Cover crops can protect all the bases – Organic Matters

The Organic Agriculture Centre of Canada is developing cover crop mixtures suitable for the Prairies. In this project it is collaborating with Jill Clapperton and Michael David at the Agriculture Canada Lethbridge Research Centre and Dean Spaner at the University of Alberta.

Cover crops are valuable in cropping systems. Typically, cover crops are sown after other spring crops are in and are tilled into the soil before they set seed. They are a useful alternative to summerfallow, with the potential to return organic matter and nutrients to the soil, while allowing for moisture recharge.

Different species have various characteristics that make them useful cover crops. Legumes and pulses host bacteria that fix nitrogen. Deep-rooted crops can improve drainage and water infiltration in the soil and also bring up nutrients from the subsoil. Crops with rapid growth can increase organic matter, prevent nutrient loss from the system and suppress weeds. Crops that differ from cash crops can disrupt pest and disease cycles.

Mixtures of various species have the po-tential to combine desirable characteristics and reduce the risks from their undesirable traits. For instance, an oat-pea mixture com-bines the nitrogen-fixing benefit of a legume with the rapid growth of a cereal. The oat will support the pea vines and reduce lodging.

The new cover crop study includes 15 seed mixtures and a total of 18 crops.

Oats is a reliable, low-cost cover, with good ability to suppress weeds. It is being tested with forage pea, faba bean, hairy vetch, woolypod vetch, crimson and Persian clover, lupin and chickling vetch. Faba bean and lupin are champions of nitrogen fixation when moisture is plentiful. Lupin grows a strong, deep taproot and acidifies the soil, increasing phosphorus availability. Chickling vetch is a legume with high water use efficiency, meaning it can produce a large amount of biomass under moisture stress. Hairy vetch improves soil tilth and helps cycle phosphorus. Woolypod vetch can produce abundant organic matter.

Sorghum-sudangrass is a fast growing, warm-season plant with the potential to add large amounts of organic matter to the soil. It has an aggressive root system that can break up hardpans in the subsoil. Sorghum-sudangrass is mixed with buckwheat and cowpea, and crotalaria, also called sun hemp, or subclover, also called subterranean clover.

Cowpea is a heat-loving legume that tolerates drought and low soil fertility. It grows quickly in warm soils and attracts many beneficial insects.

Crotalaria is a tropical legume that suppresses nematodes, resists drought and is associated with high levels of nitrogen fixation. Subclover is an excellent weed suppressor and a good nitrogen source. It is free of major diseases and relatively resistant to grasshopper damage.

The study also looks at three relatively unknown broadleaved species. Phacelia is an annual plant with a large, fibrous root system. It is a good soil conditioner and a great bee plant. Forage chicory is drought-resistant with a deep taproot. It can mobilize minerals from the subsoil. Phacelia and forage chicory are resistant to grasshoppers. Oilseed radish has a root system similar to chicory. In addition, it acidifies the soil and increases the availability of phosphorus.

Initially, this study will determine which of these crops do well under prairie conditions. Those crops that prove themselves will be studied further, to determine appropriate seeding rates, establishment methods and to optimize mixtures.

We hope that this work will help increase the options that producers have to build and strengthen soil organically, and to maintain cropping potential.

– Frick is the prairie co-ordinator for the Organic Agriculture Centre of Canada. She can be reached at 306-966-4975 or opinions expressed in this column are not necessarily those of The Western Producer. This column was written in collaboration with Gisela Duer, research associate of the organic centre in Lethbridge.



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