In Brazil, the livestock systems are mainly forage‐based, and nitrogen inputs are an uncommon practice, despite its great benefits. The objective was to evaluate the effect of nitrogen input on the physiological responses of Marandu palisadegrass (Urochloa brizantha [Hochst. ex A. Rich.] R. D. Webster) and Mombaça guineagrass (Megathyrsus maximus [Jacq.] B. K. Simon & S. W. L. Jacobs), and its impacts on the forage accumulation rate (FAR). The experiment was carried out in Sinop, MT, Brazil, in a randomized block design with a 2 × 2 × 5 factorial arrangement (two cultivars: Mombaça and Marandu; unfertilized and fertilized [50 kg N ha⁻¹ cycle⁻¹]; and five seasons: autumn 2015, winter 2015, spring 2015, summer 2015 and autumn 2016) with three replicates. The experimental period was from March 2015 to June 2016, when plots were harvested to mimic intermittent stocking. Fertilized Mombaça presented greater FAR pastures (74.0 kg DM ha⁻¹ day⁻¹) than unfertilized (26.6 kg DM ha⁻¹ day⁻¹) and Marandu fertilized (52.5 kg DM ha⁻¹ day⁻¹), with the greatest values during the summer (147.6 kg DM ha⁻¹ day⁻¹). The greatest leaf (A) and canopy photosynthesis (CP) rates occurred on fertilized pastures during the summer 2015 and autumn 2015. Marandu presented 19% greater A than Mombaça. During the winter, under water stress, Marandu had greater water use efficiency (WUE). However, during the summer 2015 and autumn 16, Mombaça had the greatest WUE (12.76 μmol CO₂/mol H₂O). In all seasons, Marandu presented the greatest chlorophyll index, which may support the greatest photosynthetic rates. It was concluded that Mombaça was highly responsive to nitrogen input during the rainy season with accumulation over 140 kg DM ha⁻¹ day⁻¹ and is recommended to intensified systems. Marandu had the greatest WUE in the lower precipitation seasons and is an alternative to a year‐round strategy in forage‐based systems.

中文翻译：

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巴西饲草系统中Marandu palisadegrass和Mombaca豚鼠对氮肥的生理响应和饲草积累

在巴西，牲畜系统主要以饲料为基础，尽管氮肥有很大好处，但氮肥的输入并不常见。目的是评估氮输入对Marandu palisadegrass（Urochloa brizantha [ Hochst。ex A. Rich。] RD Webster）和Mombaçaguineagrass（Megathyrsus maximus [Jacq。] BK Simon＆SWL Jacobs）生理反应的影响，以及它对草料积累率（FAR）的影响。该实验在巴西MT的Sinop以2×2×5因子排列的随机区组设计进行（两个品种：蒙巴萨和马兰杜；未受精和受精[50 kg N ha ^-1循环^-1]; 和五个季节：2015年秋季，2015年冬季，2015年春季，2015年夏季和2016年秋季），重复三遍。实验期为2015年3月至2016年6月，当时收获的土地用来模拟间歇性放养。受精的蒙巴萨羊的FAR牧草（74.0 kg DM ha ^-1 天^-1）比未受精的（26.6 kg DM ha ^-1 天^-1）和Marandu受精（52.5 kg DM ha ^-1 天^-1）更大。夏天（147.6千克DM ha ^-1 天^-1）。最大的叶子（A）和受精牧场的冠层光合作用（CP）速率发生在2015年夏季和2015年秋季。Marandu的A比蒙巴萨高19％。在冬季，在缺水的情况下，Marandu具有更高的用水效率（WUE）。但是，在2015年夏季和秋季16月，蒙巴萨的WUE最高（12.76μmolCO ₂ / mol H ₂ O）。在所有季节中，Marandu的叶绿素指数最高，这可能支持最大的光合速率。结论是，蒙巴萨在雨季对氮输入有高度响应，累积量超过140 kg DM ha ^-1 天^-1并且建议用于强化系统。Marandu在较低的降水季节具有最大的WUE，并且是基于饲草的系统中全年策略的替代方案。