Integrated Phytophthora blight management in vegetable crops with enhanced soil health from cover crops, reduced tillage, and brassica biofumigation

Integrated Phytophthora blight management in vegetable crops with enhanced soil health from cover crops, reduced tillage, and brassica biofumigation

Summary

The crop disease Phytophthora blight (PB) is a top concern for vegetable growers in the northeast (including the northeastern Midwest) where susceptible cucurbit and nightshade species of crops contribute to major portions of farm incomes and to the greater vegetable industry. Soil health improvement has been proposed as a fundamental component of an integrated PB management program. Certain brassica cover crops are capable of providing biofumigation services to soils with high soil-borne pathogen loads, and reduced tillage can allow for soils to regenerate functions that further mitigate soil-borne disease. This project is aimed at increasing grower awareness and adoption of integrated PB management through demonstration and research trials that incorporate novel components 1) of biofumigation with brassica cover crops and 2) reduced tillage on six NY farms and at Cornell’s Long Island Horticultural Research and Extension Center (LIHREC).

By December 2015, seven collaborating growers had completed a total of 13 on-farm trials with brassica cover crops for biofumigation. Growers experienced variable degrees of success completing the biofumigation process with fall-sown winter arugula and spring-sown mustard. Barriers to biofumigation success identified thus far were: 1) arugula will not overwinter in NY, 2) late plantings of spring mustard can reduce biomass and delay following cash crop plantings, 3) reluctance to provide sufficient fertility, pre-emptive weed control, and seedbed preparation 4) misunderstanding and reluctance to follow the steps of the biofumigation process, 5) concern about spreading disease and pests from brassica cover crops to brassica cash crops. In response to some aspects that compromised biofumigation success for growers, the research team trialed a novel late summer biofumigation as well with five interested growers. Our plot-scale trials at the LIHREC also re-formulated to integrate this treatment. To date, the project team already has spoken to researchers outside NY in the greater Great Lakes region about the project research, and to ~200 growers about biofumigation, reduced tillage, and an integrated PB management approach as a result of this project. Several growers (~5) in Long Island and the Hudson Valley region have also voiced the intent to adopt and/or expand biofumigation practices with brassica cover crops on their farms since the project began. Preliminary results generally showed a lack of evidence for effects of biofumigation on cucurbit yields in the on-farm trials, but yields of winter squash following spring sown mustards and biofumigation at the LIHREC trials were ~3 tons/ac higher than squash that was preceded with arugula (which had low biomass, and did not have biofumigation practices applied because it winterkilled) and rye cover crops. Phytophthora blight incidence was low to non-existent across sites, with no significant effects of treatment detected.

• On-Farm trial of ‘Caliente’ mustard for biofumigation, September 2015

Objectives/Performance Targets

Forty vegetable growers across three regions of NY will integrate multiple soil borne disease management practices that may include biofumigation with brassica cover crops and reduced tillage on at least an 5 acres per farm, recovering $1000 – $4000 per acre otherwise spent and/or lost on diseases like Phytophthora blight.

Accomplishments/Milestones

1) 6 growers battling PB in three distinct regions of NY are recruited by Extension and guided through the process of choosing treatments and establishing a trial including a brassica cover crop for biofumigation and reduced tillage. September 2014 – April 2015. Milestone >100% complete as of December 2015 for year one of the trials. We recruited seven (of a targeted six) growers to trial brassica cover crops for biofumigation vs. their standard practice to before a PB susceptible cash crop. All seven collaborating growers are expected to continue the second year with the reduced tillage portion of the trials.

2) 75 growers attend field days (25/region) and learn about PB and integrated approaches to managing PB and soil-borne diseases through viewing trials and from the project’s grower collaborators and research team. June 2015.

The project team added at least 60 grower contacts to this portion milestone through three regional grower twilight meetings in summer 2015; ~110 growers were previously introduced to the project and its components before the 2015 summer meetings.

3) 300 growers total attending winter conference/meeting presentations will learn about integrated approaches to managing PB and soil-borne diseases and year 1 trial results. January-March 2016.

The project team is scheduled to speak at four winter 2016 events thus far that historically draw ~30-70 attendees each.

4) 75 growers attend field days (25/region) and learn about PB and integrated approaches to managing PB and soil-borne diseases through viewing trials and from the project’s grower collaborators and research team. June 2016.

