Using Hardwood Ramial Woodchips as a Time-Saving Mulch for Weed Control

Using Hardwood Ramial Woodchips as a Time-Saving Mulch for Weed Control

Summary

Objectives/Performance Targets

To determine if using wood chips as a mulch on bedded vegetable crops will decrease the amount of time necessary to manage weed growth by at least half.

To assess the effect that wood chips will have on the germination of crop seeds, transplant establishment, vigor of vegetables and soil nutrients over time.

To see if the use of IRT plastic covers in early spring will help raise the temperature of the soil and therefore counteract the expected decrease in heating of the soil under the wood chips.

Accomplishments/Milestones

Since the start of the experiment, my wife and I decided to convert our house, which is on the farm, into a bed and breakfast. We have been working ever since (painting, painting and more painting, plus many other changes to the house and landscape) to ready the house and grounds for an opening in the late spring of ’02. At the same time my farm partner, Bob, decided to start a different business on his own. We decided therefore to cease farming on my land. Bob will keep the farm business going on a smaller scale on his own land and we may partner again in the future. We will continue to manage the 9 experimental beds however for the next two years as agreed to in the grant proposal.

I should also say that during the season we bought a hand-held Mantis rototiller in order to lessen the time it took to prepare beds for planting. This little machine helped us immensely. We will continue to use it to prepare beds in the spring.

Jeremy Barker-Plotkin, farmer and farm advisor, as well as Richard Bonanno, extension specialist on weed management, were our two farm/grant advisors. They were primarily needed to help formulate the research structure and parameters and were indeed very helpful in this way. I have gone to Jeremy for follow-up questions about possibly changing crops in the second year. I will be asking both Jeremy and Richard what their recommendations would be to decrease the high levels of potassiun and phosphorous we have in our soils, There has been little need so far for more help from either of the ‘cooperators’.

We chose 9 contiguous beds in three groups of three beds each. Each bed was divided into 3 sections, each section with either broccoli or onion transplants or beets seeded directly into the soil. Manure (only partially composted) was added to each of the nine beds in early spring. In each group one bed was to be managed without any IRT cover in the spring and without chip mulch – just hand weeding. (However, being the first year, we started off with beds that were full of weeds, so we did use black plastic on the beds in the early spring to control the growth of the weeds during the time before planting. In the 2nd and 3rd years of the experiment, use of the hand-held rototiller to weed before planting will preclude the need for early spring use of plastic on these beds.) The second bed in each group was covered with IRT plastic in early spring before planting to slow weed growth and heat up the soil before planting and placement of the wood chips. Once it was warm enough, the IRT was removed and starter plants and seeds were planted before chips were laid down. (We had decided it would be to difficult to plant through a layer of chips as originally conceived.) Chips were laid around the starter plants and around the beets once they were 1” to 2” high. (In some cases the chips were laid down at the same time as the transplants were planted.) Since the bed sections with beets were not chipped until the beets grew tall enough, weeds flourished and had to be weeded before chips were laid. In the last bed in each group the beet seeds and transplants were planted as soon as the soil was warm enough and the chips were spread soon after. While waiting for the beets to grow from seed until they were 1” to 2” high, weeds grew in large numbers. In this case there was quite a bit of weeding needed around the tiny beets before the chips could be laid down. I think this slowed the growth of the beets.

We took the soil temperatures of different parts of most of the beds at different times before and after laying down IRT and chips. However, it took a lot of time to measure temperatures of the different sections of the beds over 9 beds several times over the season, so we did not get to all the beds. We found a large variability in temperatures, which seems in part to be due to the fact that we took temperatures in different bed sections on different days, times of day or different weeks depending on our time constraints. The summer weather had great variations of temperature as well. Despite our difficulties it is clear from our data that the beds sections that were chipped had temperature readings that were from 4 to 10 degrees lower than sections without chips. It is not clear however if the IRT had much effect on the temperature of the soil. Next year we will take only one temperature reading per bed (rather than in each section) several times throughout the season and on the same day and approximate time, so that we get better data.

We tested humidity by feel in the different beds. We estimated the quality and quantity of produce by sight in each bed. And we tried to time all our activities in the beds.

