Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.

试验以湘潭县杨嘉桥镇原种场轻度污染农田为对象,早稻以‘中嘉早17号’和‘湘早籼24号’为供试品种,晚稻以‘H优518’和‘岳优27’为供试品种,采用“VIP+n”综合降镉技术,开展“VIP+n”修复技术模式区域化研究与示范工作,旨在探究不同“VIP+n”降镉技术组合模式在轻度镉污染区域的适应性,围绕轻度镉污染区域的生态、经济、种植习惯因地制宜地构建最佳“VIP+n”县域本土化技术模式。结果表明：早稻米镉含量低于晚稻;不同“VIP+n”降镉技术组合模式在轻度镉污染区域适应性良好且降镉率至少在40%以上,都能够降低稻米镉含量并使其远低于国家标准0.2 mg/kg。结论 从生态效益、经济效益和稻米降镉效果来看,“当地水稻品种+撒施石灰”修复技术组合是降低轻度重金属污染农田稻米镉含量的最佳推广模式。

研究旨在开展探究田间试验条件下铜陵市矿区附近镉重度污染农田土壤经石灰和有机物料修复后土壤镉形态的变化,为农田镉污染提供依据。通过水稻和小麦生长田间试验,研究生物有机肥、生物炭、生物肥3种有机物料与石灰配施对稻麦轮作土壤中镉形态变化的影响。研究结果显示：石灰配合有机物料施用后,小麦季土壤酸碱度范围为pH 4.72~5.39,水稻季土壤为pH 6.30~7.25,土壤有效态镉含量显著降低(P<0.05),降幅分别为1.27%~14.71%和17.72%~33.22%,土壤镉的酸溶态等活性形态向残渣态转换,实现了对镉的钝化作用。有机物料配施石灰较单独施用石灰对土壤中镉的钝化效果好,在小麦季生物有机肥配施石灰的钝化效果最好,水稻季则是生物肥配施石灰的钝化效果更好。

红壤稻田面临土壤酸化和肥力偏低的双重挑战。施石灰和秸秆还田分别是稻田土壤酸化改良和培肥的有效措施, 但二者的互作效应尚不清楚。本研究连续4年(2015—2018年)在江西省开展施石灰和秸秆还田双因素田间定位试验, 旨在探明施石灰和秸秆还田对红壤双季稻田水稻产量和氮素吸收的互作效应。结果表明, 施石灰和秸秆还田均显著提高了早、晚稻的产量和氮素吸收, 且二者具显著的协同促进效应。秸秆还田下, 施石灰使早稻产量和氮素吸收分别增加10.7%和15.5%; 而在秸秆不还田下, 增幅仅分别为4.4%和9.7%。秸秆还田下, 石灰使晚稻产量和氮素吸收分别提高18.7%和24.6%; 但在秸秆不还田下, 增幅则分别为10.5%和5.7%。施石灰对早、晚稻产量和氮素吸收的促进效应随试验年限的增加而减弱。石灰对土壤pH值的提升效应随试验年限的延长显著降低。试验4年后, 石灰对土壤有机质和全氮含量均无显著影响; 秸秆还田显著提高了土壤有机质含量, 而对全氮含量无显著影响。因此, 秸秆还田配施石灰能够协同实现双季稻增产、土壤酸化改良与培肥。本研究表明在此酸性的红壤双季稻田上每4年左右施用一次石灰为宜。

为安全利用秸秆资源,选取成都平原德阳绵竹市Cd污染稻田为研究对象,开展小区试验,研究秸秆还田配施石灰、尿素和腐熟剂对土壤特性以及2个水稻品种(低富集水稻品种川优6203、高富集水稻品种宜香2115)的Cd 吸收累积和产量的影响。结果表明：与对照相比,秸秆还田配施石灰后土壤pH值显著提高(P<0.05),土壤DOC含量轻微增加,土壤有效态Cd含量有效降低,配施尿素后土壤pH值、DOC含量和有效态Cd含量轻微增加,而配施腐熟剂则能有效降低土壤pH值,显著提高DOC含量和土壤有效态Cd含量(P<0.05)；秸秆还田配施石灰后,稻米Cd含量减少13.1%～14.4%,而配施尿素和腐熟剂后,稻米Cd含量则分别增加3.4%～13.1%和21.2%～35.6%；秸秆还田配施石灰、尿素和腐熟剂均能增加水稻产量,增幅分别为5.7%～7.1%、9.4%～9.7%和10.6%～11.4%。综合考虑水稻Cd 吸收累积以及产量,成都平原秸秆还田配施石灰技术是较为理想的秸秆安全利用模式。

Pot and field experiments were conducted to investigate the effects of water regimes on the speciation and accumulation of arsenic (As) and cadmium (Cd) in Brazilian upland rice growing in soils polluted with both As and Cd. In the pot experiment constant and intermittent flooding treatments gave 3-16 times higher As concentrations in soil solution than did aerobic conditions but Cd showed the opposite trend. Compared to arsenate, there were more marked changes in the arsenite concentrations in the soil solution as water management shifted, and therefore arsenite concentrations dominated the As speciation and bioavailability in the soil. In the field experiment As concentrations in the rice grains increased from 0.14 to 0.21 mg/kg while Cd concentrations decreased from 0.21 to 0.02 mg/kg with increasing irrigation ranging from aerobic to constantly flooding conditions. Among the various water regimes the conventional irrigation treatment produced the highest rice grain yield of 6.29 tons/ha. The As speciation analysis reveals that the accumulation of dimethylarsinic acid (from 11.3% to 61.7%) made a greater contribution to the increase in total As in brown rice in the intermittent and constant flooding treatments compared to the intermittent-aerobic treatment. Thus, water management exerted opposite effects on Cd and As speciation and bioavailability in the soil and consequently on their accumulation in the upland rice. Special care is required when irrigation regime methods are employed to mitigate the accumulation of metal(loid)s in the grain of rice grown in soils polluted with both As and Cd. (C) 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

为探究不同叶面肥阻控水稻富集镉的机制,以期为解决农田重金属镉污染和食品安全问题提供科学的依据。本研究归纳了镉对水稻的生长危害,水稻叶与叶面肥的特征包括水稻叶与水稻的养分吸收、叶面肥的种类、叶面肥的特点及叶面肥阻控水稻富集镉的机理。指出影响叶面肥阻控水稻富集镉的效果因素,如天气、温度、利用率、喷施次数和浓度等,提出与其他阻控措施相结合、开展其他种类叶面肥研究、继续叶面肥理论基础研究及加强统一管理和规范操作技术等一系列展望。