Rhizodeposition of nitrogen by red clover, white clover and ryegrass leys
Rhizodeposition of nitrogen by red clover, white clover and ryegrass leys
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DOI：
10.1016/s0038-0717(00)00183-8
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发表时间：
2001-04
影响因子：
9.7
通讯作者：
H. Høgh-Jensen;J. Schjoerring
中科院分区：
文献类型：
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作者：
H. Høgh-Jensen;J. Schjoerring
正确评价草地氮素的根际沉积对评价豆科植物的生物固氮作用、农业生态系统的氮素平衡以及草地的前茬价值都是至关重要的。使用叶饲技术，植物在田间的Mezotron中生长时被标记为15 N，在两个完整的生长季节中，未施肥的红三叶草、白色三叶草和多年生黑麦草在纯林中生长的N根沉积分别为64、71和9 gNm −2。与黑麦草混合生长的红三叶草和白色三叶草的相应值分别为89和32 gNm −2。根沉积的N化合物，包括细根，构成了80%以上的总植物来源的N在土壤中，并在所有情况下，超过了本残茬中的N量。在红三叶-黑麦草和白色三叶-黑麦草混播以及红三叶、白色三叶草和黑麦草纯林中，两个生产年度的根系沉积量分别比收获的新梢全氮增加1.05、1.52、1.26、2.21和2.77倍。在纯林和混合物的三叶草，84和92%，分别来自生物固氮。可以得出结论，根沉积提供了一个非常可观的输入N豆科草地系统生态系统N平衡和周转的后果。此外，大气来源的N在根沉积物的量可能超过在收获的枝条。
Correct assessment of the rhizodeposition of N in grassland is essential for the evaluation of biological N2-fixation of legumes, for the total N balance of agro-ecosystems, and for the pre-cropping value of grasslands. Using a leaf-feeding technique by which plants were15N labelled while growing in mezotrons in the field, the rhizodeposition of N by unfertilised red clover, white clover and perennial ryegrass growing in pure stands was shown to amount to 64, 71 and 9gNm−2, respectively, over two complete growing seasons. The corresponding values for red clover and white clover growing in mixtures with ryegrass were 89 and 32gNm−2, respectively. The rhizodeposited N compounds, including fine roots, constituted more than 80% of the total plant-derived N in the soil, and in all cases exceeded the amount of N present in stubble. In the mixtures of red clover–ryegrass and white clover–ryegrass and the pure stands of red clover, white clover and ryegrass, respectively, the rhizodeposition constituted a 1.05, 1.52, 1.26, 2.21 and 2.77 fold increase over the total N in the shoots harvested during the two production years. In pure stands and mixtures of clover, 84 and 92%, respectively, of this N derived from biological N2fixation. It is concluded that rhizodeposition provides a very substantial input of N to the legume-based grassland systems with great consequences for ecosystem N balance and turnover. Furthermore, the amount of atmospheric-derived N in the rhizodeposits may exceed that in the harvested shoots.