Progress report for FNE22-032
Project Information
This project seeks to compare weed mitigation techniques in new and established saffron fields, in order to quantify the amount of time (manpower hours per week) various techniques require as well as their impact on yield of crop.
I will compare a high-growing cover crop (buckwheat), a low-growing cover crop (red clover), putting silage tarps down at dormancy (in June or July) and doing manual weeding on saffron beds. Some beds were originally planted in 2020 and some will be planted at the start of this study. Comparisons will be made between the impacts of the weed mitigation strategies on new and on established beds.
This will help other farmers know how to mitigate weeds in their beds and make an accurate estimate of time needed for weeding their crop.
Saffron is a high-value crop. It is often stated that saffron costs more than gold; the going rate for Vermont saffron is $60/gram. It takes approximately 150 saffron flowers to produce one gram of sellable product. Saffron is produced from the fall-flowering crocus sativus, a flower that is about three inches tall. It is a perennial crop and the corms reproduce underground with each "mother corm" producing approximately three "baby or secondary corms" per year. Saffron sends up green shoots in September, which die back in June or July, then the flowers emerge in October through early December.
The beds where saffron is planted are essentially not doing anything above ground for most of the weed-growing season. This makes them a tremendous weed magnet. Saffron growers have a few options - spend hours each week weeding these empty-looking beds (and risk pulling up the saffron corms underground), cover the beds with plastic to block weeds (this can encourage voles, who love to eat saffron corms), ignore the weeds over the summer and just weed in the fall (this is a bad plan, but frequently happens and can impede the nutrients the corms get underground and if you leave it too late, you may not be able to tell the saffron from the grassy weeds), plant a complimentary crop or plant a cover crop.
Researchers at URI have mentioned planting basil as a complementary crop, but have not published results (that I could find). A commercial grower in Italy planted clover as a cover crop, but has not shared the results of that Saffron cover crop - Zafferano Emiliano - Growing Saffron. A study carried out in Iran in 2013-2014 and published in 2017 tried various cover crops with various results (all positive on weed reduction and flower production) Effects of cover crops on weeds density, agronomic characteristics, flower and corm yield of saffron (Crocus sativus L.) (fao.org)
I heard about the use of plastic sileage tarps as weed blockers at the 2021 Saffron Conference (held at UVM), but I don't believe there is published research about it. I tried putting sileage tarps down on some of my saffron beds this year after dormancy. It worked to block some weeds, but in some beds, as soon as I removed them, weeds began to grow.
So, in this experiment, I plan to start a fresh saffron research field and plant four beds of 200 corms each. On one bed, I will plant a low cover crop (red clover), on one I will plant a tall cover crop (buckwheat), on one, I will cover with sileage tarps at dormancy, and on one I will do nothing but will weed manually (with flame weeder and by hand). I will compare the results in terms of hours of work required, crop yield, predator loss, and soil and saffron quality. I will do the same on my existing saffron bed (of 5,000 - 8,000 corms) and will see if there are any differences in the established bed vs the new bed (established bed also has established weeds).
This research will help existing and prospective saffron farmers gain an understanding of the amount of time needed year-round to maintain their beds and options that can reduce that time by reducing weeds. Less weeds also means more saffron, more profit.
Cooperators
- - Technical Advisor
Research
PLANNED ACTIVITIES: In the spring of 2022, I will prepare a new saffron planting area (clear, till, and fence it). I will plant buckwheat in all the beds to prepare the soil and suppress weeds and grasses. In August 2022, I will pull up the buckwheat in all but one of the beds and will plant red clover in one bed and use a sileage tarp to cover one bed. In September 2022, I will plant four beds of 200 saffron corms each in this planting area. One bed will get saffron interplanted with the buckwheat, one bed will be planted with the red clover, and two beds will not have other crops (one will have had a month of sileage tarp coverage).
The same interventions (clover, buckwheat, tarp, and nothing) will be done to four beds of established saffron, with +/- 200 corms per bed.
Once the saffron is planted, I and an employee will spend up to three hours each week (total of up to six hours weekly) weeding the beds by hand through harvest time (October/November) and we will weigh the weekly weed harvest and record manpower hours bed by bed. We will also measure the harvest of crop per bed (number of flowers) and weigh the saffron per bed. We will send a sample of the soil from each bed to UVM for soil analysis.
