KENT A MCVAY CROPPING SYSTEMS SPECIALIST SOUTHERN AG RESEARCH CENTER MONTANA STATE UNIVERSITY Crop Rotation Benefits

Harvested biomass production is a function of: Energy Input Energy capture Losses to competition Harvest loss

Energy Input All energy comes from the sun Efficiency of energy conversion to biomass is dependent on crop management C4 vs C3  Corn vs wheat Grass vs legume  Barley vs pea

So what is the optimum system for converting energy into biomass? Full canopied forests, like this Or Native rangeland These convert a large portion of the energy received into biomass

Cropland Captures a Fraction of Total Energy Although silage corn comes close ! So would sugarcane

What about Montana? Rainfall limits production potential Average growing season limits most production to C3 metabolism: wheat, barley, peas, canola It will be hard to compete head to head against other less stressful environments.  Targeting markets is a good idea  e.g. high protein wheat  Specialty crops like camelina for special purpose industrial oils, or food grade oils, or pharmaceuticals  Crops that have multiple markets. Peas for human or animal consumption

Crop Rotation Benefits Usually a positive yield response Chance to use alternate herbicides  Cleans up some weed problems Disease pressure can be reduced Increases diversity  Spreads out planting and harvesting dates  More commodities to sell

Rotation Yield Benefits Tanaka et al Agron J. 97: Mandan, ND 1999 Previous cropCanolaCrambe Dry beanDry peaFlax Saf- flowerSoy-bean Sun- flower Spring wheatBarley Canola Crambe Dry bean Dry pea Flax Safflower Soybean Sunflower Spring wheat Barley Year 1 Year 2

Rotation Yield Benefits Tanaka et al Agron J. 97: Mandan, ND 1999 Previous cropCanolaCrambe Dry beanDry peaFlax Saf- flowerSoy-bean Sun- flower Spring wheatBarley lbs / acre Canola Crambe Dry bean Dry pea Flax Safflower Soybean Sunflower Spring wheat Barley

Rotation Yield Benefits Mandan, ND 1999 Previous cropCanolaCrambe Dry bean Dry peaFlax Saf- flower Soy- bean Sun- flower Spring wheatBarley Rot. Benefit Canola Crambe Dry bean Dry pea Flax Safflower Soybean Sunflower Spring wheat Barley Rot. Benefit Tanaka et al Agron J. 97:

Rotation Yield Benefits Year Rotation Benefit Crop Flax G. Sorghum2.35 Corn Chickpea Safflower Sunflower Lentil Proso millet Barley Buckwheat Dry Pea Canola Wheat Crambe Dry bean Soybean Tanaka et al Agron J. 97:

Alternate Herbicides Wheat-Wheat  What is the dominant weed?  Downy Brome  Wild oat Wheat –Pea: Downy Brome easily controlled with herbicides like Select, Assure, or Spartan during the Pea crop cycle Note: Research at Bozeman showed wheat/pea/fallow rotation compared to continuous wheat decreased downy brome density from 60 to 10 plants/ft 2

The Disease Triangle Environment Susceptible Host Organism Remember: All three must be present in order for the disease to be expressed

Increased Diversity Growing more crops spreads out the workload  Planting time  Spraying time  Harvest time More diversity requires greater management skills  Record keeping becomes even more critical  Time management  Rotation restrictions More commodities  greater flexibility in marketing

Crop Rotation Can Be Beneficial Yield increases Reduced need for herbicides Reduced disease pressure Diversified markets and crop management