2018 Biochar workshop tour

Workshop Tour Background

2018 report by Denis Enright

A 2 year study on the effects of biochar and compost on soil water and nutrient content was conducted in a Mt Difficulty vineyard at Cromwell, Central Otago. Treatments consisted of; pine branch biochar, compost, and mixes of the two, which were buried in a trench midway between grapevine rows. This approach was taken to cause least disruption to the roots of 5 year old vines, and would simulate placement of biochar prior to planting new vines on top of biochar. As there were no or few vine roots in the treatment zone, assessment of the treatment effects was restricted to measuring soil water and nutrient content.

That study showed that a woody biochar (with negligible nutrients) incorporated into  gravelly free draining soil can retain moisture to the same degree as an equivalent amount of grape marc compost. Biochar also had a positive synergistic effect on nutrients supplied by the compost. That is, in the presence of biochar soil nutrient levels remained higher even though the amount of compost applied was reduced.

It is proposed that further simple on farm experiments could provide long term study sites.

So during a series of biochar workshops held at Cromwell, Brightwater, Waihi, Waiuku and Gisborne (May/June 2018) small experimental sites were established using biochar produced during the workshop. At each of these locations the fresh biochar was applied to soil and will be compared with no addition of biochar in a randomised block design replicated 3 times. Samples of the biochars were retained for analyses and in the future other measurements such as soil moisture and nutrient content will be undertaken to evaluate whether there are any benefits, particularly in moisture and nutrient retention.

Cromwell – NZ Nuts Ltd workshop 24th May 2018 

Biochar was made from dried willow and eucalypt branches by flame cap pyrolysis in a bath, replicating a trough kiln. The biochar was then crushed manually and broadcast on to plots (1 by 2 metres) having a covering of short grass, midway between the rows of walnut trees, with treatments on each plot being: plot1-biochar, plot 2-nothing, plot 3-biochar, plot 4-nothing, plot 5-biochar, plot 6-nothing.

Application rate was 4.0 l/m2 which using an estimated bulk density of 0.25 equates to 10 t/ha.

Brightwater – Kaimira Wines workshop 29th May 2018

At this site biochar was made from dry chunky vine trunks and branches (diameter approximately 25 -75 mm) again using an open trough (bath) flame cap system.

The biochar was then crushed by hand, with the resulting biochar broadcast on to a strip 1m wide by 5m long directly below the vines. Starting from row 1  nearest the river, treatments were located in vine row 2 plot1-biochar, plot 2-nothing, vine row 3 plot 3-biochar, plot 4-nothing, vine row 4 plot 5-nothing, plot 6-biochar.

At the time of biochar application there was a good sward of grass and clover growing beneath the vines, while the remainder of the inter-row space had been mowed. Vine row spacing is 2.5 m.

The vines where this experiment has been established were noted for lower vigor than others within the vineyard and this is attributed to lower soil fertility than other areas due to gravelly soils associated with river nearby.

Waihi – Chaos Farm workshop 1st June 2018 

At the workshop at Chaos Farm we made biochar from mostly dry acacia branches in a small Kon Tiki kiln. The resulting biochar was top-dressed under lemon trees (circle of diameter 1.25m) at a rate of 10 t/ha (4 l/m2). Pairs of trees were chosen where biochar was applied to a tree and an adjacent tree labelled as a nil control.

The lemon tree orchard had a healthy sward of mixed species growing below the trees. Most trees looked healthy and productive, but there was evidence of some Verrucosis on trees, which causes some disfigurement of the lemon skin and borer which can ultimately kill the tree. Steve demonstrated his cyclone pump system that he has developed to spray various organic liquid nutrient solutions around his farm, as well as soil injection where nutrients are pumped into slits cut in the soil. He also demonstrated how ground up  biochar can be mixed with water and pumped out onto the land.

Waiuku –  Waipipi Organics kiwi fruit orchard  5th June 2018

Biochar here was made in the same small kontiki using dry kiwi fruit trunks that had been cut out because of PSA infection. 8 litres of biochar were applied in a shallow trench approximately 15 cm wide, 15 cm deep and 2 m long centred on one side of a vine and 1.5 m out from the stem. A further 8 litres were surface applied on a 1 m wide strip adjacent to the trench.

Gisborne –  8th June 2018

Biochar that was made in the same small kontiki used at other workshops using trunk and branch wood and leaf from apple trees previously cut out because off canker infection.

This was crushed and 8 litres applied in each of 2 shallow trenches 2 m long dug on each side of 2 apple trees. The treated areas were located in row 9, from bay 2 to bay 7. The order of treatments was: bay2-biochar, bay 3-nothing, bay 4-biochar, bay 5-nothing, bay 6-nothing, bay 7-biochar.

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