松嫩平原西部盐碱地紫花苜蓿产量和品质对刈割频次与施肥的响应

为探讨刈割频次、施肥以及二者交互作用对轻度盐碱地紫花苜蓿产量和品质的影响，采用以刈割频次（1、2、3、4次）为主处理，施肥（对照；施N肥；施P肥；施NPK复合肥）为副处理的双因素裂区试验进行研究。结果表明：同一生长季内，随着刈割频次的增加紫花苜蓿干草产量显著增加（P<0.05），3次与4次刈割分别比1次刈割增产123.8%和131.6%；施肥对干草产量无显著影响，而刈割频次与施肥的交互作用对干草产量具有显著影响（P<0.05），刈割3次并添加NPK复合肥处理的干草产量最高。刈割频次和施肥对紫花苜蓿营养品质具有不同程度的影响，二者交互作用仅对粗蛋白含量具有显著影响（P<0.05）。随着刈割频次的增加，紫花苜蓿茎叶比下降，粗蛋白、粗灰分含量和K⁺/Na⁺显著增加（P<0.05），粗脂肪和粗纤维含量显著降低（P<0.05），Ca²⁺含量先增加后降低，Ca²⁺/Na⁺则表现出先升高后稳定的趋势。施NPK复合肥使苜蓿粗蛋白和粗脂肪含量显著增加，粗纤维含量显著降低（P<0.05）。刈割频次对第二年返青率具有显著影响（P<0.05），4次刈割明显降低了苜蓿的存活率，返青率仅为12.5%，显著低于其他处理。研究表明，在松嫩平原轻度盐碱地种植紫花苜蓿，每年刈割3次并施用NPK复合肥为最佳管理方式。

Response of alfalfa yield and quality to mowing frequency and fertilization in saline-sodic land of the western Songnen Plain

To explore the effects of mowing frequency, fertilization, and their interaction on the yield and quality of alfalfa(Medicago sativa) in light saline-sodic soils, a field experiment with a split-plot design was conducted in the western Songnen Plain. The mowing frequency treatment plot(once, twice, three, and four times per year) was used as the main plot and the fertilization treatment plot(CK, N, P, and NPK) was the secondary plot. The results showed that the hay yield of alfalfa increased significantly(P<0.05) with mowing frequency increasing in the same growing season; when mowing frequency was 3 times and 4 times, the hay yield increased by 123.8% and 131.6%, respectively, compared with that of mowing once. Although the effect of fertilization on the hay yield was not significant, the interaction between mowing frequency and fertilization was significant(P<0.05). The hay yield was the highest when mowing occurred thrice and the NPK compound fertilizer was added. Mowing frequency and fertilization had different influences on the nutritional quality of alfalfa and the effect of their interaction on the crude protein content was also significant(P<0.05). With the increase in mowing frequency, the stem-leaf ratio of alfalfa decreased; the content of crude protein, content of crude ash, and ratio of K⁺/Na⁺ increased significantly(P<0.05). The content of crude fat and content of crude fiber decreased significantly(P<0.05); the content of Ca²⁺ increased first and then decreased; and the ratio of Ca²⁺/Na⁺ tended to increase first and then stabilize. Application of NPK compound fertilizer significantly increased the content of crude protein and content of crude fat of alfalfa and decreased the content of crude fiber(P<0.05). Notably, the mowing frequency decreased the greening rate of alfalfa in the second year(P<0.05), and the greening rate of alfalfa decreased significantly when mowing frequency reached 4 times than that of the other treatments, which was only 12.5%. Therefore, mowing thrice and applying NPK compound fertilizer in the same growing season was determined as the optimal management strategy when planting alfalfa in the light saline-sodic soils of the Songnen Plain.