Twenty years of farming with soil biology

Donnybrook farmer Brett Kirkpatrick has been growing vegetables and pastures using compost and biodynamic preparations for about 20 years. His experience is a valuable insight for growers considering a partial or complete adoption of biological farming principles.

Brett Kirkpatrick and Leonie Inger are fourth generation Donnybrook farmers and pioneers in the organic industry. They started growing biodynamic-certified potatoes in 1994 and four years later added cabbage, cauliflower and pumpkin to the rotation.

Their small operation is in hilly country where large scale growing is difficult. Nevertheless, prices received for organic produce means that their small holding is viable. To supplement vegetable production, 80 hectares of pasture is also utilised for rotational grazing of cattle.

While being a certified biodynamic grower, Brett is open to any form of sustainable farming. “I used to be really passionate about biodynamics, but what’s happening now is that there’s so many different paradigms under ‘sustainable farming’. A lot of today’s biological products are based on biodynamic preparations that we use to activate soil biology. Biodynamic farming is now just one tool in the toolbox.”

Brett agrees that it’s certainly a challenge to get the growth that a lot of farmers are used to. But for him, yield comes in behind profitability, sustainability and health.

His system relies heavily on soil biology, but that requires a good understanding of how biological activity is affected by conditions such as low temperatures and waterlogging.

“Each planting of brassicas (on 1,000 m2 plots) gets about four tonnes of compost during the warmer months (40t/ha), but as it gets colder we’ve found you’ve got to ramp that up to 12 tonnes (120t/ha). In winter you are literally supplying all the nutrients, whereas in the warmer months the biology is more active and able to make more available per tonne. So I think biodynamics works better with irrigation. When you have soil moisture and warmth you will get more development of the biology. But if the irrigation leaks we get a yellowness where there is excess water because it has upset the nitrogen cycling.

“We use clover and lupins or peas in green manure mixes that we pre-plant, but the main focus is feeding the soil with compost and getting nitrogen out of the atmosphere.”

Nitrogen content in dry compost is typically around 1-3%, and that is slowly released over several years. To speed up the release, Brett adds biodynamic preparations into his compost to increase biological activity and the rate of nitrogen mineralisation. Rock dusts required to supply other nutrients are also put through the compost to make them plant-available more quickly. And Brett likes to give his compost plenty of time to mineralise.

“A lot of people put compost out too soon when it hasn’t broken down sufficiently. You want to put a compost out that doesn’t smell like ammonia anymore, but smells like earth.”
Patience is indeed a key to biological farming, especially in the transition phase, and making drastic changes may lead to failure.

“I have to say that with biodynamics it takes time. So in the early stages of transitioning you may need to buffer your activities. But if you are going to put out nitrogen, put sugar or molasses with it to support the biology.”

Brett believes that balancing the soil carbon to nitrogen ratio will help to achieve a more functional soil biology.

“I think the main opportunity for conventional farmers is that compost can help buffer their nitrogen use. When they put out nitrogen they are consuming their carbon, which is going to be slowly eaten away. Compost or other carbon-based inputs can be applied with nitrogen to support the biology.”

In terms of pasture and hay paddocks, Brett’s rates are much more conservative, and he has learnt the importance of long-term monitoring for deficiencies in soil fertility.

“I’m putting out about a tonne to the acre of compost (2.5t/ha) once a year when there’s still a bit of rain to wash it in. This is combined with rotational grazing of 100 Angus and Murray Greys in 38 paddocks over 80 hectares.

“When we first changed over to biodynamics one of the first things my father noticed was that the calves on average were 50-60kg heavier than on his farm. But that doesn’t seem to be the case now. Its almost like the biodynamics complemented the nutrients that my father had been putting on for years, for a period, and then it started to decline.”

In 2014 Brett took part in a whole farm nutrient mapping project funded by South West Catchments Council. “That was a real insight and the first time we did tissue testing.” Results showed that potassium levels were pretty good in most places, sulphur was needed, and that the huge buffer of phosphorus from the days of conventional farming was starting to get low.

“We hadn’t put any phosphorus on for probably 15-20 years. Trace element deficiencies were also starting to show up.”

It is an incredible example of the time it can take before deficiencies start to appear. While realising that he could have started a nutrient monitoring and maintenance programme earlier, it seems Brett didn’t leave it too late, and it turned out to be a useful learning experience.

“A lot of the farms around me have stopped using any inputs. It was interesting to see how their farms declined much faster than mine did. Other than a few lime and dolomite amendments I was using biodynamics solely. Since I started putting other inputs in, trying to get the mineral balance right, my farm is starting to stand out again.”

This article was originally published in the WA Grower magazine in September 2016