Impacts and Contributions/Outcomes

How successful were we? I would say that in this first year, we fell short of our goals in managing the beds and in gathering and recording all the data we needed due to the needs of the rest of the farm, off-farm work and B & B preparations. This first year was a learning process. We could not keep up with all the chipping and weeding on time, so several beds or sections of beds became overrun with weeds, which severely limited the growth of some of the vegetables. (Obviously this is a sign that the reason for doing this experiment was a good one.) We didn’t get good measurements of the time it would have taken to weed beds. The total documented time spent on weeding the beds without chips was almost 6 hours. The documented time spent weeding the beds with chips and IRT was 2.5 hours. The documented time spent weeding the beds with chips and no IRT was 5 hours. I would add another six hours (provided by friends) to the total time of 13.25 hours, but I’m not sure which beds got the extra time, so this data is not very helpful. The weeding data is not sufficient and there were too many uncontrolled variables, such as incomplete documentation, incomplete weeding and different initial bed preparations, to be able top assess how much time we saved or increased in out weeding activities. This year, with the help of the rototiller for equal bed preparation and with more time for weeding and documentation, we hope to have much better data for this very important part of the project.

We did learn some valuable things from this first year. We had hoped to keep the chips separate from the soil they covered. However, every time we weeded or harvested the onions or beets, the soil and chips became mixed. When we pull up the broccoli plants this spring, we will pull up a lot of dirt into the chips. This will lead to quicker decay of the chips and therefore may mean more lock-up of the nutrients in the soil. So, in this system it is clear, at least from the first year, that it is not possible to keep the chips neatly lying on top of the soil without mixing into the soil. We will learn more as we rake the chips off the beds this spring in preparation for planting.

We learned that one inch of chips does not keep the weeds down much. Two inches is much better and 3” will keep all weeds away. We also learned that gathering the ramial wood and chipping it was heavy labor and that it may actually be more effective, given our time constraints to buy chips if we can find ramial chips to buy. Bob and I spent 30 hours collecting/piling ramial wood, transporting the chipper, chipping the wood and unloading the chips by the garden. This was a labor intensive occupation at a time in the season when we were needed in the garden.

Germination did not seem to be a problem this first year, but we have to be aware that we did not germinate in chip-covered beds. The chips were laid down after germination. This coming season I will try to plant into the chips or into furrows in the chips. We will see if the decay of chips has any bearing.

The season was a dry one and the soil under the chips retained a lot more humidity by feel. Despite this the chipped beds did not seem to produce better vegetables than the unmulched beds. However there was a strong variable that we did not eliminate due to lack of time which probably effected the growth of the vegetables. This variable was our inability to keep up with the weeding of the un-mulched beds and even of the beds that had layers of chips that were too thin and therefore let through a good number of weeds. Some beds we weeded well, many we did not get to. We had some friends help us weed twice.

Vegetable production was only fair. The broccoli was the most productive probably in part because it was easier to chip around the broccoli plants and we did not have to thin them. Heads were not all that big but there was quite a bit of shoot growth through the fall. Onions for the most part were medium to small size. Two sections had larger onions. In beds where we did not get to the weeding the onions were very small and only good for home use. The beets were also medium to small size and very small in beds with a lot of weed growth. Both onions and beets took longer than usual to gain size probably due to the dry summer and weed pressure. There seemed to be no pattern of growth between the beds that had IRT and chips placed on them and the beds with just chips and the beds with no chips at all. Some beds that were chipped had better production than those that weren’t chipped. Some had worse. One of the hand weeded beds had large beets whereas the other hand weeded beds had small growth. Unfortunately because of our inability to weed, take temperatures and carefully document our activities completely throughout the season, there were too many uncontrolled variables to be able to point to any clear reasons for the differences in production between the different beds. Without the pressure of managing, marketing, harvesting and delivering the farms produce this coming season, I will be able to focus my attention and labor on the 9 experimental beds and retrieve better data.

Soil tests taken in December show that the beds overall have very high content of phosphorous and potassium, good to high content of calcium. Soil pH ranges from 7.1 to 7.6. This is an increase in pH from last year’s 6.1 to 7.1. Perhaps too much lime was added this year. I’m not sure of the reason. The beds without chips had slightly higher alkalinity, but it is hard to imagine that chips would have had an effect on soil in just one season. It will be interesting to see soil test results this year.

Despite our time and labor difficulties this year, I feel we had a good start to our 3-year project. We have some good infrastructure for the project going forward, including IRT frames, new thoughts on a better way to record data, as well as some chips left over from last year that, with purchase of additional chips, will not require us to spend time chipping this year. In general I foresee that I will have more time to devote to the project without the need to manage the farm as a business.

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