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Deep Tillage: What’s Old Is New Again

At farm shows and in the farm press I am seeing some “new” information about the use of various deep tillage machines to break up hardpans and improve crop growth and yields. It will be interesting to see the results come in. It is always possible to learn new tricks and we must always keep an open mind when new ideas come along.

Deep tillage is not a new idea, of course, but there are new and improved machines that may accomplish things old ones did not.

My first exposure with deep tillage was a subsoiling operation by a neighbour on the farm at Milden, Sask. Soils there are mostly excellent Regina clay and heavy clay types. The heavy clay lets water in slowly, so subsoiling was to “loosen up” the heavy clay. The tractor was a ’55 Massey Harris — a big tractor for the day and the subsoiler was a single large curved spike that was to do the trick. It never became common practice so presumably was not a winner.

In the 1970s and 1980s the Solonetzic soils of Saskatchewan and Alberta were the main targets for various forms of deep tillage. Deep ripping was practiced but deep plowing was considered to be the best. It involved not only the physical act of “ tearing up” the tough B horizon (upper subsoil hardpan) but chemistry was also involved. The tough B horizon was a result of too much sodium on the clays resulting in dispersion of the clay and the formation of the ‘hardpan’. The deep plowing involved bringing up some gypsum (CaSO4) from the C horizon (lower subsoil) to mix with the high-sodium B horizon to effect a chemical as well as physical solution.

The photo shows the biggest and most elaborate plow of those days. It was built so it could set aside the topsoil, mix the B and C horizons together and on the next pass the topsoil was placed back on top. It’s quite a piece of machinery and the power and diesel fuel required was large.

The main belt of Solonetz soils is in the Stettler-Brooks area of Alberta. It is an area where the glaciers went “once over lightly” and much of what they had to work with was sodic (sodium-rich) shales. The soils that developed were Solonetz.

In the Weyburn-Radville area of Saskatchewan, some farms did big chunks of the farm — a few fields each year — and there were definite positive benefits. But, soils being what they are, there were other fields where the deep plowing turned up copious quantities of salts which were hard to get rid of. In today’s world an EC survey of the field would help identify areas with excess salts too close to surface. But deep plowing is not a precision application easily done on patches of a field.

The big advantage to Solonetz soils has been the introduction of zero till. The constant tillage with the old half-and-half farming system messed up the soil structure and left cement like lumps. But that is all gone with zero till.

Time will tell whether the new round of deep tillage will find a fit. The current machines do not do inversion so it is a much different game than the deep plowing of Solonetz soils. One thing I learned in my extension years — farmers like the idea of power; diesel fuel and steel and are always ready to give it a try.

Good luck.

J.L.(Les)Henryisaformerprofessorand extensionspecialistattheUniversityof Saskatchewan.HefarmsatDundurn,Sask. Healsorecentlyfinishedasecondprintingof Henry’sHandbookofSoilandWater”,abook thatmixesthebasicsandpracticalaspectsof soil,fertilizerandfarming.Leswillcoverthe shippingandGSTforGrainewreaders.Simply sendachequefor$50toHenryPerspectives, 143TuckerCres,Saskatoon,SK,S7H3H7,and hewilldispatchasignedbookposte-haste.

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