Cattle excreta and nitrogen fertilizer deposited on tropical grasslands are important sources of ammonia (NH3 ) emission. We conducted three field trials (wet, intermediate, and dry conditions) to quantify the NH3 emissions from urea fertilizer and simulated excretions of heifer urine and dung on warm-climate grasslands in Brazil. Heifer excreta were derived from pastures of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster cv. 'Marandu'] under three forms of N supply [without or with N-fertilization (0 or 150 kg N ha-1 yr-1 ) or mixed with forage peanut (Arachis pintoi cv 'Amarillo')]. Cumulative NH3 -N emission across rainfall conditions ranged between 7.6 to 16.6% (mean 11.7%) for urine, 1.4 to 2.9% (mean 2.0%) for dung, and 11.2 to 20.5% (mean 14.8%) for urea. Ammonia loss from urine was significantly greater than from dung under all rainfall conditions. Emission from urine and dung differ from those when urea was applied on palisadegrass. There were greater NH3 emissions from urine in the wetter times of the year. Heifer excreta from N-fertilized pasture had greater NH3 emission than excreta from the grass-legume mixture and unfertilized palisadegrass. Urea applied on palisadegrass presented greater NH3 emissions in the wet rainfall conditions compared with the dry, but did not differ from the intermediate conditions. Our study showed that N-fertilized systems increases N losses as NH3 emission from excreta, and emissions from urea fertilizer must be included in this system. Heifer excreta and urea fertilizer deposited on warm-climate grasslands increased the NH3 emission mainly under the wet conditions. This article is protected by copyright. All rights reserved.

中文翻译：

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氮供应和降雨影响奶牛排泄物的氨排放和应用于温暖气候牧场的尿素

热带草原上沉积的牛粪和氮肥是氨（NH3）排放的重要来源。我们进行了三项田间试验（潮湿、中度和干燥条件），以量化尿素肥料的 NH3 排放以及巴西温暖气候草原上的小母牛尿液和粪便的模拟排泄。小母牛排泄物来自栅栏草 [Urochloa brizantha (Hochst. ex A. Rich.) RD Webster cv. 'Marandu'] 在三种施氮形式下[不施氮或施氮（0 或 150 kg N ha-1 yr-1）或与饲料花生混合（Arachis pintoi cv 'Amarillo'）]。降雨条件下的累积 NH3 -N 排放范围为尿液的 7.6% 至 16.6%（平均 11.7%）、粪便的 1.4% 至 2.9%（平均 2.0%）和尿素的 11.2% 至 20.5%（平均 14.8%）。在所有降雨条件下，尿液中的氨损失明显大于粪便中的氨损失。尿液和粪便中的排放与将尿素施用于栅栏时的排放不同。在一年中较潮湿的时期，尿液中的 NH3 排放量更大。来自施氮牧场的小母牛排泄物比来自草豆科植物混合物和未施肥的栅栏草的排泄物具有更大的 NH3 排放。与干燥条件相比，在湿雨条件下，在栅栏上施用尿素会产生更多的 NH3 排放，但与中间条件没有区别。我们的研究表明，施氮系统会增加 N 损失，因为排泄物中的 NH3 排放必须包括在该系统中。温暖气候草地沉积的小母牛排泄物和尿素肥料主要增加潮湿条件下的NH3排放。本文受版权保护。版权所有。