Date of Award

Spring 5-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Plant, Soil, and Environmental Sciences

Advisor

Mark Hutton

Second Committee Member

Mark Hutchinson

Third Committee Member

Susan Erich

Abstract

The response of field-grown vegetable crops to reduced tillage and mulching in permanent beds was evaluated through measuring crop yields, weed pressure, earthworm counts, and soil basal respiration. Two vegetable crops (“Bush Delicata” squash and “Farao” cabbage) were started in April and May of 2016 and 2017 respectively, transplanted in late June, and harvested on 15-Sep-2016 and 25-Aug-2017. Fruit number and weight of squash, and head weight and feeding damage of cabbage were measured. These results suggest that intensive tillage (8” rototill every year) can be successfully reduced to alternating years of shallow (2”) rototilling and a less intensive form of tillage (e.g. biotill or DZT) without loss of yields. No-till as practiced in this experiment experienced major yield losses, while no-till accompanied by pre-season tarping was capable of yields that equaled or exceeded any tilled treatment. Mulching crops has a positive effect on crop yields, with a 3” compost mulch yielding the highest of any tillage/mulch combination regardless of tillage type, and with straw-mulched treatments usually yielding higher than unmulched plots but lower than compost-mulched plots.

Weed populations were also sampled once each year in the same plots, with number of weeds, percent leaf area, and number of species in a 0.25 m2 quadrant collected for each plot. Tilled treatments had similar weed pressure regardless of tillage intensity, with the exception of 2” Rototill. Weed populations were highest in No-till plots in both seasons, and lowest in Tarped plots. Compost-mulched plots had the best weed control, followed by Straw and Unmulched plots. Straw-mulched plots were inconsistent in their weed control and had major insect problems in 2017. Most plots had similar weed species, with the exception of Tarped plots, which had no perennial weeds and significantly lower weed diversity. No-till plots appeared to be shifting towards aggressive or perennial weeds, while tarping combined with compost mulch almost completely eliminated weed populations.

Soil health was measured through earthworm counts and basal soil respiration on three of the tillage treatments. Earthworm counts were performed by hand sorting at the start of the 2017 growing season, and revealed that earthworms favored plots that had high quantities of plant residue (straw-mulch). Soil respiration was measured during the growing season of 2017, utilizing the 24-hour Solvita™ basal respiration test, which was performed on minimally disturbed field-moist soil. Respiration during the growing season was not limited by temperature, but was influenced by low moisture. No-till plots had higher respiration than tilled or Tarped plots, perhaps due to diverse early-season root mass in the No-till plots.

We concluded that reducing tillage is possible from the perspective of both yields and weed pressure, especially when combined with mulches, while no-till is impractical without pre-season weed control. The best yield and weed results were found in Tarped and Compost-mulched plots. Earthworms showed clear preferences for crop residues and less disturbance, while soil respiration was controlled by moisture and may have been influenced by root presence/absence.

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