Preventing erosion of muck soils by reducing tillage in onion production: Part II

Preventing erosion of muck soils by reducing tillage in onion production: Part II

Summary

Growing onions in a minimum tillage system would drastically reduce the negative economic and environmental consequences of erosion, while sustaining long-term production of onions on muck soils. In this project, which is a cooperative effort between an onion grower and an Extension Educator, we built on our first attempt and evaluated critical improvements required for adoption of growing direct seeded onions in a minimum tillage system on muck soil on a commercial scale. Required improvements that we evaluated included, i) optimizing the use of cover crops to achieve adequate ground cover; ii) optimizing the use of fertilizer including application techniques, understanding the dynamics of nutrient availability when the cover crop is winter vs. spring killed, and the potential for reducing fertilizer rates; and iii) minimizing stand losses from damping off by using seed and in-furrow fungicide treatments.

Objectives/Performance Targets

The purpose of this project was to continue our progress towards developing a minimum tillage system for direct seeded onions grown on muck soil. Specifically, our objectives were to:

1. 1. Optimize the use of cover crops to ensure adequate ground cover.
   2. Optimize nutrient management including timing and technique of application, understanding the dynamics of nutrient availability and reducing fertilizer rates.
   3. Minimize stand losses from damping off.

In our first attempt, the oat cover crop that winter killed was too thin and gave us only 10% ground cover at planting, while the winter wheat cover crop that needed to be spring-killed was too thick and caused poor stand establishment. In this project, we continued to investigate the use of both a cover crop that is and is not winter-killed, spring barley and winter wheat, respectively, with the goal of each providing about 50% ground cover at planting.

In our first attempt at growing onions in a minimum tillage system, our techniques for applying fertilizer were inefficient. The full rate of NPK was applied in the fall. The following spring, pop-up fertilizer was applied in-furrow and urea was applied broadcast and rained in twice. Consequently, soil phosphorous was low, because a portion was lost over winter, and soil nitrate levels were low until mid-June. In this project, the grower cooperator applied the full rate of NPK in the spring prior to seeding by broadcasting and then shallow incorporating it between the cover crop rows. We also set up a small-scale small-plot trial to investigate banding P and K below the seed. Unfortunately, due to an abnormally very wet and cold April and May in 2011, we had very poor stand establishment (~33%) in this trial, and it was abandoned.

In our first attempt at growing onions in a minimum tillage system, in the wheat system, there was a release of nutrients when the residue broke down that was taken up by the onions causing a surge in growth. The dynamics of the nutrient availability in a minimum tillage system that includes a cover crop that is winter- versus spring-killed was studied in this project, because it could impact fertilizer rates, onion maturity and susceptibility to pests.

Since in our first attempt at growing onions in a minimum tillage system, the onions grown in the oat system yielded the same as those grown conventionally despite having only half as much available nitrogen, in this project, we wanted to investigate the feasibility of growing onions with lower rates of NPK. To answer this question, we included additional treatments in the small-scale small-plot trial described previously, but unfortunately due to inclement spring weather, the trial was abandoned.

In our first attempt at growing onions in a minimum tillage system, there was a 50% stand reduction in the wheat system, because the wheat residue provided ideal conditions for damping off pathogens to kill seedlings. In this project, we set up a small-scale small-plot trial within the minimum tillage wheat system to evaluate commercially available treatments for their control of damping off.

Accomplishments/Milestones

A 30 acre muck field was dedicated to this project. In September 2010, the grower cooperator seeded cover crops, winter wheat and spring barley into 10.5” rows, which were spring and winter killed, respectively. Minimum tillage wheat (MTW), minimum tillage barley (MTB) and the conventional planting systems were alternated in 15 foot wide passes (= 3 x 5 foot beds, 5 rows spaced 10.5 inch per bed) across the field with every other pass being MTW, and the passes in between alternating between conventional and MTB. In April of 2011, the field was planted into three equal 10 acre sections, each of a different variety of yellow storage onions including Festival, Safrane and Patterson. Due to the extremely wet April, Patterson was planted a few days later than the other varieties. Unfortunately, Patterson was also in a wetter section of the field and stands were very poor and it was abandoned. In general, stands were mediocre with some areas where they were excellent. To overcome such variability, data was collected from multiple sub-samples per replicate.

A composite soil test was taken in early spring and sent to the Cornell Nutrient Analysis Laboratory (CNAL). In all systems, 75 lbs, 150 lbs and 50 lbs of N, P and K was applied. For the conventional system, dry fertilizer was broadcast and incorporated via disking and culti-mulching. Using the grower’s standard equipment, a barley nurse crop was planted in 10.5 inch rows with the onions seeded precisely between them. The barley was killed a little bit late when it was greater than 5 inches tall and tillering. For the MTW system, Roundup was applied about 12 days prior to field work in the spring. In both MT systems, NPK was broadcast and incorporated precisely between the cover crop rows using a tillivator. Then, onions were seeded using the grower’s non-modified seeder, GPS and auto-steering technology to precisely seed the onions between the rows of cover crop residue.

Each variety was evaluated separately and divided into 5 replicates. Unless otherwise stated, data was collected from 2 sub-samples per replicate. Our original trial design was to include 3 sub-samples per replicate, but in the field, three proved to be too time consuming.

Ground cover – was estimated visually and by harvesting the above-ground residue in 5’ x 5’ sub-sample areas, which was oven-dried to obtain dry weight, on May 5 and Sep 9. It was originally planned to collect ground cover residue samples monthly, but this proved also to be too time consuming.

