The first and most important point when considering deep ripping is, simply, is it necessary and will it improve the soil and crop yields?

We must first determine that a plough plan or compaction zone does exist within an area that will affect plant growth, and also that it can be economically broken up, and in so doing improve crop or pasture production.

Our History

Our property is 12 miles west of Yerong Creek in a 450mm (18 inch) annual average rainfall belt. The country is gently undulating to flat.

In conjunction with a mate next door, I had looked at, and considered, some form of deep ripping for some time prior to 1980, when we attended a Field Day at Mr Murdoch’s property at Holbrook, to look at what he was doing with an Agrowplow.

After seeing what he was achieving, both in soil improvement and extra pasture production, and seeing a machine working in the field, we were sold on the ideas and decided to purchase an agrowplow.

We bought a second-hand chisel plough and agrow tyne assemblies and rigged up a 10 row machine 3 metres (10 feet) wide.

We first tried it in September 1980, and between then and February 1981 ripped some 140-160 ha (350-400 acres). There was some summer rain that year and we eagerly ripped every chance we could get, in all different soil types and varying conditions.

Then came the first crunch. Conditions changed and we hardly used the ripper again for 16 months, due to either soil conditions being unsuitable, or simply not having time to sit on a tractor doing only o,Skm per hour (4 mph).

To get a good result soil conditions need to be right. The subsoil needs to be damp enough to pull through, but dry enough to shatter. If it is too wet, the point will simply make a hole through the soil, without shattering between the tynes, and this does not disturb much of the hard pan. The top needs to be damp, not wet. Getting enough traction, without too much wheelslip, can be a problem with a ripper. We have certainly noted a difference since going to a tractor with Front Wheel Assist, and trailing machines also seem to be better than linkage units.

We have also added coulters to the plough with the intention of working some pasture paddocks during winter and spring, without killing the grass. However, this is only moderately successful, as moisture and grass cover need to be exactly right to achieve a good result.

We have now settled down to trying to do about 40 ha (100 acres) per year. While this is not a lot, it is an achievable target, and if conditions are suitable, more can be done.

Soil Types

One of the main factors determining the presence or otherwise of a hard pan in our area is soil type. We have three distinct soil types to cope with, and only one responds greatly to ripping.

There is black clay country, fairly flat and with a phi of 5.8 to 6.5. Here there is no great difference between topsoil and subsoil, and gypsum applied to the topsoil has far more effect than ripping.

Figure 1. Effect of ripping in 1981 on yield of wheat

Also, this soil cracks naturally when it dries out, and many of these cracks go down quite deep, thus breaking any pan that may be present.

The second soil type is brown loam with a yellow clay subsoil. This soil is fairly acid, with a pH of 4.5 to 5.0, and a subsoil that is structurally very unsound. Some hard pan does exist here, but ripping doesn’t have very much effect. Lime applied to the topsoil is having a very marked effect, raising the pH and increasing crop yields. However, as pH rises and soil structure improves, we may find more of a pan developing here.

The third soil type is red loam with a red clay subsoil. This country has a pH of 5.0 to 6.2 and a distinct pan. It is quite easy to find about 10-15cm (4-0”) deep.

We have been ripping these soils 16-20cm (7-8’) deep, which achieves a good shattering across the full width of the machine 12-15cm (5-6”) deep.

Examination of wheat plants grown here after ripping shows root growth far in excess of unripped areas. At least 50-60% more roots get through the pan, and thus have greater access to moisture and nutrients. The soil will also hold a lot more moisture after ripping, although this can be a disadvantage sometimes in wet conditions, as well as reducing runoff for dams, etc.

Economics

Ripping is an expensive operation. In the case of the agrowplow, about 7.5 kW (10 hp) per tyne is needed, which means only a 3 metre (10 foot) machine behind a 75 kW (100 hp) tractor. Under good conditions 5-6 kW (7-8 hp)/tyne would be enough, but ten is needed to handle all conditions.

Ripping is also a slow speed operation. To achieve the best results, about 6.5 km per hour (4 mph) is maximum speed, which means only about 2 ha (5 acres) per hour with a 75 kW (100 hp) tractor. It is, therefore, not a job to be done in the middle of cropping, or similar busy periods. This slowness is probably the most limiting factor although individual labour and machinery availability would govern this.

Point wear is the other main expense. We are, in fact, working in ground that has never seen a plough share before, and point wear reflects this. We began by hard surfacing the points, which works fairly well, but you need to be very keen on welding, as two sets of points are needed each day in our country, and in more abrasive soil four or five can be needed. Also, each point will only take about four to five hard surface applications before wearing out. We are now using worn out wideline points, welded onto the front of the agrow point and with the edges cut off to make them about 7.5cm (3”) wide. These also last about half a day, but are much easier and quicker to put on than hard surfacing, and the main points last a lot longer.

The only drawback with this system is that, if there are a lot of roots, etc, in the ground, the welded on points will break off, and it is surprising how much you will rip up from 20cm (8”) deep, even in country that has been farmed for 100 years.

General Observations

There is no doubt that, on soil with a distinct hard pan, ripping that pan will have a beneficial and economic effect. It would also appear that country that has been direct drilled for some time will benefit from ripping every 6-8 years. While direct drilling improves soil structure in the top zone, the soil is never aerated lower down, and so soil that is prone to packing during wet winters, etc, will become tight. Ripping, even to 12-15cm (5”-6”), will alleviate this.

We have recently cleared and, for the first time, cropped a small area and I ripped this before cropping. Here, the ripper really worked well, with the tight, hard packed soil cracking and opening up for the first time.

I think that probably ripping may have a wider application in higher rainfall grazing areas than it does in ours, where the soil is worked less, and sometimes never, and is subject to more stock while it is wet. This must have a packing effect over time, and ripping can only benefit in these areas.

In conclusion, we have found ripping to be moderately successful, although not to the extent we at first imagined. It does have a place in our type of country, but you must be sure that there is a pan there to rip, and that it can be removed satisfactorily and economically.