Work on this project to improve yields of cold weather shiitake strains has proceeded as planned. The first year focused on putting in place the infrastructure to be used to test the hypothesis that irrigation can improve yields of cold weather shiitake by concentrating the fruiting period and improving quality of mushrooms. Three hundred logs were inoculated with cold weather shiitake in spring 2016, and a new laying yard set up for the project (summer 2016). Visual inspection in Fall 2016 showed very good mycelium colonization across these logs. Irrigation options were researched and discussed with the project adviser, and a system installed consisting of a single irrigation line feeding sprinklers, gravity fed from 2 shallow wells and a group of four 285 gallon storage tanks. Total capacity of the system is around 2500 gallons.
Storage tanks were purchased as the dry winter or 2015/16 showed that the recharge rate of our existing wells was not sufficient to deliver the required flow rate/duration. In 2017 the system had sufficient capacity to deliver the irrigation required.
A set of logs inoculated in in Spring 2015 was irrigated in October 2016 as test run for the full irrigation trials. We had mixed results – there was no obvious concentration of fruiting period on the irrigated logs, but the quality and size of fruit was improved.
In Spring 2017 we irrigated the logs during the natural fruiting cycles to encourage fruiting to concentrate over a period of days rather than weeks. Our first natural fruiting of 2017 occurred in April. Shiitake pins were observed on the 18th, and the experiment logs were immediately irrigated for 2 hours and covered with shade cloth to conserve moisture. They were irrigated again for 2 hours the following day. Growth proceeded over the following week. However there was no observable difference in the number of pins on irrigated and control logs, suggesting that irrigation had not encouraged further fruiting. However weather during that week was dry and windy windy and fruits began to dry before forming fully. Further irrigation was carried out three times daily for periods of 10 minutes, and the logs were kept under shade cloth. When harvesting began on 25th April, it was clear that whilst irrigation had not increased the number of individual fruits on logs, the irrigated logs produced larger and better quality fruit, and that fruits on the control logs had dried and stopped growing before being fully formed. One irrigated log produced over 2lbs of shiitake, however most of the irrigated logs produced around 0.5lb, with non-irrigated logs producing between less 0.25lb of saleable mushrooms.
At the beginning of October 2017 temperatures dipped and pinning was observed on 10th October. However, high daytime temperatures over the following two weeks including a run of days in the high 70s, led to there being no worthwhile Fall harvest. We irrigated daily for 2 hours but no difference was observed, with just the occasional mushroom fruiting from irrigated and non-irrigated logs. In total the 270 experiment logs produced only 15lbs mushrooms in Fall 2017.
We would like to find out how water availability in the very early stages of fruiting affects the production of cold weather strains of shiitake. Specifically, by providing targeted irrigation, using different flow rates and timing to existing logs and to an experimental group of logs of different tree species inoculated with different strains we will find out whether the timing of fruiting can be manipulated so that harvest can be carried out more effectively, so lowering the risk of stunted growth, predation, and frost damage. We will measure and compare production (both quantity and quality) from logs irrigated under different regimes with existing production logs, and then the newly inoculated logs to see if different tree species and shiitake strains respond differently to irrigation.
In Spring 2016, 270 logs were inoculated, consisting of three groups of 90 logs (beech, oak and maple). Each group was further divided into three and inoculated with 3 different CW strains – Bellweather, Miss Happiness and Snowcap.
In Summer 2016 a new laying yard was designed & constructed, using two surface wells of around 1200 gallons capacity supplemented by a further 1200 gallons of water stored in plastic totes.
The irrigation system is gravity fed, delivering just over 300 GPH through 1/2 inch hose.
The aim was to develop a system that can be replicated in a variety of locations, including remote areas, in keeping with the low-tech nature of cold weather shiitake cultivation, the system was very simple but effective. After sourcing the used 275 totes, the only additional materials were 3 inch to 1/2inch connectors and a hose sprinkler head.
The first irrigation trials were held in Fall 2016, using 200 logs that were inoculated in 2014 and which we knew produced an average of .75lb of mushrooms per flush in 2015. When logs began to fruit naturally they were irrigated to try to stimulate a full fruiting on each log. This provided some initial results to compare with non-irrigated logs. Although there was no concentration in the fruiting period and no difference in the number of mushrooms per log, irrigated logs did produce larger and denser fruit which were more marketable.
In Spring and Fall 2017 we irrigated half of the spring 2016 inoculated logs, ie different species and shiitake strains to fine-tune our findings and see if certain combinations of wood species and shiitake strain respond differently to irrigation.
The study has shown three main findings so far:
- irrigation does not effectively stimulate full fruiting on cold weather logs
- there may be some encouragement of fruiting on smaller logs but this is marginal
- irrigation does improve the quality and size of mushrooms particularly when used in conjunction with shade cloth and fruiting blankets, compared to non irrigated mushrooms. The difference are particularly noticeable in dry conditions. Therefore irrigation has potential to save crops that are at risk from dry and or windy conditions.
We have met all our project milestones, we had a strongly colonized group of logs to work on, a new area to allow safe and easy movement between log stacks, along with an irrigation line which brings water to the laying yard, using gravity from a well and water storage facility higher up the hill.
Winter 2015/16 was very dry, and our surface wells’ water storage was much lower than previous years. Dry weather through 2016 meant that they never achieved full capacity and following discussions with the project adviser is was clear that additional storage capacity was needed. This was been installed and we have sufficient capacity to implement irrigation regimes as planned
In October 2016 we tested the irrigation on a group of 150 logs that were inoculated in 2015, before the current project began. Results of irrigation were mixed – irrigation did not seem to affect the period of time take for a log to fully fruit, but the quality of fruits grown under irrigation was clearly higher, both in terms of size of individual mushrooms and their texture, density and visual appeal.
Education & Outreach Activities and Participation Summary
A presentation will be made at the NOFA winter conference on February 18th 2018, and a webinar will be held for other shiitake growers in February too.
Gained awareness that small amounts of watering fruited logs can improve size, texture and appearance of shiitake
The project has shown that while irrigation does not noticeably concentrate the fruiting period of cold weather shiitake, it can improve size and quality of fruit, particularly during dry and or windy weather, by helping conserve moisture in the fruit, particularly in conjunction with shade cloth and fruiting blankets. Whether or not this will have wide applicability is unknown, but I will be circulating results of the project among existing growers, and presenting at the NOFA winter conference and will ask for feedback on whether other growers have a problem with fruits drying on logs before becoming fully formed.