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Soil C:N:P stoichiometry plays a vital role in nutrient cycling in ecosystems, but its importance to P transformation in paddy soil remains unclear. We investigated the effect of soil C:N:P stoichiometry on P mobility and uptake under long-term fertilization. Three treatments, CK (no fertilization), NPK (inorganic nitrogen, phosphorus and potassium fertilization) and NPKM (combined inorganic NPK fertilizer and manure application), were selected from two long-term experiments of paddy soil that were initiated in 1991 and 1982 in Chongqing and Suining, respectively. The results showed that in comparison the control treatment, under long-term fertilization, soil pH decreased. In comparison with the NPK and CK treatments, the NPKM treatment significantly increased soil nutrient contents, P uptake and phosphatase activities. In comparison to the CK treatment, the NPK and NPKM treatments significantly decreased soil C:N, C:P and N:P ratios. In comparison to NPK and CK treatments, the NPKM treatment decreased residual-P at both sites. Compared with CK treatment, the NPKM treatments increased labile-P and moderately labile-P by 987% and 144%, respectively, and NPK treatment increased these factors by 823% and 125%, respectively, at the Chongqing site. At the Suining site, with NPKM treatment, increases in labile-P and moderately labile-P were 706% and 73%, respectively, and with NPK treatment, the increases were 529% and 47%, respectively. In contrast, non-labile-P was significantly decreased with NPKM treatment in comparison to that with NPK and CK treatments. Moreover, increases in soil C:N and C:P ratios decreased the labile-P pools and increased non-labile-P pools. A path analysis indicated that soil C:N:P stoichiometry indirectly controlled P uptake by directly affecting P transformation from non-labile to labile-P pools. Moreover, the non-labile-P in soil with high SOM and P content directly affected P uptake, indicating that soil P transformation is mainly driven by soil C and P in paddy soil. In conclusion, understanding mechanism of P mobility influenced by soil C:N:P stoichiometry could be helpful to manage soil P fertility under long-term fertilization in paddy soils of these regions.

In this study, Hydroponic endivia with completely decomposed distiller’s grains, tea residue and extraction of commercial organic manure were applied to study its effects on growth and nutritional quality of endivia, as compared with modified Hoagland nutrient. The results showed that the root-shoot ratio of endivia under all treatment conditions was higher than that in CK group. Among them, treatment Ⅳ exhibited best improve efficiency; the treatment of Ⅰ, Ⅱ, Ⅴ, Ⅵ were beneficial to reduce the nitrate content. The treatment Ⅰ significantly increased the content of VC and soluble sugar. The soluble protein content of treatment Ⅴ was the highest. Above all, the application of tea residue and commercial organic fertilizer extracts in the actual production of hydroponic lettuce needs further and deeper research.

Straw of Solanum photeinocarpum accessions originating from two climatic-ecological zones (Chengdu, in the Mountain-Central Subtropical-Cold Zone; and Ya'an, in the Central Subtropical-Long Spring and Summer-Drought Zone) and their reciprocal F1 hybrids were added to Cd-contaminated soil, and their effects on the growth and Cd accumulation of lettuce were evaluated. Addition of S. photeinocarpum straw significantly increased biomass and decreased Cd content of lettuce, especially the straw of F1 hybrids raised from a Chengdu pollen donor. Shoot biomass was increased by 26.87%and the shoot Cd content was decreased by 25.86% compared with those of the control. The chlorophyll content and net photosynthetic rate were increased in response to the addition of S. photeinocarpum straw, and the effects of straw of reciprocal F1 hybrids were superior to those of the parents. Application of S. photeinocarpum straw promoted osmoticas (soluble sugar, soluble protein, free proline) contents and activities of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT)], reduced malondialdehyde (MDA) accumulation, and thus effectively improved the resistance of lettuce to Cd stress. S. photeinocarpum straw increased soil pH and organic matter content, and consequently decreased soil exchangeable Cd content, the strongest effect was achieved by application of S. photeinocarpum straw of reciprocal F1 hybrids raised from a Chengdu pollen donor, in response to which the soil exchangeable Cd content was decreased by 29.62% compared with that of the control. Therefore, the application of S. photeinocarpum straw in Cd-contaminated soil promoted growth and reduced the risk of Cd contamination of lettuce plants. The effects of straw from reciprocal F1 hybrids derived from a Chengdu pollen donor were superior to those of straw from the parents, and thus may be effectively used to improve the safe production of lettuce in Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

Two pot experiments were conducted to study the effects of intercropping with cadmium (Cd) accumulator plant Eclipta prostrata and hyperaccumulator plant Crassocephalum crepidioides on the growth and Cd accumulation of tomato seedlings. In the preliminary experiment, intercropping with E. prostrata and C. crepidioides promoted the growth and decreased the Cd content in roots and shoots of tomato seedlings. In the further experiment, intercropping with E. prostrata and C. crepidioides had the same effects on the growth and Cd content of tomato seedlings as the preliminary experiment. In the further experiment, when three plant species (E. prostrate, C. crepidioides and tomato) intercropping together, the root and shoot biomasses of tomato seedlings got the maximum, and the Cd content in tomato seedlings got the minimum. Compared with the monoculture of tomato, three plant species intercropping increased the root and shoot biomasses of tomato seedlings by 49.28% and 64.19%, respectively, and decreased the Cd contents in roots and shoots of tomato seedlings by 17.35% and 22.35%, respectively. Intercropping with E. prostrata and C. crepidioides also increased the photosynthetic pigment content and enhanced the antioxidant enzyme activity of tomato seedlings. For accumulator and hyperaccumulator plants, intercropping with tomato inhibited the growth of E. prostrata and C. crepidioides, while increased the Cd content in two plant species. Therefore, intercropping with E. prostrata and C. crepidioides could promote the growth and reduce the Cd uptake of tomato seedlings, and three plant species intercropping together was the best combination. [ABSTRACT FROM AUTHOR]