Preventing erosion of muck soils by reducing tillage in onion production
The problem with using conventional tillage practices for onion production on muck soils is that it results in the subsidence of muck via wind and water erosion and oxidation of organic matter at a rate of one foot every 10 years, which is not sustainable for preserving these non-renewable natural resources for long-term productivity. Onions are one of the most valuable vegetable crops produced in New York State with the majority of the 13 000 acres being grown on muck soil. Producing onions using conventional tillage practices results in degradation of soil health and increased subsidence. This leads to increased fertilizer and crop protection chemical input to maintain productivity, resulting only in increased subsidence and declining productivity at ever increasing costs. It is a scientifically proven fact that wind and water erosion, and subsidence decreases as ground cover increases and cultivation decreases. In this project, we developed and evaluated growing onions from direct seed in reduced tillage production systems using oat and wheat cover crops on muck soil on a commercial scale. This was the first attempt of its kind, and a success with the minimum tillage systems producing comparable yields to the conventional system, having reduced onion thrips and bacterial rots, and significant reductions in soil compaction and reduced wind erosion compared to the conventional.
To develop, demonstrate and evaluate the production of growing direct seeded onions in a minimum tillage system in muck soil on a commercial scale.
- This was the first attempt anywhere at growing direct seeded onions in a minimum tillage system on muck soil on a commercial size. The trial was successfully established, and evaluations carried out on available soil nutrients, stand establishment, plant size, pest pressure, yield and bulb size.
Preliminary results were presented at the Annual Elba Muck Onion Twilight Meeting on August 5, 2008, where 40 onion growers, allied industry representatives and Cornell Cooperative Extension professionals were in attendance.
This research project was highlighted on the front page of the newspaper, the Batavia “Daily News” on August 19, 2008, along with the other 2008 Partnership project funded by NESARE that was conducted by Hoepting, “Maximizing onion yield and economic feasibility of growing onions from plug transplants”.
Preliminary results of this project were presented by Hoepting to 12 Cornell research faculty and Extension Educators at the onion session of the Annual Agriculture In-Service training in Ithaca, NY, on November 12, 2008.
Minimum Tillage Systems Established: Growing direct seeded onions using a conventional system was compared to using minimum tillage using oats and wheat cover crops in side by side comparisons in the same field with each system being 10 acres. In September of 2008, in the minimum tillage plots, 470 lbs of 12-19-21 NPK fertilizer was broadcast and incorporated, and seeded to 50 lbs each of oats and wheat in 10.5 inch rows. The following spring, 600 lbs of 16-17-25 NPK was broadcast and incorporated at the conventional site and Roundup was applied to the wheat. In the minimum tillage sites, onions were seeded between the cover crop rows using a regular onion seeder with coulters mounted on it and auto-steering technology. Three and 5 gal per acre of 6-24-6 NPK was applied in-furrow at planting in the conventional and minimum tillage sites, respectively. In the spring through at least the end of June, ground cover was 0%, ~ 10% and ~ 60% in the conventional (not including barley windbreaks), minimum tillage oats and minimum tillage wheat systems, respectively.
Stand Establishment: The minimum tillage with wheat site had significantly the lowest stand establishment in the trial on May-14 (5.9 seeds per foot), Jun-19 (3.3 seeds per foot) and Jul-31 (2.9 seeds per foot). No significant differences occurred in stand establishment between the conventional and the minimum tillage wheat site (seeds per foot: May-14 conv.- 6.6, oats- 6.8; Jun-19: conv.- 5.8, oats- 5.9; Jul-31: conv.-5.6, oats- 6.1). The reason why the minimum tillage wheat site had a stand that was almost half of the conventional and minimum tillage site with oats was because the wheat cover crop resulted in ~60% ground cover, which prevented the sun from heating up the muck and held in the moisture, which caused high loses to seedling damping off. In the future, seed treatments to control damping off will be used.
Fertility: In the spring, the minimum tillage sites had low levels of P according to Cornell nutrient analysis tests taken just prior to planting, indicating that a portion of the P added in the fall was lost over winter. A total of 95 lbs of nitrogen was applied to the minimum tillage sites including in the furrow at planting and 2 broadcast applications at the 1st and 3rd leaf stages, compared to 122 lbs of total nitrogen applied to the conventional site, one broadcast and incorporated application prior to planting, and one broadcast at the 1st true leaf stage. Soil nitrate tests showed that available nitrate was very low to low (8.5 to 20.5 ppm) on Apr-24, May-14, May-21 and Jun-4 in both the minimum tillage sites, which was 1.7 to 5.5 times less than the available nitrate in the conventional site (34 to 72 ppm). After the second broadcast application of urea on Jun-19, available nitrate levels were finally acceptable in the minimum tillage sites (oats – 23.5 ppm; wheat – 36.5 ppm), but were still 2 to 3 times less than in the conventional site. By mid-July, the onions in the minimum tillage oats site had observably lighter green foliage than the minimum tillage wheat and the conventional sites. It is suspected, that during July, there is a release of nutrients when the wheat residue breaks down that is taken up by the onions.