NA

5) 300 growers total attending winter conference/meeting presentations will learn about integrated approaches to managing PB and soil-borne diseases and project results. January-March 2017.

NA

6) 1500 beneficiaries total nationally will learn about our biofumigation with brassica cover crops and integrated approaches to managing PB and soil-borne diseases via the above contacts, and Extension materials posted online, a webinar, and an instructional video. Ongoing until September 2017.

The project team is ahead of schedule on a portion of this milestone, with one collaborator having spoken to researchers in the greater Great Lakes region (including Canada) about the project components. The team is also building an online page of project-related information as an on-demand resource that is expected to substantially increase exposure to the project and its components: http://ulster.cce.cornell.edu/agriculture/crop-production/integrated-phytophthora-blight-management-in-vegetable-crops-with-enhanced-soil-health-from-cover-crops-reduced-tillage-and-bras. We have also been taking video footage intended for development of an educational video and animations.

7) 40 growers in three distinct regions of NY (10-15/region) are mentored by our grower collaborators and/or Extension in implementing integrated approaches to PB and/or soil-borne disease management in each respective region represented in the project. Ongoing until September 2017.

In addition to our six formal core collaborators, four other Hudson Valley region growers trialed brassica cover cropsfor biofumigation in fall 2014 and/or in late summer 2015 under the guidance of Extension, and at least 2 to 3 other Hudson Valley growers plan to trial biofumigation in spring 2016. Two area growers have voiced the intent to use biofumigation again. Other growers in Long Island are also continuing to adopt biofumigation for various soil-borne diseases.

• Voluntary informal grower trial of “Caliente’ mustard for biofumigation, Hudson Valley 2015
• Project handout used at summer grower meetings
• Summer project-related grower twilight meeting announcement

Impacts and Contributions/Outcomes

From March to December 2015, the project team was focused on the year-one field research portion of the project. Four initial grower collaborators (two in the Hudson Valley, and two in Western NY) decided to trial a fall-sown ‘Nemat’ arugula biofumigation cover crop in August 2014 with the intent to let the crop overwinter and be subjected to the biofumigation process in Spring 2015. Each arugula crop suffered complete winterkill even with timely fall seeding (early-mid September); four other Hudson Valley growers informally trialing ‘Nemat’ arugula in 2014 also experienced complete winterkill. Both western NY arugula sites were planted late (~early October) and suffered a significant snowstorm (3-6’) in early November; thus the opportunity to collect biomass samples was lost, but it was observed beforehand to be negligible nonetheless. Both of these sites were considered failed and therefore omitted form further data collection.

Two growers from Long Island joined the team of grower-collaborators in Spring 2015. Along with the two Hudson Valley growers, four trials of spring-sown ‘Caliente’ mustard were planted. No Western NY growers opted for spring-planted mustards, citing difficulty in fitting it into their rotations. All four spring plantings were successful, but a wet, cool spring delayed planting until the first week of May at the Hudson valley sites; both Long Island sites had timely plantings in early April. Spring conditions became hot and dry by early May and remained so in Long Island through summer 2015. The Hudson Valley did not receive significant rain until the latter few weeks before the cover crops were terminated for biofumigation. Cover crop biomass suffered in both locations due to weather conditions, but particularly in Long Island, which had precipitation ≥ 3” below the 20 yr average for May, and July-September. One site in the Hudson Valley suffered from significant weed competition, and from flea beetles and variable germination; arugula at this site also suffered similarly from apparent low fertility and weeds. This site highlighted the need for thorough site preparation and ample fertility for biofumigation cover crops to succeed. These plantings were subsequently considered failed and were omitted from data collection due to exceptionally poor/diluted cover crop performance. The remaining three growers successfully used their spring cover crops for biofumigation. All sites followed their biofumigation cover crops and their respective controls (rye or bare fallow) with pumpkin cash crops.

Due to the lost potential of overwintering arugula and the difficulties of fitting timely spring mustard plantings into rotations, the research team decided to open a third late summer planting option to growers. This option allows growers to fill a niche in their rotations after early vegetable crops. These biofumigant cover crops are planted the first week of August and grown for ~50-60 days, and then mowed and incorporated for a late fall biofumigation followed by a winter rye cover crop. This treatment was also accordingly added to our plot scale trials as well, in replacement of the failed winter arugula treatment. Four of our grower-collaborators opted to trial biofumigants at this timing; another Hudson Valley grower who grew and an exemplary half-acre trial stand (originally intended to be an informal trial) was asked to be an additional grower collaborator. All five trials of this late summer planting were successful with timely seeding, sufficient fertility, and timely termination and appropriate biofumigation steps. Winter rye was seeded in mid-October after the ten-day biofumigation period at each site.