Stand establishment –as planned, in each sub-sample, the number of plants emerged per 3 feet of row for each of the 5 rows per bed were counted at the first true leaf stage on May 10 and at the 3-4 leaf stage on Jun 3.

Fertility – a composite soil sample was collected per replicate per system per variety at the 4 leaf stage on Jun 30, which was submitted to CNAL for complete nutrient analysis. Composite soil samples for available nitrate were collected in the same manner as described for the complete nutrient analysis tests. Samples were kept cool in the field and dried completely in a microwave oven within 12 hours of collection. Available nitrate was measured on Jun 14, Jul 8 and Aug 5. Also on Aug 5 when the plants were at the 9 leaf stage, the inner four leaves of 10 randomly selected plants per replicate per system per variety were collected and sent to CNAL for plant tissue analysis.

Plant size – on 10 randomly selected plants per sub-sample, number of leaves per plant and plant height were measured on Jun 29, Jul 15-16 and Aug 11-12. Neck diameter was measured on Aug 11-12.

Pest pressure – On Jul 15-16 and Aug 11-12, number of onion thrips and Botrytis leaf blight lesions per plant (outer 3 leaves) were counted on 10 and 6 randomly selected plants per sub-sample, respectively. At harvest, rotten bulbs were counted.

Soil temperature and moisture – were not measured, because our data loggers were in use for another project.

Yield and grade – on Sep 13-14, all of the onions in two sub-sample areas of 5 feet x 5 feet were pulled, weighed and graded according to size ; jumbo – 2-3 inch, medium – 1.25-2 inch and small – 0.75-1.25 inch. The grower also kept track of yield from the different tillage systems on a large scale.

Economic analysis – the grower will provide costs for inputs and average onion selling prices, which will be included in the final report.

All data has been collected and is in the process of being entered and analyzed in preparation for the final report.

We wanted to investigate banding fertilizer below the seed as an alternative to broadcasting and incorporating it in minimum tillage systems. When fertilizer is banded, rates may be reduced because it is located where it is most available to the plants, resulting in potential savings on fertilizer costs and reduced water pollution. Within each system, treatments were to include: 1) 100% NPK broadcast, 2) 100% NPK banded and, 3) 75% NPK banded for a total of 9 treatments. This was set up as a small-plot trial with 5 replications within the large minimum tillage field. Unfortunately, we quickly discovered that without fitting the ground in the spring, it gets very hard (even muck), and we were not able to set up the fertilizer in bands using our custom designed push seeder. Even on a large scale, although banding fertilizer in a minimum tillage system may be possible, it would take a lot of horse power. Instead of evaluating banding, we set up a trial to evaluate reduced fertilizer rates with only broadcasted and incorporated applications of 100%, 75% and 50% NPK. Unfortunately, the stand establishment in this trial was very poor (~33%), so this trial was abandoned.

Commercially available seed treatments, 1) Pro Gro, 2) Pro Gro + Farmore D300 and 3) Pro Gro + Cornet + Allegiance, were evaluated with and without Ridomil applied as an in-furrow treatment, for a total of 6 treatments. All treatments included Pro Gro and mancozeb, which was applied in-furrow, for protection against the soil borne disease, onion smut. Also, all treatments included Trigard seed treatment for control of onion maggot. The commercially treated seed (cv. Infinity) was provided to us by Nunhem’s Seed Company. The trial was set up as a small-plot randomized complete block design with 5 replications within one of the minimum tillage wheat systems. Each treatment-replicate consisted of a single 20 foot row. We planted the trial using our push seeder on May 9. Stand counts were taken weekly from loop- to 2-leaf stages on May 25, Jun 2, Jun 9 and Jun 15. All of the remaining onions were pulled out of the field on Sep 9, windrowed, and then topped and weighed on Oct 12. Data needs to be entered and analyzed in time for the final report.

It was planned to feature this project at Annual Elba Muck Onion Twilight grower meeting in early August, but with the mediocre stands, we decided that this would not be the best year to showcase minimum tillage onions, if we wanted to encourage grower adoption. With data entry and analysis behind due to a shortage in technical support for Hoepting, a presentation at the Empire Expo in 2012 has been delayed. Plans are still in place to distribute project results via the Cornel Vegetable Program newsletter and website and future grower meetings as appropriate.

Impacts and Contributions/Outcomes

Despite the 2011 onion growing season being one of the worst on record, our grower cooperator remains optimistic that onions can be grown in a minimum tillage system. His plan is to alternate this 30 acre field with minimum tillage direct seeded onions and onions grown from transplants. The early harvest of the transplanted crop will ensure enough time to get a cover crop established in the fall. Direct seeded main and late season onions are harvested later and proper establishment of a cover crop would not always be feasible. In our 2008 study, by keeping a minimum of 30% ground cover in the 10 acre minimum tillage wheat cover crop system, a minimum of 13.16 million cubic inches of soil was kept on the ground and not eroded by the wind.

Our 2008 study demonstrated that onions in the minimum tillage system yielded the same as those grown in the conventional system, despite having only one third of the available nitrogen. The onions grown in the minimum tillage system also had significantly fewer onion thrips and less bacterial diseases. It is these encouraging results that convinced our grower cooperator to reduce the rate of nitrogen that he uses from 125 lbs to 75 lbs, a savings of 50 lbs per acre.

Collaborators: