Last week, I called to a Grassland Agro trial plot established on a farm near Dromcollogher, Co Limerick. Two products were on trial in a newly reseeded paddock on the farm of Hugh Brennan, brother of Charlie, Grassland Agro sales representative for the region.

Hugh sowed kale in the paddock last July and had it grazed last winter with a view to reseeding the six-acre paddock back to grass this year. Soil tests revealed the paddock was low in phosphorus (P) and potassium (K). Soil pH was 6.6, with P index 1 and K index 2.

Hugh’s land and the surrounding area is high in molybdenum, so as a rule of thumb, little or no lime is spread.

In the past, Hugh has found that spreading lime ties up selenium and iodine in the soil which can cause problems with grazing cows.  

Trial treatments

The paddock (Figure 1) was sprayed with Roundup, ploughed, tilled and the grass seed set at the end of June (26 June).

The reseed cost before the special treatments was €328/acre (see Table 1). The grass seed mix used for the whole paddock was the Kerry TS3 mix. The field was split into three treatment areas.

In the two-acre area shaded yellow (number 1) on the paddock map, Hugh sowed the grass seed with three bags of 10:10:20 and nothing else.

In the two-acre area shaded red (number 2), Hugh sowed the grass seed with three bags of 10:10:20 plus Physiolith at a rate of 200kg/acre. Physiolith is a granular top dressing (similar to fertilizer) that is spread with a spinner.

Around the headlands, Hugh sowed grass seed with three bags of 10:10:20 and then a product called Stimgrass was sprayed on at two litres per acre when the grass seeds were being sprayed with Legumex five weeks after sowing (end of July). The other two trial plots were also sprayed with Legumex with no added Stimgrass.

Results

Grassland Agro specialist PJ O’Connor called to the paddock on 19 August (about eight weeks after sowing) and took measurements on the amount of grass in each of the areas within the paddock.

His results (Table 2) showed that the yellow shaded area, which received only 10:10:20, had a cover of 1,800kg DM/ha.

The area shaded red that received Physiolith at sowing had a cover of 2,300kg DM/ha and the headlands, which had Stimgrass mixed with the Legumex, had a cover of 2,960kg DM/ha. So, when PJ took the cuts, there was a significant difference in the volume of grass between the three treatments.

When I called in to see the paddock on 4 September, there was well over 3,000kg of lush green grass across the whole paddock and it badly needed to be cut for silage to let light down to the grass roots.

To the naked eye, due to the high yield of grass, there wasn’t any noticeable visible difference between the treatments.

Why the difference?

I asked Charlie and Hugh to explain the differences. Charlie said: “Stimgrass is a seaweed-based agent, which is a mixture of nitric nitrogen and magnesium oxide.

“It prevents the check in growth when you spray young reseeds with a herbicide. It also helps to anchor the young seedlings better, promoting root development.

“The other product used, Physiolith, is a granular soil conditioner product mix of magnesium and marine calcium that neutralises the soil surface and is used instead of ground limestone in areas high in molybdenum.

“It has a neutralising value of 39.5% compared to ground limestone which would have a neutralising value of over 90%.”

Costs

We then discussed the extra costs involved in each of the treatments. Stimgrass retails at €12/litre, so for an additional investment of €48 for two acres in this six-acre paddock, Hugh saw a return of 900kg of grass dry matter according to PJ’s cutting weights.

If we value the grass silage at €130/t utilised, it means for the €48 investment Hugh got back about €120 worth of grass silage.

In the other treatment plot, Physiolith retails at €270/t, so for an investment of €108, Hugh saw 400kg more grass, according to the estimates. Again, if we value the grass silage at €130/t utilised, it means for a €108 investment Hugh got about €55 worth of grass silage.

Grassland sales representative Charlie Brennan said that normally he would expect higher yields with the Physiolith product, but because August was so dry, the granular product hadn’t been activated on the soil surface as well as possible.

Justifying the cost

I argued with PJ and Charlie that the timing of the extra grass produced with Stimgrass in a young reseed is maybe not as significant or as valuable to the farmer in the first grazing and that young seedings should be nipped off at a cover of 500kg to 600kg rather than let go into higher covers.

PJ said: “That may be true, but there is a real value to growing more grass and where we see even more significant differences using Stimgrass is in established paddocks that are sprayed for docks mid-season between silage cuts.

“The paddocks that get Stimgrass with the herbicide aren’t checked in growth the same way as paddocks that get herbicide only. You can get significant differences in the volume of silage conserved and that can be big money for the farmer.”

* Hugh Brennan farms at Knockacraig, Dromcollogher, Co Limerick. He milks 140 spring-calving cows, supplying Kerry Group.

Spraying for docks between silage cuts

After visiting the new reseeds, we called over the road to John Molyneaux, who has been using Physiolith for the last number of years and had just used Stimgrass between silage cuts.

John said he is using Physiolith mainly due to the convenience of being able to spread it with the spinner, rather than spreading lime.

John’s land is also in a high-molybdenum region, so he hasn’t used ground lime for years because selenium and iodine were a big problem and spreading lime made the problems worse.

John had just scanned the cows, with only one cow from 97 milking showing up not in-calf. Milk solids production is at about 480kg per cow from a Holstein Friesian and Jersey crossbred herd.

In 2008, John covered his whole farm with four bags of Physiolith per acre. Three years later, in 2011, another four bags per acre was spread and, in 2014, another two bags per acre were spread.

John will soil sample his entire farm this autumn to see how soil fertility has changed.

As well as Physiolith, John has been spreading Optigrass (13:2.2:4.2) to improve P and K.

Charlie Brennan from Grassland Agro maintains that the Physiolith soil conditioner product should improve the surface pH and calcium for soil structure, which improves the P availability and rooting structure. John is going to soil test the farm this autumn.

John also used Stimgrass mixed in with Osmonds Pastureclean after first-cut silage on a paddock he was closing again for second-cut. He left one strip unsprayed and he said there was a noticeable drop in yield in that strip.