Grassland farmers are being reminded that maintenance applications of Phosphate at soil Index 2 still provide a yield benefit.
Research from CF Fertilisers UK Ltd. (formerly GrowHow) looked at nutrient programmes for grass silage. The results show that 1.2 tonnes additional dry matter can be grown with regular applications of P2O5 to maintain the land at soil index 2.
Dr George Fisher, grassland consultant with CF Fertilisers, explains more about the research: “The fertiliser manual RB209 recommends maintenance dressings at soil index 2 to hold fertility at this target level. There shouldn’t be a yield response at this level, but we wanted to check this because there is growing evidence, some scientific, some anecdotal, that there is one.
“We tested three rates of Phosphate spilt over three silage cuts – half of the total was used for the first cut and the remainder applied for the second and third cuts. The rates we used were zero, 80, which is the RB209 recommendation to maintain soil P index at 2, and 120 kg/ha. The results were clear – 80kg of phosphate delivered over 1.2 tonnes DM/ha more grass than not applying anything but there was no benefit from going up to 120.”
Extra grass is of course a benefit, but it is worth putting some figures on how this small change can make savings across the business. The application cost for 80kg P2O5 will be around £45/ha but the additional feed for livestock is worth more than that.
“To replace the lost silage potential with purchased feed would cost more than the initial £45 outlay on fertiliser. 1.2 tonnes DM is equivalent to 4 tonnes of fresh silage which costs around £80. If you wanted to make up the shortfall with concentrates you would expect the cost to be around £275.”
Dr Fisher stresses that these figures are based on the results from trials but, on farm, energy content and dry matter content of grass will vary; however, the fact remains maintenance dressings at index 2 are good for grass production in the season of application – and keep ground in good shape for the following years.
“Keeping soil at target nutrient soil indexes is sound grassland management in any case, but the fact that you can expect an immediate return makes opting to apply maintenance phosphate a straightforward decision,” concludes Dr Fisher.
