Halo‐hydromorphism limits productivity in approximately 100 million hectares worldwide. Tall wheatgrass (Thinopyrum ponticum) is a species widely used in these environments for its seeding potential, being the addition of nitrogen a considered technological tool to increase forage quality and production. The objective of the study was to determine the impact of nitrogen fertilization on the capture and use of resources (radiation, water and nitrogen) in a cool season perennial sward growing in contrasting halo‐hydromorphic conditions. Cultivated pastures from three independent sites were used. Sites were described according to the degree of halo‐hydromorphism using soil salinity and water table attributes (salinity and depth) as environmental indicators: low HHM site [electrical conductivity (EC1:2.5) 0.97 dS/m; water table salinity 2.03 dS/m; depth 85 cm], intermediate HHM site (EC1:2.5 3.86 dS/m; water table salinity 7.40 dS/m; depth 134 cm) and high HHM site (EC1:2.5 4.49 dS/m; water table salinity 7.85 dS/m; depth 31 cm). At each site, a late spring regrowth (~750°Cd) was studied by applying two treatments (n = 5): without (N0) and nitrogen fertilization (N150; 150 kg/ha of nitrogen in the form of urea). The response of tall wheatgrass to nitrogen fertilization in halo‐hydromorphic conditions depends on soil salinity and water table attributes. N150 treatments production was twice as high as in N0 in low HHM and intermediate HHM environments (from 1750 to 3500 kgDM/ha and from 1080 to 1985 kgDM/ha, respectively). Meanwhile, in high HHM conditions, forage production was only 40% higher when nitrogen was added (from 625 to 870 kgDM/ha). In low HHM the higher N150 production was related to tiller density and size, whereas in intermediate HHM and high HHM was linked only to tiller size. In N150 treatments, the nitrogen nutrition index was negatively affected with the increase in HHM conditions (0.77, 0.62 and 0.55 for low HHM, intermediate HHM and high HHM, respectively). Instead, nitrogen nutrition index of N0 was similar in all the environments (~0.42). In N150, forage production capacity analysed in terms of radiation and water use efficiency (RUE and WUE, respectively) was similar in low HHM and intermediate HHM environments (RUE ~0.81 gDM/Mj and WUE ~13 kgDM/mm). These findings emphasize the importance of conducting analyses based on resource use and capture to understand productive responses to the increase in growth‐limiting factors. Furthermore, they contribute to the identification of environments suitable for nitrogen fertilization.

中文翻译：

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晕环水态改变高小麦草牧场的氮肥反应：资源的捕获和利用、分蘖动态和饲料生产

晕水态现象限制了全球约 1 亿公顷土地的生产力。高大的小麦草（偃麦草）是一种因其播种潜力而在这些环境中广泛使用的物种，添加氮是提高饲料质量和产量的公认技术工具。该研究的目的是确定氮肥对在对比晕水形态条件下生长的冷季多年生草丛中资源（辐射、水和氮）的捕获和利用的影响。使用来自三个独立地点的耕种牧场。使用土壤盐度和地下水位属性（盐度和深度）作为环境指标，根据晕水形态程度来描述地点：低HHM位点[电导率（EC1:2.5）0.97dS/m；地下水位盐度2.03 dS/m；深度85厘米]，中间HHM站点（EC1:2.53.86dS/米；地下水位盐度7.40 dS/m；深度 134 厘米）和高HHM位点（欧共体1:2.54.49 分秒/米；地下水位盐度7.85 dS/m；深度 31 厘米）。在每个地点，通过应用两种处理方法来研究晚春再生（~750°Cd）（n= 5)：没有（N0）和氮肥（N150；150公斤/公顷尿素形式的氮）。在晕水形态条件下，高小麦草对氮肥的响应取决于土壤盐度和地下水位属性。 N150处理的产量是N0处理的两倍低HHM和中间HHM环境（分别为 1750 至 3500 kgDM/ha 和 1080 至 1985 kgDM/ha）。与此同时，在高HHM在这种条件下，添加氮（从 625 公斤干物质/公顷增加到 870 公斤干物质/公顷）时，草料产量仅增加了 40%。在低HHMN150 产量较高与分蘖密度和大小有关，而在中间HHM和高HHM仅与分蘖大小相关。在N150处理中，随着HHM条件的增加，氮营养指数受到负面影响（0.77、0.62和0.55）低HHM,中间HHM和高HHM， 分别）。相反，N0 的氮营养指数在所有环境中都相似（~0.42）。在 N150 中，根据辐射和水分利用效率（分别为 RUE 和 WUE）分析的草料生产能力与低HHM和中间HHM环境（RUE ~0.81 gDM/Mj 和 WUE ~13 kgDM/mm）。这些发现强调了基于资源利用和捕获进行分析的重要性，以了解对增长限制因素增加的生产性反应。此外，它们有助于确定适合氮肥施肥的环境。