"Glenfalloch", Holbrook, NSW 2644
Today I have been asked to give a few thoughts on my experiences with soil compaction.
Starting from the beginning when I acquired my share of the family property, there were few paddocks that had been used for cropping. The total area of 2429 ha (6000 acres) had been a grazing proposition. So on my half of the property, I started to clear dead timber and stumps, then disc ploughed the paddocks and sowed to oats undersown with clover and rye. We worked on a plan of cultivating our worst country as quickly as possible, to grow feed to increase stocking numbers. We had tremendous response and quickly advanced to 7-10 sheep/ha (3-4 sheep/acre) stocking rate, along with annual applications of superphosphate at 90kg per ha. On the re-run, we now have picked out our wettest paddocks and sown to phalaris, for grazing and seed production, and the better drained country comes into a cropping phase.
In 1972 we noted a big fall off in feed production, and consequently had to lower our sheep numbers. Our agronomist at that time diagnosed our problem as Pithium root rot, and trials were set up. In the meantime, we decided to try a few things of our own. One was to combine super and oats into a paddock in the autumn, just to give us winter grazing.
It was very successful, but I had the wrong tynes on the combine. This has since been rectified. We had tried chisel ploughs in 1954-3b period, but they went out of fashion, because of the rough nature of the paddock after working and also in those days tractors didn’t have comfortable seats, as we have today.
About 1976 I hired a plough from Geoff Wallace and results looked promising. We also tried another plough used in ripping in the tobacco and sugar industry. I then purchased a Wallace plough and worked a problem area. Super lime, clover, rye and oats were dropped on the surface and covering harrows were dragged behind the combine. Results were fantastic. We had a few mechanical problems with the Wallace plough and so decided to pursue our search for something different. I secured two Agrow tynes from our local agent for a trial run. We put these to a very searching test, which they passed. Trailing model Agrowplows were not available at the time, so we built our 9 tyne unit, using Agrow tynes. We built disc coulters on the front, similar to the Wallace plough allowing us to aerate a paddock without destroying the pasture for stock. Results are very good but we revert back to our original position in about 3 years.
Time of aerating is very hard to pick, In 1981 it was very wet from June to August. We started to plough in spring - it was a very short spring and the later worked country dried out quickly. Next year, 1982, we tried June, but we picked a drought, so the country ploughed was not satisfactory until autumn 1983. After the drought, the country was very bare, so we combined oats, rye and super straight in after our first fall of rain on February 1, and the results were very good. With regard to ‘deep ripping’, in 1982, the ‘drought year’, we had enough rain in April to rip one paddock about 25cm (10”) deep, using 6 tynes. This was a long established cropping area. We then harrowed and sowed to oats. We had 118mm (470 points) of rain till harvest time, when at this stage it was about l.5m (5 feet) high. We cut it for hay, and it averaged a little under 7.5 t/ha (3 tons/acre). In a wet year it may have been waterlogged.
So I feel there are many things to take into account when advocating ripping or aerating country. Firstly, it has no effect in some soil types. Secondly, time of carrying out the ripping is a point that requires thought and luck with the following rains.
Our country has a hard pan on the top, 4cm (1½”), I feel mostly caused by stock. Sheep-foot rollers used in road construction are a good example. In the older cropping areas there is a different problem altogether caused perhaps by continuous ploughing and working at a consistent depth.
We have carried out lime trials and the results were interesting: 1.25 t/ha (½ ton/acre) raised the pH from 4.2 to 4.4 and we still had a l5% aluminium problem. But 2.5 t/ha (1 ton/acre) took the pH from 4.2 to 4.9 and removed the aluminium. This was on a problem paddock. So this year we have sown this paddock to phalaris for seed production and incorporated the lime at 2,5 t/ha (1 ton/acre). When the phalaris becomes well established I think we will Agrow it to a depth of 15-16cm (6-7”) to allow the roots to penetrate to Lower levels. We have better growth on paddocks that have plants with a more fibrous root system. Lime costs are very high $l40/ha ($56 /acre) so it is quite an expensive operation.
In 1961, half of an old phalaris paddock was aerated to 15-18cm (6-7”) in August, It was stripped for seed in late December, then had stock put in the paddock. It was very noticeable that the stock ate the grass and phalaris stalks on the aerated section, and hardly grazed on the untreated area. It obviously must have been sweeter and more palatable.
In conclusion, I feel some people tend to jump on a tractor and either go too fast when working the soil or, in the case of ripping, put the implement in as deep as possible without thought on where the hard pan or problem area is. Also, I feel that speed of operation with any implement can be very damaging to the structure of the soil, particularly if moisture levels are low,
I think when we establish more deep-rooted type pasture species in our paddocks, such as phalaris and lucerne, it will tend to overcome to a certain extent our compaction problem and allow the soil to breathe. Any further increase in stocking numbers will be cattle rather than sheep, which tend to compact the soil.