Abstract
A reliable method to rapidly assess the potassium (K) status of alfalfa (Medicago sativa L.) would enhance the ability of producers and crop consultants to make timely decisions regarding K fertilization. Recently introduced to the agricultural market are portable, hand‐held, ion‐specific electrodes, that allow direct measurement of K in plant sap. The objective of this study was to compare the potassium ion‐specific electrode (KSE) meter to flame photometry as a tool to estimate the K status of alfalfa. A total of 75 fields in the low deserts of California and Arizona were sampled in June and again in November‐December of 1995. Seventy‐five mid‐stems from each field were collected and chopped into 1 cm pieces. Sap was extracted from half the sample and analyzed for K concentration with the KSE meter. Sap readings were taken either immediately in the field (method 1) or after transport to the laboratory (method 2). The other half of the sample was oven dried at 60°C and analyzed for K concentration via flame photometry. Sap K concentration by method 1 was well correlated (r2=0.68) with flame photometry; field pressed, but laboratory analyzed samples (method 2) were not as well correlated. In conclusion, the KSE meter could be used as a quick and inexpensive tool to monitor the K concentration of alfalfa mid‐stems if samples are extracted and read immediately in the field.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
