Sunday, 15 July 2007

How to Save Water.

I just re-watched ‘How to save the world , one man, one cow, one planet’ about biodynamic agriculture in India where it was claimed that biodynamic practices have improved the water holding capacity of soil to the extent that it has reduced irrigation by 50%.
Having just experienced the driest season on record, the creeks stopped running for the first time since we have been here, 24 years. The plants in the valley are particularly ‘soft’, as they are normally on the waterlogged side by July through to October although yields where down the plants faired very well. The house gardens are rarely ever watered anyway & always do well. The ‘lawn ‘around the house is watered for fire protection & air-conditioning last season every 14 days on average. The veggie garden needed no more than water every 10- 12 days. (Except for getting seeds up.) When it rains here & it does often with annual rainfall average of 1100mm, all the water infiltrates into the soil like a giant sponge.

The key is not as most people think, organic matter but quality humus that makes the difference. The regular use of biodynamic horn manure (500) & quality compost made with biodynamic compost preparations make all the difference.
Regular applications of 500 will see improvements in soil structure via
· : Increased water holding capacity.
· Increased earthworm activity.
· Improved crumb structure in soil = more air & water can be stored.
· Increased clover nodulation
· greater root penetration
· Increased micro flora = more availability of nutrients & trace elements.
· Stabilizing pH.
With this in mind I thought you may be interested in this research

study shows.
One of the claimed benefits of BD practises, especially the application of ‘500’ is the improvement of soil structure and soil biological activity with the subsequent deepening of the root zone resulting in improved water infiltration and soil moisture retention.
A recent comparative study of soil and plant characteristics on adjoining Bio-Dynamic and conventional dairy farms in Victoria seem to bear this claim out. The study, carried out by Simon Cock of the La Trobe University School of Agriculture concluded that root growth of pasture species in the BD subsoil (B horizon) was significantly greater than in the conventional subsoil. The study showed that this fact was responsible:
* for the longer interval between summer irrigations (14-21 days on the BD as opposed to 5-10 days on conventional); and
* for the more favourable balance of species in the BD pasture.
The soil type of the adjoining properties is a red-brown earth having a clay B horizon with poor structure which tends to reduce water holding capacity and root growth. Deep-ripping is commonly used to loosen the B horizon of such soils. This was done on the conventional paddock in 1971, 1979 and in 1982. The BD paddock was deep-ripped in 1963 in the first year after conversion to BD practises. Up to that time superphosphate had been applied at a rate of 600 kg/ha annually. Since conversion (23w years at time of study) no fertiliser, including lime or gypsum, had been applied to the BD pasture. On the other hand the conventional paddock routinely received 800kg/ha of super and 50kg of urea per year.
The study found that the presence of the high quality species of white clover and ryegrass in the BD pasture had not declined in favour of the more
moisture-stress resistant species, paspalum despite the longer irrigation interval. This fact indicated an improvement of soil physical properties in the BD soil profile, a conclusion which was supported by the following properties in the BD soil’s B horizon:
increased plant-available water.
less slaking and dispersion and more water stable aggregates.
decreased soil strength at the A/B horizon interface.
increased root proliferation down the soil profile.
Tests done during the study have indicated that in the BD soil, water is more freely infiltrated into the B horizon compared with the conventional soil. The report states “This ability to infiltrate water into the clay subsoil and store it there as plant-available water would mean that more of the BD soil profile is accessible for water extraction by roots. The suggestion that the conventional soil is unable to allow water to infiltrate into the B horizon is consistent with observations of severe pugging and waterlogging throughout winter.” It was also noted that after irrigation the conventional topsoil remained saturated for days, reflecting the inability of the soil to freely drain water into the B horizon of this soil.
Other points made were: “The ability of plants to extract water effectively requires a good soil-root absorbing relationship. This is reflected in the ability of roots to explore the soil volume. Total root length and new white root growth data from the BD soil indicate not only the potential to extract water from a greater volume of soil, but also the ability to penetrate and explore the soil profile to depth.” and that “the BD soil is able to be infiltrated and stores and extracts water from a larger proportion of the soil profile”.
NEWS LEAF #21 autumn 1994 page 23


Kate said...

Thanks Deb. Have you any research on the comparison of organic practices with BD practices in water-holding capacity ?

Kate said...

I would be interested to read what you do in the veg garden in particular, in relation to water and also fertilising etc. Also if you could remind us again about when it is best to sow and plant, according to BD ways.