then there is only 500grams of seed per kg, therefore double your recommended sowing rate. Some can be as high as 500% seed coating, which means that there is only 200grams of seed in 1 kg of coated seed product. Ensure you are taking this into account when trying to optimise your plants per square metre establishment rate.

Let's look at two different scenarios and assess the cost of planting.

Bob Farmer has sourced two potential suppliers of Premier Digit grass to plant in January, once it dries out a bit. Reg’s Rural supplies has Premier Digit for sale at $30/kg. Flash Gordon’s Online Seed Sales has Premier Digit for sale at $25/kg.

Flash Gordon seed test

  • 95% Purity, 2% other material and 3% other seeds
  • 10 Day Germination: 35%

Reg’s Rural Supplies

  • 95% Purity, 4% other material and 1% other seed
  • 10 Day Germination: 52%

Using the 10-day germination rate to compare the cost of the seed, Reg’s Rural supplies is $58/kg and Flash Gordon’s is $71/kg. Therefore, if you adjust the recommended sowing rate according to the germination and the seed coating %, these costs can really blow out your establishment costs. Lowest cost seed is not always the best value.

Most importantly sowing tropical grasses on the tablelands must consider the risk of importing tropical weeds with their seed. Seed with extremely low or zero “other seed” % in the purity test is crucial to ensure you do not end up buying an expensive weed seed.

For more information about pastures, contact Phil Cranney or Clare Edwards.

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