Lawns in the cool-humid region typically consist of mixtures or blends of cool-season turfgrass species and cultivars. To maintain a desirable aesthetic appearance and maximize seasonal greenness, many lawns receive supplemental irrigation. Turfgrass breeders have developed superior cultivars with reduced water needs, but the exact proportion of these grasses to include in lawn seed blends to reduce irrigation needs has not been well documented. A field study was conducted to determine the irrigation requirements of various blend ratios (0, 25, 50, 75, and 100%, w/w) of drought-tolerant (DT) and drought-susceptible (DS) Kentucky bluegrass (Poa pratensis L., KBG) and turf-type tall fescue [Schedonorus arundinaceus (Schreb.) Durmort., syn. Festuca arundinacea Schreb.; TF] cultivars at two mowing heights (5.1 or 8.9 cm). Supplemental irrigation requirements were determined over a 74-d deficit irrigation period using a 70% green coverage threshold (GCT₇₀) approach, where 12.7 mm of supplemental irrigation was applied if an individual plot fell below GCT₇₀ using digital image analysis. Total irrigation needs ranged from 66.7 to 176.9 mm, and TF generally required the least irrigation. For KBG, a blend containing ≥75% DT cultivar required the longest time to reach GCT₇₀ (25–33 d), the least irrigation (94–110 mm), and provided the highest overall visual quality. The TF responses were more variable, and the magnitude of differences among cultivar blends was less compared with KBG. These results indicate that where blending of cultivars is desired, the inclusion of cultivars with demonstrated drought tolerance in blends is important for reducing lawn irrigation needs.

中文翻译：

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北部过渡区肯塔基兰草和高羊茅混合物的最低灌溉要求

凉爽潮湿地区的草坪通常由凉爽季节草坪草品种和栽培品种的混合物组成。为了保持理想的美学外观并最大限度地增加季节性绿化，许多草坪接受了补充灌溉。草坪育种者已经开发出需水量减少的优良栽培品种，但这些草在草坪种子混合物中包含的确切比例以减少灌溉需求尚未得到充分记录。进行了一项实地研究，以确定耐旱 (DT) 和易旱 (DS) 肯塔基早熟禾 ( Poa pratensis ) 的各种混合比例（0、25、50、75 和 100%，w/w）的灌溉需求L., KBG) 和草皮型高羊茅 [ Schedonorus arundinaceus (Schreb.) Durmort., syn. 羊茅施雷布。TF] 两种割草高度（5.1 或 8.9 厘米）的栽培品种。补充灌溉要求是使用 70% 绿色覆盖阈值 (GCT ₇₀ ) 方法在74 天亏缺灌溉期间确定的，如果单个地块使用数字图像分析低于 GCT _70，则应用 12.7 毫米的补充灌溉。总灌溉需求范围从 66.7 到 176.9 毫米，TF 通常需要最少的灌溉。对于 KBG，含有 ≥75% DT 品种的混合物需要最长时间才能达到 GCT ₇₀（25-33 天），最少的灌溉（94-110 毫米），并提供最高的整体视觉质量。TF 响应变化更大，与 KBG 相比，品种混合之间的差异幅度较小。这些结果表明，在需要混合栽培品种的情况下，在混合品种中加入具有耐旱性的栽培品种对于减少草坪灌溉需求很重要。