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United States Department of Agriculture

Agricultural Research Service

Research Overview
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1 - Cover Crops
2 - Conservation Tillage
3 - Organic Potato Production
4 - BioEnergy Research-Oilseeds: Biodiesel
5 - BioEnergy Research-Perennial Biomass Crops: Ethanol
6 - BioEnergy Research-Biochar
Cover Crops

The Columbia Basin of eastern Washington provides ideal conditions for high potato yields of up to 40 tons/acre. In the Basin, potatoes are grown on light textured soils that are low in organic matter and highly susceptible to leaching and wind erosion especially after harvest. Cover crops can play a vital role in filling open gaps in crop rotations where soil is left bare and further provide protective mulches under conventional tillage systems. The use of cover crops may serve as an alternative to fumigation as well as mitigating losses to soil and environmental quality.

Cover Crop

Additional benefits of cover crops in annual production systems include decreasing soil erosion, sequestering excess soil nitrogen, replenishing soil organic matter reserves, suppressing weeds and nematodes, increasing the size and activity of the soil micro-flora, as well as enhancing microbial populations antagonistic to pathogenic organisms (Figure 1). Various Brassica spp. and other cover crop systems have been evaluated in the PNW for their effects on individual crops, but research evaluating the impact of various cover crops on pest control and carbon and nitrogen dynamics in a total cropping system has not been conducted. Pest and nutrient problems are most effectively managed throughout the total cropping system rather than isolating a particular problem in an individual crop. Grasses and grains, because of their ability to quickly establish in the fall produce an extensive root system, that has been shown to be more efficient than legumes at capturing soil nitrate and preventing its late fall and winter leaching to ground water. Several studies have shown that certain cover crops (Sorghum sudanense, Brassica spp.) are also effective in reducing the incidence of pathogenic fungi, plant parasitic nematodes, and weeds  through the production of secondary plant compounds (cyanogenic and isothiocyanate compounds).

Soil Microbial Responses to Soil Fumigation and Mustard (Brassica hirta) Cover Crops in Potato Production Systems: On-farm trials demonstrated that fumigation significantly reduced selected soil pathogens and nematodes, but had minor affects on microbial functions. Although the mustard cover crop did not reduce the presence of plant pathogens, the incidence of disease caused by soil pathogens was not fully expressed and exhibited no reduction in tuber yield.



Nitrogen Transformation and Availability to Potatoes from Mustard Cover Crop: Mustard cover crop recovered 34 to 51% of the 50 lbs of 15N fertilizer applied. Nearly 30 % of the N in the cover crop biomass was taken up by the following potato crop. The mustard cover crop contributed 27 to 36 lbs N acre-1 towards the N requirement of a subsequent potato crop, saving farmers $19-25 / acre at current fertilizer prices.

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Last Modified: 4/5/2012
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