Deep placement of nitrogen fertilizer in autumn improves N utilization by spring tea (Camellia sinensis L.)

Abstract

Background The efficient use of fertilizers depends very much on their proper placement, and the effects of fertilizer placement on the woody perennial plant tea (Camellia sinensis L.) are not clearly understood. Methods A 15N mini‐plot field experiment was conducted to investigate the effects of four common techniques of fertilizer placement techniques. 15N‐labeled urea was applied in October by surface broadcasting, surface broadcasting with 3–5 cm soil incorporation, shallow (3–5 cm), and deep (10–15 cm) side dressing (DSD). The proportion of N derived from 15N‐labeled fertilizer (Ndff%) was estimated in root, and soil samples were collected 15 and 43 days after fertilization (DAA15 and DAA43) and in young shoots collected in the following spring. Results Most fertilizer 15N was located in the soil near the placement position at DAA15 and 15N had moved downward but maintained a similar distribution in the soil profile at DAA43. The distribution of fibrous root Ndff% in the soil profile was very similar to that of soil Ndff%. DSD resulted in the highest shoot Ndff%, the estimated amount of 15N in young shoot derived from 15N‐label fertilizer (shoot 15N), and its percentage related to the amount of 15N‐labeled fertilizer input (REFN%). Thus, DSD of urea as basal application in autumn maintained a higher and prolonged N supply in the middle and deep soil layers, thereby improving fertilizer‐N absorption and utilization in the following spring tea. However, direct broadcasting of urea on the soil surface resulted in low N availability in the soil and utilization by tea plants. Conclusion Our results demonstrate that DSD of N fertilization should be recommended for tea planting to increase N use efficiency and reduce environmental losses in forms of runoff and volatilization.