Effect of EM Bokashi application on control of secondary soil salinization

In order to ameliorate saline-alkaline soil, EM Bokashi has been applied to rice production in conjunction with subdrainage in Ningxia Autonomous Region and Zhejiang Province. The preliminary results can be summarized as follows： EM Bokashi can increase soil organic matter content, improve soil porosity and permeability, and raise the soil＇s levels of available nutrients; and EM Bokashi combined with subdrainage treatment is more effective in controlling secondary soil salinization and raising the grain yield and quality than other treatments. The results suggest that EM Bokashi can reduce the necessary amount of chemical fertilizer application, thereby improving the agricultural environment, and that the introduction of EM Bokashi into systems of secondary soil salinization control systems has resulted in significant benefits.

Prevention and Management of Soil Secondary Salinization in Paddy Field Irrigation Area

By analyzing the process of soil salt accumulation in irrigation area, and discussing the change of irrigation and drainage methods for drought transformed into water, the control scheme of soil secondary salinization in Wujiazi Irrigation Area was analyzed concretely, and the experience was summarized. After in-depth discussion, the importance of irrigation and drainage methods in the prevention and control of soil secondary salinization in irrigation areas was analyzed.

Effect of Different K^+/Mg^(2+) Ration Nutrient Solutions on Soil Salinity

Using simulated soil column experiments, the effects of different dosages and ratios of KCI and MgCI2 mixture on salinization nutrient ions in the secondary salinization soil which had 3 years of planting were studied, with the aim to provide the theory basis for the remediation of secondary salinization soil. Results showed that the content of soil K-, Mg2＋, CI- and the total salinity were increased, with the increasing concentrations of nutrient solution, while Na＋, Ca2＋ and HCO3- contents were reduced. Compared with originals oil, soil K＋, Na＋, Ca2＋, Mg2＋, CI- and total soil salinity were decreased, and HCO3- and SO42 were increased. In terms of the variation of soil total charge, the change ranges in 1：1 treatment varied small, but the residual of soil cationic decreased with increasing application of K＋ in the 2：1 treatment. It could be concluded that balanced and low application fertilizer could alleviate the soil saline, decrease the soil nutrition leaching and improve the balance among ions, while excess fertilization could accelerate the imbalance of zwitterions.

Carbon storage in a wolfberry plantation chronosequence established on a secondary saline land in an arid irrigated area of Gansu Province,China

Carbon（C） storage has received significant attention for its relevance to agricultural security and climate change. Afforestation can increase C storage in terrestrial ecosystems, and has been recognized as an important measure to offset CO_2 emissions. In order to analyze the C benefits of planting wolfberry（Lycium barbarum L.） on the secondary saline lands in arid areas, we conducted a case study on the dynamics of biomass carbon（BC） storage and soil organic carbon（SOC） storage in different-aged wolfberry plantations（4-, 7-and 11-year-old） established on a secondary saline land as well as on the influence of wolfberry plantations on C storage in the plant-soil system in an arid irrigated area（Jingtai County） of Gansu Province, China. The C sequestration and its potential in the wolfberry plantations of Gansu Province were also evaluated. An intact secondary saline land was selected as control. Results show that wolfberry planting could decrease soil salinity, and increase BC, SOC and litter C storage of the secondary saline land significantly, especially in the first 4 years after planting. The aboveground and belowground BC storage values in the intact secondary saline land（control） accounted for only 1.0% and 1.2% of those in the wolfberry plantations, respectively. Compared to the intact secondary saline land, the SOC storage values in the 4-, 7-and 11-year-old wolfberry plantations increased by 36.4%, 37.3% and 43.3%, respectively, and the SOC storage in the wolfberry plantations occupied more than 92% of the ecosystem C storage. The average BC and SOC sequestration rates of the wolfberry plantations for the age group of 0–11 years were 0.73 and 3.30 Mg C/（hm^2·a）, respectively. There were no significant difference in BC and SOC storage between the 7-year-old and 11-year-old wolfberry plantations, which may be due in part to the large amounts of C offtakes in new branches and fruits. In Gansu Province, the C storage in the wolfberry plantations has reached up to 3.574 Tg in 2013, and the C sequestration potential of the existing wolfberry plantations was 0.134 Tg C/a. These results indicate that wolfberry planting is an ideal agricultural model to restore the degraded saline lands and increase the C sequestration capacity of agricultural lands in arid areas.

