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Increasing periods after seeding under twice‐annually harvested alfalfa reduces soil carbon and nitrogen stocks in a semiarid environment
Land Degradation & Development ( IF 4.7 ) Pub Date : 2020-02-28 , DOI: 10.1002/ldr.3592
Wei Wang 1, 2 , Zheng‐Guo Cheng 1 , Meng‐Ying Li 1 , Bao‐Zhong Wang 1 , Ji‐Yuan Li 1 , Wei Wang 1 , Yong‐Zhong Su 2 , Asfa Batool 1 , You‐Cai Xiong 1
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It is unclear how multi‐year planting of alfalfa affects soil carbon and nitrogen stocks. We investigated alfalfa fields which had been seeded at the start of the first year and then harvested twice a year for 2, 5,8, 10 and 20 years (wheat field, CK) in the semiarid Loess Plateau. In general, soil water storage tended to drop from the second to eighth year and then tended to increase in the tenth and twentieth years, displaying a V‐shaped curve. Compared with CK, soil organic carbon (SOC) under alfalfa was significantly improved at the second year. It started to decrease to the lowest level at the eighth year, and then recovered to increasing at the tenth and twentieth years. Interestingly, soil C/N ratio, microbial biomass carbon, easily oxidizable organic carbon, and high fraction organic carbon followed a similar trend as SOC did, falling to lows in the eighth year, that is, 8.28 and 18.1 mg kg−1 and 1.91 and 10.2 g kg−1, respectively. Notably, light fraction organic carbon and particulate organic carbon increased up to their highest values in the eighth year (1.78 and 2.81 g kg−1). Moreover, soil NH4+‐N, NO3‐N, and microbial biomass nitrogen fell, following a similar dynamic as SOC. It can be argued that soil C and N sequestration be were weakened in successive planting years due to enhanced mineralization rates of C and N pools. The possible mechanism causing such phenomenon is also discussed. Multi‐year planting of alfalfa reduced the soil C and N stocks; therefore, alfalfa fields should be replanted in successive years only for an optimum number of years of planting.

中文翻译:

在每年两次收获的苜蓿中播种后增加的时期会减少半干旱环境中的土壤碳和氮储量

苜蓿的多年种植如何影响土壤碳和氮储量尚不清楚。我们调查了第一年开始时播种的苜蓿田,然后在半干旱的黄土高原每年收获两次,分别收获2、5、8、10和20年(小麦田,CK)。一般而言,土壤储水量从第二年下降到第八年,然后在第十和第二十年增加,呈V形曲线。与CK相比,苜蓿第二年的土壤有机碳(SOC)显着提高。它开始下降到第八年的最低水平,然后在第十和第二十年恢复到上升。有趣的是,土壤碳氮比,微生物生物量碳,易氧化的有机碳和高比例的有机碳遵循与SOC类似的趋势,-1和1.91和10.2克千克-1 分别。值得注意的是,轻质有机碳和颗粒状有机碳增加到第八年的最高值(1.78和2.81 g kg -1)。此外,土壤NH 4 + -N,NO 3 -- N和微生物生物量氮下降,其动态与SOC相似。可以说,由于C和N库的矿化速率提高,在连续种植年中土壤C和N的固存被削弱了。还讨论了导致这种现象的可能机制。苜蓿的多年种植减少了土壤的碳和氮储量;因此,苜蓿田地应仅在最佳种植年限内连续几年进行补植。
更新日期:2020-02-28
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