Cover Crops and Strip Tillage to Promote Soil Quality, Environmental Sustainability, Food Safety, and Profitability in Cucurbit Cropping Systems

Project Overview

Project Type: Research and Education
Funds awarded in 2014: $198,353.00
Projected End Date: 09/30/2017
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Project Coordinator:
Dr. Ajay Nair
Department of Horticulture, Iowa State University

Annual Reports


  • Fruits: melons
  • Vegetables: cucurbits


  • Crop Production: cover crops, strip tillage


    Field experiments investigating the effect of cover crops and tillage on muskmelon production and food safety (Iowa State University) and cucumber and acorn squash production (Michigan State University) were conducted. At Iowa State University a split-split-plot design with four replications was used. The main plot factor was cover crop, consisting of cereal rye (R), cereal rye-vetch mixture (R+V), or no cover crop (NC). Sub-plot factor was tillage consisting of conventional tillage (CT) or strip tillage (ST). An additional treatment of Listeria innocua, a non-pathogenic surrogate for the human pathogen Listeria monocytogenes was applied to the soil in Oct. following cover crop seeding or in May before cover crop termination.  The experiment was designed to compare the effects of different tillage and cover crops practices on soil fertility and health, weed pressure, plant growth, NO3-N leaching, marketable yield, fruit quality and frequency of contamination of muskmelon fruit. 

    In 2015 weed density was unaffected by cover crop treatments but was higher under CT.  In 2016, NC treatment produced higher weed biomass than R or R+V, however, tillage had no effect on weed biomass.   Soil temperature was increased by CT but only in the early part of growing season. Soil moisture was generally greater in ST. Increased NO3-N levels were observed in CT treatments in both years.  Leaching of NO3-N was decreased by ST at one sampling date in 2015 and during the early season in 2016.  Plant growth was generally greater under CT, with greater vine length in both years and higher SPAD and petiole sap N values in 2016.  During both years CT plots produced significantly greater marketable yields, though ST yields were acceptable.  In 2016, R and R+V and ST increased total soluble solids and produced more spherically shaped fruits.  In R plots, flesh thickness of muskmelon fruit was greater than NC for only one year.   Soil microbial biomass carbon (MBC) was greatest under R-CT in 2015 and R+V-CT in 2016.  In both years NC-CT had the lowest MBC.  Microbial functional diversity, measured with Biolog-EcoPlate® was similar for all treatments in 2015.  In 2016, NC had the lowest measures of microbial functional diversity.Winter survival of Oct. applied L. innocua ranged from 88%-100% for all cover × tillage treatments for both years. In 2015, R and R+V treatment significantly decreased the population of soilborne L. innocua as compared to NC treatment, however, treatments had no effect on contamination of fruit for either year, the frequency of contamination ranged from 0%-22%. On farm trial conducted at Glenwood Farms, Albion, IA showed higher winter squash yields in a plasticulture based system as compared to ST, however, average fruit weight was higher for ST. 

    Research conducted in Michigan consisted of both research farm and on-farm trials evaluating the impact of cover crops (none, rye or rye-vetch) and tillage [Conventional till (CT) or strip-till (ST)] on winter squash and cucumbers. In 2014, cucumber yields were greater in the ST-bare treatment compared to all other treatments except CT+rye.  Within ST treatments, both rye and rye-vetch cover crops reduced cucumber yield. In 2015, no effects of either tillage or cover crop on cucumber yields were detected. Tillage and cover crops influenced the emergence and growth of various weed species in both years.  In general, an increase in the abundance of horsenettle (a perennial), and large crabgrass (a summer annual) in was observed in ST treatments. A short-term acorn squash trial showed that strip tillage by itself had no effect on acorn squash yield in 2015 or 2016, however, in 2015, strip-tillage combined with a winter rye cover crop reduced crop yields relative to all other treatments.  On farm-trial in Michigan at Forgotten Harvest, Fenton, MI showed butternut squash yields from highest to lowest as follows:  Plasticulture > ST = CT > No-till.  The plasticulture system had higher costs, but fewer weeds and higher N availability than the other treatments.  In 2016, yields were ranked as follows:  ST > NT =  CT.