不同土壤改良措施对大棚菜地高度盐渍化土壤改良效果研究

设施菜地土壤次生盐渍化现象普遍,严重制约了设施蔬菜的可持续发展。以高度和超高度大棚次生盐渍化土壤为对象,研究不同土壤改良措施对大棚青菜产量、氮肥利用率及土壤性状的影响。在两种盐渍化程度的大棚土壤上分别开展田间试验,设置相同的6个处理:不施氮肥(0%N)、常规施氮(100%N)、施石灰氮+常规施氮(Lime+100%N)、施石灰氮+减氮20%(Lime+80%N)、施石灰氮+填闲玉米+常规施氮(Lime+corn+100%N)和施石灰氮+填闲玉米+减氮20%(Lime+corn+80%N)。结果表明:与100%N处理相比,Lime+corn+80%N处理的青菜产量在高度、超高度次生盐渍化土壤上分别增产91.8%(11.3 t/hm^(2))和62.2%(5.6 t/hm^(2)),显著提高了氮肥利用率。在高度盐渍化土壤上,与100%N处理相比,施石灰氮可使土壤电导率降低16.0%~19.7%(P<0.05),对土壤pH无显著影响;与施石灰氮处理(Lime+100%N和Lime+80%N)相比,土壤电导率在Lime+corn+100%N和Lime+corn+80%N处理下分别降低了49.4%和55.2%(P<0.05),土壤pH升高3.4%和12.6%。在超高度盐渍化土壤上,与100%N处理相比,施石灰氮处理对土壤电导率无显著影响,可使土壤p H升高14.1%~16.0%(P<0.05);与施石灰氮处理相比,土壤电导率在Lime+corn+100%N和Lime+corn+80%N处理下分别降低了43.7%和49.2%(P<0.05)。不同土壤改良措施在高度盐渍化土壤上显著提高了土壤孔隙度,降低了土壤有效磷和速效钾含量,而在超高度盐渍化土壤上影响不显著。

果菜秸秆生物炭吸附设施土壤硝态氮性能与机制研究

在农业生产中,过量偏施氮肥导致的硝酸盐富集是次生盐渍化、酸化等土壤障碍的重要诱因。生物炭因良好的吸附特性逐渐成为缓解盐渍化的土壤调理剂,但果菜秸秆生物炭对硝酸盐等离子的吸附研究鲜见报道。以甜椒、番茄和茄子3种果菜秸秆为原料热解制备生物炭,进行硝态氮吸附试验。通过扫描电镜(SEM)和傅里叶近红外光谱(FTIR)等技术对生物炭吸附前、后表面形貌、官能团等进行表征分析,利用吸附动力学模型和等温吸附模型等进行拟合分析,综合模型参数和形貌表征解析果菜秸秆生物炭的吸附性能和机制。研究结果表明,3种果菜秸秆生物炭对硝态氮均具有一定吸附能力,茄子秸秆生物炭吸附能力最强,最大理论平衡吸附量为114.788 mg/g,其次为番茄(29.736 mg/g)和甜椒(9.759 mg/g);茄子和甜椒秸秆生物炭吸附性能优于玉米、稻壳等大田作物秸秆生物炭,吸附过程符合准二级动力学模型,受化学键吸附、表面吸附和内扩散吸附过程的控制,番茄秸秆生物炭吸附过程符合准一级动力学模型,主要为物理吸附;FTIR分析显示,3种生物炭均含有羟基、甲基、亚甲基、羧基和羰基官能团,除此之外,甜椒和茄子秸秆生物炭还含有醚键,番茄秸秆生物炭含有醇羟基。因此,3种果菜秸秆生物炭对硝态氮均具有吸附能力,茄子秸秆生物炭吸附能力最强,受孔隙填充、官能团和络合作用等多种理化机制的影响,具有消减土壤次生盐渍化的潜力。本研究对盐渍化土壤修复和果菜秸秆资源化利用具有理论意义。

宁北盐碱地土壤微生物的分离和抗菌活性筛选

从宁北盐碱土壤中分离得到具有一定形态特征的单菌落45株,利用基因组提取技术,对菌株16S rRNA序列进行测序及菌属鉴定。结果显示,有16株放线菌,含13株链霉菌属,3株拟无枝酸菌属。抗菌活性实验结果表明,16株菌株均具有抑菌活性,其中,12株菌株次级代谢产物对普通变形杆菌具有显著抗菌活性,12株菌株次级代谢产物对金黄色葡萄球菌具有明显抑制活性,9株菌株次级代谢产物对白色念珠菌具有一定的生长抑制活性。研究表明,从宁北盐碱土壤中分离得到的微生物菌株具有较强抗菌或抑菌活性,不仅丰富了特殊生境微生物资源,也为进一步从活性菌株中分离抗菌活性先导化合物奠定了基础。

