Argall Family wrote:
> I am newly subscribed to Sanet. I have had a (very small) certified organic
> orchard in south eastern Australia for some years, previously did some
> conventional cattle farming, also very small.
>
> Steve Diver wrote
>
> >1. Why did the researchers suggest that natural sources of
> nitrogen such as legumes (clovers, vetches, cover crops)
> cause as much acidification as chemical nitrogen sources
> (ammonium nitrate, anhydrous ammonia, etc.)???
>
> This generalisation about plant effects does seem to need qualification.
> Acacia spp actually raise pH while also fixing nitrogen. Hence, the value of
> allowing/encouraging natural [here in Australia] regeneration of wattle
> [Acacia] trees in an orchard when it is young. The wattles, a major pioneer
> species here, grow quickly, most of them would if left alone fall over at
> age 15-20, but if removed at 3 years or so will noto nly have done a major
> job opening rock with invasive root systems, but also will (easily observed)
> produce a nitrogen effect in the root area, for other trees/plants/pasture
> for a couple of years at least. The rotting root systems also provide soil
> benefit, apart from the nitrogen nodulation. These trees do not sucker,
> unlike the nitrogen fixing pioneer Alder.
>
> Sadly, these facts on the value of wattles are known better to permaculture
> people than to conventional farmers here, who clear out wattles (woody
> weeds) and plant pasture adding superphosphate, believing that the rapid
> performance of the newly cleared land is due to the phosphorus when it is
> probably almost entirely due to the clearance of the nitrogen fixers and the
> sulphuric acid in the super bag.
>
> I would think a major distinction should be made between use of legumes as
> rotation, where they die or are dug back in, and constant maintenance of a
> leguminous pasture. I have always had the (intuitive) view that no nitrogen
> fixing plant with any brains, any more than any other organism, is concerned
> about looking after others rather than itself. Maximum nitrogen effects are
> likely to arise from allowing a succession away from the nitrogen fixer.
> Keeping a nitrogen fixer in one place for a long time is likely to have
> deleterious effects as with any other monoculture.
>
> Which is not to say that I disagree with the following, which emphasises
> that it is not the legumes per se but the cultural practices associated with
> their use which impact on soil negatively or positively.
>
> >If you think [Steve said] about long-term studies and real life situations
> where
> side by side farms are managed by organic or conventional
> methods, I am pretty sure you'd find wide enough differences
> in soil quality characteristics to disprove the statement that
> nitrogen from legumes is just as harmful as chemical nitrogen....
> especially when viewed from a whole farm perspective, there are
> humus complexes and soil foodwebs that can bind and fix nitrogen
> thus preventing its ability to contribute towards soil acidification.
>
> Steve also wrote:
>
> >Interestingly, compost is known to raise the pH of acid soils
> closer to neutral, as well as lowering the pH of basic soils
> closer to neutral. Compost helps soils adjust towards neutral
> whether the pH is high or low.
>
> ...which is why it is useful to regard composting as essentially simply an
> acceleration, centralisation and intensification of good soil building
> techniques, with some further health benefits if high temperatures are
> established.
>
> One green manure technique for bringing available calcium into the
> biological content of the soil, which is inexpensive on a small property, is
> to spread inexpensive feed oats and cut the young (calcium scavenging) crop,
> before it goes to seed.
>
> Dennis Argall
>
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