June (No. 497)
Soil management: the organic way
David and Barbara Bruer, of Temple Bruer wines at Langhorne Creek in South Australia, have adopted organic farming practices at the vineyard and winery since the early 1990s, when they converted Temple Bruer to a fully-certified organic grapegrowing operation.
The couple regularly conduct organic vineyard management forums for interested growers and winemakers at their vineyard near Strathalbyn, the most recent being the Organic Soil Management Forum held in May.
Along with David Bruer’s personal presentation on composting methods used on the property, the forum featured guest speakers Chris Penfold of Adelaide University, Phil Barnett of Australian Perry Agricultural Laboratory (APAL) and Katie Webster of EcoResearch.
Penfold spoke on mid-row management and soil health; Barnett on soil analysis to balance soils for healthy vines and quality fruit; and Webster on organic matter management in vineyards.
Grapegrower & Winemaker caught up with David and Barbara Bruer before the May forum, to discuss organic soil management principles, and how these are applied at Temple Bruer.
“Couch is the most difficult weed to control at Temple Bruer,” David Bruer began. “There are other weeds such as grasses, annual weeds like fat hen, a variety of thistles but none are particularly difficult to control and we don’t do any specific treatment for any special weed. We utilise mechanical cultivation and then hand weeding of any few remaining weeds that aren’t caught in the cultivation process.
“Mulch is an important part of weed control too. We clean up the vineyard in spring and apply compost as a mulch in spring to a depth of 6-7 cm just under the vine. The compost is composed of winery waste and sawdust. We find it breaks down reasonably quickly over a 9-12 month timeframe. There is very little left in place by the following spring.
“We’ve never considered cost-effectiveness of our weed control program as a part of what we do. Cost is irrelevant, we’re organic, we don’t want to use herbicides, even organic herbicides. So we’ve never thought to crunch the numbers on cost-effectiveness of organic weed control versus non-organic methods.
“We find our mulch is a refuge for small animals and insects which comprise the rich biodiversity here. We wouldn’t have this biodiversity if we used herbicides. We have healthier vines which can handle stress of any kind better,” Bruer said.
“Our cover crop is sown in mid-to-late May. The entire vineyard is sown with the same mixture. Our vineyard is quite homogeneous. It is a mixture of 50% oats, 20% faba bean, 20% field peas and 10% vetch. We chose this ratio based on the soil and plant tissue analysis,” Bruer said.
“The mixture was chosen to correct deficiencies in nitrogen and carbon content. The legumes improve the nitrogen content and the cereals improve the carbon content. We have improved our soils and they are much better than when we bought the land, but the total organic carbon and nitrogen levels are still too low. Our cereal/legume cover cropping regime will stay for a few years more.
“The cover crop mixture is sown using a combination rotary tiller and seeder and takes just one pass. It would normally take us three to four days to plant the cover crop, depending on the weather conditions at the time of sowing. Then we cultivate it into the soil using an off-set disc in September.” The mulch is then covered with a thin layer of soil which is sourced from the mid-row using a channel plough.
“Without doubt, compost is much cheaper to make than to buy. We bought compost one year and it cost $5000 in freight alone and the total bill was about $10,000 for 200m3 of compost.
“We make our compost with sawdust, lees and grape marc. The process takes about three months before the material is ready for use on the vineyard. The lees and marc have to be disposed of anyway as winery waste. If we didn’t compost this, we’d have to freight it away as part of a waste management plan, which is just an added expense.
“Sawdust is a waste product and we get this free, the only actual cost is carting the sawdust which is about $500.
“We turn our compost 12-15 times in that three-month period, and the turning takes about three or four hours. I’d cost that out at $40 per hour using a front-end loader, so $2250 in total for turning.
“So, looking at the total cost for our process of making compost, we’d pay about $2750 to get our 200m3 of compost, which works out to be $14/m3.
“We use a rate approximately equal to the rate we harvest grapes. That is, about 10 tonnes/hectare or 20m3/hectare.”
Pest and disease
“We do not think that our organic soil management/floor management systems have had an effect on pest control directly. However, we do not have any serious pest problems. So it is probably the entire organic process which helps in this regard.”
Organic vineyard management forums are held regularly throughout the year at Temple Bruer. Details are available on the winery’s website www.templebruer.com.au or by contacting Barbara Bruer on (08) 8331 1952 or email email@example.com