¹⁵N Study on the Fate of Foliarly Applied Urea Nitrogen in Tea Plant (Camellia sinensisL.)

The foliar absorption of urea‐n by Kentucky bluegrass turf

“…Roots may have a lower requirement for N, as indicated by the percent reduced N in the roots vs. shoots and leaves ( Table 4). The percent of absorbed N translocated to the roots in this study, averaging approximately 15%, is similar to the value (10% to 12%) reported for olive following foliar application of urea (17) but considerably greater than the 2% or less recovered in the roots of soybean (13,14) and tea (12 15 N analysis) was 60% and 47% of the 5 g N m~2 application for the plus-N and minus-N bluegrass, respectively. Assuming that the urea is not washed off the foliage and into the soil by rain or irrigation, as much as half of the applied urea-N could conceivably be lost from the turf system with subsequent mowing and removal of leaf clippings.…”

“…Nitrate concentrations were essentially constant over the 48 hr period in all tissues escept the N-replete leaves, in which NC>3~-N decreased by approximately one third. DISCUSSION Previous studies on the uptake of foliar applied urea have estimated absorption by (a) a washing procedure to measure the urea remaining on the foliage (1,2,5), (b) increases in tissue N (7), and (c) use of •*• N-labelled urea to quantify absorption(11,12,13,14).The results of this investigation indicate that, at least for Kentucky bluegrass, estimates of foliar N absorption by washing do not agree with uptake determined by •*• N analysis. The overestimation of urea uptake by the washing method in these experiments is most likely due to volatile loss Downloaded by [University of Auckland Library] at 12:16 22 March 2015…”

Role of Foliar Fertilization on Plant Nutrition

“…According to Nakagawa et al (1981), theanine and arginine are the predominant amino acids of the tea leaves and they are responsible for the good quality of green tea. Karasuyama et al (1985) traced the pathway of foliar-applied [ 15 N]urea in tea plants and found that it is assimilated into glutamine first and then to other amino acids. Arginine synthesized from urea-N is accumulated in the leaves, but theanine synthesis is much less.…”

Absorption of foliar-applied urea-15N and the impact of low nitrogen, potassium, magnesium and sulfur nutritional status in tea (Camellia sinensisL.) plants

“…Some previous works revealed the importance of sufficient and balanced nutrition, with an emphasis on N and other nutrients including K, Mg and S (Ruan et al 1998(Ruan et al , 2013. Urea applied to mature leaves of tea plants is readily absorbed and assimilated into amino acids, caffeine and protein in the young shoots (Karasuyama et al 1985). Therefore, foliar urea application provides an alternative fertilization strategy minimizing the potential risk of nutrient leaching loss compared with conventional soil fertilization (Gooding and Davies 1992;Dong et al 2005).…”