ACTUAL ACTIVITIES: I had the area for the new beds cleared (tree and brush removal), but when I went to till it and install the fence, it was too rocky to work with, so I instead got 12" high raised bed planters and filled each with 9 cubic yards of professional planting mix (bagged, which contained perlite). The buckwheat I planted failed to take in any of the beds (old or new), but the clover did. Weeding took far longer than six hours per week in the established bed - the weeds were relentless (mostly grass and raspberries but also an invasive - Carolina Horse Nettle - that is a horror and rightly nicknamed "Satan's Tomato"). We wound up not weighing the weeds, but there were a lot. At least two wheelbarrows worth per week. The raised beds with pro soil had zero weeds.
I sent soil samples to UVM right in the midst of saffron flowering. The results were interesting (this was my first time ever doing soil testing). In the bagged professional soil, the bed with the clover was super low on potassium, and all of the plots (except for the established one where buckwheat was planted but didn't take) needed a lot more limestone.
The saffron harvest in the new plantings (raised beds with professional planting mix) was decent -- four and a half grams of deydrated saffron from 1,000 corms planted (avg 200 plants per gram). The plants were obviously healthy and robust with lots of green shoots post-harvest (noticeably less robust in the bed with the clover cover crop). The saffron harvest in the established beds was meager - about a half a gram. Shoots came up in most of the established plots, but there wasn't a lot of flowering. The plot that I had tarped during weeding season had no flowers or greens, and when I dug through the earth I found no corms -- indicative of voles getting in under the tarp, where they're invesible to owls and hawks, and eating the corms. The green shoots of the established plants are also less dark green, less tall, and generally less robust than those in the raised beds. The soil was very compacted in the established beds too.
I will be presenting my research to date at the Saffron COnference in Burlington in March. I look forward to seeing how the harvest is for year two of the raised beds as the first year (2020) of the established beds had a good yield also, so we'll see how the winter and weeding season go next year.
Starting in May 2023, we will again begin weeding the eight beds (established and new, with same four interventions) and record time spent weeding plus weed harvest by weight (and by plant type, if known). Once the saffron goes dormant (in June or July), the sileage tarp beds (new and established) will be covered over until September. The other beds will continue to be weeded with time spent weeding and weight of weeds measured. The sileage tarps will be removed in September and these beds will join the others in the weeding measurements. In September, soil from all the beds will be sent to UVM for analysis. Once harvest starts, we will add number of flowers, weight of saffron harvest, and post-harvest soil sample for analysis. If any rodent incursions are visible (tunnels), we will document those, too.
ACTUAL ACTIVITIES: I had the area for the new beds cleared (tree and brush removal), but when I went to till it and install the fence, it was too rocky to work with, so I instead got 12" high raised bed planters and filled each with 9 cubic yards of professional planting mix (bagged, which contained perlite). The buckwheat I planted failed to take in any of the beds (old or new), but the clover did. Weeding took far longer than six hours per week in the established bed - the weeds were relentless (mostly grass and raspberries but also an invasive - Carolina Horse Nettle - that is a horror and rightly nicknamed "Satan's Tomato"). We wound up not weighing the weeds, but there were a lot. At least two wheelbarrows worth per week. The raised beds with pro soil had zero weeds.
I sent soil samples to UVM right in the midst of saffron flowering. The results were interesting (this was my first time ever doing soil testing). In the bagged professional soil, the bed with the clover was super low on potassium, and all of the plots (except for the established one where buckwheat was planted but didn't take) needed a lot more limestone.
The saffron harvest in the new plantings (raised beds with professional planting mix) was decent -- four and a half grams of deydrated saffron from 1,000 corms planted (avg 200 plants per gram). The plants were obviously healthy and robust with lots of green shoots post-harvest (noticeably less robust in the bed with the clover cover crop). The saffron harvest in the established beds was meager - about a half a gram. Shoots came up in most of the established plots, but there wasn't a lot of flowering. The plot that I had tarped during weeding season had no flowers or greens, and when I dug through the earth I found no corms -- indicative of voles getting in under the tarp, where they're invesible to owls and hawks, and eating the corms. The green shoots of the established plants are also less dark green, less tall, and generally less robust than those in the raised beds. The soil was very compacted in the established beds too.
I will be presenting my research to date at the Saffron COnference in Burlington in March. I look forward to seeing how the harvest is for year two of the raised beds as the first year (2020) of the established beds had a good yield also, so we'll see how the winter and weeding season go next year.
Well, so far, I think the raised beds and fresh and clean balanced soil that contains vermiculite or perlite is probably the key to success. I'm going to be experimenting more as the project continues. I don't know if the cover crops really did anything (except deplete nutrients in one case), so I'll be curious to see the second year of the project what happens.