An Online Platform for Sustainable Water Management for Ontario Sod Producers 2014 Season Update Kyle McFadden January 30, 2015
Overview In 2014, 26 weather stations in four configurations were installed at 18 of the 19 sod farming operations from the previous year. Comparatively, in 2013, 29 stations were installed in three configurations. One sod grower opted out; reducing the number of installations by two, and conditions prevented the installation of another station at another site. Throughout the year, one station was stolen and another was removed due to harvest. The 24 remaining stations will be left in the field over winter to monitor soil moisture until freeze-up and to measure soil moisture after the spring thaw. The spring soil moisture readings will assist in verifying the initial values for soil water balance models. The three-level soil moisture sensors, C-Probes, were replaced with a single-level soil moisture probe, Stevens probe. To address soil moisture sensor malfunctions and to reduce the number of accidents resulting in damage, a new type of soil moisture sensor was installed. The Stevens soil moisture probe replaced the C-Probe soil moisture sensor at eight sites. This probe allows for simultaneous observation of soil moisture and soil temperature. The probe is buried in the ground, with only a data cable exiting the surface. By running the cable underground to the station pole, the risk of instrument damage is greatly reduced. The Stevens probe measures soil moisture and temperature at a depth of 10 cm as it was determined that sod roots typically draw water from within 10 to 20 cm of the surface. Figure 1: 2014 station deployments, Victory Sod Wet was stolen in October, and Young Sod was removed due to harvest on October 1.
General climate observations for 2014 season Sensors were installed for the beginning of August. Although measured temperature values are only available at Full weather stations, calculated temperature maximum and minimum estimates are available to all participants. These values are intended to help growers visualize the relationship between evapotranspiration and temperature. Figure 2 outlines deviations from the 30-year normal values for maximum daily temperature, minimum daily temperature, and daily rainfall at one of the stations. Daily values are averaged and plotted in ten day periods. Figure 2: 10 Day Temperature and Rain Deviation from 30 Year Normals for a sod field Temperature and rainfall deviation from normal values indicated that May-June was wetter and warmer than normal, July-August was cooler than normal, and September-October was warmer than normal. Seasonal rainfall values indicated that the sites received more rainfall than normal, with September 11-20 cooler than normal. The comparatively cool summer temperatures combined with consistent and timely rainfall allowed for less irrigation to be applied during the season. Evapotranspiration estimation is another very useful tool in helping growers to make decisions about efficient irrigation. For www.turfmonitor.com, evapotranspiration was calculated using the Priestley-Taylor equation with a coefficient of 1.26. This equation allows an estimate of the evapotranspiration when there are a limited number of measured weather parameters, such is the case for the rain only and rain-and-soil moisture stations in this project. Ideally, the amount of evapotranspiration lost will match the amount of water gained by rainfall and irrigation to create a balanced water budget for the sod. Figures 3 and 4 compare rainfall and irrigation events to calculated evapotranspiration amounts at a station in fiveday periods from April 1 to Oct 31. Figure 6 provides a colour-coded Soil Water Balance chart for the same station. The grower applied irrigation during the periods of June 26-30, July 1-5, July 21-25, and September 1-5. These irrigation events occurred after extended periods of higher evapotranspiration than rainfall. Several periods experienced significant rainfall which replenished soil moisture lost through evapotranspiration. This station received 715.7 mm of rainfall and 76.2 mm of irrigation. Irrigation data was available from June 1 through October 31. The total evapotranspiration amount from April 1 to October 31 was 551 mm. Although the total amount of water applied exceeded the amount of water lost due to transpiration, irrigation was beneficial for sod health during June and July. 3
Figure 3: Five day Rainfall, Irrigation, and Evapotranspiration data for a sod field Figure 4: Five Day Balance of Rainfall, Irrigation, and Evapotranspiration Figure 5: Five Day coded Water Balance Chart using rainfall and ignoring irrigation 4
Soil Moisture Figure 6 shows the seasonal Soil Moisture Profile from a C-Probe at the same station as Figures 3, 4, and 5. Both Irrigation events and rainfall events are shown. The irrigation events on June 26 and July 2 penetrated to a depth of 20 cm, but did not penetrate to 30 cm. The producer used the available tools to irrigate only when necessary and only to a depth at which sod roots can use the added moisture. Figure 6: Seasonal Soil Moisture Profile for a sod field The Stevens soil moisture probe differs from the C-Probe in that only one level of soil moisture is monitored. Additionally, soil temperature is recorded simultaneously to soil moisture. Figure 7 shows the seasonal soil moisture and temperature profile at a different sod field. The distinct descending staircase pattern of crop water use is seen starting August 20 and continues to decrease until September 1. The soil moisture curve during this period begins to level starting August 31. This horizontal pattern occurs when the sod roots have used the available soil moisture and irrigation may be needed to prevent the sod from becoming dormant. Figure 7: Seasonal Soil Moisture and Temperature Profile from a Stevens Probe 5
