Final report for FNE24-075
Project Information
This project sought to identify the best time for planting a cover crop before no-till planting garlic into it so that the cover-crop residue would not interfere with mechanical cultivation. We planted 3 different successions of oat-pea cover crop in 500-foot beds and tilled one row just before planting garlic for a bare earth control. We then planted 2 rows of garlic each with 6-inch in-row spacing. We found that the earlier a cover crop is planted and the more residue is present, the better the soil was able to drain, less erosion occurred, and yield was higher. We found that the cover crop residue did not interfere with mechanical cultivation at any stage of maturity. We plan to propose a talk about these findings at the New England Vegetable and Fruit Conference in December 2026.
The objective of this project is to find the ideal time to plant an oat/pea cover crop before no-till planting garlic into it. The ideal planting time maximizes biomass production up to the point when cover crop residue makes mechanical cultivation of weeds unfeasible. To determine the ideal planting time we will plant 4 successions (spaced 3 weeks apart) of oat-pea cover crop and a bare-earth control. Then we will document the differences in erosion control, weed suppression, feasibility of mechanical weed control, and yield.
The goal of this study is to develop a cost effective way to grow garlic, avoiding plastic mulch. While growing garlic in plastic mulch is a proven and cost effective system, it is wasteful and has potential negative environmental effects from micro plastics.
Another method of weed suppression in garlic is straw mulch, which is effective, but costly. In addition to the cost of the straw itself, small-scale garlic growers often do not have the equipment to efficiently spread straw mulch on garlic beds. Therefore, labor costs associated with this method are also high.
No till planting into rolled cover crops is a widely used method in herbicide based growing systems providing soil health benefits and weed suppression. When weeds grow through the mulch however, hand weeding is the only option for organic farmers, without herbicides in their toolbox.
For all the reasons stated above we have adopted the bare earth method on our farm which reliably produces good garlic yields with no or minimal hand weeding. It is more profitable for us than the other growing methods, because mechanical cultivation takes very little time. We are noticing that the soil is taking a toll. We avoid bare earth going into the winter wherever we can because we have seen soil washout, loss of soil structure and a higher rate of compaction in beds that skipped the cover cropping cycle. To close this cover cropping gap in garlic production and protect the soil through the winter, we want to find out if there is a way to have some benefits of a cover crop, while still being able to use conventional mechanical weed control tools in the following year.
This trial proposes to plant an oat and pea cover-crop at different intervals, successively closer to the first frost date. This will ensure that, at each successive interval, the cover crop would be smaller. Thus we will be able to determine the point at which the cover crop is still effective at controlling erosion, while also being manageable enough to not interfere with the mechanical cultivator. Although the cover crop would be insufficient at suppressing weed growth, as long as the mechanical cultivator is able to pass through the garlic rows unobstructed by leftover debris, this does not pose an issue. We will determine if the cover crop, at that stage, is still able to control erosion and preserve soil structure.
Benedikt Dairy is a dairy and vegetable farm established in 2011, with a small dairy operation. In 2014, the farm expanded into vegetable production. The 12- acre vegetable operation runs primarily on a CSA model, with additional vegetable, dairy, and meat sales made in the farm store. In 2022, gross sales amounted to $432,000, approximately $100,000 of which was income from vegetable production. Max and Melissa Blindow of Benedikt Dairy have 9 years of experience running a successful vegetable operation in Goffstown, NH. Having grown garlic successfully for many years, they are trying to find ways to reduce the cost in production, especially labor, required to grow a successful garlic crop while not compromising on their commitment to soil health.
The relevant resources at the disposal of the farm to aid in the completion of the study are as follows: New Holland T-5 tractor, labor, K.U.L.T. KRESS Argus Hoe (2-row mechanical cultivator with sweeps and finger weeders), Forigo G35 Stone burier (primary/secondary tillage before cover crop), APV air seeder (cover-crop seeder), flail mower, undercutter for harvest. For this project, in lieu of a no-till drill, we used a drip tape irrigation layer which created a furrow and produced a similar result.
Cooperators
- - Technical Advisor
Research
This trial took place in 5 adjacent 500-foot by 5-foot beds. We used three successive planting dates for the oat/pea cover crop mixture, as well as a bare-earth control. Weather didn't permit a fourth cover crop succession. Five 500-foot beds were tilled using a Forigo G-35 stone burier. Oat/pea cover crop was seeded at a rate of 150lb/acre using an APV air seeder. Each bed was planted with 2 rows of garlic 30” apart at a 6-inch in row spacing. Our farm is located in USDA growing zone 6a. The beds were prepared and cover-crop was seeded on the following dates: 8/10, 8/28, 9/28. These beds were mowed on 11/14, and our bare-earth control bed was tilled on the same day. On November 14th, the cover crops were at the following growth stages:
First planting (8/10): Peas were flowering, oats in boot stage, 3ft
Second planting (8/28): Peas not yet flowering, oats in beginning of flag leaf stage, 1.5ft
Third Planting(9/28): Peas beginning to vine, oats in the tillering stage, no stem yet for the most part, 6 inches tall.
