Visions of a more precise soil biology

Includes bibliographical references (pages 389-390).Soils have often been viewed as a black box. Soil biology is difficult to study with the precision we would wish, due to the presence of considerable soil heterogeneity, a huge diversity of organisms, and a plethora of interacting processes taking place in a complex physical-chemical environment. We have isolated a tiny fraction of the known organisms, and the possible interactions of soil parent materials, landscape, land use, depth and time with the biota mean that we are to some extent still fumbling in the dark. There have been great advances, but we argue that the pace of advance could be faster. To progress, science needs new theory and concepts but also acceptable methodologies. Coherent and generally accepted theoretical knowledge exists in many areas, but there is a shortage of valid and exact methods to test new and sometimes even old hypotheses. New methods add knowledge, but they also can add to the confusion if they are not tied to the existing knowledge base. We speculate on how to improve soil biology through improving the way we perform and interpret research. Can we deal with soil variability? Can we measure the critical variables with adequate precision to test our hypotheses? Can we avoid reinventing the wheel? Can we find a balance between the freedom to test new and maybe even controversial ideas and the control and direction of research required by society?

Temperature sensitivity of decomposition in relation to soil organic matter pools: Critique and outlook

Knorr et al. (2005) concluded that soil organic carbon pools with longer turnover times are more sensitive to temperature. We show that this conclusion is equivocal, largely dependent on their specific selection of data and does not persist when the data set of Kätterer et al. (1998) is analysed in a more appropriate way. Further, we analyse how statistical properties of the model parameters may interfere with correlative analyses that relate the Q 10 of soil respiration with the basal rate, where the latter is taken as a proxy for soil organic matter quality. We demonstrate that negative parameter correlations between Qio-values and base respiration rates are statistically expected and not necessarily provide evidence for a higher temperature sensitivity of low quality soil organic matter. Consequently, we propose it is premature to conclude that stable soil carbon is more sensitive to temperature than labile carbon

Temperature sensitivity of decomposition in relation to soil organic matter pools: critique and outlook

Knorr et al. (2005) concluded that soil organic carbon pools with longer turnover times are more sensitive to temperature. We show that this conclusion is equivocal, largely dependent on their specific selection of data and does not persist when the data set of Kätterer et al. (1998) is analysed in a more appropriate way. Further, we analyse how statistical properties of the model parameters may interfere with correlative analyses that relate the Q₁₀ of soil respiration with the basal rate, where the latter is taken as a proxy for soil organic matter quality. We demonstrate that negative parameter correlations between Q₁₀-values and base respiration rates are statistically expected and not necessarily provide evidence for a higher temperature sensitivity of low quality soil organic matter. Consequently, we propose it is premature to conclude that stable soil carbon is more sensitive to temperature than labile carbon

On the Potts model partition function in an external field

We study the partition function of Potts model in an external (magnetic) field, and its connections with the zero-field Potts model partition function. Using a deletion-contraction formulation for the partition function Z for this model, we show that it can be expanded in terms of the zero-field partition function. We also show that Z can be written as a sum over the spanning trees, and the spanning forests, of a graph G. Our results extend to Z the well-known spanning tree expansion for the zero-field partition function that arises though its connections with the Tutte polynomial

Biochar addition persistently increased soil fertility and yields in maizesoybean rotations over 10 years in sub-humid regions of Kenya

Open Access ArticleApplication of biochar has been shown to increase soil fertility and enable soil carbon sequestration, indicating potential for agricultural and environmental benefits from using locally produced biochar on African smallholder farms. However, previous studies have been rather short-term and little is known about the longer-term effects of biochar application on crop yields. Biochar contains ash, but the potential liming effect and nutrient release from ash may be short-lasting. To investigate long-term effects, we set up a series of field trials replicated at three sites in Kenya in 2006. The trials are still on-going and are possibly the longest biochar trials in sub-Saharan Africa. Here, we report effects on crop yield and soil properties over 10 years after applying biochar, produced mainly from Acacia spp., at a rate of 50 + 50 Mg ha−1 during the first two seasons. Maize (Zea mays) and soybean (Glycine max) were grown in rotation, with or without inorganic fertiliser, and crop yield was monitored. For comparison of soil properties, additional plots were kept in bare fallow. Biochar addition slightly increased soil porosity, pH, plant-available phosphorus and soil water-holding capacity. Crop yield responded positively to biochar at all sites and yield responses were similar with and without mineral fertiliser, i.e., the effects of biochar and mineral fertiliser were additive. The seasonal yield increase due to biochar application was in average around 1.2 Mg ha−1 for maize and 0.4 Mg for soybean, independently of fertilisation, over seasons and sites. Application of mineral fertiliser to maize increased maize yield by 1.6 Mg ha−1 and the subsequent, unfertilized soybean yield by 0.6 Mg ha−1, illustrating a carry-over effect. Most importantly, the effect on maize and soybean yield of adding biochar to soil persisted over the whole 10-year period. Analysis of the carbon (C) balance in topsoil indicated that about 40% of biochar C was apparently lost through mineralization, erosion or vertical translocation. Moreover, changes in soil carbon/nitrogen ratios indicated that biochar application increased nitrogen mineralization from native soil organic matter

MUC-1 gene is associated with prostate cancer death: a 20-year follow-up of a population-based study in Sweden

Anti-adhesion mucins have proven to play an important part in the biology of several types of cancer. Therefore, we test the hypothesis that altered expression of MUC-1 is associated with prostate cancer progression. We retrieved archival tumour tissue from a population-based cohort of 195 men with localised prostate cancer (T1a-b, Nx, M0) that has been followed for up to 20 years with watchful waiting. Semi-automated, quantitative immunohistochemistry was undertaken to evaluate MUC-1 expression. We modelled prostate cancer-specific death as a function of MUC-1 levels accounting for age, Gleason grade and tumour extent, and calculated age-adjusted and multivariate adjusted hazard ratios (HR). Men that had tumours with an MUC-intensity lower or higher than normal tissue had a higher risk of dying in prostate cancer, independent of tumour extent and Gleason score (HR 5.1 and 4.5, respectively). Adjustment for Gleason grade and tumour stage did not alter the results. Men with a Gleason score ⩾7 and MUC-1 deviating from the normal had a 17 (RR=17.1 95% confidence interval=2.3–128) times higher risk to die in prostate cancer compared with men with Gleason score <7 and normal MUC-1 intensity. In summary, our data show that MUC-1 is an independent prognostic marker for prostate cancer death

The Role of Bile in the Regulation of Exocrine Pancreatic Secretion

As early as 1926 Mellanby (1) was able to show that introduction of bile into the duodenum of anesthetized cats produces a copious flow of pancreatic juice. In conscious dogs, Ivy & Lueth (2) reported, bile is only a weak stimulant of pancreatic secretion. Diversion of bile from the duodenum, however, did not influence pancreatic volume secretion stimulated by a meal (3,4). Moreover, Thomas & Crider (5) observed that bile not only failed to stimulate the secretion of pancreatic juice but also abolished the pancreatic response to intraduodenally administered peptone or soap