基于重量法的畜禽粪肥全盐量测定方法

针对农用固体粪肥（畜禽粪肥）全盐量/水溶性盐总量的检测方法缺乏标准化、测定方法和步骤不统一的问题，开展了重量法测定畜禽粪肥中全盐量的试验研究并验证了新方法的可行性，旨在为农业生产提供更准确、可靠的畜禽粪肥质量评估手段。首先通过完全随机试验开展样水比例、振荡参数、浸提方式、浸出液吸取量的参数优化研究，其次对全盐量影响较大的参数（振荡频率、离心时间和浸出液吸取量）采用正交试验设计形成9个处理进一步优化粪肥浸出液提取条件，最后开展加标回收试验考察方法精密度和准确度。结果表明，以畜禽固体粪污为主要来源直接使用或发酵后供农业使用的畜禽粪肥中全盐量/水溶性盐总量为0～3%时，其测定的最佳参数条件是样水比为1:5、振荡参数为150 r/min和3 min、离心参数为4 000 r/min和8 min、浸出液吸取量为20～50 mL；采用重量法在该参数条件下测定6种不同类型的畜禽粪肥样品中全盐量，相对标准偏差在3.7%～13.8%、加标回收率在89.0%～106.1%，能够满足实验室分析质量控制要求。该方法试剂用量少、节约成本、准确度和精密度好，可大批量用于畜禽粪肥全盐量测试提高效率。

Determination of the total salt content of livestock and poultry manureusing gravimetric method

Livestock and poultry manure is often used as organic fertilizer in the farmland surrounding large-scale farms, which is an effective method for recycling manure in agricultural settings. However, the salt content of livestock and poultry manure has not received sufficient attention in terms of the risk of salinization of agricultural land. Before applying livestock and poultry manure to fields, it is crucial to determine its total salt content or water-soluble salt content for salt analysis and management of saline-alkaline land. Unfortunately, there is a lack of standards and methods for determining the total salt content of livestock manure both domestically and internationally. Given the absence of standardized detection methods, the non-uniformity of determination methods, and the loss of potential salt residue, we conducted experimental research by gravimetric method. This study aimed to determine the total salt content in livestock and poultry manure and validate the feasibility, with the goal of providing a more accurate and reliable means of assessing the quality of livestock and poultry manure for agricultural production. Firstly, we conducted a completely randomized trial to optimize the sample-to-water ratio, oscillation parameters, leaching method, and leachate uptake. Subsequently, an orthogonal experimental design was used to evaluate three key parameters, including oscillation frequency, centrifugation time, and leachate uptake. Nine treatment combinations were formed to optimize the conditions for manure leachate extraction. Finally, a spiked recovery test was performed to assess the precision and accuracy of the method. The results indicated that the optimal conditions for determining the total salt or water-soluble salt content in livestock manure, with solid manure as the primary source, were as follows: a ratio of 1:5 for sample-to-water, oscillation at 150 r/min for 3 minutes, centrifugation at 4 000 r/min for 8 minutes, and leachate uptake of 20-50 mL. Moreover, it has been demonstrated that centrifugation can effectively replace the existing air suction filtration method for obtaining leachate. There was a significant correlation observed between the turbidity of the leachate from livestock and poultry manure and the centrifugation parameters, as well as the results of total salt determination. Leachate uptake volume had the greatest influence on the total salt content in the leachate from livestock and poultry manure, oscillation frequency took the second place, and centrifugation time had the weakest effect. According to the gravimetric method, we determined the total salt content of six different livestock manure samples under these optimized parameter conditions. The measured results exhibited relative standard deviations (RSDs) ranging from 3.7% to 13.8% and recovery rates ranging from 89.0% to 106.1%, meeting the requirements of analytical quality control in the laboratory. The established gravimetric method for determining the total salt content in livestock manure offers advantages such as low reagent usage, cost savings, high accuracy and precision, and practicality. It can be applied on a large scale to test the total salt content in livestock manure, thereby improving efficiency. This study provides a scientific foundation for the research and development a technology of salt reduction, and contributes to the sustainable development of integrated crop-livestock agriculture.