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【Objective】The present paper aimed to study the occurrence form of cadmium (Cd) accumulation in soil aggregates of Cd-contaminated brown calcareous soil matrices of paddy fields in the Karst area of northwestern Guangxi, and to provide data reference for safe rice production in this type of Cd-contaminated paddy fields in the region. 【Method】The sampled soil aggregates were separated into five aggregates as ＞ 2.000 mm, 1.000-2.000 mm, 0.050-1.000 mm, 0.074-0.250 mm and ＜0.074 mm, the composition of soil aggregates particle size, Cd content of different particle size aggregates and their main occurrence patterns from 0-20, 20-30, 30-50 and 50-80 cm depth profiles in the Karst area of northwest Guangxi were studied.【Result】The proportion of 0.250-1.000 mm size aggregates in each profile was stable, above 30.00%, with no significant difference between profiles (P＞0.05), the proportion of ＞2.000 mm size aggregates in the 0-20 cm soil profile (tillage layer) was the largest (40.20%), and as the depth of the profile increased, the proportion of ＞2.000 mm size aggregates decreased rapidly, and the proportion of ＜0.250 mm size aggregates showed a gradual increasing trend. Analysis of the Cd content of agglomerates of different particle sizes showed that, in 0-20, 20-30 and 30-50 cm soil profiles, Cd was mainly enriched in ＞2.000 mm particle size aggregates, with contents as high as 2.22, 1.66 and 0.95 mg/kg, respectively, and in the 50-80 cm soil profile, Cd was mainly enriched in 1.000-2.000 mm particle size aggregates. ＞2.000 mm particle size aggregates contributed most to the whole soil Cd content in the 0-30 cm soil layer. The occurrence form of Cd in the aggregates at different profile depths showed obvious differences, the proportion of Cd in aggregates of all particle sizes in the 0-20 cm profile was mainly in the organic matter binding state, with the smallest proportion of Cd in the exchangeable state (except for ＜0.074 mm particle size aggregates), and the proportion of Cd in the exchangeable state in the aggregates increased greatly with the increase of the depth of the profile, when the profile depth was increased to under 30 cm, the Cd in the aggregates mainly existed in carbonate bound state, and with minimal content in the residue lattice state.【Conclusion】In the typical Cd-contaminated brown calcareous soil matrices of paddy fields in the Karst area of northwestern Guangxi, the Cd is mainly enriched in aggregates of ＞2.000 mm and 1.000-2.000 mm particle size, the Cd in the aggregates of each particle size in the 0-20 cm tillage soil is mainly in the form of organic matter bound state, and with the smallest proportion in the form of exchangeable state. With the increase of the profile depth, the proportion of exchangeable Cd increases greatly, while the proportion of Cd in the stable form decreases significantly. Therefore, in the actual production process, it should focus on improving the content of large particle size soil aggregates and avoiding excessive intensive ploughing and deep tilling, reducing the exchangeable state Cd content in the ploughed soil, and ultimately reducing the risk of excessive Cd in rice during rice production. [ABSTRACT FROM AUTHOR]

【Objective】The study aimed to analyze the situation of safe utilization of farmland based on CiteSpace, so as to provide reference basis for sustainable use of cultivated land resource in China.【Method】CiteSpace VI was used to analyze the information of 1419 literatures in the field of farmland safe utilization from 2000 to 2022 from China National Knowledge Infrastructure（CNKI）. Price theory was used to calculate the core author group, and the conservation and utilization situation of cultivated land resources in China was evaluated.