They were flail mown directly prior to planting. The no-till transplanter available through the local conservation district was a drop-tube style planter that did not allow for upright planting of the garlic cloves. Thus, we decided to lay drip tape with our drip tape layer, which created a furrow like a no-till planter would have. We then planted by hand in the furrows at a 6-inch in-row spacing, and closed the furrows by driving a tracked mini skid-steer over them. 
Due to reliance on rainfall for cover crop germination, precise timing of cover crop seeding is challenging. We were therefore only able to plant three out of four planned cover crop treatments.
We were planning to use a no-till transplanter to plant the garlic, but we realized that the design of the transplanter did not allow us to place every garlic bulb upright, which is required for growing hard-neck garlic successfully. The work-around we used (using our drip-tape layer to create a furrow and using our mini skid steer tracks to close the furrow) simulated a no-till transplanter which could be used for this method of growing garlic.
We noticed a significant amount of mustard growing to viable seed stage in the cover crops, which became an issue in 2025 with significant weed pressure. Depending on the local seed bank, oats and peas alone may not be sufficient to eliminate all weed pressure during the growing season.
Prior to planting, cover crops were flail mown. Figure 1 shows the clear difference between cover crop planting dates in terms of volume of cover crop residue. Figure 2 shows the stubble after garlic was planted, with the later 9/28 planting having significantly less residue than the other plantings.
Spring of 2025 had significantly more rain than average (a record 13 inches in May alone), which made mechanical cultivation exceedingly difficult as we were unable to drive machines on the wet field. As a result, we were only able to begin mechanical cultivation starting 6/5 and weed control was nonexistent until then. Notably, we had to wait longer to drive equipment onto our bare earth treatment due to drainage issues which weren’t as pronounced in the cover-crop treatments, and thus we were able to do an extra cultivation pass over the cover-cropped beds.
We observed significant wash-out in our bare-earth bed, with mild erosion in our 9/28 cover-crop planting, and very little erosion in the first two plantings (figure 3). The improved drainage and erosion prevention provided by the cover crop root systems and residue was noticeable in all cover crop plantings, but we noticed that the maturity of the cover crops corresponded directly to their effectiveness. The sooner a cover crop can be planted, the better for drainage and erosion prevention. Figure 4 (taken on 3/31/25) illustrates the improved drainage provided by the cover crops with standing water visible most prominently in the bare earth bed, with less in the 9/28 bed and none in the others.
Debris from all cover crops (flail mown directly before planting the garlic on 11/14) did not interfere with mechanical cultivation whatsoever (Figure 5). Their decomposition was far enough along to allow our Kult Kress Argus Hoe cultivator to pass over the beds unobstructed.
Our yields were as follows:
8/10 cover crop planting (average over 2 rows): 305.5lbs
8/28 Cover Crop Planting: 245lbs
9/28 Cover Crop Planting: 212lbs
Bare earth: 205lbs
The yield records indicate that planting cover crops sooner slightly impacts yield favorably. Because of factors like weed pressure and erratic weather, however, it is hard to say how accurate these yield results are, and further study is needed to verify these results. Figure 7 shows the extent of the in-row weeds on 7/22 at harvest, with a greater variety of weeds seen in the bare-earth bed.
The objective of this project was to find the ideal time to plant an oat/pea cover crop before no-till planting garlic into it. The ideal planting time maximizes biomass production up to the point of cover crop residue makes mechanical cultivation of weeds unfeasible. Despite unpredictable weather interferences with the study, we were still able to observe a clear result. We found that cover-cropping maximises yield, decreases erosion, and improves drainage, and that there was no interference with mechanical cultivation at any stage of maturity or amount of residue. We found a direct linear correlation between cover crop maturity at garlic planting time, amount of erosion, and yield. Earlier cover crop plantings resulted in less erosion and higher yield than later cover crop plantings and bare-earth cultivation. (See Fig. 7)
By planting cover crops earlier, we will be able to drive on the field earlier to mechanically cultivate, reducing or eliminating the need for hand weeding labor. We will see improved yields, and better soil structure with less nutrient loss due to erosion.
Education & outreach activities and participation summary
Participation summary:
We plan to propose a talk at the New England Vegetable and Fruit Conference in December of 2026.
This grant project will be featured in the UNH Extension newsletter.
We will offer a presentation to the New Hampshire Vegetable and Berry Growers Association annual meeting in March 2026.
Learning Outcomes
We showed that no-till planting into cover crop residue is not only possible in mechanically cultivated garlic, but that increased residue is beneficial to soil health and crop yield when using such cultivation methods. In 2025 there was an unusually wet spring. Cultivation was only possible on the high residue treatments, which was an unexpected benefit.
Project Outcomes
We learned that more residue comes with no downsides in our growing system, so we will establish a cover crop on the early side going forward. Our trial shows that any cover crop planting date is better than no cover crop, so if an early planting window is missed it is still worth it to plant later.
Our methodology provided us with a fairly clear result. We faced some difficulty due to weather, which affected our planting windows and cover crop germination. We did answer our question, and determined that it is possible to no-till plant garlic into heavy cover crop residue without interfering with mechanical cultivation. If we were to run the study again under more favorable weather conditions, we may have found a more pronounced result. We believe that any farmer with mechanically cultivated garlic or who is considering overwintered cover crops can benefit from the results of this trial.