Reliable and valid information about plant water status is a critical input variable for optimizing citrus orchard growth. Precisely managing citrus water stress during all phenological stages enables maximized production by: avoiding drought stress during flowering and fruit sets; achieving appropriate sugar levels; and maintaining fruit quality by, for example, avoiding peel creasing for example.

Controlled water status can best be precisely achieved by monitoring the Stem-Water Potential (SWP) values regularly. After five  successful years of experimentation and development, Saturas’ Stemsense^TM sensors were installed in mature commercial citrus orchards around the world, and at the leading research phytotron in Israel.

This paper provides a brief overview of three commercial case studies in China, Spain and Israel and results from the experimental phtotron in Israel.

China layout

Three  Saturas Stemsense^TM sensors were installed in an OR (Clementine) citrus orchard in the Hongjing farm, China. The Stemsense^TM sensors were installed randomly in the orchard to represent the whole orchard status. The Stemsens^TM sensors measured daily mid-day SWP values.

Results and conclusions

Figure 1 illustrates seasonal values of Saturas Stemsense^TM mid-day  SWP values, daily ET₀ and irrigation volume. Of note, is the positive and significant response to irrigation and changes in evapotranspiration. Note, for example,  the rain stoppage from Aug 23^th  to Aug 30^th, as reflected by the gradually increasing SWP values.

Figure 1 – Seasonal values of Saturas’ Stemsense^TM Mid-Day SWP values, daily ET₀ and irrigation volume.

Spain layout

Five Saturas Stemsense^TM sensors were installed in a lemon orchard in the Velcarda farm, Spain.

The Stemsense^TM sensors were installed randomly in the orchard to represent the whole orchard status. The Stemsense^TM sensors measured daily mid-day SWP values.

Results and conclusions

Figure 2 illustrates seasonal values of Saturas Stemsense^TM mid-day  SWP values, daily ET₀ and irrigation volume. The Saturas Stemsense^TM sensors showed a highly correlative response to irrigation and changes in evapotranspiration Note, for example, the increase in SWP values during late July- early Aug, the influence of the small irrigation on Aug 2^nd, and the response of the trees to the regular irrigation started on Aug 13^th.

Figure 2 – Seasonal values of Saturas’ Stemsense^TM Mid-Day SWP values, daily ET₀ and irrigation volume.

Israel –  layout

Six Saturas Stemsens^TM sensors were installed in a Michal (Clementine) citrus orchard in the Gvaot HaHoresh farm, Israel. The Stemsense^TM sensors were installed randomly in the orchard to represent the whole orchard status. The Stemsens^TM sensors measured daily mid-day SWP values.

Results and conclusions

Figure 3 illustrates the seasonal values of Saturas Stemsense^TM mid-day SWP values, manual pressure chamber measurements, daily ET₀ and irrigation volumes. The sensors showed highly correlative response to irrigation and changes in evapotranspiration, and a positive correlation to manual pressure chamber measurements.

Figure 3 – Seasonal values of Saturas Stemsense^TM Mid-Day SWP values, manual pressure chamber measurements, daily ET_0, and irrigation volume.

Phytotron –  layout

Six Saturas Stemsense^TM sensors were installed in lemon trees grown in a controlled growing room in Saturas’ experimental facility in Israel.
This facility enables us to broaden our knowledge on sensor performance In a controlled environment. Saturas always tests new designs in the phytotron to validate the performance of the sensors. After finding for reliability, internal validity and replicability, Saturas installs a representative number of units in the experimental outdoor plot to  monitor, analyze and evaluate the performance of the sensors in outdoor conditions. This stage contains both drought trials and frequent manual pressure chamber measurements.

Figure 4 illustrates the seasonal values of Stemsense^TM mid-day SWP values, manual pressure chamber measurements and irrigation volume. The trees were irrigated weekly to examine the changes in SWP  values, and the response time and correlation to manual pressure chamber measurements.

Results and conclusions

Saturas Stemsense^TM sensors showed a very rapid response to irrigation and a positive and significant correlation to manual pressure chamber measurements.

Figure 4 – Seasonal values of Saturas Stemsense^TM Mid-Day SWP values, manual pressure chamber measurements_,and irrigation amounts.

Conclusions

The StemSense^TM sensors, in these four case studies, demonstrated high measures of correlation to environmental stimuli such as ET, precipitation and irrigation while delivering reliable and valid SWP values over time. The commercial utility of StemSense sensors is mutli-layered. The specific result of these studies demonstrates that the Saturas StemSense^TM sensors contributes reliable and valid information to the grower, critical for making good decisions for scheduling irrigation.
In addition, the experimental and commerical aplications demonstrated a high correlation to manual pressure chamber measurements. Replicability of experimental outcomes has allowed Saturas to expand into the apple, avocado, cherry, almond, kiwi, vine markets.  For more information visit Saturas Ag.