Foliar uptake and partitioning of urea-N by strawberry plants as affected by timing of supply and plant N status

SummaryFoliar spraying with urea is not as common in strawberry as in many other perennial crops, but may be a good approach to improve plant N status if soil-N availability and/or root uptake are insufficient to meet short-term plant N demand.The aims of this work were to examine possible differences in uptake and partitioning of foliar-N applied to strawberry plants at anthesis (T0) or at first fruit ripening (FFR; T1), and to examine if the level of soil-N fertilisation in the Spring affected uptake and partitioning at FFR. Foliar-N was applied to both leaf surfaces as a 1% (w/v) urea solution, using urea enriched with 9.883 atomic % 15N. Measurements and analyses were carried out 5 d after application. At FFR, foliar-N was applied to plants that had received soil-N levels of 0, 55 or 110 kg ha–1 (N0, N1 or N2). There was an effect of leaf age on the amount of urea solution adsorbed by leaves, which was higher in older than in younger leaves. Leaf-uptake of N was lower under treatment N1 at anthesis than at FFR, when an average of 99% of applied N was taken up. This was due, principally, to differences in leaf adsorption of urea solution between the two periods, with a possible minor effect of the larger leaf area at FFR than at anthesis due to differences in accumulated soil-N of 55 kg ha–1 and 19 kg ha–1, applied by T1 and T0 in treatment N1 respectively. At FFR, soil-N supply had no effect on the ability of leaves to absorb foliar-N. Nitrogen absorbed by leaves at the beginning of fruit harvest (FFR) was partitioned, preferentially, into the fruits; while significant amounts were retained in the leaves at anthesis. In conclusion, foliar spraying with urea represents a useful technique to increase strawberry N-content in the short period reported here. The high recovery of sprayed N indicates that this is an effective way to fertilise strawberry plants as an alternative or complement to soil-N supply.