Overview of radar performance Radar has been used as a supplementary tool for predicting rainfall amounts for the purpose of this project. The turf stations span four different radar bases: Buffalo, Cleveland, Detroit, and Fort Drum. Some of the stations are beneath one radar station, whereas others are beneath two or even three where the radars over-lap each other. In cases where the stations are beneath more than one radar, the predicted rainfall values from each radar are averaged. Figure 8 shows the total radar estimated and measured rainfall at all 26 stations from August 1 to October 31. Overall, the accuracy between radar-estimated rainfall and station measured rainfall was 74.7 %. Stations covered exclusively or jointly by Fort Drum radar had an average accuracy of 63.5 %. Stations not covered by Fort Drum radar had an accuracy of 81.8 %. In 2013, Fort Drum radar was unavailable for 21.34 % of the period from June 1 to September 30 and had an accuracy of 58.33 % over the same period. Previously, this downtime was thought to have negatively affected the accuracy of Fort Drum radar rainfall estimates. However, for the period of April 1 to October 31, 2014, Fort Drum radar experienced only 4.15 % downtime. For this same period, Fort Drum radar had an accuracy of 57.1 %. Downtime at this radar site does not explain the inaccuracy this season. It is therefore still advised that stations covered by Fort Drum radar should use radar predictions only as a supplementary tool to other weather monitoring equipment. Figure 8: 2014 Radar Estimated and Station Measured Rainfall Website Use During the period of June 16 through September 30, 2014, www.turfmonitor.com received 10774 hits. Over the same period in 2013, the website received 10662 hits, an increase of 1.01 %. From April 1 to October 31, 2014 there were 20684 total web hits. The most viewed tools on the website were Daily Rainfall Map with 14.7 % of 6
total website hits; Daily Evapotranspiration Map (13 %); Spraycast (2.7 %); 24 Hour Rainfall Map (2.4 %); and My Weather (2.1%). Last season, the top five most used tools on the website were Daily Rainfall Map with 11.9% of total hits; Evapotranspiration Map (10.5%); Livedata (5.3%); My Weather (4.3%); and Soil Moisture (2.3%). Users with a login provided 8.3 % of total page views. Water Check Book Resulting from the data collected over the past two seasons, we have developed a new Web App to assist sod growers in accessing soil moisture levels in their fields. Featuring soil water balance information and a field water check, the mobile app allows you to view site specific information to assist with determining irrigation requirements. This app features an updated evapotranspiration calculation that further refines the existing method. Calculations are driven using station data if available. When data is not available, interpolated data from nearby sources is used. Accessible from your mobile device, via www.turfmonitor.com/swb or by scanning the above QR code, the web app allows you to easily select your field based on your current location, as reported by your mobile device, or to select a specific location using the provided map. After selecting your location, you can choose to view the soil water balance or a water check of the field. Figure 9: Location Selection Screen The water check page allows you to select the date range for the period in question. This date range may include future dates as the app features a five-day forecast for rainfall and evapotranspiration. After you specify a date 7
range, daily rain and evapotranspiration values are presented in graphical and tabular form. Forecasted data, if any, is easily distinguished via shading effects on the graph and orange text in the table. You can use the historical and forecast data to aid in scheduling irrigation events. The app also offers you the climatological soil water balance for your selected field. A colour-coded soil water balance chart also provides you with the accumulated rainfall and evapotranspiration values for each five day period. Five day groupings and starting date are controlled by your specified planting date. Both the water check and soil water balance pages use a crop coefficient curve to determine crop specific evapotranspiration. The crop-coefficient method improves on the existing reference evapotranspiration calculation to provide additional accuracy to the models. Figure 10: Sample screen captures of the Water Check page (left) and Soil Water Balance page (right) Future development for the web app would include different levels of data collection to meet different budgets and data needs. No on-site station for rain data utilizes radar and data interpolation. A low cost CoCoRaHS manual rain gauge could be used to provide actual rainfall measurements for the site. Automated rainfall measurement could be provided through a WeatherFarm-Davis station, or radio-telemetry. Furthermore, a complete automated weather station with soil sensors can be used to provide data for the web app. 8
