SUSTAINABLE POTATO CROPPING SYSTEMS FOR IRRIGATED AGRICULTURE IN THE PACIFIC NORTHWEST
Location: Vegetable and Forage Crops Production Research
Title: REDUCED TILLAGE IN A THREE YEAR POTATO ROTATION
Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: March 31, 2005
Publication Date: April 4, 2005
Citation: Collins, H.P., Boydston, R.A., Alva, A.K., Pierce, F., Hamm, P. 2005. Reduced tillage in a three year potato rotation. Proceedings Washington State Potato Conference. Vol 44: 13-26, 2005.
Interpretive Summary: Conventional field cropping systems have been criticized as being unsustainable because they contribute to environmental degradation (on-farm and off-farm), and are often economically uncertain. Reducing production costs, through the use of conservation tillage and reducing inputs as a means of increasing environmental and economic sustainability of cropping systems are needed. Long-term effects of agricultural practices on the soil micro-flora have shown that tillage, crop rotation, incorporation of cover crops, and residue management significantly influence the size of the microbial biomass, microbial populations, and their activities as well as SOM and C and N cycles. The major focus of this research is to evaluate the processes controlling soil biological activity and community structure of the soil micro-flora, and understand the mechanisms controlling carbon and nitrogen cycling and trace gas (CO2, N2O, CH4) fluxes under reduced tillage in irrigated potato production systems. After two years of reduced tillage little change has been observed in microbial communities or activities. We have found that a significant amount of N is lost (0.86 kg N/ha/d) as N2O within 12 hours of fertigation. This may account for as much as 50% of the N lost annually from potato fields.
Tillage in most crop rotations is used to prepare seed-beds, control weeds and other pests, manage crop residues, reduce soil compaction, and incorporate fertilizer and pesticides. However, excessive tillage increases soil erosion, reduces soil carbon, increases fuel and labor needs, and reduces soil moisture. Adopting conservation tillage to reduce erosion, increase N use efficiency, and build organic matter would improve soil and environmental quality under irrigated farming systems. The objectives of this research are to develop a reduced tillage system in potato based rotations using existing field equipment with minor modifications. Specific objectives are to determine the effects of reduced tillage on 1) weed dynamics, 2) soil organisms and their activities (i. microflora, ii. plant pathogens, iii. nematodes, and iv. insects), 3) carbon and nitrogen cycling and trace gas (CO2, N2O, CH4) fluxes, and 4) changes in nitrogen use efficiency. After two years of reduced tillage little change has been observed in microbial communities or activities. There were no significant differences found in potato, sweet corn or field corn yields between treatments receiving variable fertilizer rates or timing of fertilizer applications under center pivot irrigation. Populations of several plant pathogenic fungi trended to increase with higher fertilization rates under both tillage regimes. Pythium and V. dahliae populations within the conventional tilled potato treatment were greater than the reduced tillage treatment. Whereas, Fusarium populations were greater under reduced tillage for potato as well as the two corn treatments. We also have found that a significant amount of N is lost (0.86 kg N/ha d-1) as N2O within 12 hours of fertigation under laboratory conditions. This may account for as much as 50% of the N lost annually from potato fields.