Hybrid Mulching Effects on Vegetable Crop Productivity, Weed Dynamics and Soil Quality

Hybrid Mulching Effects on Vegetable Crop Productivity, Weed Dynamics and Soil Quality

Summary

It is critical that we reconsider the intensive tillage used in our current cropping systems. Ironically, as farmers work towards more sustainable cropping systems by reducing their reliance on herbicides, the frequency and intensity of tillage often increases and, consequently, soil quality declines. In northern agronomic zones, the surface residues in no-till systems result in cool spring soil temperatures resulting in poor crop emergence and generally unacceptable yields. The “hybrid-mulch” system described by Louis Lego offers a solution to the soil temperature problem by exploiting the thermal properties of black plastic-covered beds.

We propose systems comparison and associated “component” experiments to be conducted at the University of Maine Farms, and commercial farms. These experiments will investigate cash crop performance, selected soil quality parameters and weed seed bank dynamics over the three-year life of a hybrid-mulch system. A 3-year vegetable rotation will be grown in hybrid mulched perennial beds, in hybrid mulched annual beds, and in conventional spring-formed beds.

Objectives/Performance Targets

On-farm and Experiment station research will demonstrate and develop refinements to the hybrid mulch production system tailoring it to Maine and other northern growing conditions.

Three hundred farmers will observe the hybrid mulch cropping system. Thirty-five farmers will use the hybrid mulch system in at least one of their fields resulting in: decreased tillage, improvements in soil health, decreased weed competition, and increased economic returns.

Accomplishments/Milestones

Eighty-five mixed vegetable growers observed the hybrid annual beds established in the fall of 2004 during meetings held at Highmoor Farm in September of 2005, July and September of 2006. Additionally, 125 growers learned about the project at the Maine Small Fruit and Vegetable Growers Association winter meeting held in January of 2005. During the 2006 growing season 85 mixed vegetable growers attended the Highmoor Farm summer tour and learned about the hybrid mulched beds and the crop rotation study. In 2007, a total of 75 growers visited the experiment site at Highmoor to learn about the research we are conducting with the hybrid mulching system.

Two experiments were established at Highmoor farm in the fall of 2004. One experiment to compare three crop rotations over a three-year period in hybrid mulched perennial beds (1, tomatoes-cucumbers-pumpkins; 2, pumpkins-cucumbers-tomatoes; 3, pumpkins-tomatoes-cucumbers). The second experiment (systems experiment) was to compare hybrid mulched perennial beds, hybrid mulched annual beds with the inter-row cover crop managed either by mowing or by herbicides, and conventional spring-formed beds. The beds were established in late October, 2004, much later than expected due to the frequent rains experienced during August and September. Fortunately, October and November were milder than usual allowing the inter-row cover crop to get partially established. Our team has some concerns about how well the system may work with such a late planting and will create additional research plots in the fall of 2005. Because of the difficulties due to the weather in the fall of 2004 no grower field plots were set-up.

The experimental plots established in 2004 were planted with cash crops in June of 2005. The crops were harvested and the data summarized. Initial evaluation of the yields in the rotational study appears to indicate little yield loss due to competition between the cash crop and the inter-row mulch. The inter-row area had been seeded with perennial rye, however, by the end of the 2005-growing season the living mulch is nearly 100% Dutch white clover. The inter-row area of the crop rotation study was easily managed by mowing the cover crop three times during the growing season prior to the time the vines of the cucurbit crops ran off the plastic filling the inter-row area. All of these beds were in excellent shape going into the 2005/2006 winter and were planted again in 2006. In 2005, tomatoes, cucumbers, and pumpkins were planted in 3 replicated plots randomly arranged. In the second cropping year of the study, 2006, tomatoes were planted in plots previously growing pumpkins or cucumbers while cucumbers were planted in plots that had been planted to tomatoes in 2005. Adjacent to the rotation study new spring made beds were planted in plots of tomatoes, cucumbers, and pumpkins. Cucumber yields harvested from the rotation study in 2006 were similar to yields observed in 2005 and were greater than yields obtained in newly made spring beds. Data is being recorded on all activities associated with growing the crop in these studies including frequency of mowing, length of time to harvest plots, yield and quality of crops harvested.

In the fall of 2005 on farm research plots were established at three grower locations, University of Maine, Highmoor Farm and Roger’s Farm. Weekly visits were made to grower locations to evaluate the fall made beds and crop development. In general, the fall made beds at grower locations exhibited reduced growth compared to adjacent spring made beds. Grower experience with the fall made beds indicated that were not fertigated indicated a reduction in plant growth and yield presumably due to reduced fertility and competition with the living mulch between the plastic beds.

In 2005, two additional growers came forward saying that after seeing some of the initial experiments with perennial beds they had began using the system in 2003. In their system beds are made in the spring using conventional methods and the plastic is kept in place for the following year. Prior to planting in the second year herbicide is used to kill any weeded in the inter-bed area prior to transplanting the cash crop. A balanced fertilizer solution is applied through the drip irrigation system. The grower experience using fall made beds and beds kept in place over two growing seasons combined with herbicide applications to control weeds between beds and fertigation to supply nutrients were generally positive.

Data from the Highmoor farm experiments in 2007 indicate the importance of supplemental irrigation. The experiment plots at Highmoor have been in place for three or two growing seasons. In both experiments we saw yield reductions in the perennial beds compared to conventionally made spring beds. There were clear differences in plant growth apparently due to moisture stress. Tensiometers placed in the perennial beds and spring made beds indicated much more water stress in the perennial beds compared to the spring made beds.
We are analyzing the data from the past three years of the Highmoor Farm rotational trial to determine overall economic impact of using perennial beds system. This analysis is to be completed by the summer of 2008.

Impacts and Contributions/Outcomes

Several of the growers we have communicated with regarding the project are very enthusiastic. However, the issue of time management of making planting beds in the fall is difficult to solve, particularly during wet falls. The two growers currently using beds multiple years are making the beds in the normal fashion in the spring and simply keeping the beds in place until the plastic becomes unusable. One of the growers has commented that tomatoes on second year plastic are easier to manage. The growers new to the project in 2005 were less optimistic about the use of fall made beds used in the 2006 season believing they saw reductions in plant growth and yield sue to reduced fertility. In 2007, no new growers participated in the project and two dropped out citing a lack in crop performance under the system.

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