Potassium Management Under Water Stress in California Crop Production
In recent years, the drought ravaging California (DWR. 2016) has imposed various challenges to farmers across the state, ranging from loss of acres planted to plant death. Water stress can have detrimental effects on crop physiology such as decreased vegetative growth and reproductive processes, leaf injuries and induced abscission, reduced fruit set/loss of yield, decreased water potential, reduced stomatal conductance and decreased CO2 and gaseous processes (i.e. influences RUBISCO and ethylene biosynthesis, specifically the carboxylase portion) (Iglesias, 2007). In recent years, agronomic techniques have been incorporated into farming systems to alleviate the effects of water stress on crop physiology.
Potassium plays an important role in the development of roots and proper function of stomates in crops (IPNI. 1998; Garcia-Tejero et al., 2010). The development of an adequate root system is essential in the anchoring of tree crops and the uptake of nutrients and water. Under soil water deficit, crops tend to search for moisture at lower soil depths due to the lack of soil moisture at shallow soil depths (Goldhammer and Fereres. 2005). Thus, developing an adequate root system can assist in alleviating the negative physiological impact water deficit can have in crops. Furthermore, the stomates are essential in respiration by opening and closing during high and low transpiration demand. In turn, potassium plays an essential role in the functionality of the guard cells surrounding the stomates. When stomates open, potassium decreases the water potential of stomates, and water enters the guard cells. When stomates close, potassium and water exits the guard cells (Figure 1) (Daszkowska-Golec and Szarejko, 2013). Under potassium deficiency, this process can become less efficient and potentially lead to excessive loss of water. Moreover, potassium provides turgidity during photosynthesis and elevated stress. In order to allow for greater plant water-use efficiency during periods of high stress, adequate levels of potassium is important (Garcia-Tejero et al. 2010).
Adequate levels of potassium can help develop a rich root density system, which in turn, can allow for greater soil moisture uptake from deep soil depths. Potassium also plays a fundamental function in stomatal conductance, allowing for the preservation of water under stress (transpiration). Ultimately, water stress can vary in the extent of damage it will have on crop physiology as different environmental factors such as topography, temperature, crop cultivar, cultural practices and pest pressure can add additional stress on crops. The use of potassium, along with good management practices, can be a tool in limiting physiological damage.
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- Nate Mendez, Crop Advisor