不同绿肥种植模式下玉米秸秆腐解特征研究

【目的】玉米是中国第一大粮食作物,如何处理大量的玉米秸秆成为玉米种植区面临的关键问题之一,深入研究冬种绿肥对玉米秸秆腐解释放的影响,对农业可持续发展具有重要意义。【方法】采用尼龙网袋法,通过对红壤旱地空闲 (YCK)及紫花苜蓿(YZ)、 黑麦草(YH)、 肥田萝卜(YL)绿肥种植模式下玉米秸秆177 d的腐解量和养分释放的监测,分析玉米秸秆腐解速率及碳、 氮、 磷、 钾的释放规律。【结果】四种种植模式下,玉米秸秆腐解及养分释放均呈现前期快后期慢的规律,7 d的腐解和养分释放速率均达到最大。翻压177 d时,四种种植模式下(YCK、 YZ、 YH、 YL)玉米秸秆累积腐解量分别为23.41、 21.22、 20.86和20.95 g,玉米秸秆碳累积释放量分别为12.38、 11.07、 11.18、 11.36 g ,与YCK种植模式相比,YZ、 YH、 YL种植模式秸秆累积腐解量分别显著降低了9.3%、 10.9%、 10.5%,碳累积释放量则分别显著降低了10.6%、 9.7%和8.3%; 各处理氮累积释放量分别为479.46、 513.04、 442.58和530.20 mg,相比YCK种植模式,种植绿肥对玉米秸秆氮累积释放量的影响不显著,而YH种植模式较YZ和YL种植模式则显著降低了13.7%和16.5%。各处理磷累积释放量分别为58.10、 57.91、 58.47和59.47 mg,且YL种植模式较YCK种植模式显著提高了2.35%; 翻压 28 d时,各处理钾累积释放量为487.20、 444.85、 456.94和434.55 mg,分别占加入量的100.0%、 91.3%、 93.8%和89.2%,且三个种植模式均显著低于YCK种植模式,42 d时各处理的钾均全部释放。从玉米秸秆碳与氮、 磷、 钾比来看,翻压177 d时,与YCK种植模式相比,YZ和YL种植模式玉米秸秆碳氮比显著增加了102.8%、 91.6%; YZ、 YH、 YL种植模式碳磷比分别显著增加了48.4%、 72.4%、 147.0%。翻压 28 d时,YH种植模式玉米秸秆碳钾比较YL种植模式显著提高。【结论】玉米秸秆腐解及其养分释放速率均在翻压后第7天达到最大值,之后腐解和养分释放速率减缓。与空闲相比,种植绿肥能显著减缓玉米秸秆腐化和秸秆中碳和钾的释放,而种植紫花苜蓿和肥田萝卜能促进玉米秸秆氮素释放,种植黑麦草则减缓了玉米秸秆氮素释放。种植肥田萝卜能显著促进玉米秸秆磷素释放。冬季种植肥田萝卜既对玉米秸秆还田后氮素释放有一定促进作用,又能增加红壤中磷的有效性,同时还能减缓玉米秸秆钾的释放,使钾释放更为长效,是一种土壤培肥和秸秆养分释放较好的绿肥种植模式。

Study on decomposition of maize straw under different green manure cropping patterns

[Objectives] Maize (Zea mays L) is the largest grain crop in China, how to treat large amount of maize straw is one of key problems. Studying the effect of different winter green manure on the decomposition of maize straw is very important for the development of sustainable agriculture. [Methods] We used nylon bags under four different green manure cropping patterns [winter fallow (YCK), Medicago sativa L. (YZ), Lolium perenne L. (YH), Raphanus sativus L. (YL)] to assess residue decomposition dynamic and major nutrients release [carbon (C), nitrogen (N), phosphorus (P) and potassium (K)]of maize straw within 177 days in red soil. [Results] The decomposition and nutrient release rates in maize straw were fast in the early stage and slow in the later stage under the four different green manure cropping patterns. The maximum decomposition and nutrient release rates both appeared at the 7th day after the maize straw was plowed into the red soil. At the 177th day, the cumulative decomposition amounts in the maize straw were 23. 41, 21. 22, 20. 86 and 20. 95 g respectively under four green manure cropping patterns ( YCK, YZ, YH, YL), and compared to YCK, YZ, YH and YL treatments were significantly decreased by 9. 3% , 10. 9% , 10. 5% respectively; the cumulative carbon release amounts were 12. 38, 11. 07, 11. 18, 11. 36 g respectively, were also significantly reduced by 10. 6% , 9. 7% and 8. 3%respectively under the three treatments, compared to YCK. The cumulative N release amounts under each treatment were 479. 46, 513. 04, 442. 58 and 530. 20 mg respectively, compared with YCK, there was no significant difference under green manure treatments; but the cumulative N release amounts under YH was 13. 7% and 16. 5%lower than that under YZ and YL. For phosphorus, the cumulative release amounts were 58. 10, 57. 91, 58. 47 and 59. 47 mg respectively, YL treatment significantly increased by 2. 35% compared to YCK. At the 28th day, the cumulative release amount of K in each treatment was 487. 20, 444. 85, 456. 94 and 434. 55 mg, the cumulative release amount of K under YCK reached 100% , those under YZ, YH and YL reached 91. 31% , 93. 79% and 89. 19% respectively, which were significantly decreased compared to the YCK, all the treatments released K completely at the 42th day. The C / N, C / P and C / K ratios in the maize straw in the YZ, YH and YL were significantly higher than that in the YCK at the 177th day. [Conclusion] The maximum rates of the cumulative decomposition and nutrient release in the maize straw appear at the 7 days and get slow in the later time. Planting green manure can significantly slow down the decomposition rate of maize straw and release rates of C and K;cultivating Medicago sativa L. (YZ) and Raphanus sativus L. (YL) can promote N release of maize straw, Lolium perenne L. ( YH) can inhibit maize straw N release, Raphanus sativus L. ( YL) could significantly promote P release. Planting Raphanus sativus L. not only can promote N release, but increase the effectiveness of phosphorus in the red soil. While it can reduce the rate of potassium release from maize straw, make the straw potassium more effective. So that, considering of improving soil fertility and reasonable straw nurients release, Raphanus sativus L is the better winter green manure after the maize harvested.