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Disproportionately high N-mineralisation rates from green manures at low temperatures – implications for modeling and management in cool temperate agro-ecosystems

机译：低温下绿肥中氮矿化的比例过高-对凉爽的温带农业生态系统的建模和管理的影响

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We examined the decomposition of Medicago lupulina, Melilotus alba and Poa pratensis at 3, 9, and 25 °C during 4 weeks. There was a strong temperature effect on the rate of CO2 evolution, and thus the extent of energy exhaustion from the added substrates. However, there was no concomitant retardation of N mineralisation at low temperatures. In the analysis of variance of mineralized N the residue type gave a 10 times larger contribution to the regression than the temperature (T), whereas for CO2 evolution residue type and temperature were equally important contributors. This indicates that although the temperature has a statistically significant effect on N-mineralisation it is substantially less than compared with the effect on carbon mineralisation in the materials examined. The retardation of carbon mineralisation was least strong in Melilotus alba that had a relatively low cellulose content, and a higher content of low molecular compounds. Though more research will be necessary to consolidate and explain this phenomena, it is likely that an important factor is a decrease in the bioavailability of C-rich polymers at low temperatures, and thus a preferential utilization of N-rich low molecular substances. Nitrification was not effectively deterred at 3 °C. Thus, in terms of management, it is pertinent to reconsider the timing of green manure and catch crop incorporation in cool temperate climate regions, since the rapid release of nitrogen, coupled with the relatively undeterred nitrification may result in a high N leaching risk by early incorporation, but a low risk for N immobilization at late incorporation, if N rich residues are used.
机译：我们在4周内于3、9和25°C下检查了紫花苜蓿，白苜蓿和南美大草原的分解。温度对CO 2释放速率有很强的影响，因此能量从添加的底物中耗尽。但是，在低温下没有伴随的N矿化延迟。在分析矿化氮的方差时，残留物类型对回归的贡献比温度（T）大10倍，而对于CO2演化，残留物类型和温度是同等重要的贡献者。这表明，尽管温度对氮矿化有统计学上的显着影响，但与所研究材料对碳矿化的影响相比，其影响要小得多。碳白化的延迟在具有相对较低的纤维素含量和较高的低分子化合物含量的白蜀葵中最弱。尽管需要更多的研究来巩固和解释这种现象，但重要的因素可能是富含C的聚合物在低温下的生物利用度降低，因此优先利用富含N的低分子物质。在3°C下不能有效阻止硝化作用。因此，在管理方面，有必要重新考虑在凉爽的温带气候区绿肥和捕获农作物的时机，因为氮的快速释放以及相对未抑制的硝化作用可能导致早期氮的高浸出风险。掺入，但如果使用富含N的残基，则后期掺入N的风险较低。

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