Plant Health: On Jun-19, the conventional site had significantly more leaves per plant (4.8) and the tallest plants (41.5 cm), while the minimum tillage oats site had significantly the fewest leaves per plant (3.5) and the shortest plants (25.2 cm). This is likely a reflection of the more available nitrogen in the conventional site. By Jul-31, there were no significant differences in plant height, and the minimum tillage wheat had significantly more leaves per plant (10) than the conventional (8) and the minimum tillage oats (8). The extra vegetative growth of the onion plants in the minimum tillage wheat site is a result of the stand being about 50% thinner than in the other systems, due to early damping off. It is normal behavior for onions to produce larger plants and bulbs when spacing is thinner.
Pest Pressure: On Jul-31, the onions grown in the minimum tillage oats system had significantly lower onion thrips per plant (1.0) than the conventional (3.9) and minimum tillage wheat (8.2) systems. On Aug-19, onions grown in the minimum tillage oats system had the lowest number of onion thrips per plant (7.2), which was not significantly different than the minimum tillage wheat (11.2). Both of the minimum tillage systems had significantly lower onion thrips per plant than the conventional system (25.2), which had 2.2 to 3.4 times more thrips per plant than the minimum tillage systems. We suspect that there is a relationship between reduced nitrogen fertility, lighter green plant tissue and reduced onion thrips pressure. On Jul-31, the conventional system also had significantly more Purple Blotch lesions per plant (0.8) than the minimum tillage systems (oats – 0.3; wheat – 0.4). By Aug-19, there were no significant differences in Purple Blotch among treatments. The minimum tillage wheat system had significantly fewer Botrytis leaf blight lesions per plant (26.4) than the other two systems (conv.- 44.3; oats- 45.5) on Aug-19. Also on Aug-19, the conventional system had significantly higher incidence of bacterial cankers (58%) than the minimum tillage wheat treatment (27.5%). The minimum tillage oats system (40.6%) was not significantly different than the other two systems. We suspect that the minimum tillage wheat system has improved aeration due to the reduced stand, which is less favorable for development of leaf disease. In general, there is a trend towards reduced pest pressure with the lower fertility minimum tillage systems, compared to the conventional.
Soil Health and Reduced Wind Erosion: Penetrometer readings were taken on Jul-31, both the minimum tillage systems had significantly less compaction within the top 6 inches (oats- 89 psi; wheat- 69 psi) compared to the conventional (125 psi). No significant differences were detected at 6-12 inches deep. By August, we observed that in the minimum tillage wheat system, approximately 30% of the ground was covered with wheat residue. The soil underneath the wheat residue was approximately 0.7 inches above the surrounding bare ground, because the wheat residue prevented the muck soil from eroding away by the wind. We estimate that the wheat cover resulted in 30.2 inch3 per ft2 that was not eroded by the wind, representing a 25% reduction in the normal rate of muck subsidence (i.e. 1 foot every 10 years equal to 119.5 inch3 per ft2). If this minimum tillage practice were continued, the useful life of the muck could be extended by 25%.
Yield: Neither of the minimum tillage systems yielded significantly different than the conventional (40.6 lb per 25 ft2), although the minimum tillage oats (43.8 lb per 25 ft2) yielded significantly higher than the minimum tillage wheat (38.5 lb per 25 ft2), despite having the poorest growth and lowest available nitrogen during the growing season. Despite having the lowest total yield, the minimum tillage wheat had significantly 4.7 and 7.8 times more jumbo weight, 2 times more medium weight, and 3.4 and 3.8 times less small weight, than the conventional and minimum tillage oats, respectively. The minimum tillage oats system yielded almost twice as much jumbo weight as the conventional.
Overall, our first attempt at growing direct seeded onions using a minimum tillage system in muck soil was a success with comparable yields to the conventional system, reduced onion thrips and bacterial rots, and significant reductions in soil compaction and reduced wind erosion.
Impacts and Contributions/Outcomes
- As a result of the success of this project, the grower cooperator plans to continue to pursue growing direct seeded onions in a minimum tillage system in 2009-2010. He plans to modify the rates of the cover crops and fertility program, as well as use a seed treatment with efficacy against damping off. It is also likely that another grower in the Elba Muckland will trial growing transplanted onions in a minimum tillage system.
The results from this project which showed that the treatment(s) that had the least amount of available nitrogen and lightest green leaf color also had significantly lower onion thrips and bacterial canker, lead to the pursuing of a Pest Management Education Program (PMEP) grant by Cornell University researchers and Hoepting, which plans to take a multidisciplinary approach to a thorough investigation of the interactions among fertility and pest management. If it is found that onions can be grown with lower nutrient requirements without compromising yield, but reducing pest pressure, there is tremendous potential for onion growers to save thousands of dollars in the input costs of fertilizer and pesticide sprays.
In this study alone, 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.
Dept. of Horticulture, Cornell University
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