Obtaining sustainable high yield and suitable soil nutrient management is crucial for cultivate alfalfa grassland. However, the information on the trade‐offs between soil nutrient and productivity of alfalfa grassland following long‐term cultivation under intensive agricultural management is scare. Six alfalfa grasslands of different ages under a highly intensive agricultural management system were chosen for this study. It was shown that long‐term planting of alfalfa reduced soil nutrients overall. In the 0–100, 100–200, and 200–300 cm layers, the highest values of soil organic carbon (SOC), soil total nitrogen (TN), and soil total phosphorus (TP) content were observed in one‐year‐old alfalfa grassland. SOC, TN, and TP contents in each 100 cm soil layers linearly declined with increasing stand age, and decreasing rates of SOC and TN (4.31 and 0.03 g kg⁻¹ yr⁻¹) in the 0–100 cm layer were higher than other two soil layers. The SOC storage (SOC_S) and TN storage (TN_S) in 0–20 cm soil were significantly higher than other soil profiles in six alfalfa grasslands of different ages. SOC_S and TN_S in 0–100 cm, especially in upper 40 cm soil, decreased over time until the fourth year, and gradually increased in the fifth and sixth years. While in the third and fourth years, productivity reached peak value (3.13 and 3.12 t ha⁻¹), and then reduced. Correlation analysis showed productivity was significantly negatively correlated with SOC_S and TN_S in 0–100 cm soil depth. The decline in soil nutrients affected alfalfa growth and then feedback its productivity, and the optimal stand age of alfalfa grasslands should not be longer than 6 years for the limitation of soil nutrient, especially SOC storage. To acquire sustainable high productivity of artificial alfalfa grassland, our study suggested that more organic and nitrogen/phosphorus fertilizers should be applied to the upper soil layer beginning in the third year after planting.

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不同年龄的苜蓿草地的牧草产量与土壤养分之间的权衡

获得可持续的高产和适当的土壤养分管理对苜蓿草地的种植至关重要。但是，关于在集约化农业管理下长期种植后苜蓿草地土壤养分与生产力之间的权衡取舍的信息很少。本研究选择了在高度集约化农业管理体系下的六个不同年龄的苜蓿草原。结果表明，长期种植紫花苜蓿总体上减少了土壤养分。在0–100、100–200和200–300厘米的层中，一年内观察到了土壤有机碳（SOC），土壤总氮（TN）和土壤总磷（TP）的最大值。老苜蓿草原。每100厘米土壤层中的SOC，TN和TP含量随着林分年龄的增加以及SOC和TN的比率降低而线性下降（4.31和0。0–100 cm层的^-1 yr ^-1）高于其他两个土壤层。在6-20个不同年龄的苜蓿草地上，0–20 cm土壤中的SOC储存量（SOC _S）和TN储存量（TN _S）显着高于其他土壤剖面。SOC _S和TN _S在0–100 cm中，尤其是在40 cm以上的土壤中，直到第四年随时间下降，并在第五和第六年逐渐增加。在第三和第四年，生产率达到峰值（3.13和3.12 t ha ^-1），然后下降。相关分析表明，生产率与SOC _S和TN _S显着负相关。在0–100厘米的土壤深度中。土壤养分的减少影响苜蓿的生长，进而反馈其生产力，并且由于土壤养分的限制，尤其是SOC的储存，苜蓿草原的最佳林分年龄不应超过6年。为了获得可持续的人工苜蓿草地高生产力，我们的研究表明，从种植后的第三年开始，应在土壤上层施用更多的有机肥料和氮/磷肥料。