【Result】From 2000 to 2022, the problem of heavy metal pollution in farmland in China had become more and more serious. The number of annual publications in the field of safe utilization research had been rising rapidly in a wavy fashion. Since 2003, experts and scholars had paid more and more attention to this research field. Analysis of the main research strength results showed that the University of Chinese Academy of Sciences, Institute of Soil Sciences of Chinese Academy of Sciences, Agro-environmental Protection Institute of Ministry of Agriculture and Social Affairs, Institute of Geographic Sciences and Natural Resources Research of Chinese Academy of Sciences and College of Resources and Environment of Yunnan Agricultural University were the top 5 institutions of publishing articles, with 70, 63, 36, 35 and 19 articles published respectively. However, other research institutions had low connectivity density and weak cooperation basis. Chen Tongbin, Song Bo, Luo Yongming, Zhan Fangdong and Wu Longhua were the top 5 authors with 24, 20, 17, 15 and 15 articles published respectively, but the centrality of the top 10 authors was low, ranging from 0 to 0.06. Results of keyword co-occurrence and cluster analysis showed that source resolution, passivation remediation, passivation agent, biochar, cadmium pollution, wheat and health risk emerged keywords in recent years, and the intensity of the emergence was 5.30, 5.19, 4.57, 4.75, 4.64, 3.34 and 3.81, respectively. The above keywords related topics were the main research directions of current and future research fields of farmland safety use; Phytoremediation, safe production of crop and heavy metal pollution and risk assessment of farmland soil were the trending research point of many experts and scholars.【Conclusion】From 2000 to 2022, the problem of heavy metal pollution in farmland in China has become increasingly serious. The number of annual articles published in the field of farmland safety utilization has risen rapidly in a wavy way on the whole. However, the centrality of the top 10 authors in the number of articles published is low, and the connection density between most research institutions is low, and the basis for cooperation is weak. Therefore, it is suggested to further strengthen the collaborative innovation research among core authors and promote the cooperation and exchange between research institutions, so as to promote the rapid development of farmland safe use research, promoting the protection and utilization of cultivated land resources in China. [ABSTRACT FROM AUTHOR]

【Objective】The study aimed to analyze the characteristics of cadmium (Cd) absorption and accumulation in different rice varieties under Cd polluted field in karst area of northwest Guangxi, so as to provide a reference for the safe production of rice in the region.【Method】19 rice varieties mainly cultivated in northwest Guangxi were used as test materials by the method of filed plot experiment, the production traits, yield and Cd content in different parts of rice were measured, and the characteristics of Cd enrichment and transport in different rice varieties were analyzed. After that, the low accumulation of rice varieties was recommended for the regional planting.【Result】The yield of 19 rice varieties was obviously different. Among them, the yield of Shenliangyou 9569 was 627.8 kg/667 m² significantly higher than that of other rice varieties (P<0.05, the same as below), and Yahangjinzhan had the lowest yield (429.5 kg/667 m²);The average content of Cd in different parts of rice was root>brown rice>straw>chaff. Among them the content of Cd in brown rice of Teyou 6811, H Liangyou 991 and Wushansimiao was 0.35, 0.37 and 0.37 mg/kg respectively all significantly lower than that of other varieties, and significantly reduced to 68.5%, 66.7% and 66.7% respectively when compared with the highest Cd content rice varieties Hengfengyou 777;The Cd enrichment coefficient in brown rice of Hengfengyou 777 was the highest, when Teyou 6811, H Liangyou 991, Yahangjinzhan and Wushansimiao had the lowest Cd enrichment coefficient in brown rice which significantly than the other varieties; As for the Cd transfer factor (TF) of different parts of rice, the transfer factor of root-to-straw was the lowest, and the transfer factor of chaff-to-brown rice was the highest (except for Xiangyou 1126), the transfer factor of chaff-to-brown rice of Teyou 6811, H Liangyou 991 and Wushansilmiao were significantly lower than those of other varieties. The TF of chaff-to-brown rice of Teyou 6811, H Liangyou 991 and Wushansilmiao were significantly lower than those of other varieties. Correlation analysis showed that content of Cd in brown rice was significantly positively correlated with Cd content in root, and extremely significant correlation (P<0.01) with the TF of chaff-to-brown rice and the Cd enrichment coefficient in brown rice.【Conclusion】The Cd content, Cd enrichment coefficient in brown rice and TF of chaff-to-brown rice of Teyou 6811, H Liangyou 991 and Wushansimiao were relatively low, indicating that the varieties mentioned above have the potential of low Cd accumulation. The varieties should be promoted as low Cd accumulation ones in karst area of northwest Guangxi with other remediation techniques. However, Hengfengyou 777, Yixiang 2239, Fengliangyou 3305, Xiangyou 1126, F You 498 and Guang 8 Youhuazhan account have a higher content of Cd in brown rice, therefor, they should not be recommended to be planted in the polluted fields with soil Cd content greater than 1.12 mg/kg in karst area of northwest Guangxi. [ABSTRACT FROM AUTHOR]

