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Crimper rollers: One route to organic no-till farming

There is a ‘new’ technique for killing green manures / cover crops that’s been causing quite a stir in North America over the last few years.  That the North Americans have only found out about this technique recently and NZ only just now speaks loads for our insularity as it was pioneered in South America in the 1980s [1]!  In a nutshell, the cover crop is grown until it’s in full flower, then it is killed by rolling it with a special roller with ‘blades’ that crimp (not cut) the stems.  Amazingly, rolling the crop without crimping it, or mowing it, wont kill it.  The crimping has some unknown physiological effect that makes the crop just lie down and die.  The result is a thick mulch on top of the soil, which protects it and suppresses weeds.  This is then ideal for planting a crop through as the need for weeding is minimised and as the mulch rots down it releases nutrients feeding the growing crop.  The result is organic no-till farming with all the benefits that brings such as no tillage or cultivation for weed control, soil protection, higher earthworm populations etc.  That this can be done with such a low-tech approach is even better.  In S. America, they often use animals to pull the crimper-rollers - how organic is that!

With so much going for it, we just had to try it in NZ, so the BHU, with money from the Sustainable Farming Fund, did some trials.  While the technique worked, we discovered a number of caveats.  It’s essential that the crops are in full flower as this is the point when plants switch from vegetative to reproductive growth.  If they have not turned fully reproductive then they won’t give up the fight and will put up new shoots.  For Canterbury, the time of full flowering for many cereal and legume cover crops is often later than the normal planting time of many cash crops.  The situation may well be different further north.  It’s essential to choose the right species, as some are less susceptible to crimping than others.  We found some slight regrowth in oats (Avena sativa) and could not touch common vetch (Vicia sativa) which grew right back, while rye (Secale cereale) and tick beans (Vicia faba) were completely killed.  However, overseas black oat (Avena strigosa) and hairy vetch (Vicia villosa) are killed, indeed rye and hairy vetch are the mainstay of cover crops in N. America.  Its also important to get good weed control at cover crop establishment, otherwise the weeds will remain small while the cover crop stands and then happily growth through the mulch to have free reign.  This happened in the BHU trials with grass and clover from the previous gone-to-seed pasture.  This fortuitously showed up another issue: nitrogen lockup.  The pure rye stand was dominated by clover while the mixtures and pure legume stands had up to 75% grass indicating that the rye had taken up a lot of N during its growth, which was now locked up in its dead remains.  This would be a big issue for the following crop, as it would suffer from a serious nitrogen deficiency.  It would therefore appear essential to use cereal legume mixes.  We were hoping to test for such issues at the BHU, but the huge mass of mulch was impossible to drill through with the equipment we had.  We believe that only the disk version of the cross-slot drill could cope with so much residue [2].  An alternative may be to drill into the standing crop and then crimper roll it. 

This is a rather long list of caveats, however, where the seasons are the right length, and cover crops are well matched with the following crop, crimper rolling is proving a godsend, is widely practices in S. America, and is being rapidly taken up in the North.  If you want to read the report to the SFF its available at http://www.merfield.com/research/initial-trials-of-a-crimper-roller-in-new-zealand.pdf and the Rodale Institute (Soil and Health’s equivalent in the USA) has a lot of information, pictures, discussion etc. http://www.newfarm.org/depts/notill/index.shtml.  While there were a number of issues, we believe that crimper rolling has potential in NZ in the right situations and also in the home garden where tools such as spades could be used to crimp the crop and that further investigations are needed.  Thanks to Ivan Barnett, the SFF, BHU and Holger Karl. 

1.         Ribeiro, M.F., No-tillage equipment for small farms in Brazil, in Conservation agriculture, a worldwide challenge. First World Congress on conservation agriculture, Madrid, Spain, 1-5 October, 2001. Volume 1: keynote contributions, García-Torres, L., Benites, J., and Martínez-Vilela, A., Editors. 2001, European Conservation Agriculture Federation Córdoba, Spain. p. 237-243.

2.         Baker, C.J. and Saxton, K.E., eds. No-tillage Seeding in Conservation Agriculture, 2nd Edition. 2007, Food and Agriculture Organization of the United Nations: Wallingford, UK. 352.

Picture of BHU crimper roller

Photo of the crimper roller built for the BHU trials. Click on image for large (776 kb) picture.

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Copyright 2008 Charles N. Merfield.