灌溉量和垄高对次生盐渍地玉米土壤水盐运移变化及产量的影响

为探究宁夏扬黄灌区因多年地面灌溉引起的地下水位上升、次生盐渍化突显等难题,本试验以宁夏红寺堡移民区为研究点,选定典型试验区域开展定位试验监测,设置高效滴灌下不同灌溉量(2160、2700 m^(3)·hm^(-2)和3240 m^(3)·hm^(-2))和起垄高度(20、30 cm和40 cm)2个因素3个水平,通过大田试验研究不同组合处理下的次生盐渍地水盐运移变化规律以及其对玉米生长指标、产量和水分利用效率的影响。结果表明,灌水定额一定时,随垄高增加,0~60 cm土层含水率逐渐降低;相同垄高下,随灌水定额增大,各土层含水率逐渐增加,并且深土层明显高于浅土层。垄作滴灌可以有效降低垄上土壤盐分含量,而各处理土壤深层均不同程度积盐,其中T9处理(3240 m^(3)·hm^(-2)和40 cm组合)40~60 cm土层积盐最明显。T6处理(2700 m^(3)·hm^(-2)和40 cm组合)各项生长指标及产量均优于其他各处理,产量达6597.15 kg·hm^(-2),T5(2700 m^(3)·hm^(-2)和30 cm组合)水分利用效率最高,达到1.53 kg·m-3。通过回归分析发现,玉米产量最大值时和水分利用效率(WUE)最大值时的灌水量和垄高值不同,进一步利用空间分析方法得出,灌水量2685~2730 m^(3)·hm^(-2)和垄高36~39 cm时,玉米产量、WUE均达最大值的90%以上。

Preliminary validation of SMOS sea surface salinity measurements in the South China Sea

The SMOS(soil moisture and ocean salinity) mission undertaken by the European Space Agency(ESA) has provided sea surface salinity(SSS) measurements at global scale since 2009.Validation of SSS values retrieved from SMOS data has been done globally and regionally.However,the accuracy of SSS measurements by SMOS in the China seas has not been examined in detail.In this study,we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea(SCS) expedition during autumn 2011.The comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass data.Accuracy in terms of bias and root mean square error(RMS) of the SSS retrieved using three different sea surface roughness models is very consistent,regardless of ascending or descending orbits.When ascending and descending measurements are combined for comparison,the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements,with bias-0.33 practical salinity units and RMS 0.74.We also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved SSS.The SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS measurements.Therefore,accuracy of retrieved SSS shows a relationship with distance between the validation sites and land.

Validation and correction of sea surface salinity retrieval from SMAP

In this study, sea surface salinity(SSS) Level 3(L3) daily product derived from soil moisture active passive(SMAP)during the year 2016, was validated and compared with SSS daily products derived from soil Moisture and ocean salinity(SMOS) and in-situ measurements. Generally, the root mean square error(RMSE) of the daily SSS products is larger along the coastal areas and at high latitudes and is smaller in the tropical regions and open oceans. Comparisons between the two types of daily satellite SSS product revealed that the RMSE was higher in the daily SMOS product than in the SMAP, whereas the bias of the daily SMOS was observed to be less than that of the SMAP when compared with Argo floats data. In addition, the latitude-dependent bias and RMSE of the SMAP SSS were found to be primarily influenced by the precipitation and the sea surface temperature(SST). Then, a regression analysis method which has adopted the precipitation and SST data was used to correct the larger bias of the daily SMAP product. It was confirmed that the corrected daily SMAP product could be used for assimilation in high-resolution forecast models, due to the fact that it was demonstrated to be unbiased and much closer to the in-situ measurements than the original uncorrected SMAP product.