The research team held three regional grower twilight meetings to talk about the project and general Phytophthora blight management in late September. Approximately 60 participants attended the meetings combined. The meetings allowed participants to view the late summer planted mustard cover crop plots, and at the Long Island site we demonstrated the mowing, tilling, and soil surface-packing steps used in the biofumigation process.

The research team collected data on pumpkin yield and Phytophthora blight incidence at three sites (two in Long Island and one in the Hudson Valley) for a total of four replications (one site had two replications) of standard grower practice vs. biofumigated treatment comparisons. Data was also collected from a kubocha winter squash response cash crop at the LIHREC trials. The results from this dataset are preliminary in the context of this project- the core measure of treatment response in being examined is the potential cumulative effects of biofumigation and reduced tillage treatment exhibited in the second project year.

For mustard biofumigant cover crops, between 1305- 5391 lbs/acre of biomass (containing 735-2017 lbs/ac C and 45-164 lbs/ac N) were returned to soils at the farm sites. For arugula (winterkilled), 761-2174 lbs/ac of biomass (containing 288 to 671 lbs/ac of C and 22-80 lbs/ac of N) were returned to soils. Biofumigant cover crop biomass was generally lower than usual at the Long Island sites in particular due to droughty conditions. Evidence of statistical yield and phytophthora blight incidence differences in the on-farm trials due to biofumigation vs. standard practice was lacking (p > 0.10). Phytophthora incidence was generally very low across all treatments, likely due to dry conditions that persisted throughout the summer.

At the plot-scale trials at the LIHREC, the only difference in individual treatments was seen in winter squash yields following an arugula/white clover treatment, which yielded 5.4 tons/ac lower than the other treatments. When treatments sharing similar attributes were contrasted as groups though, there were distinct differences in yield between spring mustard biofumigated treatments and the treatments that contained arugula (which had low fall biomass and winterkilled rather than being terminated by the biofumigation process), and/or the winter rye control. This occurred despite low mustard biomass (1609 lbs/ac containing 665 lbs/ac C and 45 lbs/ac N) due to droughty conditions. Spring-biofumigated treatments yielded 3 tons/ac greater when contrasted with the arugula and rye containing group and yielded 3.8 tons/ac greater when compared to the arugula-containing treatments alone (p < 0.01). There was marginal evidence of a 1.5 ton/ac greater yield of squash following spring-biofumigated treatments compared to the rye control alone (p = 0.109). Because of the lack of evidence that Phytophthora blight affected yields though, we hypothesize that the differences observed in yield thus far may be from 1) differences in fertility as affected by the mustard cover crops, and/or 2) by generally reduced low-level soil-borne pathogen loads as affected by biofumigation in the spring mustard treatments.

The opportunity to better detect preliminary potential treatment differences in our trials was hindered by loss of some trial sites (lowered statistical power) and by general lack of Phytophthora incidence in the field this year. Nonetheless, anecdotal evidence suggests that growers that have been involved in this project thus far under the guidance of Extension (either formally or informally) have generally shown notable gains in understanding how to manage brassica cover crops, the biofumigation process, and Phytophthora blight in general. For the research team also, the process of working with growers on-farm has highlighted what the barriers to successful adoption of brassica cover crops and biofumigation may be for growers across the state and greater Northeast region, and what components may improved research and educational efforts.

• Well nourished, lush ‘Nemat’ arugula cover crop at informal trial site; 15″ tall after 45 days of fall growth
• “Accord” trial site: Spring ‘Caliente’ mustard and rolled rye control treatment
• Late summer-sown ‘Caliente’ mustard trial, 5′ tall stand
• Mustard seedlings suffering from file beetles, high weed pressure emerging
• Plot trials at LIHREC, mustard biomass was relatively low due to drought
• Biofumigation cover crop biomass graphs
• Winterkilled ‘Nemat’ arugula at informal trial site, April 2015
• Well nourished, lush mustard plants; large leaves, approaching 3′ at flowering
• Healthy, weed-free mustard stand
• Pumpkin and winter squash yields at LIHREC and on-farm sites in NY following biofumigants and control treatments

Collaborators: