Silicon-calcium fertilizer increased rice yield and quality by improving soil health.

It is important to ensure the nutritional quality and safe production of rice. Here, plot experiments were used to analyze the effects of three soil amendments-10 t ha-1 of biochar (BC), 1.5 t ha-1 of lime (LM), and 2.25 t ha-1 of silicon-calcium fertilizer (SC)-on the soil characteristics, rice yield and quality of double-cropping rice grown in mildly cadmium-polluted paddy fields. Compared with the control treatment (CK), the BC and SC treatments significantly improved rice processing, appearance and nutritional quality, but reduced cooking quality. All three soil amendments significantly reduced cadmium (Cd) content in brown rice. Soil amendments could significantly increase soil pH and reduce soil available Cd content. The application of the BC and SC treatments increased the content of each nutrient index in the soil (SOM, NN, AP, AK). Correlation analysis showed that the improvement in rice processing, appearance, and nutritional quality was mainly affected by the comprehensive effects of soil SOM, NN, AP and AK; the hygiene quality was mainly affected by soil pH and available Cd. In terms of benefit analysis combined with cost, the SC treatment had the highest benefit effect. Taken together, in mildly cadmium-polluted paddy fields, the application of silicon-calcium fertilizer improved the soil quality, thereby increased the yield and quality of rice, and had the best effect on increasing income.

Mechanisms insights into Cd passivation in soil by lignin biochar: Transition from flooding to natural air-drying.

Biochar shows great potential in soil cadmium pollution treatment, however, the effect and mechanisms of biochar on cadmium passivation (CP) during the long-term process of soil from flooding to natural air-drying are not clear. In this study, a 300-day experiment was conducted to keep the flooded water level constant for the first 100 days and then dried naturally. Mechanisms of CP by lignin biochar (LBC) were analyzed through chemical analysis, FTIR-2D-COS, EEMs-PARAFAC, ultraviolet spectroscopy characterizations, and microbial community distribution of soil. Results showed that application of LBC results in rapid CP ratio in soil within 35 days, mainly in the residual and Fe-Mn bound states (total 72.80%). CP ratio further increased to 90.89% with water evaporation. The CP mechanisms include precipitation, electrostatic effect, humus complexation, and microbial remediation by promoting the propagation of fungi such as Penicillium and Trichoderma. Evaporation of water promoted the colonization of aerobic microorganisms and then increased the degree of soil humification and aromatization, thereby enhancing the cadmium passivation. Simultaneously, the biochar could reduce the relative abundance of plant pathogens in soil from 1.8% to 0.03% and the freshness index (ß/α) from 0.64 to 0.16, favoring crop growth and promoting carbon sequestration and emission reduction.

Difference in Cd accumulation among varieties with different growth duration corresponding to typical agro-climate condition in rice ratooning system.

Introduction: The ratoon rice planting area is gradually expanding, but there has been relatively little research on ratoon rice grains contaminated with Cd. Methods: In this study, five ratoon rice varieties were selected and divided into three groups according to early-maturity (growth duration: 100-110 days), mid-maturity (growth duration: 110-120 days) and late-maturity (growth duration: 120-130 days) varieties. Field experiments were done to study the differences in Cd accumulation among ratoon rice varieties with different growth duration. Results: The results showed that the Cd accumulation and concentration of grains spikelet at each growth stage in the main crop were in the order of late-maturity > mid-maturity > early-maturity varieties. However, the trends in Cd concentration and accumulation in grains spikelet during the ratoon crop were the opposite. Analysis found that as the growth duration of the variety extended, the accumulated temperature and daily average temperature in the main crop increased, which significantly increased the translocation factors of Cd from root, stem, and leaf to grains spikelet, and increased the daily average Cd accumulation rate in grains spikelet. The daily average temperature in the ratoon crop increased as the growth duration shortened. The early-maturity variety had higher Cd accumulation in stubble, which promoted the translocation of Cd from the root, stem, and leaf of the plant to the grains spikelet. Discussion: Therefore, appropriately shortening the growth duration of the main crop and extending the growth duration of the ratoon crop are important ways to reduce Cd accumulation in ratoon rice in areas with mild Cd pollution.

Soil Cd bioavailability response characteristics to microbes in paddy fields with co-incorporation of milk vetch, rice straw and amendments.

Excessive heavy metals in soils can threaten food security and soil health. New practical technology is urgently needed to remediate cadmium (Cd) contaminated paddies in many parts of the world. Chinese milk vetch (M), rice straw (R), and soil amendments can reduce Cd activity in soil; however, the mechanism underlying this reduction is not well understood. This study explored the impact of co-incorporation of milk vetch, rice straw, and either lime (L), sesbania biochar (B), or sepiolite on soil Cd bioavailability through field experiments. The results indicated that the rice grain Cd concentrations in soil treated with milk vetch + rice straw + fertilizer (MRF, 16.6 %), milk vetch + rice straw + fertilizer + sesbania biochar (MRFB, 50.1 %), and milk vetch + rice straw + fertilizer + lime (MRFL, 48.3 %) were significantly lower than those in soil treated with fertilizer (F). The acid-soluble Cd concentrations influenced rice grain Cd uptake and were 33.9 % and 47.5 % lower for the MRFB and MRFL treatments, respectively, than for F alone. A decrease in acid-soluble Cd (AciCd) was accompanied by a decrease in Eh and increases in pH, Fe2+, cation exchange capacity, and dissolved organic carbon. The MRFB treatment promoted iron plaque (IP) formation on the rice root surface. The relative abundances of Desulfobacterota and Verrucomicrobiota were higher for the MRFB treatment than for the other treatments. A partial least squares path model confirmed that Aci-Cd and low-crystalline IP (IP-Feh) influenced the rice grain Cd concentration.

Selection of pollution-safe head cabbage: Interaction of multiple heavy metals in soil on bioaccumulation and transfer.

Screening for pollution-safe cultivars (PSCs) is a cost-effective strategy for reducing health risks of crops in heavy metal (HM)-contaminated soils. In this study, 13 head cabbages were grown in multi-HMs contaminated soil, and their accumulation characteristics, interaction of HM types, and health risks assessment using Monte Carlo simulation were examined. Results showed that the edible part of head cabbage is susceptible to HM contamination, with 84.62% of varieties polluted. The average bio-concentration ability of HMs in head cabbage was Cd> > Hg > Cr > As>Pb. Among five HMs, Cd and As contributed more to potential health risks (accounting for 20.8%-48.5%). Significant positive correlations were observed between HM accumulation and co-occurring HMs in soil. Genotypic variations in HM accumulation suggested the potential for reducing health risks through crop screening. G7 is a recommended variety for head cabbage cultivation in areas with multiple HM contamination, while G3 could serve as a suitable alternative for heavily Hg-contaminated soils.

The Expression of IbMYB1 Is Essential to Maintain the Purple Color of Leaf and Storage Root in Sweet Potato [Ipomoea batatas (L.) Lam].

IbMYB1 was one of the major anthocyanin biosynthesis regulatory genes that has been identified and utilized in purple-fleshed sweet potato breeding. At least three members of this gene, namely, IbMYB1-1, -2a, and -2b, have been reported. We found that IbMYB1-2a and -2b are not necessary for anthocyanin accumulation in a variety of cultivated species (hexaploid) with purple shoots or purplish rings/spots of flesh. Transcriptomic and quantitative reverse transcription PCR (RT-qPCR) analyses revealed that persistent and vigorous expression of IbMYB1 is essential to maintain the purple color of leaves and storage roots in this type of cultivated species, which did not contain IbMYB1-2 gene members. Compared with IbbHLH2, IbMYB1 is an early response gene of anthocyanin biosynthesis in sweet potato. It cannot exclude the possibility that other MYBs participate in this gene regulation networks. Twenty-two MYB-like genes were identified from 156 MYBs to be highly positively or negatively correlated with the anthocyanin content in leaves or flesh. Even so, the IbMYB1 was most coordinately expressed with anthocyanin biosynthesis genes. Differences in flanking and coding sequences confirm that IbMYB2s, the highest similarity genes of IbMYB1, are not the members of IbMYB1. This phenomenon indicates that there may be more members of IbMYB1 in sweet potato, and the genetic complementation of these members is involved in the regulation of anthocyanin biosynthesis. The 3' flanking sequence of IbMYB1-1 is homologous to the retrotransposon sequence of TNT1-94. Transposon movement is involved in the formation of multiple members of IbMYB1. This study provides critical insights into the expression patterns of IbMYB1, which are involved in the regulation of anthocyanin biosynthesis in the leaf and storage root. Notably, our study also emphasized the presence of a multiple member of IbMYB1 for genetic improvement.

Integrated transcriptome and microRNA profiles analysis reveals molecular mechanisms underlying the consecutive monoculture problem of Polygonatum odoratum.

Polygonatum odoratum is a historically traditional Chinese medicine plant. However, the consecutive monoculture problem (CMP) widespread in other Chinese medicine limiting their cultivation on a large scale. In this study, the physiological data showed the adverse effect of CMP on the growth of P. odoratum under the consecutive cropping (CC) compared with the first cropping (FC). Then the high-throughput sequencing of miRNA and mRNA libraries of leaves and roots from FC and CC P. odoratum plants identified 671 differentially expressed genes (DEGs) and 184 differentially expressed miRNAs and revealed that the DEGs and target genes of the miRNAs were mainly involved in starch and sucrose metabolism, phenylpropanoid and brassinosteroid biosynthesis. The KEGG analysis revealed that the DEGs between CC and FC roots were enriched in the plant-pathogen interaction pathway. This study provided the expression regulation of genes related to CMP of P. odoratum but also suggested that CMP may result in the serious damage of pathogens to roots and cause the slow growth in the consecutive cropping plants.

Phosphate-modified ferric-based material remediates lead and arsenic co-contaminated soil and enhances maize seedling growth.

Soil heavy metal pollution, especially lead (Pb) and arsenic (As), is a global issue that requires urgent attention. In the present study, phosphate-modified ferric-based material (PFM) was used to remedy Pb and As co-contaminated soil. The remediation potential of PFM on Pb and As co-contaminated soil was studied by static culture experiments, and the effect on maize (Zea mays L.) seedling growth was studied using pot experiments. The results showed that the bioavailability of Pb and As in the soil and their accumulation in the seedlings were reduced when PFM was added to the soil. At 2-6 wt% PFM, the remediation rates of Pb and As reached 57%-82% and 62%-76%, respectively, and their accumulation in the seedlings decreased by 27.8%-68% and 55.6%-70%. The optimal amount of PFM was 4 wt% of the soil. There was a linear correlation between the amount of DTPA-extractable Pb or NaHCO3-extractable As in the soil and the amount of Pb or As accumulated by the seedlings. The correlation coefficients of Pb and As reached 0.7690-0.8166 and 0.9982-0.9779. Seedling growth was also promoted. Compared with the controls, the seedling emergence rate increased by 1.4%-4%, plant height increased by 4.1%-12.4%, plant weight increased by 29.6%-37%, and the root length increased by 5%-52%. In summary, PFM offers an environmentally friendly approach with excellent potential for the remediation of Pb and As co-contaminated soil.

[Relationships between initial chemical composition of forest leaf litters and their decomposition rates in degraded red soil hilly region of Southern China].

A pot experiment with litter bags was conducted to study the relationships between the initial chemical composition of 8 kind forest leaf litters and 4 kind mixed leaf litters and their decomposition rates in degraded red soil hilly region of Southern China. Comparing with needle-leaf litters, broad-leaf litters had significantly higher contents of N, P, K, and Mg, but significantly lower contents of lignin and C. The decomposition rates of test litters were significantly positively correlated with the litters initial contents of N, P, K, and Mg (P < 0.05), and negatively correlated with the initial contents of lignin and C as well as the lignin/N, lignin/P, and C/P ratios (P < 0. 05). The lignin content explained 54.3% of the variation in litter decomposition rates, being the key affecting factor. Litters C, N, and P contents also had close correlations with the decomposition rates, and together with lignin content, contributed 81.4% of the variation. It was suggested that in the process of vegetation restoration in degraded red soil hilly region of Southern China, introducing broad-leaf trees with lower lignin and higher N and P contents would benefit the acceleration of forest litters decomposition and the restoration of soil fertility.

[Effects of cadmium on rice seed germination].

With 319 rice varieties as test objects, this paper studied the effects of cadmium on their seed germination. The results showed that after treated with 10 mg x L(-1) of Cd2+, seed germination rate was less affected, but root growth was restrained evidently. Cadmium had more serious impact on root than on sprout. Different rice varieties had different germination responses to Cd2+, with the sequence of conventional rice (Japonica rice) > hybrid rice (Indianica rice) > conventional rice (Indianica rice). The root length and number of two-line sterilities were restrained more strongly than those of three-line sterilities. Based on their responses to Cd2+, the test 319 varieties were clustered into 3 types, i.e., endurant type, medium type, and sensitive type.

[Dynamics of soil water under Vernicia fordii plantation in hilly red soil region of Southern China].

By using time domain reflectometry (TDR) , a fixed-position monitoring was made on the dynamic characteristics of soil water under Vernicia fordii plantation in the hilly red soil region of Southern China. The results showed that there was a significant difference in the soil water storage among different months, and the dynamics of soil water could be described as the phases of accumulation, depletion, and stabilization. Soil water had a significant variation in its vertical distribution, and the variation pattern differed in different seasons. Significant correlations existed between soil water storage and meteorological factors such as relative humidity (RH) , air temperature (t) , vapor pressure deficit (VPD) and rainfall (R) (P < 0. 05). After rain, soil water loss had a significant hyperbolic correlation with drought duration, while soil water storage had a significant linear negative correlation with this duration (P < 0. 05). With the extension of drought duration after rain, soil water loss tended to vary gently with increasing soil depth.