    Studies at Iowa State University and Michigan State University show that rolled cover crop mulch can be an effective way to control weeds, especially in the early part of the growing season.  It can also help to produce fruits that are cleaner than conventional tillage systems. Yields in ST vary and largely depend proper management of rye residue (roller crimping, strip-tilling). In this study, microbial measures of soil health were generally not increased under ST, likely because all sampling was done in the tilled in-row area, and did not take into account the no-till conditions of the between-row area.  Vegetable growers may find reduced yield under ST acceptable if weed pressure and NO3-N can be reduced while soil health is improved.  Measures of plant growth and soil N indicate that muskmelon and other cucurbit crops under ST may benefit from increased rates of N fertilizer.


    Reduced tillage has been widely adopted in production of agronomic crops for its potential to improve soil health and reduce input costs. Despite this vegetable growers continue to rely on conventional tillage (CT) to incorporate crop residue, control weeds, and to prepare a loose seed bed for planting. Conventional tillage may negatively affect water infiltration, soil biodiversity, and increase nitrate leaching, erosion and weed germination. The detrimental effects of CT stems from the inversion and disturbance of soil across the entire field. In contrast, strip-tillage (ST) only disturbs the soil in a narrow 15-30 cm strip where the cash crop will be planted, leaving the unplanted area intact. Most growers utilizing a strip tillage system combine it with the use of cover crops. These cover crops, seeded in the fall and terminated (using a roller crimper) in the spring can offer many benefits including weed suppression, reduction in erosion, addition of organic matter, and cleaner produce. The roller crimper method terminates the cover crop non-chemically, leaving the soil undisturbed, and serves as an excellent biodegradable mulch protecting the soil and suppressing weeds.

    Cucurbit growers in the North Central region face several critical challenges including increases in extreme rainfall events, increased soil erosion, decreased soil quality, and increased risks of fruit contamination with soil-borne plant and human pathogens. For example, recent outbreaks associated with foodborne illness threatened livelihood of melon growers, with Listeria monocytogenes and Salmonella killing consumers throughout the United States. Soil-borne fruit pathogens also significantly affect cucurbit production by reducing yields and grower profits. Adoption of reduced tillage practices, coupled with cover crop residues may help buffer cucurbits from rainfall extremes, improve soil quality and health, and also reduce growth and dispersal of both human and plant pathogens. This collaborative study (Iowa State and Michigan State) investigated the use of cover crops combined with strip tillage to 1) moderate soil moisture extremes; 2) reduce soil erosion, runoff and leaching; 3) reduce or eliminate Listeria spp. from contaminated cantaloupe fields and Phytophthora capsisi from winter squash fields; and 4) improve crop profitability. We hypothesize that cover crops mulches left on the soil surface under ST will promote water infiltration, reduce soil splash and leaching, conserve soil moisture, and form a barrier between the fruit and the soil thereby reducing pathogen spread and survival.

    Project objectives:

    This project explored the feasibility of using the strip-till / roller-crimper system in Midwest muskmelon production. The first objective was to determine the effect of tillage and cover crops on the plant growth and yield of muskmelon (cv. Aphrodite). Secondly this project investigated the effects on soil quality and fertility in the root zone.
    Additionally, we wanted to determine if rolled cover crop mulch would prevent the spread of Listeria innocua from contaminated soil to the surface of the fruit. L. innocua is a harmless species of bacteria that in the same genus as the pathogenic L. monocytogenes, both share a similar physiology and growth habit. L. innocua has been widely used as a surrogate for L. monocytogenes in studies of food safety and food processing. Research conducted in Michigan consisted of both research farm and on-farm trials evaluating the impact of cover crops (none, rye or rye-vetch) and tillage (CT or ST) on winter squash and cucumbers. 

    On-farm trials were an integral part of the project at both locations and included commercial cucurbit growers. An important aspect of these trials was to expose growers to conservation tillage and equipment such as roller crimper so that they can experience the technology and make informed decision on soil health and quality at their respective farms. Grower organizations such as Practical Farmers of Iowa, Iowa Fruit and Vegetable Growers Association, and Michigan Vegetable Council partnered to set up on-farm trials and played a key role in information dissemination. 

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.