[Objective] In order to provide a reference for rice safety production in cadmium polluted rice fields in Guangxi, the effects of mulberry branch, cassava stalk and bagasse biochar on cadmium (Cd) uptake by rice were studied. [Method] Biochar was prepared from three crop straws of mulberry, cassava and sugarcane bagasse for pot experiment of rice in Cd polluted paddy soil [the experiment set : Mulberry branch biochar applied quantity l. S % (MBl), applied quantity 3. 0 % (MB2), applied quantity 4. S % (MB3); Cassava stalk biochar applied quantity 1. S % (CBl), applied quantity 3. 0 % (CB2), applied quantity 4. S % (CB3); Bagasse biochar applied quantity 1. S % (SBl), applied quantity 3. 0 % (SB2), applied quantity 4. 5 % (SB3); Applied quantity 0 as control (CK)]. The soil pH, soil available cadmium, and the content of cadmium in rice and rice straw were analyzed after rice harvest. [Result] The application of biochar treatment all increased soil pH and the pH of paddy soil treatement with mulberry branch biochar was significantly higher than CK, cassava stalk biochar (except CB3 treatment) and bagasse biochar(P < 0. 05, the same as below). The content of available cadmium in soil decreased significantly, and the treated with mulberry branch biochar was significantly lower than that of bagasse biochar, but not significantly different from that of cassava stalk biochar(except CB3 treatment) (P > 0. OS). The content of Cd in rice grain was lower than CK, among which, the content of of Cd in rice could be reduced by 69. 48 %, 70. 54 % and 74. 70 % by applying the mulberry branch biochar (MBl, MB2 and MB3) than CK; The content of Cd in rice treated with CBl, CB2 and CB3 was significantly reduction to 7. 14 %, 40. S4 % and 41. 46 % than CK respectively; The content of Cd in rice was significantly reduced by 29. 57 %,31. 87 % and 38. 37 % when applying SB 1, SB2 and SB3 than CK. The results of correlation analysis showed that, the content of Cd in rice was highly significantly negatively correlated with soil pH (P < 0. 01, the same as below) and significantly positively correlated with soil available cadmium and highly significantly positively correlated with cadmium content of rice straw. [Conclusion]Application of biocarbon from mulberry branches, cassava stalks and bagasse could effectively reduce the absorption of Cd in rice, and among them application of 4. 5 % mulberry branch biochar was the best, which could maximally decrease the risk of Cd pollution in rice production. [ABSTRACT FROM AUTHOR]

[Objective] To provide a basis for the adjustment of eucalyptus leaves and eucalyptus forest land, the effects of eucalyptus leaves accretion on the resistance physiological of maize were studied. [Method]The five treatments were set as follows: mature eucalyptus leaves 0g/pot (CK) ; mature eucalyptus leaves from 3-month-old tree, 225 g/pot; mature eucalyptus leaves from 3-month old tree, 652 g/pot; mature eucalyptus leaves from 1-year-old tree, 225 g/pot; mature eucalyptus leaves from 1-year-old tree, 652 g/pot. The experiments were conducted with three replications in a complete random block design. And the contents of chlorophyll and activity of SOD/POD/CAT in maize were analyzed in the jointing stage and the maturation stage. [Result] The content of chlorophyll a and chlorophyll b in maize leave were decreased with the increase of accretion amount and leafage of eucalyptus leaves. The activity of SOD in maize (leaves and root) was increased with the increase of accretion amount and the leafage of eucalyptus leaves; The activity of POD in maize with eucalyptus leaves accretion (leaves and roots) was significantly higher than that of the control. As corn plant grew, the activity of POD in maize leaves was decreased, but the activity of POD in maize roots was significantly increased. The activity of CAT in maize leaves was increased significantly in the maturation stage, the activity of CAT in maize roots was significantly higher than that of the control, and it increased with the accretion amount and the leafage of eucalyptus leaves. [Conclusion]The eucalyptus leaves accretion treatment reduced the content of chlorophyll a and chlorophyll b in maize leaves, and affected its photosynthesis function. In order to alleviate the chemical stress from the decomposition of eucalyptus leaves, Maize regulated the activity of antioxidant enzymes in its body. [ABSTRACT FROM AUTHOR]