Characteristics and Development of Agricultural Soil in Hetao Irrigation District,Inner Mongolia

Hetao Irrigation District is located in the cold and arid region of Hetao Plain,Inner Mongolia,where the agricultural soil has unique characteristics.Although the agricultural soil properties in Hetao Irrigation Districts have been reported,the overall characteristics remain unclear.Through literature review and investigation,the overall characteristics,development patterns,and related reasons were explored,consequently providing theoretical support for enhancing soil utilization and formulating sustainable soil development strategies.The results showed that the agricultural soil in Hetao Irrigation District originated from the sedimentary layer and anthropogenic mellowing produced by the diversions of the Yellow River.The soil has periodic secondary salinization characteristics,accompanied by a slightly increasing pH value over time.It has low soil organic contents with a stable changing trend,low nitrogen,and phosphorus contents but high potassium and sulfur content,uneven nutrient distribution,diverse production performance,weak but stable ecological performance,and heterogeneous soil quality with a stable change trend.These findings indicate that this kind of soil can be used to plant diverse crops tolerant to different saline-alkali and requiring various nutrients.This agricultural soil is sustainable,but it is also faced with the problems of increased saline-alkali,nutrient loss,and pollution.

Improving the Facility Soil by Combining Soil Amendment with Agronomic Measures

[Objectives]To study the remediation methods of secondary salinization and cadmium pollution in facility soil.[Methods]Two kinds of soil amendments,potassium fulvic acid and limestone powder,were selected to be applied alone or combined together to plant maize to carry out field experiments.Their effects on watermelon yield,watermelon cadmium content,soil available nitrogen,phosphorus,potassium and water-soluble salts were studied.[Results]The application of potassium fulvic acid,limestone powder and their combined application increased the yield and soluble solids of watermelon to different degrees.The contents of seven heavy metals including cadmium,copper,zinc,arsenic,lead,mercury and chromium in the watermelon of all treatments were all lower than the food safety limit stipulated in the national standard.During the harvest period of maize seedlings,all treatments could increase soil pH and decrease soil cadmium availability.In particular,3000 kg/ha of limestone powder and 1500 kg/ha of potassium fulvic acid had the best effect on reducing soil available cadmium content.In reducing soil available cadmium content,there were significant differences between single application of amendment and combined application treatments.In addition,compared with the control CK,all treatments decreased soil available nitrogen,phosphorus,potassium and water-soluble salt content.[Conclusions]Potassium fulvic acid,limestone powder and their combined application can increase the yield of watermelon,and can significantly reduce the available cadmium,nitrogen,phosphorus,potassium and water-soluble salt content in the facility soil of maize cultivation.

巢湖流域种植模式改变对养分表观平衡及土壤化学性质的影响

为明确巢湖流域内的农田养分平衡状况,制定面源污染防控措施,本研究以巢湖流域传统休耕-水稻种植模式(n=26)作为参照,选取该区域典型的大棚番茄-水稻轮作模式(由休耕-水稻种植模式转变而来,n=26)为研究对象,探究不同种植模式下的养分盈亏状况,并分析种植模式改变对土壤化学性质的影响。结果表明,休耕-水稻种植模式下氮盈余34.02 kg·hm^(-2)·a^(-1),其盈余率为16.7%;磷和钾分别亏损2.96、13.71 kg·hm^(-2)·a^(-1),两者亏损率分别为9.1%和19.7%。大棚番茄-水稻轮作模式下氮、磷、钾盈余量分别为589.27、194.93、144.22 kg·hm^(-2)·a^(-1),三者盈余率分别为61.5%、66.4%、26.9%。长期大量施肥下,大棚番茄-水稻轮作导致土壤积累的硝态氮、铵态氮、有效磷和速效钾含量分别为休耕-水稻种植模式土壤的50.05、7.05、1.95倍和1.72倍。对比休耕-水稻种植模式,大棚番茄-水稻轮作模式下过量施用氮肥导致土壤pH平均下降了0.83个单位,电导率平均增加了0.73 mS·cm^(-1),该模式下土壤呈明显的酸化和盐渍化趋势。研究表明,当前巢湖流域大棚番茄-水稻轮作模式下的养分收支呈盈余状态,土壤积累了大量速效养分,存在一定的流失风险。

