Thursday, 29 November 2018

In The Field, number 01: Pretty green stripes

‘In The Field’ is intended to be a series of blogposts that will run here as long as I can source suitable content. Farmers operating in Australia can send me photos of their farms and descriptions of the steps that they take to overcome problems that they face in their routine working lives. An exchange will likely result in some questions and answers. I don’t know how many of these posts will be produced but I have long felt that farmers needed a bigger voice in the broader community.

This is a barley field on a farm managed by John Stevenson outside Lockhart, a town situated in the Riverina in southern NSW, between the Murrumbidgee River and the Victorian border. “Some of our barley meets the strict criteria of correct grain size, colour and protein content to be used for malt production ([a] key ingredient of beer),” John told me via DM.

“Our barley which doesn’t meet [those] criteria is mainly used as stock feed, either within Australia or overseas. Barley is an important ingredient of feed rations across many parts of the livestock sector. There is usually a $30-40/tonne premium for malt barley but this varies with supply and demand.” So John earns more money if his barley is of a quality that enables it to be used for brewing.

Malting is a process whereby grains of barley have water added to them and are allowed to germinate, but then they are dried to halt the process before it completes. The partially-germinated barley is called “malt”.

The challenge

Removing weeds from cropped fields so that the moisture stored in the subsoil is not wasted by their growth. 

“The barley was harvested two weeks ago,” John told me, referring to the photo (above) he had sent. “The grain has been removed and some of the straw has been baled to feed cattle at a reasonable cost. Following a very dry year November has been wet. Not all of the grain is collected in the harvester and there is always a proportion of grain ‘loss’. 

“As you can see this lost grain germinates and effectively is now a ‘weed’.”

Keeping moisture in the ground is critical for farmers to succeed and, if left to grow, weeds will use moisture that would better be preserved for the crop to come the next year. “The biggest limitation to our crop production is moisture and we are able to store moisture in the soil for next year’s crops. The green rows you see are actually using/wasting next year’s crop water. If we don’t control the weeds the soil will dry out completely in these strips.”

John explained that subsoil is everything below the topsoil. “Our hot summers generally dry out the top 30cm of the profile. The moisture we carry forward for the next crop is below that level. Our roots can grow down to 1.8-2m on some of our soils.”

The pretty green stripes in the photo are actually bad news, but how to remove weeds?

The solution

“We could dig them out (known as ‘cultivation’) but this removes the valuable mulch which protects the fragile soil surface from wind, sun and rain,” John told me.

“Our modern-day alternative is glyphosate, a chemical which is in the press a lot these days. I have been using glyphosate for this purpose for nearly 30 years and it has revolutionised sustainable farming.”

Glyphosate was developed by the chemical company Monsanto and was marketed under the product name Roundup but is now produced by many companies around the world. But why is digging out the weeds a bad idea?

John explains that “cultivation” is digging out the weeds, like a gardener would do with a spade or a fork. But it can be destructive of the topsoil. “Our topsoil is only 5cm to 10cm deep and very prone to erosion if exposed to the elements. The mulch is a thin layer of crop residue on the soil but also the standing crop residue from this year which is about 150mm high.” So the stubble that is left in the field after the harvest protects the topsoil that has to be in good condition in anticipation of the next year’s sowing.

John also told me that cultivation destroys soil structure. “Soil particles are bound together by the soil microbiology and there are important drainage channels through the soil made by decaying plant roots and soil-borne insect life.”

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