连续施用无害化污泥堆肥对沙质潮土肥力的影响

【目的】 研究连续施用无害化污泥堆肥对土壤肥力和环境质量的影响，为无害化污泥资源化利用提供理论依据和技术支撑。 【方法】 通过2013—2015年田间定位试验，每年按照当地农民施肥量在小麦和玉米季分别施用N 225 kg/hm2、P₂O₅ 86 kg/hm2和K₂O 113 kg/hm2 (CK) 基础上，施用无害化污泥堆肥15 t/hm2 (W1)、30 t/hm2 (W2) 和45 t/hm2 (W3)，共四个处理，每个处理3次重复。小麦、玉米收获后，采集0—20 cm土层样品，测定常规土壤理化性质、重金属含量以及微生物量碳氮 (SMBC、SMBN)。采用内梅罗指数法计算土壤pH、有机质、全氮、有效磷和速效钾分肥力系数IFI_i，以及土壤综合肥力指数 (integrated fertility index，IFI)。 【结果】 1)施用污泥堆肥处理IFI在试验的第三年 (2015年) 玉米季达到最大值，与CK相比，W1、W2和W3处理IFI分别显著提升了57.3%、95.2%和127.5% (P < 0.05)，说明连续施用污泥堆肥可以有效提高土壤肥力水平，其中W3处理效果最明显。2) SMBC和SMBN含量随污泥堆肥施用时间增加而增加。相同作物同一污泥堆肥施用量处理，第三年 (2015年) 的SMBC和SMBN含量均显著高于第一年 (2013年)。W1、W2和W3处理SMBC含量在2015年小麦季达到最大值，较CK分别显著提高了109.9%、176.2%和216.8% ( P < 0.05)；W1、W2和W3处理SMBN含量在2015年玉米季达到最大值，较CK分别显著提高了55.6%、100.5%和162.3% ( P < 0.05)。3)施污泥堆肥处理的土壤和植物籽粒中重金属含量分别低于国家环境质量二级标准 (GB15618—1995) 和国家农产品质量安全规定的限量值。根据土壤肥力分级参考标准 (NY/T 391—2000)，2015年玉米季W2和W3处理的土壤肥力已经达到I级，培肥作用显著，但长期大量施用导致的土壤重金属累积风险还需长期监测。 【结论】 施用重金属含量达到国家标准的无害化污泥堆肥，可以在短期内有效提升沙质潮土的土壤肥力质量，改善土壤微生物学特性。本试验条件下，连续施用45 t/hm2污泥堆肥效果最显著，沙质潮土的土壤肥力质量在第三年就达到I级，此时土壤和作物籽粒中重金属含量均低于国家相关标准限值。长期大量施用是否会带来重金属累积还需继续监测。

Effects of continuous application of non-hazardous sewage sludge compost on fertility of sandy fluvo-aquic soil

【Objectives】 In order to provide theoretical basis and technical support for the utilization of harmless sludge, a study was conducted to investigate the effects of non-hazardous sewage sludge compost on soil fertility and environment quality. 【Methods】 Experiments were conducted in wheat-maize rotation system during 2013 to 2015. At the base of applying N 225 kg/hm2, P₂O₅ 86 kg/hm2 and K₂O 113 kg/hm2 (CK), sewage sludge compost was applied at rates of 15 t/hm2 (W1), 30 t/hm2 (W2) and 45 t/hm2 (W3) before the sowing of wheat and maize. After every harvest, the soil samples of 0–20 cm depth were collected, basic physical and chemical properties, heavy metal contents and soil microbial biomass carbon and nitrogen contents (SMBC and SMBN) were analyzed. The individual soil fertility index of pH, organic matter, total N, available P and available K (IFI_i) were calculated, and the soil integrated fertility index (IFI) was obtained using modified Nemero formula to evaluate the soil fertility quality. 【Results】 1) IFI in sludge-treated soils increased with the experimental years. Compared with CK, IFI of W1, W2 and W3 treatments were significantly (P < 0.05) increased by 57.3%, 95.2% and 127.5% in 2015 maize season, respectively, indicating that applying sewage sludge compost effectively improved the soil fertility. 2) SMBC and SMBN contents were increased with the experimental years as well. The SMBC and SMBN contents of the same treatment in the same harvest season were significantly improved from 2013 to 2015. In 2015, the highest SMBC content was in wheat season, which were significantly increased by 109.9%, 176.2% and 216.8% in W1, W2 and W3, compared with the CK; the highest SMBN content was in maize season, which were significantly raised by 55.6%, 100.5% and 162.3% in W1, W2 and W3 treatments, compared with the CK ( P < 0.05). 3) The heavy metal contents in both sludge-treated soils and plant grains were far below the national environmental quality standards GB15618–1995 and the limits in the " agricultural product quality safety regulations of the state”. Referring to the standard of the Soil Fertility Classification Standard (NY/T 391–2000), soil fertility of W2 and W3 treatments met the first grade after three year’s continuous application. 【Conclusions】 Applying high rate of non-hazardous sewage sludge compost is proved effective in improvement of soil fertility and soil microbial properties in a sandy fluvo-aquic soil. Under the experimental condition, applying 45 t/hm2 of sewage sludge compost for three years is the most prominent treatment which increases fluvo-aquic soil fertility to grade I, without leading to obvious heavy metal accumulation in soils and grains. Long term monitoring is still needed for the food and ecosystem safety in the future.