Seasonal fluctuations in the nitrogen content of the sultana vine

Abstract

Estimates were made of dry matter and nitrogen contents of parts of sultana vines sampled a t frequent intervals from October to January in one season and January to July in the following season. From early October until the commencement of leaf drop in February there was a linear increase in the amount of nitrogen in the annual aerial growth. This nitrogen was present mainly in the laminae and fruit. After February the amount of nitrogen in the fruit continued to increase while that in the leaves decreased. The loss from the leaves could be partly accounted for by translocation to fruit or woody tissues and the remainder by leaf fall. The data obtained gave no indication of the best time for applying nitrogen to sultana vines. The amount of nitrogen in stems, and also the percentage of nitrogen in trunks, main roots, and feeder roots, increased to July, which suggested that root absorption from the soil continued throughout autumn. It is suggested that the total nitrogen content of laminae gives the most reliable indication of seasonal nitrogen uptake provided that due allowance is made for time of sampling. '