Under-sowing maize with companion grass mixes as winter grazing for sheep is returning a profit for a Pembrokeshire livestock farm while protecting soils.

Mathew Van Dijk under-sowed five hectares (ha) of maize at Arnold’s Hill Farm, near Haverfordwest, as a Farming Connect focus farm project to weigh up the economic and environmental benefits of this approach.

The figures from that trial have now been published and show the system to be a profitable one.

The grass yielded an average of 2.5-3tDM/ha to provide 5,240 sheep grazing days from December 2021 to April 2022.

At an income of £0.90/head/week, this yielded an income of £674; the total input cost for grass seed and drilling was £435.

Mr Van Dijk says the principle aim of under-sowing had been to prevent the loss of soil organic matter and nutrient leaching which occurs when fields used for growing maize are left bare over the winter.

“These figures show that it is economically viable too,’’ he says.

Aside from undersowing the trial area, Mr Van Dijk had been so convinced by the research  around this system that he extended under-sowing beyond the trial area to incorporate his entire 28ha crop in 2021.

He is growing more maize this year - 51ha - and will under-sow 36ha of that.

The remainder is its third year under maize so he will be planting it with winter barley or winter wheat instead.

Many of Mr Van Dijk’s fields have a sloping aspect therefore there is a risk of soil losses and run-off when they are bare because there is no root structure to hold onto the soil.

However sowing a crop or cover after the harvest can be problematic because of autumn soil condition and late sowing – but under-sowing provides a potential solution.

It is already widely practiced in the Netherlands where cover crop establishment after maize cultivation on sandy soils is obliged by law. As a consequence, nearly all maize fields are under-sown.

The grass cover crop at Arnold’s Hill Farm was drilled at the beginning of July 2021 by Pembrokeshire contractor James George using a Zocon tine drill.

The crop of Augustus maize was harvested at the end of September and yielded around 43t/ha (17t/acre), similar to previous years when the crop was not under-sown.

After harvesting, the grass cover was left to bulk up before grazing from December onwards.

To compare performance, for the trial four different seed mixes were used - Italian ryegrass, a straight tetraploid perennial ryegrass, an Italian ryegrass with winter vetch and an Italian ryegrass with berseem clover.

The plots that provided the most cover were the Italian ryegrass and the Italian ryegrass and vetch mix.

However agronomist Gareth Williams, of Procam, the advisor on the Farming Connect project, says incorporating vetch delivered additional benefits as it is nitrogen-fixing and high in protein. 

As he had anticipated, the plot incorporating the berseem clover was negatively affected by the maize herbicide.

The target period for sowing a cover crop into maize is from one week after the last herbicide is applied, when maize plants are at the six- or seven-leaf stage.

Mr Williams says this prevents them from being smothered by the grass.

“The ley in this trial established well, and there was no negative impact on the maize yield,’’ he says.

Under-sowing also helps to retain nitrogen in the soil - 40 kg N/ha, Mr Williams calculates.

“This is good for the soil but also financially important when fertiliser prices are so high,’’ he says.

Of the four grass mixes trialled, Mr Van Dijk is opting to grow Italian ryegrass this year.

“From a commercial point of view it offers the most bulk but we will see how the plots we planted last year with vetch and clover behave, to see if those offered benefits to the soil beyond that of the Italian ryegrass,’’ he says.