By Nate Dalman, Horticulture Researcher III, Co-Director, Horticulture
This year we conducted a field variety trial with eight bell pepper varieties under evaluation. Some of the varieties are in the early stages of development by private industry plant breeders. The purpose of this breeding work is to develop varieties that have better yields and stronger resistance to a multitude of diseases than varieties currently on the market. With that in mind, the plants are evaluated on traits such as time from transplant to maturity, yield, fruit size and disease presence. Another part of this project was continuing our research on testing mulch types. Typically, plastic mulch is used in production to control weeds, but it results in a large amount of plastic waste at the end of the growing season. Alternative mulches are biodegradable and don’t need to be discarded, they can instead be incorporated into the soil. We evaluated a paper mulch in comparison to plastic to determine which controls weeds better and if they influence soil moisture or microbial activity in the soil.
Plot installation began in mid-June, which was a little later than normal due to the delayed planting conditions this spring. Plants were transplanted and soil moisture monitoring equipment was put in place the next day after the beds were formed and the mulches laid down. From then on, it was just a long wait for the fruit to mature and yield data to be collected. However, during that time, an intern from the University of Minnesota Morris regularly recorded soil moisture data in both mulch types and took several soil samples to measure the amount of respiration occurring, which is an indicator of how much microbial activity is taking place. Data was collected from June through August when the internship ended. Fruit began to mature in late August, so weekly harvests began and occurred through the end of September.
Not all the data has been fully analyzed, but we do have some preliminary results about how the mulches and varieties performed. First, there was no difference in soil moisture or respiration levels indicating that mulch type does not have an impact on those properties. Growers would not need to utilize different irrigation techniques when switching from one mulch type to another. As for weed control, biomass samples were taken at the end of the season from several locations in each mulch type and all sample sites produced no weed biomass, indicating that both mulch types were very effective at controlling weeds. This was especially good to know because one concern is that a paper mulch will deteriorate too quickly and allow weeds through but that was not the case in this situation.
Yield data appears to be very similar between the paper and plastic mulch which is an exciting result because it indicates growers can produce peppers in a more sustainable way without taking a hit to their yields or profits. Among the eight varieties, differences in fruit size and yields are quite minimal, indicating the varieties with an increased number of traits for disease resistance can still maintain good yields which is not always the case. However, there is still more data analyzation to be completed in terms of yield data. We will release the full results when available.
Based on our experience, if you are a grower who typically uses a plastic mulch, I invite you to try switching a portion of your system over to paper to see if it works for you. You might be especially happy with the ease of cleanup at the end of the season. Instead of ripping up and hauling away loads of plastic, the paper is easily tilled into the soil where it then breaks down rapidly. As for the varieties, the breeders will determine which ones they want to release to the market, and which need more breeding work. Again, stay tuned for more results and please feel free to contact us with any questions about this project or alternative mulches in general.