[Analysis on Driving Factors, Reduction Potential, and Environmental Effect of Inorganic Fertilizer Input in Chongqing].

In this study, we sought to quantify the effect of planting structure change on fertilizer input and environmental cost in Chongqing and develop scientific and rational strategies for chemical fertilizer reduction. Based on the crop fertilizer quota standard and large sample farmer survey data under the medium productivity level in Chongqing, we evaluated and analyzed the application reduction potential and environmental benefits of fertilizer with the difference method and life cycle assessment. The results showed that:① since Chongqing became a municipality directly under the central government (1997), Chongqing crop planting structure had greatly changed, and the proportion of food crop (rice, corn, wheat, bean, and potato) decreased by 21%. The area of fruits and vegetables increased from 3.36×105 hm2 to 1.05×106 hm2, and their proportion increased by 20%. ② Nearly 55% of fertilizers had been consumed by vegetable (37%) and citrus production systems, and 11%, 12%, and 12% of fertilizers were consumed by rice, corn, and potato, respectively. ③ The total fertilizer reduction of the Chongqing planting industry could reach up to 1.69×105 tons during the period of "the 14th Five-Year Plan," with a fertilizer reduction potential of 18.6%. The fertilizer reduction potential (reduction amount) of rice, corn, citrus, and vegetables would reach 0.3% (2.9×102 tons), 12% (1.45×104 tons), 21% (3.65×104 tons), and 30% (1.18×105 tons), respectively. On the other hand, the rape system was insufficient in phosphorus potassium fertilizers, and the corn tended to be insufficient in potash fertilizer. ④ The current production level was low, and the nitrogen loss, greenhouse gas emissions, and eutrophication potential in the planting industry of Chongqing reached 1.81×105 tons (N), 1.43×107 tons (CO2-eq), and 1.74×105 tons (PO4-eq). With the increase in the realization degree of the crop quota standard (60%-100%), the reactive nitrogen loss, greenhouse gas emissions, and eutrophication potential decreased by 14.9%-24.9%, 10.1%-16.7%, and 13.8%-23%, respectively. The structure of the planting industry in Chongqing significantly changed, the total fertilizer consumption in Chongqing tended to decline gradually, and the fertilization intensity of commercial crops stayed at a high level. The agricultural fertilizer reduction potential and the reactive nitrogen and greenhouse gas emission reduction potential were large, especially for citrus and vegetable production systems. However, it is also necessary to pay attention to insufficient corn potash fertilizer and rape phosphorus potassium fertilizer investment and carry out collaborative promotion of fertilizer reduction.

Harvesting more grain zinc of wheat for human health.

Increasing grain zinc (Zn) concentration of cereals for minimizing Zn malnutrition in two billion people represents an important global humanitarian challenge. Grain Zn in field-grown wheat at the global scale ranges from 20.4 to 30.5 mg kg-1, showing a solid gap to the biofortification target for human health (40 mg kg-1). Through a group of field experiments, we found that the low grain Zn was not closely linked to historical replacements of varieties during the Green Revolution, but greatly aggravated by phosphorus (P) overuse or insufficient nitrogen (N) application. We also conducted a total of 320-pair plots field experiments and found an average increase of 10.5 mg kg-1 by foliar Zn application. We conclude that an integrated strategy, including not only Zn-responsive genotypes, but of a similar importance, Zn application and field N and P management, are required to harvest more grain Zn and meanwhile ensure better yield in wheat-dominant areas.

[Dynamic change of phosphorus leaching of neutral purple soil at different re-wetting rate].

Re-wetting was one of the most common forms of abiotic stresses experienced by soils. To investigate the effects of soil re-wetting rate on phosphorus (P) leaching and the relationship between soil microbial biomass carbon (MBC) and forms of P in leachate; five kinds of neutral purple soils of different fertilizer treatments were analyzed using simulating lab test at re-wetting rate of 0 h, 2 h, 4 h, 24 h and 48 h. The results showed that: (1) The lowest content of MBC appeared at the rate of 2 h during the soil re-wetting process, and the content of MBC increased with the reducing re-wetting rate. (2) Slower re-wetting helped to enhance soil microbial activity and the enhancement effect of organic fertilizer with NPK fertilizer (MNPK) was more significant. (3) The P leaching events of all fertilizer treatments occurred mainly at rapid re-wetting rates such as 0 h, 2 h, 4 h. Slower re-wetting was an important measure to prevent P leaching especially for the soils applied with chemical fertilizers, and it was of great significance in the field management of P. (4) Dissolved organic phosphorus (DOP) was the primary leaching part in leachate, and the variation range of ratio of total dissolved phosphorus (TDP) to total phosphorus (TP) and DOP to TP was 35.42%-85.99% and 29.74%-78.58% respectively. (5) With the reducing of re-wetting rate, significant negative correlation was observed between MBC and TP, TDP as well as DOP in the leachate (P < 0.05). To sum up, it was speculated that the P in soil leachate mainly came from soil microorganisms.

