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This past Friday and Saturday, I was on a fieldtrip with some of the 2nd year students. This year I had managed to organise a trip to visit Tarwyn Park in the upper Hunter valley, the property which is now relatively well known in Australia through the work by Peter Andrews. I had read Peter's book and I was interested to see the place for myself, and my students were enthusiastic when I suggested this. So last Friday was the big day as we arrived around 2 pm.

Tarwyn Park is located on the relatively flood plain of little valley with mostly sandstone hills from Wollemi National Park around. The floodplain looks impressively green compared to the surrounding hill slopes. We were met by a welcoming committee including Mr Peter Andrews and Mr Duane Norris. We spent about 3 hours walking around the place, or at least part of it, while Peter explained his ideas to us.

Peter's ideas have recently been gaining some momentum here and here, and I thought I should write a summary of my own thoughts about the visit and about what I think of Natural Sequence Farming and Peter's ideas. To start with the verdict: I think the core has some good ideas which are worth pursuing but these are also rather well known and embedded in existing knowledge. What is great is that Peter manages to communicate these ideas to a wider group of people than anyone else. I am not convinced that the overall concept should be accepted as the general rule for farming in Australia. I will explain.

I am convinced that modern agriculture has caused problems and has changed the hydrology of the landscape. Increased runoff and therefore increased stream velocities and erosion are symptoms of this. Dryland salinity has always been related to changes in hydrology, but as I have commented earlier, the views on the causes of dryland salinity have been changing. In fact, it is now more likely that there is a strong link between land degradation and dryland salinity.

Somewhat novel about Peter Andrews' concept is the idea of slowing down the water in the landscape and thus increasing the retention time. To some this is downright heresy. What is further novel is to use this water to increase biomass production and increasing soil carbon by mulching the biomass. Increased soil carbon in return will increase water retention and thus strengthening the cycle. The somewhat new part is the link between carbon and water, the rest is of course strongly embedded in conservation tillage. The link of using water more efficiently to produce more carbon is no entirely new. Another thinker in sustainability who has also been working on the carbon water link is of course Bill Mollison. I was reading Bill Mollison's books when I was still an undergraduate in Wageningen in the 1980's and spent some time studying biological agriculture. Many of the concepts Peter Andrews has come up with have also been raised by Bill Mollison earlier. What is interesting is that Bill Mollison is of course a die-hard greenie and Peter Andrews is more your stock standard Australian farmer. I think this is in fact great news: Peter is reaching a whole lot of people who will never read Bill Mollison.

Slowing down the water in the floodplain is a good idea and particularly the combination with increased biomass production, mulching and minimising the loss of nutrients does the trick. In the floodplain pasture landscape that Peter is working with this achieves great results. Whether we can grow wheat in that way is however a major question. In the end we would like some production from the landscape and thus we would like to harvest some of the biomass/carbon. The main thing to watch is of course the loss of carbon/nutrients and the replacement of those nutrients and carbon with biomass. This means that long term rotations and pasture/wheat systems are most effective, but as agronomists we already knew that from biological farming experiments in the Europe. The problem proponents of biological farming always ran into was the fact that such a system was not profitable and therefore not acceptable for the majority of farmers. Peter is arguing that such a system is profitable for grazing systems. I think it is as long as you can manage the loss of nutrients through production.

Slowing down the water in Peter’s system basically increases the buffering capacity of the landscape, or in other words, it creates a better resilience. This means you are able to manage droughts better, but you will have to watch your carbon stocks and rebuild.

Slowing down the water is of course heresy in light of the traditional thinking in dryland salinity. This will probably increase deep drainage and thus would traditionally be seen as a problem in relation to rising water tables. However, this paradigm is currently under scrutiny.As Dr. John Williams pointed out to me, the increased recharge in Peter Andrews' system also creates a shallow fresh water lens on top of any saline groundwater. This will work as long as the recharge is low in salinity. Any soils which are inherently saline or have high soluble salts (such as carbonates) will of course behave differently. So what will work in the sandstone and shale derived soils at Tarwyn Park might not work elsewhere if the parent material is more saline. I don't believe that the biological system will reduce the salt load. It can only do that if some of the salt is a nutrient based salt or if it gets stored in the landscape, to be released at a later point.

Slowing down water is also heresy from the level of the Murray Darling Basin, as this would further reduce flows in the system, similar to the effects of plantation forests. But again, we should ask ourselves, what was the original system. If white settlers have cleared the landscape, than this would have increased the flows into the system. All we are doing with increased landscape water storage is restoring some of the original flows. This is of course not good news for irrigators and Adelaide, but that might be inevitable if we want to restore the landscape. Tarwyn Park is in the Hunter, so it mainly affects the mining and the vineyards down stream in the Hunter. In a way, what the approach is doing is water harvesting and increasing infiltration and recharge.

So the core of Peter's ideas are embedded in existing and well established ideas about biological farming and about water harvesting. They are not controversial to me. It will work as long as you have low salinity soils, low salinity input water and a relatively flat landscape and you are close to a water source. It also will work better in grazing systems as the nutrient loss can be managed better. Wheat and other cropping systems would really have to think hard about rotations and carbon balances.

All the rest of the ideas from Peter are only layering around this core and some of it I really cannot see any use for, or I find a bit silly. Call me a heretic if you want, but at least I am honest. I am happy to be proven wrong.

Comments

Tragedy is, it's likely to become a coal mine. To quote Gerry Harvey (from today's Sydney Morning Herald, 25/11/10): "The place should be a bloody shrine, not a hole in the ground."

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  • Willem (Hydrology Research Laboratory)

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Aimed at generating discussion on water research and water management in Australia
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