Response of Cynodon dactylon (L.) Pers. to ammonium and nitrate nutrition

Bachelor Thesis


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University of Cape Town

Plants that come early in succession predominantly prefer_ ammonium form of nitrogen than nitrate. The hypothesis that Cynodon dactylon (L.) Pers., a grass in the primary succession stage would respond well when supplied with ammonium than nitrate fertiliser was tested. Seedlings of Cynodon dactylon were grown in culture solution and fertilised with either ammonium sulphate or potassium nitrate at ~ continuous concentrations of 200 ppm, 400 ppm and 600 ppm in the growth chamber. In support of my hypothesis, growth of Cynodon dactylon was greater from ammonium than nitrate nutrition in terms of aboveground and total plants yields at 200 ppm and 400 ppm and this was associated with efficient utilisation of this form of nitrogen by this species. Production from the nitrate treatments was restricted and showed no change with increase in external nitrogen supply. Decreased dry weights from the ammonium nutrition at 600 ppm were associated with toxicity of ammonium ions in plant tissues. High levels of nitrogen measured from the nitrate treatments were associated with the soluble nitrogen that was not assimilated for yield increase by this grass, Uptake of ammonium ion was shown to result· in high of uptake phosphorus. This study shows that Cynodon dactylon has the capacity for increased growth under ammonium nutrition while this was limited in the nitrate nutrition. However, response is restricted when excessively fertilised with ammonium nitrogen.