[Objective] In order to provide a scientific reference for the management of fertilizing in pitaya orchard in Guangxi ,the status of soil nutrients and heavy metals were investigated and evaluated. [Method] The contents of organic matter (OM), nutrients N, P, K, Ca, Mg, Fe,Zn and harmful and heavy metal elements in soil samples of 33 pitaya orchards were collected from main pitaya producing areas of Guangxi were determined. [Result]Soil pH of pitaya orchards in Guangxi was low, 69.7 % pitaya orchards were in acidic and strong acid range; soil organic matter content was abundant; the available nitrogen was shortage,while available P was higher;available K was not distributed uniform;The available Ca, available Mg, available Fe were higher but available Zn was very shortage. The contents of organic matter, total N, P,and K in soil obviously increased with the increasing of cropping years, when pH value and the contents of available nitrogen declined with the increase of planting years ;The contents of heavy metals in soil increased with the increasing of planting years. [Conclusion] On the whole, lower soil pH and lower content of soil available nitrogen, zinc and higher content of soil available phosphorus, iron are the mainly problems in soil of pitaya orchard at present; with the soil acidification and total nutrient and heavy metals accumulated with the in­ creasing of planting yean? in soil, which also exacerbated the risk of contamination in the soil environment of the pitaya orchard in Guangxi. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of leaf barrier combined passivation on the accumulation and transport of cadmium in rice, a field experiment was set up in Guangxi Province. In this study, amino acid chelated selenium nutrient liquid fertilizer and active silicon fertilizer were chosen as leaf barrier agents. Calcium silicon fertilizer and shell powder were chosen as soil passivation agents. Seven treatments were set up, as follows：（1）Rice grown conventionally without special treatment（CK）（; 2）Spraying of 6 000 mL·hm-2 selenium fertilizer at booting stage（Se400）（; 3）Basal application of 3 000 kg·hm-2 silicon calcium fertilizer and 6 000 mL·hm-2 selenium fertilizer sprayed at booting stage（Se400GG）（; 4）Basal application of 3 000 kg·hm-2 shell powder and 6 000 mL·hm-2 selenium fertilizer sprayed at booting stage（Se400BK）（; 5）Spraying of 15 000 mL·hm-2 active silicon fertilizer at booting stage（Si1000）;（6）Basal application of 3 000 kg · hm-2 silicon calcium fertilizer and 15 000 mL · hm-2 active silicon fertilizer sprayed at booting stage（Si1000GG）; and（7）Basal application of 3 000 kg·hm-2 shell powder and 15 000 mL·hm-2 active silicon fertilizer sprayed at booting stage（Si1000BK）. The cadmium content in rice grains, husks, shoots, and roots was determined after harvest. The results showed that compared with CK treatment, all treatments reduced the cadmium content in rice grains to differing degrees, with the effect of the leaf barrier combined with soil passivation being the greatest. The cadmium content in rice grains treated with Se400GG decreased the most, with a decrease of 88.13%; the cadmium content in rice was（0.18±0.01）mg·kg-1, lower than the rice cadmium limit of 0.2 mg·kg-1（1 GB 2762—2017）. The cadmium content in grains decreased by 56.77% after Si1000GG treatment. The two treatments of Si1000 and Se400 with a separate foliar barrier were less effective：the cadmium content in grains only decreased by 18.28% and 9.03%. The main reason why the treatments reduce the content of cadmium in rice grains is that the enrichment and transport coefficients of different parts of the rice are reduced. The root-to-straw transfer factor of Se400GG and Si1000GG treated rice decreased by 84.93% and 72.60%, and the bioconcentration factors of rice grains decreased by 87.88% and 56.06%, while the root-to-straw transfer factor of Se400 and Si1000 treated rice only decreased by 46.58% and 38.36% and the bioconcentration factors of rice decreased by only 12.12% and 15.91%. Leaf barrier combined passivation technology, especially Se400GG, can more effectively block the uptake and transport of cadmium by rice and reduce the content of cadmium in rice grains, which is worthy of being popularized and applied in low-cadmium polluted rice fields. [ABSTRACT FROM AUTHOR]

