[Effect of Ca-bentonite on Cu and Zn Forms in Compost and Soil, and Their Absorption by Chinese Cabbage].

Aerobic composting was conducted to evaluate the effects of the different ratios (0%, 2.5%, 5%, 7.5%, and 10%) of Ca-bentonite (CB) on the speciation of Cu and Zn during pig manure composting, while pot experiment was performed to investigate the role of CB-added compost on the bio-availability of Cu and Zn to Chinese cabbage and its biomass. The results showed that the exchangeable fractions of Cu and Zn decreased, while their oxidized and residual fractions gradually increased during composting; CB addition reduced the distribution ratios of bio-available Cu and Zn in mature compost by approximately 19.84%-48.90% and 4.94%-16.39%, compared to those in the 0% CB-added treatment, and the best result was found in the 10% CB-added treatment.. Meanwhile, the pot experiment confirmed that the addition of compost considerably increased soil organic matter (OM) and electrical conductivity (EC) but decreased soil pH value. On the contrary, the application of CB effectively decreased EC and increased soil pH but inhibited OM mineralization in soil as compared to non-amended treatment. While addition of compost significantly increased plant dry biomass as compared to that with soil alone, maximum biomass was obtained[(6.51±0.34) g·pot-1] in 10% CB-added compost. After the application of CB-added compost, the contents of the bio-available factions of Cu in the harvested soil increased, while the contents of the exchangeable fractions of Zn decreased by 38.91%, 43.69%, 46.02%, 45.12%, and 54.65%, respectively. The absorption of Cu and Zn by Chinese cabbage was considerably reduced after the application of compost, while the uptake of Zn in the plant declined as the CB rates increased, and the absorption of Cu increased. The study indicated that 10% CB addition could significantly reduce the bioavailability of Cu and Zn in compost, and also showed a continuous effect on restricting the bioavailability of Zn after land utilization. Meanwhile CB amendment enhanced Chinese cabbage biomass and reduced the uptake of Zn.

[Effect of Alkali Solids Amendment on Sewage Sludge Aerobic Composting and the Potential of Related Products on Infertile Soil Amelioration].

Aiming to evaluate the influence of alkali solids amendment on the sewage sludge aerobic composting and to declare the potential of related composts on infertile soil amelioration, sewage sludge and sawdust mixture were amended with straw biochar, hardwood biochar, fly ash and lime by 10% addition ratio in dry weight during the aerobic composting process; finally, potential of the related composts on the infertile soil amelioration was investigated by pot experiment. The results showed that the alkali solids amendment could prolong the thermophilic phase, and promote the composting material heat inactivation. Addition of straw and hardwood biochar facilitated more than 21.65% and 18.16% organic matter degradation. During the composting, the compost pH decreased at the beginning and then gradually increased before reached values of 6.78-7.33, while the fly ash and lime amendments could lead to higher pH values in the beginning stage. The alkali solids amendment reduced the salinity of the compost with final products EC lower than 3000 µS·cm-1. The addition of straw and hardwood biochar could increase the total nitrogen content by reducing the ammonia loss at the beginning, while the fly ash and lime amendments would result in ammonia loss in the beginning stage. Despite the composting variation, the contents of nitrate increased and the ammonium salt content decreased gradually. The biochar addition can accelerate the nitrate transformation while the fly ash and lime amendment had slight inhibitory effect on the nitrate transformation and plant germination. The pot experiment revealed that applying compost products could significantly improve the brassica growth, Cu and Zn micronutrients accumulation since the compost addition could increase the soil organic carbon content, as well as soil N, P, and K contents. Compared with the non-amended compost, the alkali solids amendment could slightly reduce the Cu and Zn micronutrients accumulation, while the fertile potentials were acceptable. The study indicated that straw and hardwood biochar were more suitable than fly ash and lime as compost amendment, and the related compost products had great potential on infertile soil amelioration.