Abstract Plant use efficiency of applied N is estimated to be around 50 % for most crops. In coastal plain sandy soils particularly, leaching along with volatilization in warmer climates may be a predominant pathway for N loss to the environment. A replicated field study to determine both crop N requirement and recovery efficiency of N (REN) in tomatoes (var. BHN 602) grown on sandy soils under a plastic-mulched bed system was conducted in north Florida. Isotope labeled-ammonium nitrate (15NH415NO3) was applied in spring at four different N rates (0, 168, 224, 280 kg N ha−1). A subsequent study in the fall was conducted in order to determine the recovery of residual N fertilizer in tomatoes. In spring, no appreciable response to applied fertilizer N rate above 168 kg N ha−1 (lowest rate) were observed, indicating recommended N rates may be more than what is required. On average, approximately, 62 % of N accumulation in the plant came from fertilizer, whereas 38 % came from soil N. In the fall, recovery of residual 15N fertilizer at harvest ranged from 1.9 to 5.4 kg N ha−1. At the end of both studies, a 15N balance was calculated to estimate total crop and soil recovery of N fertilizer, where approximately 15.4 % of applied 15N fertilizer was recovered. Unrecovered N in this study shows that optimizing N fertilizer management in warmer climates is critical in order to avoid unnecessary excess application of fertilizer and minimize loss of N to the environment.

中文翻译：

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15N技术对沙质土壤番茄施用和残留氮肥的回收效率

摘要 对于大多数作物，施氮的植物利用效率估计约为 50%。特别是在沿海平原沙质土壤中，在温暖气候下随着挥发的淋溶可能是 N 向环境流失的主要途径。在佛罗里达州北部进行了一项重复的田间研究，以确定在塑料覆盖床系统下生长在沙质土壤上的西红柿（变种 BHN 602）中的作物氮需求量和氮回收效率（REN）。同位素标记的硝酸铵 (15NH415NO3) 在春季以四种不同的 N 比率（0、168、224、280 kg N ha-1）施用。随后在秋季进行了一项研究，以确定番茄中残留氮肥的回收率。在春季，未观察到对高于 168 kg N ha-1（最低比率）的施氮量的显着响应，指示推荐的 N 比率可能超过所需的比率。平均而言，植物中大约 62% 的氮积累来自肥料，而 38% 来自土壤 N。在秋季，收获时残留的 15N 肥料的回收范围为 1.9 至 5.4 kg N ha-1。在两项研究结束时，计算了 15N 平衡以估计氮肥的总作物和土壤恢复，其中大约 15.4% 的施用 15N 肥料被回收。本研究中未回收的氮表明，在温暖气候下优化氮肥管理对于避免不必要的过量施肥和最大限度地减少氮向环境的损失至关重要。收获时残留的 15N 肥料的回收率为 1.9 至 5.4 kg N ha-1。在两项研究结束时，计算了 15N 平衡以估计氮肥的总作物和土壤恢复，其中大约 15.4% 的施用 15N 肥料被回收。本研究中未回收的氮表明，在温暖气候下优化氮肥管理对于避免不必要的过量施肥和最大限度地减少氮向环境的损失至关重要。收获时残留的 15N 肥料的回收率为 1.9 至 5.4 kg N ha-1。在两项研究结束时，计算了 15N 平衡以估计氮肥的总作物和土壤恢复，其中大约 15.4% 的施用 15N 肥料被回收。本研究中未回收的氮表明，在温暖气候下优化氮肥管理对于避免不必要的过量施肥和最大限度地减少氮向环境的损失至关重要。