Intensification of agriculture worldwide has led to a growing awareness on their environmental impacts, namely on soil quality and long term impact on crop productivity. As a consequence, there is an increasing concern regarding best agricultural management practices and their impact on physical, chemical and biological soil properties. In the Centre region of Portugal, maize is one of the most important arable crops and represents more than 32% of the cultivated area. Maize fields have been intensively managed under conventional practices, but increasing land degradation is leading farmers to adopt improved management practices, such as the application of composted sludge from urban wastewater treatment plants. This study aims to assess the long term impact of composted sludge application as soil amendment in maize cropping fields. The study was performed in Baixo Mondego, in central region of Portugal, largely devoted to agriculture and where maize is one of the most relevant crops. The study was performed in two study sites with similar soil and weather characteristics - one managed under conventional practices, with intensive application of fertilizers, and another field where a significant part of mineral fertilizers is replaced by composted sludge. Both sites use these agricultural management practices for more than 5 years. In 2018, two soil sampling campaigns were performed to assess the physical (texture and bulk density) and chemical soil properties (organic matter content, total nitrogen, total and extractable phosphorus, exchangeable cation (K+, Ca2+, Na+, Mg2+) and heavy metals (Cd, Cr, Pb, Zn and Ni)). Results show that composted sludge improves soil organic matter content (1.2% vs. 2.2%), total (2747 mg kg-1 vs. 1134 mg kg-1) and available phosphorous (821.85 mg kg-1 vs. 98.44 mg kg-1) comparing with conventional management practices. Higher contents of heavy metals, specifically Cu, Zn, Cd and Cr, were found in the field with sludge application than in the conventional one, which may represent a long term risk for soil contamination. Information regarding the long term impacts of best management practices on soil quality is relevant and should guide farmers and policy makers to attain agricultural sustainability.
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机译：全球农业的强化导致对环境影响的提高意识，即土壤质量和对作物生产力的长期影响。因此，有关最佳农业管理实践及其对物理，化学和生物土壤性质的影响，越来越令人担忧。在葡萄牙的中心地区，玉米是最重要的耕作作物之一，占耕地面积的32％以上。玉米领域在传统实践下集中管理，但越来越大的土地退化是领先的农民，采用改进的管理实践，例如从城市废水处理厂的应用堆肥污泥的应用。本研究旨在评估堆肥污泥申请作为玉米种植领域的土壤修正的长期影响。该研究在Baixo Mondego进行，在葡萄牙中部地区，主要致力于农业，玉米是最相关的作物之一。该研究在两种研究地点进行了类似的土壤和天气特征 - 在传统实践下管理，密集应用肥料，另一个领域通过堆肥污泥取代了矿物肥料的重要组成部分。两个站点使用这些农业管理措施超过5年。 2018年，进行了两种土壤采样运动，以评估物理（质地和散装密度）和化学土壤性质（有机物质含量，总氮，总和可萃取的磷，可交换阳离子（K +，Ca2 +，Na +，Mg2 +）和重金属（CD，CR，PB，Zn和Ni））。结果表明，堆肥污泥改善了土壤有机质含量（1.2％vs.2％），总共（2747mg kg -1，1134mg kg-1）和可用的磷（821.85mg kg -1和98.44 mg kg-1 ）与传统管理实践相比。在污泥施加的领域中发现了比传统污染的污泥施用的较高的重金属，特别是Cu，Zn，Cd和Cr的含量更高，这可能代表土壤污染的长期风险。有关土壤质量最佳管理实践的长期影响的信息是相关的，应该指导农民和决策者获得农业可持续性。
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