Challenges Over the course of the project, there were a few challenges that could be improved upon for future years. 1. Wet and Cool Season - This season was cool and wet, particularly in the summer time, thus many of the growers did not need to irrigate. In future years, growers who have irrigation available and are actually required to use it may benefit even more from the tools available as they learn to interpret and apply the data that is being measured. 2. Reliability of Radar While data gaps were reduced over last year, Fort Drum radar predictions were still inaccurate. Processing data from an additional radar station may improve the accuracy for stations only covered by Fort Drum radar. 3. Irrigation Log It would be useful to provide a web form where the growers could fill out the dates and approximate times that they irrigated on the field with the weather station. Although it was possible to do estimations which could then be confirmed with the grower, a log sheet would be a more efficient way of recording irrigation events. Project Outcomes & Conclusions This project contributed to the enhancement of sustainable water usage and environmental stewardship in Ontario s sod-farming industry. The site-specific weather tools delivered through the TurfMonitor.com website assisted the participating growers in making informed irrigation management decisions. Many features on the website were also openly available, providing both a service to the sod industry as a whole and an educational opportunity for the general public. A new mobile app was developed to assist sod growers in accessing soil moisture levels in their fields. Featuring soil water balance information and a field water check, the mobile app allows growers to view site specific information to assist with determining irrigation requirements. This app features an updated evapotranspiration calculation utilizing crop coefficients to further refine the existing models. The new soil moisture probe reduced the number of problems associated with soil moisture sensor malfunctions. The reduced surface exposure also minimized damage to the soil moisture sensors caused by farm equipment. Valuable benchmark data was also collected from several farms, including total amounts of water (rain and irrigation) applied along with soil moisture profiles that illustrate the effectiveness of each water event. Evapotranspiration calculations are very useful for sod growers because they serve as a water balance for their sod. Growers were able to consult the site-specific evapotranspiration calculations and graphs along with other website tools and weather data when determining required irrigation amounts. Growers should strive to replace only the water that is lost to evapotranspiration. Any water applied above this amount is likely to be unused. Actual temperature measurements were available for those participants who had a full weather station, while all other participants were provided with temperature estimates. The temperature estimates and values are presented in order to help the growers understand and visualize the direct relationship between temperature and evapotranspiration. Specifically, as the temperature increases, evapotranspiration also increases since the sod is required to uptake more water to keep from drying out quickly. This project also demonstrated the use of radar as a tool for predicting rainfall amounts. The radar estimates were generally fairly accurate, with some year-to-year variability. Accuracy was found to be highest when comparing 9
total rainfall amounts to total radar-predicted rainfall amounts. Since sod growers are aware of the sometimes imperfect predictions by radar, showing that radar can very often predict rainfall amounts to within 80-98% accuracy is a great incentive to use it as a rainfall amount prediction tool. It would be advised that areas that have found to be less accurate than this should use the radar as a supplementary tool to other weather monitoring equipment. Active website use indicates a high level of interest in the tools provided. Feedback from the participating project sod growers has been positive. Many have expressed interest in continuing participation in future seasons. The growers have said that the tools have helped them to keep an accurate record of rainfall and to estimate when and how much to irrigate in an environmentally and economically conscious manner. This project has not only benefitted the participants, but has also contributed to the sod industry and Ontario agriculture as a whole. This project has benchmarked how much water is used on 26 sod fields, and has measured the soil moisture at 11 locations. The most prominent benefit for other farming industries is the use of radar as an advisory tool to estimate rainfall quantities for a specific location, and to distinguish between rainfall and irrigation events. Overall, the level of participation and enthusiasm from sod growers is a testament to the success of this project. All working deliverables were met, and the project contributed to the improvement of environmental stewardship in Ontario by investigating tools that help make irrigation practices on sod farms more efficient. 10