Nitrogen (N) deficiency has detrimental effects on productivity and the profit of producers in areas where signal grass [ (Stapf) R.D. Webster (syn. Stapf.)] cv. Basilisk is grown for seed production. The objective of this paper was to clarify the effects of indicators of signal grass plant N status on seed yield (SY), SY components, yield formation, seed quality, panicle growth parameters, and remobilization of vegetative N on seed growth. Germinable pure SY, harvest index (HI), and N harvest index (NHI) were also measured. Different rates of N fertilizer application (0, 50, 100, and 150 kg ha) were applied after the cleaning cut to both the first crop (October - January) and the second crop (February - May) in 2010–2011 and 2011–2012, on a sandy loam soil representative of soils used for seed production in Brazil. Although the N nutrition index (NNI) increased at key developmental stages, the highest values were near to 0.85. This suggests that all crops were maintained under N-limiting conditions. In N-limited crops, a strong relationship was detected between NNI and accumulated N deficit throughout the study period with relative SY. A low NNI after the cleaning cut was found to restrict fertile tiller number (FTN), spikelets per panicle, and spikelet density m measured at anthesis. In all crops, at harvest, NNI at anthesis increased germinable pure SY, FTN, number of seeds per panicle, HI, NHI, and amount of remobilized N to seeds, but not thousand seed weight (TSW), seed germination, panicle dry matter (DM) accumulation rate, and individual seed growth rate. Regression analyses suggested that the NNI, accumulated N deficit, aboveground plant biomass (AGPB), and N content were better associated with relative SY than with plant N concentration (PNC). The study shows that the NNI quantifies the intensity and duration of N deficiency in signal grass and should be considered in research studies and for application in seed production fields to improve N fertilization recommendations.

中文翻译：

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分析和预测信号草种子作物对植物氮状况的响应


氮 (N) 缺乏会对信号草 [ (Stapf) RD Webster (syn. Stapf.)] cv. 地区的生产力和生产者利润产生不利影响。蛇怪的种植是为了生产种子。本文的目的是阐明信号草植物氮状况指标对种子产量（SY）、SY组成、产量形成、种子品质、穗生长参数以及营养氮再利用对种子生长的影响。还测量了可发芽的纯 SY、收获指数 (HI) 和氮收获指数 (NHI)。 2010-2011 年和 2011-2011 年第一茬作物（10 月至 1 月）和第二茬作物（2 月至 5 月）清刈后施用不同比例的氮肥（0、50、100 和 150 千克公顷）。 2012 年，在代表巴西种子生产土壤的沙壤土上。虽然氮营养指数（NNI）在关键发育阶段有所增加，但最高值接近0.85。这表明所有作物都维持在氮限制条件下。在限氮作物中，在整个研究期间，NNI 和累积氮亏缺与相对 SY 之间存在密切关系。发现清洁切割后的低 NNI 会限制可育分蘖数 (FTN)、每穗的小穗数和花期时测量的小穗密度。在所有作物中，收获时，花期 NNI 增加了可发芽纯 SY、FTN、每穗种子数、HI、NHI 和种子再利用 N 量，但不增加千粒重 (TSW)、种子发芽率、穗干物质(DM)积累率和个体种子生长率。回归分析表明，NNI、累积氮亏缺、地上植物生物量 (AGPB) 和氮含量与相对 SY 的相关性比与植物氮浓度 (PNC) 的相关性更好。 研究表明，NNI 量化了信号草缺氮的强度和持续时间，应在研究和种子生产领域的应用中予以考虑，以改进施氮肥建议。