How can fertilization regimes and durations shape earthworm gut microbiota in a long-term field experiment?

The positive roles of earthworms on soil functionality has been extensively documented. The capacity of the earthworm gut microbiota on decomposition and nutrient cycling under long-term fertilization in field conditions has rarely been studied. Here, we report the structural, taxonomic, and functional responses of Eisenia foetida and Pheretima guillelmi gut microbiota to different fertilization regimes and durations using 16S rRNA gene-based Illumina sequencing and high-throughput quantitative PCR techniques. Our results revealed that the core gut microbiota, especially the fermentative bacteria were mainly sourced from the soil, but strongly stimulated with species-specificity, potential benefits for the host and soil health. The functional compositions of gut microbiota were altered by fertilization with fertilization duration being more influential than fertilization regimes. Moreover, the combination of organic and inorganic fertilization with the longer duration resulted in a higher richness and connectivity in the gut microbiota, and also their functional potential related to carbon (C), nitrogen, and phosphorus cycling, particularly the labile C decomposition, denitrification, and phosphate mobilization. We also found that long-term inorganic fertilization increased the abundance of pathogenic bacteria in the P. guillelmi gut. This study demonstrates that understanding earthworm gut microbiota can provide insights into how agricultural practices can potentially alter soil ecosystem functions through the interactions between soil and earthworm gut microbiotas.

[Assessment of rice achievable productivity and its application in rice production management division: a case study in Fuyang County of Zhejiang Province, East China].

Rice productivity is the key factor affecting rice production and its sustainable development. Based on the gradation of cultivated land quality at county-level, this paper evaluated the rice productivity in Fuyang County of Zhejiang Province, and, through selected sampling field investigation and according to the land productivity index of paddy field quality, a model for assessing rice achievable productivity was established, aimed to analyze the regional rice productivity and its achievable productivity. In the study area, there was a positive correlation between the land productivity index and rice yield. For single cropping rice, its achievable productivity was 1.70 x 10(5) t, being 1.6 times of its realistic productivity (1.04 x 10(5) t). In 2009, the realistic rice productivity per unit area was 7676 kg x hm(-2), and the achievable productivity was 8831 kg x hm(-2), with a production potentiality of +15%, a big potential of rice production capacity in the county. Through the analyses of rice productivity, relative superiority of rice production scale, and its growth potential index in the villages and towns, the rice production of Fuyang County was divided into three regions, i. e., key enhancement region, optimization construction region, and development protection region.

[Effects of Sedum plumbizincicola--Oryza sativa rotation and phosphate amendment on Cd and Zn uptake by O. sativa].

In a pot experiment, hyperaccumulator Sedum plumbizincicola and low-cadmium accumulating Oryza sativa cultivar "Zhongxiang No. 1" were planted in rotation on a heavy metals-polluted soil, and calcium magnesium phosphate (Ca-P) and rock phosphate (P-R) were amended, aimed to study the effects of the rotation and phosphate amendment on the growth of the two plants and the zinc- and cadmium accumulation in their shoots. After the amendment of 50 g P-R x kg(-1), the Zn and Cd uptake by S. plumbizincicola was 11.5 mg x pot(-1) and 0 x 79 mg x pot(-1), respectively, being significantly higher than that after the amendment of 4 g Ca-P x kg(-1). After the planting of S. plumbizincicola, the Zn and Cd concentrations in "Zhongxiang No. 1" increased, but the amendment of Ca-P decreased the accumulation of Zn and Cd in rice shoot significantly. The rotation with S. plumbizincicola and the amendment of Ca-P and P-R could immobilize the Zn and Cd in the contaminated soil as indicated by the quantitative change of NH4OAc-extractable Cd and Zn, and the efficiency of amendment with Ca-P was better than that of amendment with P-R. Field trial showed that amendment with Ca-P could not only increase the rice yield, but also reduce the Zn and Cd accumulation in rice shoot to a certain extent.

[Effect of planting densities on yields and zinc and cadmium uptake by Sedum plumbizincicola].

A field plot experiment was conducted to study the effects of planting densities on the growth and heavy metals uptake by Sedum plumbizincicola. The results showed that yields of Sedum plumbizincicola were enhanced with the increase of planting density; however, there was no further increase when planting density was too high. With planting density increasing from 1.1 x 10(5) plants per hm2 to 4.4 x 10(5) plants per hm2, Cd and Zn uptake of aboveground Sedum plumbizincicola increased from 0.208 kg x hm(-2) to 0.631 kg x hm(-2), from 13.2 kg x hm(-2) to 58.7 kg x hm(-2), respectively; yet, there was no significant enhancement between the planting density of 4.4 x 10(5) plants per hm2 and 1.0 x 10(6) plants per hmb2. When planting density was 4.4 x 10(5) plants per hm2, the Cd and Zn removal rates in contaminated soil were 21.1%, 4.60%, respectively. Appropriate planting density would benefit Cd and Zn uptake of aboveground Sedum plumbizincicola, and shorten phytoremediation period.

[Assessing soil Zn content using decision tree analysis].

Taking Fuyang county of Zhejiang Province as the study area, the present study estimated soil Zn concentration (divided by its local background value into G1, G2, G3, G4 and G5) using CART methods, based on 184 soil samples (0-20 cm). The environmental factors used to infer the Zn concentration rules included soil types, pH, organic matter, agricultural land uses, industry plant types, road and village density. The other 41 soil samples were used to test the prediction results. The Zn concentration classes estimated by CART have accuracy in attribution to the right classes of 80.49%. This is a 21.95% improvement on Zn classes estimated by ordinary Kriging method. Concretely, it improved the precision much for G1, G3 and G4, while obtained similar precision for G2 and G5. Moreover, CART provided some insights into the sources of current soil Zn contents. The categories of industrial plants play the most important role in separating the high and low level of Zn concentration (G1, G2 and G3, G4, G5), and the pH value, soil types and agricultural types play important roles in differentiation among G1 and G2, and among G3, G4 and G5.