Decimetric-scale two-dimensional distribution of soil phosphorus after 20 years of tillage management and maintenance phosphorus fertilization

Improving soil test P assessment at plot scale is essential for productivity in conservation agriculture systems. We characterized the distribution of Mehlich-3 P (P-M3) concentrations at the decimetric scale with depth on either side of the sowing row in no-till (NT) and moldboard plow (MP) plots fertilized with 35 kg P ha(-1) every 2-yr in a corn-soybean rotation (20-yr). A total of 996 soil samples (83 samples x 2 depths [0-5 and 5-20 cm] x 6 plots [3 blocks each MP and NT]) were collected at corn harvest in 2012. The average PM3 concentrations in the 0-to 5-cm layer were 35.7 and 63.4 mg kg(-1) in MP and NT, respectively. The PM3 concentration in the 5-to 20-cm depth was similar between MP and NT and averaged 32.0 mg kg-1. The horizontal distribution of PM3 concentrations in these plots was less sensitive to extrinsic factors including tillage, P fertilization and soil depth. High coefficients of variation were associated with PM3 data in both MP (77 and 63% at 0-5 and 5-20 cm, respectively) and NT plots (46 and 66% at 0-5 and 5-20 cm, respectively). It is possible that this strong overall variability overshadowed any PM3 pattern that could have been introduced by NT management. Geostatistical semivariance analysis indicated a predominance of random spatial dependence in most plots, except two plots (one MP and one NT) with moderate spatial structures. The 2-D geospatial model related to tillage was not detected by the sampling grid used at this experimental site. Therefore, a similar sampling strategy would be appropriate and could be recommended for these two tillage systems in this long-term corn-soybean rotation

Restraint stress and anti-tumor immune response in mice

Psychological stress modulates the immune system through the hypothalamic-pituitary-adrenal axis, the sympatho-adrenomedullary axis and the opioid system. According to literature data, restraint stress increases the immune cell apoptosis, decreases the spleen and thymus cell content, the natural killer (NK) activity in the spleen, and it compromises the anti-tumor immune response in mice. We immobilized mice in two consecutive nights, and then determined the cell number, apoptosis, NK cell content, NK activity and the level of cytokine mRNAs (TNF-β, TNF-α, IL-4, IL-5, IL-1α, IFN-γ, IL-2, IL-6, IL-1β and IL-3) in the thymus and spleen. No consistent changes were detected in any of the immune parameters either in C57Bl/6 or in DBA/2 mice. Stressed or control B6 mice were injected with B16 melanoma cells immediately after the immobilization or one week later. No significant differences were found in the growth of primary tumors and lung metastases in stressed and control animals. Taken together, our mice, kept in a general-purpose non-SPF animal house, seemed to be refractory to the stress-induced immunomodulation. Our interpretation is that stress-induced immunomodulation can occur only in mice isolated from any background stressors, or rather natural stimuli, throughout their life