广西设施栽培土壤主要养分积累特征

采集广西区内不同大棚年限的设施栽培土壤及露地栽培的耕层土壤样品,分析土壤pH、水溶性盐、有机质、碱解氮、速效磷、速效钾以及全量氮、全量磷和全量钾含量的变化情况。结果表明:随着大棚年限的延长,广西设施栽培土壤酸化更明显,连续栽培10年后,土壤pH降低了0.34个单位;水溶性盐含量是露地栽培的3倍以上,且随着大棚使用年限的延长,设施土壤出现次生盐渍化的程度也越严重,以中、轻度盐渍化为主;设施栽培土壤有机质、碱解氮、速效磷、速效钾、全氮及全磷含量均显著高于露地土壤,总体上随着大棚年限的延长而逐年积累,尤其是磷元素积累增幅较大,生产中应采取适当措施控制磷肥的施用量,防止土壤中磷素过度富集而导致作物营养不均衡,从而影响作物的产量和品质。

新疆绿洲土壤次生盐渍化治理研究

地貌学科理论对绿洲学科影响深远。按地貌特征对绿洲进行分类,有助于认识不同绿洲土壤次生盐渍化形成特点,找出治理之道。按照地貌特征,新疆绿洲可分为4种,即山前倾斜平原绿洲、沙漠内大河两岸型平原绿洲、山谷阶地型绿洲和极干旱盆地坎儿井型绿洲。绿洲地貌特征不同,其土壤次生盐渍化治理的关键也有所不同。新时代,现代管水和用水方式为各类绿洲土壤次生盐渍化治理创造了条件。绿洲土壤次生盐渍化研究有助于推进新疆重难点区域土壤次生盐渍化治理。

不同施肥模式对设施芹菜土壤次生盐渍化改良研究

本研究旨在改良设施土壤次生盐渍化,探索一种能够治理退化耕地、提高经济效益的综合治理模式。以河北唐山设施芹菜次生盐渍化土壤为研究对象,以常规施肥(CF)为对照,研究不同施肥模式(OF、SC、FF)对次生盐渍化土壤生化指标、微生物多样性及芹菜品质、产量的影响。结果表明:与CF处理相比,各施肥处理均降低了土壤pH和水溶性盐总量,添施有机肥(OF)后土壤有机质、有效磷、速效钾和缓效钾分别提高19.90%、2.39%、15.13%、0.15%,添施土壤调理剂(SC)后土壤有机质显著增加15.17%,添施功能肥(FF)也有增加土壤有机质、有效磷含量的趋势;设施土壤中阴离子以SO_(4)^(2-)为主,阳离子以Ca^(2+)离子为主;SC处理提升了土壤细菌群落丰富度和多样性,增加变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)的相对丰度,降低放线菌门(Actinobacteriota)、绿弯菌门(Chloroflexi)丰度,芹菜产量显著增加27.07%。添施土壤调理剂较OF、SC处理可提高设施芹菜可溶性固形物含量,降低硝酸盐含量。因此,添施土壤调理剂(SC)对设施次生盐渍化土壤改良及芹菜增产提质效果最佳。

西苕溪流域菜地土壤肥力状况与磷素流失风险

菜地土壤集约化利用程度高,容易出现养分不平衡和过量积累等问题,严重影响蔬菜产业的可持续发展。本文基于西苕溪流域露地和设施栽培模式下菜地土壤肥力状况和主要障碍因子分析,探究了菜地土壤磷素流失风险阈值。结果表明:露地菜地土壤pH值显著低于设施菜地(P<0.05);设施菜地土壤全钾、速效钾、有效磷、水溶性磷含量和水溶性盐总量、电导率显著高于露地菜地(P<0.05)。2种栽培模式下95.8%菜地土壤处于Ⅱ级肥力水平。土壤水溶性磷与Mehlich 3-P的关系可用分段线性回归方程表征,估算得出露地和设施菜地土壤磷素流失风险阈值分别为102.7、128.7 mg/kg,超过对应阈值的样本数分别占总数的65.0%和83.3%。综上所述,西苕溪流域内露地和设施菜地土壤酸化状况较为严重,磷素潜在流失风险非常高,其中设施菜地土壤次生盐渍化问题更为突出。

