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Definitions: What is No-Till?

No-till is defined by the author [Bill Crabtree] as sowing without prior cultivation while disturbing less than 20% of the topsoil. There are many different tillage terms-however I believe the main and/or useful ones are:

• Multiple tillage-two or more tillages before seeding (replaces the term ‘conventional tillage’);
• Reduced tillage-one pass of full soil disturbance prior to seeding;
• Direct drilling- one pass seeding with a full-cut or greater than 20% topsoil disturbance;
• No-tillage-knife point or disc seeding with 5-20% topsoil disturbance; and
• Zero-tillage-disc seeding without soil throw (but note that some discs do throw soil).

From an agronomic point of view each system has different implications. Water harvesting, soil firmness, nutrient mineralization, herbicide efficacy, crop safety, soil drying, stubble handling, fertilizer placement, diseases and insects all react differently to tillage or lack of it. From a farmer’s point of view they also effect horsepower requirements, cost of the seeder, paddock trafficability, ability to chase moisture, soil stability and timeliness of sowing.

Obviously none of these tillage terms are perfect. Factors such as wider row spacings and the presence of harrows also change the amount of soil disturbance. No-till sowing of pulse crops, with knife points, on wide rows, may throw less soil than a disc zero-till operation. Heavy harrows can move significant amounts of topsoil and fill in the furrows.

There is also the confusing term of ‘minimum tillage’. It has a different definition in all regions of Australia and indeed globally. This term in Western Australia has traditionally meant one working before seeding, the same as reduced tillage. Nowadays the minimum tillage term has become less specific. The term is probably best used as an umbrella to all the other ‘less tillage systems’.

The term ‘conservation tillage’ is not used much in Australia. This term encompasses minimum soil disturbance, residue cover on the soil and rotations and globally it has helped farmers to better understand what the full no-till approach is trying to achieve. Different regions of the globe have been enthusiastically looking for ways to fit multi-species cover crops into their no-till farming systems along with their cash crops. The lead for this approach came from Brasil, one of the global hot spots for broad scale adoption of no-till technology.

In sandy loam soils that do respond to deep cultivation, some farmers deep rip on wide rows without topsoil inversion on less than 20% of the soil. This technique is called strip till in the United States may still be considered no-till. This terminology is a little controversial globally. The argument is that plant roots, like tillage radish cover crops, should be used to soften hardpans instead of tillage. This is hard to achieve in environments where annual rainfall may only total 150 mm.

-From “Search for Sustainability with No-Till Bill in Dryland Agriculture, 2010 with additions in January 2014

 

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