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Plant Physiology Research

Plant Physiology Research Agenda 2016:

Peter Jeranyama

  1. Irrigation water management and Tile drainage. Irrigation scheduling continues to be a major challenge in cranberry production. Many growers tend to rely on the 1 inch per week “rule” from rain and irrigation despite evidence that in most years this results in some weeks with inadequate water and others with excess. This project tested wireless tensiometers, non-digital tensiometers and farmer practice for irrigation management. When the tensiometer was used to decide when to water, irrigation was initiated only when the tension reading was -5 kPa and stopped at -2kPa. The grower method of 1 inch per week was used as control. In each method, volumetric moisture sensor readings were taken and canopy temperatures were continuously monitored using a data logger. Cranberry plant density and yield components were measured.  The results showed that the grower practice had tension readings of -2 kPa or less and consistently wetter than the tensiometer method. On average, the volumetric water content of grower practice was 26 % and 17 % with the tensiometer method. Fruit rot was 7% higher and yield was 24% lower under the grower practice relative to the tensiometer method. It is highly likely that irrigation based on detecting available moisture in the soil and irrigating only when the moisture is inadequate to support plant growth results in better cranberry yield and less fruit rot.

     Effect of average soil tension in July and August on cranberry fruit yield  
    Fig 1. Effect of average soil tension in July and August on cranberry fruit yield

    Volumetric water content distribution during berry formation on a bog in Carver, MA
    Fig 2.  Volumetric water content distribution during berry formation on a bog in Carver, MA
  2. Irrigation cycling in cranberry frost protection: The objectives of this project are to (i) demonstrate the efficacy of automated irrigation cycling for cranberry frost protection by evaluating cranberry buds for frost damage following frost events with cycling implemented (ii) determine the effective set points for automated frost cycling by evaluating several options selected from grower experience and the literature on the science of frost protection, (iii) quantify the amount of water applied and fuel used during the evaluated cycling protocols for both mild and severe frost events and compare to water use in a non-cycled protocol, (iv) field test various sensors and compare temperature measurements of the bud/canopy and (v)synthesize the information gathered and develop BMP guidance for the use of automated irrigation cycling in cranberry frost protection.
  3. Sun scald Research. High summer temperatures (> 95oF) could potentially cause physiological stresses on cranberry vines. If these high temperatures occur during fruit set, sun scalding could result and further weaken the immunity of the fruit/vines so that they become more susceptible to fruit rot.  Other possible physiological stresses that could occur include cessation of cell expansion, cell wall synthesis, poor stomatal conductance and low photosynthesis rates that in turn affect fruit yield. Plants in general have a cooling mechanism of hydrating themselves through a process called transpiration. Could it be possible that the transpiration process is inadequate to cool the vines? If so, can in-day brief sprinkling through the irrigation system be a solution. What are the temperature ranges that should be used to decide when to initiate and when to stop the sprinkling without wetting the vines to the extent of encouraging fruit rot pathogens? This project seeks to compare a pre-dawn irrigation event in anticipation of a hot summer day versus in-day brief sprinkling of the vines to avoid sun scald on developing fruit.