Nitrogen Cycling in an Alfalfa and Bromegrass Sward via Litterfall and Harvest Losses
Nitrogen Cycling in an Alfalfa and Bromegrass Sward via Litterfall and Harvest Losses
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苜蓿和雀麦草田中的氮循环通过垃圾掉落和收获损失
DOI：
10.2134/agronj1995.00021962008700060008x
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发表时间：
1995
期刊：
影响因子：
2.1
通讯作者：
A. Slinkard
中科院分区：
文献类型：
--
作者：
G. Tomm;F. Walley;C. Kessel;A. Slinkard
地下转移的N从豆科植物相关的草已被广泛记录，但是，通过植物材料的分解和重吸收释放的N的N转移仍然知之甚少。本研究旨在（i）评估苜蓿（Medicago sativa L.）和草地雀麦（Bromus riparius Rhem.）和（ii）确定从地上植物组分转移的N的量。凋落物和收获损失进行了量化超过3年。氮转移估计使用15 N同位素稀释技术。苜蓿和雀麦通过凋落物流失向土壤归还的N分别为13和4kg N ha-1 yr-1。苜蓿通过收获损失向土壤中额外返回15 kg N ha-1 yr-1;雀麦额外贡献7 kg N ha-1 yr-1。雀麦草仍然是N 2固定苜蓿的N源，即使它是N-有限的，苜蓿成功地竞争与N-胁迫雀麦草从凋落物和收获损失的有效N。与雀麦相比，苜蓿从凋落物和收获损失中积累的氮量是雀麦的两倍（2和1 kg N ha-1 yr-1）。显然，苜蓿是有效氮的强有力的竞争者，同时也是循环氮的源和库。苜蓿和雀麦通过分解地上部分的氮素转移总量非常相似（1 kg N ha-1 yr-1）。因此，苜蓿和雀麦草之间的净流量是可以忽略不计的，并没有净N的贡献，苜蓿相关雀麦草凋落物和收获损失的分解检测。我们的结论是，虽然苜蓿释放更多的N通过分解凋落物和收获损失比雀麦，苜蓿也吸收更多的再循环N。因此，发表的估计苜蓿和雀麦之间的净N转移，不能解释的凋落物和收获损失的N输入。
Belowground transfer of N from legumes to associated grasses has been extensively documented ; however, transfer of N via decomposition of plant material and reabsorption of released N remains poorly understood. This study was conducted to (i) assess the intensity of litterfall and harvest losses of alfalfa (Medicago sativa L.) and meadow bromegrass (Bromus riparius Rhem.) under field conditions and (ii) determine the quantity of N transferred from aboveground plant components. Litterfall and harvest losses were quantified over 3 yr. Nitrogen transfer was estimated using the 15 N isotope dilution technique. The return of N to the soil via litterfall losses of alfalfa and bromegrass was 13 and 4 kg N ha -1 yr -1 , respectively. Alfalfa returned an additional 15 kg N ha -1 yr -1 to the soil via harvest losses ; bromegrass contributed an additional 7 kg N ha -1 yr -1 . Bromegrass remained a source of N to the N 2 -fixing alfalfa, even though it was N-limited, and alfalfa successfully competed with the N-stressed bromegrass for available N derived from litterfall and harvest losses. Alfalfa accumulated twice the amount of N from litterfall and harvest losses compared with bromegrass (2 vs. 1 kg N ha -1 yr -1 ). Clearly, alfalfa was a strong competitor for available N and acted as both a source and a strong sink for recycled N. The total amount of N transferred from alfalfa to bromegrass and vice versa via decomposition of aboveground plant components was found to be remarkably similar ( 1 kg N ha -1 yr -1 ). Therefore, the net flow of N between alfalfa and bromegrass was negligible, and no net N contribution of alfalfa to associated bromegrass from the decomposition of litterfall and harvest losses was detected. We concluded that, although alfalfa released more N through the decomposition of litterfall and harvest losses than bromegrass, alfalfa also reabsorbed more recycled N. Published estimates of net N transfer between alfalfa and bromegrass, therefore, could not be explained by the input of N from litterfall and harvest losses.