Effect of nitrogen concentration of urea ammonium nitrate, and application level, on the dry matter and chemical composition of Pennisetum clandestinum and Cynodon hybrid dryland pastures

Abstract

Liaraquid urea ammonium nitrate (UAN) was applied to dryland Pennisetum clandestinum (Kikuyu (Chiov)) and Cynodon hybrid (Coastcross II (L.) (Pers.)) pastures at two levels (207 and 414 kg N/ha/season) and at three concentrations (10,5; 21 and 42% N) of nitrogen. The degree of leaf scorch increased as both the amount of N and the concentration of UAN increased, but persisted in all treatment combinations for between 10 and 14 days only. Scorch did not appear to materially affect yields measured six weeks after UAN application. Significant interactive effects were evident between the quantity of N applied and UAN concentration in estimates of yield and many of the quality factors. In general, however, herbage yield declined with increasing N concentration in the UAN at the low N (207 kg N/ha) level, but was highest at the 21% N concentration when the amount of N applied was twice this level (414 kg N/ha). Herbage N, K, Ca and Mg content generally declined as N concentration in the UAN increased, but P levels responded positively to increased UAN concentration. UAN appeared to be most effective as a nitrogen carrier when it was diluted two to four‐fold.