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Nitrogen Response and Soil Microbial Activity in Potato Cropping Systems As Affected by Fumigation

Start Date: 2016
Principal Investigator: Carl Rosen
Organization: University of Minnesota, Department of Soil, Water, and Climate
Status: Complete

Background Info

Fumigation is routinely used by potato growers to control soil-borne diseases. While the use of fumigation temporarily reduces disease incidence, it also eliminates the populations of beneficial soil organisms. Therefore once fumigation is used, repeated applications are necessary every time potatoes are grown in the rotation. Fumigation can have both positive and negative effects on nutrient use efficiency. Potato root systems are often healthier following fumigation due to a lower disease incidence, which may in turn lower nutrient inputs. In contrast, fumigation substantially alters microbial diversity and could have negative impacts on nutrient cycling over time.

Objectives

Determine the interactive effects of fumigation and nitrogen fertility on potato yield and quality

Characterize the effect of fumigation on soil microbial activity and nitrogen transformations

Evaluate the effects of microbial inoculants on tuber yield and quality in fumigated and non-fumigated soil

Key Findings

Fumigation increased tuber yield and size relative to the non-fumigated control plots. While tuber yield and size increased with increasing N rate, fumigation lowered the N requirement for bulking. Fumigation with Vapam improved plant stand relative to the non-fumigated control, while fumigation with Chloropicrin did not, raising the. possibility, that Vapam is more effective at controlling some pathogen that reduces stand. The two fumigated treatments had slightly higher leaflet chlorophyll contents than thenon-fumigated control, as well as higher petiole NO3-N concentrations early int eh season and higher N uptake into both vines and tubers, indicating that fumigation improves the ability of plants to acquire N from the soil. Fumigation had no clear effect on tuber sugar content, though it slightly improved the color of French fries made from the end of the tuber. Overall, fumigation treatment appeared to affect soil N cycling process and overall microbial activity negatively, but plants in fumigated plots had higher tuber yields, larger tubers, and greater ability to take up N than those in non-fumigated plots.

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