Long-term fertilisation causes excess supply and loss of phosphorus in purple paddy soil.

BACKGROUND: Phosphorus (P) loss from cropland is accelerating the eutrophication of waters around the world such as the Three Gorges Reservoir (TGR) in China. We investigated whether purple paddy soil under long-term P applications was a major source of P efflux to the TGR. RESULTS: Substantial surplus P in the plough layer (0-20 cm) was evident after 15-year P applications. Available P (Olsen-P) in the plough layer ranged from 1.9 to 42.4 mg kg(-1) and some of which will exceed the threshold of 30 mg kg(-1) for environmental concern within 7 years of P application (inorganic NPK with or without organic fertiliser). Between 30 and 70% of Olsen-P was leached out of the 0-30 cm soil layer. Surplus P resulted in high P concentrations in the surface water during the rice cropping season, and these concentrations exceeded those in most waters of the TGR and exceeded the critical level for eutrophication (0.1 mg L(-1)) during the first 10 days after rice planting. Furthermore, total P in run-off due to rainfall events exceeded the level for eutrophication, with a total loss of 43.2-147.9 g P ha(-1) depending on the fertilisation. CONCLUSION: Current agronomic P management in purple paddy soil is environmentally unsustainable in terms of the adverse impact on surface water quality. Integrated P management practices are urgently required to optimise crop yield while minimising P loss in order to protect surface water quality in the TGR region.

Gambogenic acid-induced time- and dose-dependent growth inhibition and apoptosis involving Akt pathway inactivation in U251 glioblastoma cells.

Glioblastoma multiforme is the most common and aggressive type of primary brain tumor. Uncontrolled activation of the PI3K/Akt signaling pathway resulting from genetic alterations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and epidermal growth factor receptor (EGFR) correlates with poor prognosis and resistance to chemotherapy and radiotherapy of glioblastomas. In this study, we found that gambogenic acid (GNA), a polyprenylated xanthone isolated from the traditional medicine gamboge, efficiently arrested the cell cycle at the G(0)/G(1) phase by specifically repressing the expression of cyclin D1 and cyclin E, suppressed cell proliferation, colony formation and cell migration, and induced caspase-dependent apoptosis in U251 glioblastoma cells in a time- and dose-dependent manner. The pro-apoptotic effect of GNA on U251 cells was shown to be mediated through inactivation of the Akt pathway, because GNA efficiently suppressed the expression level of EGFR and reduced the phosphorylation of Akt (T308) and GSK3ß (S9). Furthermore, the combined treatment with LY294002, a specific inhibitor of the PI3K/Akt kinase pathway, and GNA showed a synergistic or additive effect on the growth of U251 cells. Our results showed that GNA is a promising therapeutic agent for glioblastomas.

[Dynamic characteristics of phosphorus in purple paddy soil and its environmental Impact].

The dynamic characteristics of phosphorus (P) in the surface water and runoff of paddy field with different P fertilizing treatments were investigated using the field experiment under the independent irrigation system as well as its environmental impact. The results showed that the concentration of total phosphorus (TP) in the surface water increased as the fertilizing amounts enhanced and reached the peak values after 24 h for all treatments in range of 0.928-3.824 mg/L. And the fluctuation of TP concentration in surface water was drastic during the first 30 days with the average contents of 0.259-1.433 mg/L which exceeded the critic values of eutrophication. Therefore, the field managements such as inter-tillage and drainage should be avoided during the time. After 40 days, the TP concentration declined slowly and then came to stabilization with low values after 60 days. The contents of different P forms in the runoff water increased with the improved amounts of precipitation and fertilizing and above 50% was dissolved phosphorus (DP). The DP was the dominant one in the P loss of the purple paddy soil and the loss load changed between 0.358 and 2.579 kg/hm2. Additionally, the P loss more easily occurred for the treatment of utilizing the cattle manure than that of straw, approximately 40% of loss load higher. Both the loss load and apparent P loss ratio evidently declined with the treatment of fertilizer combined with straw, suggesting that it was the better measure for reducing the P loss in the paddy field.