Soils under ‘unprecedented pressure’ agronomist warns

Soil health and cultivation took centre-stage as farmers gathered at a Suffolk trial site to get clued up on the latest thinking about crop growing techniques this month.

More than 200 growers from across East Anglia visited agronomy firm Agrovista's Regional Development Site near Framlingham to see cutting edge agronomy at work, with insights on how to maintain yields and profits in an increasingly uncertain future.

But agronomist Graeme Barrett warned soils faced unprecedented pressures as heavy machinery and changing farming methods took their toll.

MORE - Farming has become 'too isolated' says grower who wants to share best practice"The characteristics of many farmed soils have altered because of changing farm systems," he explained. "Increasingly heavy machinery can reduce soil porosity and water absorption as well as organic matter levels, adversely affecting the productivity and resilience of soils."

The key to creating and maintaining healthy soil was understanding the relationship between the physical structure, biology and chemical processes within the soil, and the farming practices that affected them, he advised.

"A standard soil test measures P (phosphorus), K (potassium), Mg (magnesium) and pH (acid to alkaline scale 1-14), but this tells you nothing about the availability of those nutrients or the underlying health of the soil," he said.

Agrovista's new soil offer focuses on optimising pH, ensuring correct nutrient balances and enhancing soil biology, as well as understanding soil textures and capabilities to maintain structure, maximising water efficiency and optimising porosity with a minimum of cultivations, he said.

The pH was a key driver for nutrient availability, he said, followed by organic matter. Ideally, levels needed to be around 6.5 and 5% respectively, he advised.

Carbon to nitrogen ratio in organic matter was also important and needed to be around 10-12:1, he said.

If low, he advised looking at an organic material with a high carbon to nitrogen (C:N) ratio, such as chopped straw or compost.

"If the ratio is on target, use a balance of differing C:N ratios to maintain the situation."

Phosphorous availability was also important - on alkaline soils substantial amounts of phosphorus (P) in trisodium phosphate (TSP) can be locked up in just a few weeks, so growers need to have accurate assessments and switch to diammmonium phosphate (DAP) in these areas, he said.

Other tests include iron content, which can act as an early indicator of compaction; soil structure, which affects root penetration; and water availability and aeration. All this is backed up with tissue testing to monitor what the growing crop is actually taking up.

Agrovista is carrying out investigative work into matching wheat varieties to high- or low-till cultivations at the site. Plots have been overlaid with a range of fungicide and plant growth regulator (PGR) inputs as well as biostimulants.

Agrovista technical manager Mark Hemmant said some of the work was at the forefront of agronomic thinking, and would help the company deliver more tailored and site-specific advice.

Four wheat varieties have been established on large-scale plots, either direct drilled with a John Deere 750a or cultivated using a combination of tines and discs before drilling.

"Not many farmers direct drill, so you might ask why is Agrovista spending time and money on this," said Mr Hemmant. "We believe we have to look ahead, anticipate which way things might go, whether driven by politics or economics. We need to get data ready."

The varieties include a fast-developing variety, KWS Siskin, a slow developer, KWS Barrel and two of the highest yielding feed wheats, RGT Gravity and Sartorial.

"In the three trials we harvested last year, RGT Gravity performed the same regardless of establishment method. However, there were significant differences in the performances of both KWS Barrel and KWS Siskin under the high and low regimes at each of two sites," said Mr Hemmant.

This year at Framlingham all the varieties established better under low till. "This was a bit of a quirk because it was so dry - we think it was down to soil moisture preservation," said he added.

New soil husbandry trials at Framlingham are assessing the effect of five different cultivation systems on soil health, ranging from ploughing to direct drilling, with and without cover crops.

The trials site, organised jointly with East Anglian machinery dealer P Tuckwell Ltd, was hosted by Tuckwell Farms at Kettleburgh Lodge Farm, Framlingham.