What can you tell me about intercropping commercial field crops?
C.R.SaskatchewanAnswer: Intensive cropping systems, rotations, and crop diversification including intercropping have been shown to be successful in some areas of the Northern Plains. Intensive cropping utilizes soil water more efficiently than fallow, reduces erosion, rebuilds soil organic matter through residue and root die-back, increases soil microbiological activity and diversity, increases nutrient availability through nitrogen carry-over, and subsequently increases yield and quality while allowing for reduced inputs.A few common intercrop systems have proven effective in the northern plains. As with any new cropping system, its best to (1) make sure you have an adequate market outlet, (2) familiarize yourself with new planting and harvesting techniques associated with different grains, and (3) plant at the appropriate time into a well-prepared seedbed. For some fall-seeded crops, a no-till seeding into short cereal stubble can be very effective, especially with small-seeded species like canola. This helps to prevent wind erosion and desiccation of the germinating seed. The following two scenarios have proved to be effective in the northern plains.Lentils and FlaxThe intercropping of flax and lentils is adapted to North Dakota, but is susceptible to weed pressure. Weeds are typically a problem with lentils and flax, especially early in the growing season since the young crop isn’t as competitive with many annual weeds like mustards. Post-emergence harrowing can be effective, but is site-specific in studies in ND and Washington State, and is often harmful to young plants. Results of intercropping lentils and flax in Saskatchewan are variable and are generally not recommended by the Saskatchewan Pulse Growers. In order to prevent weed problems in this cropping system, use this intercrop in rotation with cereals and forages if your soil and moisture allow. Crop rotations and high crop diversity both temporally and spatially is often a reliable management tool in preventing weeds and other crop pests. The ATTRA publication Farmscaping to Enhance Biological Control includes information on diversifying landscapes to mitigate problems associated with crop pests and disease.Peas and Canola (Rapeseed)Fall-planted winter peas fix nitrogen, reduce soil erosion, and help to limit soil moisture loss through soil cover and effective water cycling. They can be harvested for seed, combined with winter wheat for forage, grown for green manure to help build soil organic matter, or combined with winter cereals or canola as a multiple crop. Canola is a crop that might be appropriate to your area. The paper by McGill University echoes the conclusions of Grant et al. (2002) in stating that winter peas, which fix atmospheric nitrogen in large amounts, can supply nitrogen to the canola crop or to the following year’s cereal grain. Canola can be planted in the fall and is known to help reduce disease problems in cereal and legume rotations, so it can have a good place in a wheat-legume rotation. Miller et al. (2003) have shown that pulse crops, notably peas and lentils, can have a positive impact on subsequent wheat yield in the northern plains, with more consistent results on clay soil than loamy soil. This has been attributed to increased water availability for wheat following pulses, and to an increase in nitrogen availability for wheat following pulses. The bottom line, it can be argued, is that intercropping of pulses and oilseeds can (1) increase water use efficiency for subsequent crops, (2) increase nitrogen carry-over for subsequent crops, (3) increase biodiversity and associated ecological services, such as reduction in pest and disease problems, and (4) diversify cropping enterprises and thereby spreading out economic risk.References:Carr, P., G. Martin, and B. Melchior. 1994. Alternative Crops and Diversified Cropping Systems in Southwestern North Dakota. Dickinson, ND: North Dakota State University, Dickinson Research Extension Center.Grant, C.A., G.A. Peterson, and C.A. Campbell. 2002. Nutrient Considerations for Diversified Cropping Systems in the Northern Great Plains, in Agron. J. 94:186-198.Ecological Agriculture Projects. 1991. Intercropping canola and peas. McGill University.Miller, P., Y. Gan, B. McConkey, and C. McDonald. 2003. Pulse Crops for the Northern Great Plains: II. Cropping Sequence Effects on Cereal, Oilseed, and Pulse Crops, in Agron. J. 95:980-986.Saskatchewan Pulse Growers. Chapter 7: Lentils, in Pulse Production Manual 2000. (PDF)Stephen Machado, Brian Tuck, and Christopher Humphreys. 2005. Alternative Rotation Crops: Peas (Pisum sativum), in Dryland Agricultural Research Annual Report. Oregon State University.ATTRA Publications:Farmscaping to Enhance Biological ControlIntercropping Principles and Production PracticesAdditional Resource:Sustainable Agriculture Network. Diversifying Cropping Systems. USDA: Sustainable Agriculture Research and Education Program.