土壤调理剂与有机肥减量对设施黏壤土有机蔬菜生长和盐渍化改良的影响

在黏壤土背景下分析土壤调理剂与有机肥减量对设施黏壤土有机蔬菜生长和盐渍化改良的影响,为改良土壤和提高产量提供依据。以黄瓜为供试材料,设置有机肥减量和有机肥减量情况下配施微生物菌剂、土壤改良剂的处理,分析有机肥减量和不同土壤调理剂及用量对土壤化学性质和黄瓜产量、品质的影响。结果表明,有机肥减量处理的黄瓜产量与常规施肥相比无显著差异,同等用量下微生物菌剂处理与土壤改良剂处理黄瓜产量无显著差异,随着土壤改良剂用量的增加产量逐渐增加且达显著水平。有机肥减量施肥并配施调理剂可显著增加黄瓜的可溶性蛋白水平,但对黄瓜的硝态氮和还原性VC无显著影响。减量施肥不能降低土壤全盐水平,配施调理剂后全盐含量显著降低,微生物菌剂和土壤改良剂处理土壤全盐含量无显著差异。有机肥减量及配施土壤调理剂土壤养分无显著差异。在土壤质地为黏壤土时,土壤调理剂的添加可改变表层土壤盐分、增加蔬菜产量,但对土壤养分影响较小,需建立长期定位试验进行基础性研究。

多功能菌株的筛选及其在次生盐渍化土壤中的应用

次生盐渍化和土传病害是导致设施栽培连作障碍的主要因素,为了缓解设施栽培的连作障碍,从土壤中筛选多功能菌株并应用于连作障碍土壤中成为一种新的研究思路。文章通过对12株菌株的硝酸盐降解能力、产胞外聚合物(EPS)能力、降碱能力、抑菌能力进行验证,优选出硝酸盐降解能力最强的假单胞菌(Pseudomonas sp.)N11,EPS产量最高的琼氏不动杆菌(A c ine tobacte r junii)S27,抑菌效果最好的解淀粉芽孢杆菌(Bac illus amyloliquefacie ns)Y2,并将其制成混合菌剂运用于次生盐渍化土壤中。实验组对土壤中硝酸盐的降解率可达31.71%,而对照组仅为15.28%,说明混合菌剂降盐效果显著。筛选出的多功能菌株,可有效改善连作障碍土壤的次生盐渍化和土传病害问题,为提高设施蔬菜栽培产量提供可靠的技术手段。

土壤pH和SO_(4)^(2−)含量对设施菜地土壤障碍强还原处理修复的响应

设施蔬菜地常面临硫酸根(SO_(4)^(2−))累积等次生盐渍化问题。强还原土壤消毒方法(Reductive Soil Disinfestation,RSD)能够有效改良退化土壤,但RSD处理过程中SO_(4)^(2−)转化产物及RSD对次生盐渍化的长期改良效果尚不清楚。为探究土壤初始pH和SO_(4)^(2−)含量对RSD处理过程中SO_(4)^(2−)去除效果、转化产物及种植作物过程中土壤理化性质的影响,设置5个处理:无处理对照、淹水+紫花苜蓿粉(RSD)、RSD+石灰调节土壤pH至7.30、RSD+SO_(4)^(2−)(添加量为4000 mg·kg^(−1))、RSD+石灰+SO_(4)^(2−)(同上),处理结束后盆栽种植二茬黄瓜(Cucumis sativus L.),每个处理3个重复。结果表明,RSD处理后,土壤pH显著升高,EC值降低,土壤可溶性SO_(4)^(2−)-S含量降低了330-728 mg·kg^(−1),未施和施用SO_(4)^(2−)处理可溶性SO_(4)^(2−)含量分别降低了83.6%-93.3%、35.0%-42.1%。未施SO_(4)^(2−)处理中土壤总硫和SO_(4)^(2−)沉淀含量基本不变,吸附态SO 42−含量略有降低,表明减少的SO_(4)^(2−)主要转化为有机态硫,且施用石灰提高土壤pH可促进SO_(4)^(2−)转化为有机硫。土壤在晾干和后续种植作物过程中,RSD处理转化的有机硫再次矿化为SO_(4)^(2−),导致土壤盐分回升和pH值降低。种植一茬黄瓜后,各处理SO_(4)^(2−)含量已上升至处理前水平。同时,RSD处理后由于NO3−的完全脱除土壤面临缺氮风险,种植过程中施用了大量铵态氮肥,导致土壤进一步酸化和次生盐渍化。种植两茬黄瓜后,各处理土壤pH值降低了2.02-2.36,EC值增加了0.201-0.233 mS·cm−1。综上,对于SO_(4)^(2−)初始含量高的土壤,由于有机硫迅速矿化,RSD处理后土壤将面临盐分回升及再次盐渍化风险。RSD处理后应选用合适的肥料品种结合科学施肥方式,以维持RSD处理对土壤次生盐渍化的长期改良效果。