【Objective】 The effects of selenium fertilizer and silicon fertilizer on the accumulation of cadmium in rice were researched to provide reference for the technical system of obstruction of cadmium in rice. 【Method】The field experiment was carried out，and the main varieties of rice cultivar Baixiang 139 and Zhongguangxiang No. 1 in Guangxi Guiping were selected as the test materials for selenium fertilizer spraying test，respectively: ‘JuFuXi' chelated selenium foliar fertilizer (containing Na2SeO34. 38 g • L-1 ) as the selenium source， set different spraying selenium fertilizer times(0，1，2 times) as three treatments. Silica fertilizer spraying test ： ‘RongDiMei' active silicon leaf fertilizer for the silicon source，with a different dilution factor (water control，diluted 300 times，diluted 500 times) set 3 treatments. The effects of different treatments on soil basic physical and chemical properties，soil total cadmium content，rice yield and total cadmium and selenium contents in rice were tested. 【Result】 (i) The effect of selenium on the yield of rice was not obvious ，and the yield of rice was increased by 4. 58 % - 8. 71 % under the treatment of spraying silicon la fertilizer compared with the control， but the difference was not obvious between different silicon fertilizer treatments. (ii) The application of selenium fertilizer significantly inhibited the accumulation of cadmium in the rice of Baixiang 139. The effect of spraying selenium fertilizer on the booting stage and the first 3 days of heading date was better，the results showed that the content of cadmium in the rice was 0. 03 mg • kg-1, which was 83.33 % lower than that of the control. However, the effect of selenium on the accumulation of cadmium in Zhongguangxiang No. 1 rice was not obvious, (iii) Spraying diluted 300 times and diluted 500 times of the 'Rong- dimei' , the contents of cadmium in the Baixiang 139 rice were 17. 14 % and 11.43 % lower than those in the control. The contents of cadmium in Zhongguangxiang No. 1 were decreased by 67. 31 % and 30. 77 % respectively. 【Conclusion】 The effect of seleniumon the yield of rice was not significant, but the application of silicon fertilizer could significantly increase the yield of rice. Spraying selenium fertilizer could effectively reduce the cadmium content of Baixiang 139 , but had no significant effect on Zhongguangxiang No. 1 rice. The application of different concentrations of silicon fertilizer could significantly reduce the content of heavy metal cadmium in two cultivars. [ABSTRACT FROM AUTHOR]

Microbial community and diversity is an important indicator for monitoring soil quality. Herein, High-throughput sequencing was used to explore microbial communities and diversity of paddy soil under four tillage managements, including conventional tillage CT, no-tillage (NT) , ridge conventional tillage ( RCT) , ridge no-tillage ( RNT). The results showed that there were 10 different dominant microbes in paddy soil at phylum, namely Proteobacteria, Chlorofiexi, Nitrospirae, Barteroidetes, Acidobarteria, Firmieutes , Artinobarteria , Verrueomicrobia, Planrtomycetes and Crenarckaeota, and among them, Proteobarteriaand Chlorofiexi accounting for highest proportion. Compared to CT, NT, RCT and RNT reduced the proportions of Crenarckaeota and Firmicutes in paddy soil, while increased the proportion ofNitrospirae in paddy soil, the effect was more prominent in RCT treatment. Compared to CT, NT increased the paddy soil microbial diversity index ( Chao 1, PD whole tree, Observed species index) , the ridge tillages (RCT, RNT) significantly increased the paddy soil microbial diversity index (Chao 1 ,PD whole tree, Observed species index) , which RCT had most significant effect on index of microbial diversity. Tillage managements changed the paddy soil microbial community and diversity index, which ridge tillage generate greater benefits for soil microbe toward diversification. [ABSTRACT FROM AUTHOR]