Stress wavelet properties are inherently involved in the process of the drop-shatter method of assessment on soil structural characteristics. The analogies between wavelet analysis and the drop-shatter process are based on two factors: scale and resolution. By carefully following the requirements of wavelet analysis, a standard procedure of soil fragmentation and sieving is described. Following this procedure, a set of equations can be derived from which surface contacting energy between soil aggregates of a specific scale can be calculated. The resultant values in fact mirror the multi-resolutions of wavelets.
Natural soil clods as well as artificial structured soil cores were used for fragmentation. Though the experiment can do well on natural soil clods, and it is precise enough in predicting structural state of a sub-dimensional clods of 8 mm, its use on artificial soil cores produced a set of data that was quite chaotic. The unique behavior experienced in the process of fragmentation of artificial soil structure indicates that there is no distinct stage between mother soil clods (cores) and its constituent primary particles. Such a state should result from an excessively large impact energy (too low a resolution in the wavelet analysis) for each drop stroke impact.
With an ultimate goal for soil process simulation, the construction of the experiment for artificial structured soil core preparation brings the traditional methods of sample preparation a step forward further by creating an environment much nearer to the field conditions experienced in natural soils. Still, extensive refinements are needed, especially for the mode of water application, cycle and intensity of management. 相似文献
The study was carried out on the reclaimed lands of a bore-hole sulphur mine. The cropping of two succeeding cuts of alfalfa (Medicago sativa L.) was determined and its chemical composition was analyzed. Alfalfa was cultivated on waste lime (flotation tailings), enriched with a humus layer. The levels of basic nutrients, total S, total F, Ca, P, Mg, K, Na, Fe and Mn were determined in alfalfa. The biomass of an average crop was 6830 kg ha–1 in the first cut and 14300 kg ha–1 in the second one. The yields of dry matter as well as of crude and true proteins were positively correlated with the phosphorus level in the dry matter of alfalfa (P < 0.01). The level of total sulphur was positively linearly correlated with the phosphorus content (P < 0.01). No harmful accumulation of sulphur or fluoride was observed. A deficiency of phosphorus in alfalfa and an abnormal Ca:P weight ratio was found. The S total level was positively correlated with N total concentration. (P < 0.01). The percentage of true protein in crude protein was negatively correlated with total sulphur (P < 0.01). The level of nonprotein nitrogen compounds was positively correlated with S total level (P < 0.01). 相似文献
Limitations to the respiratory activity of heterotrophic soil microorganisms exert important controls of CO2 efflux from soils. In the northeastern US, ecosystem nutrient status varies across the landscape and changes with forest succession following disturbance, likely impacting soil microbial processes regulating the transformation and emission of carbon (C). We tested whether nitrogen (N) or phosphorus (P) limit the mineralization of soil organic C (SOC) or that of added C sources in the Oe horizon of successional and mature northern hardwood forests in three locations in central New Hampshire, USA. Added N reduced mineralization of C from SOC and from added leaf litter and cellulose. Added P did not affect mineralization from SOC; however, it did enhance mineralization of litter- and cellulose- C in organic horizons from all forest locations. Added N increased microbial biomass N and K2SO4-extractable DON pools, but added P had no effect. Microbial biomass C increased with litter addition but did not respond to either nutrient. The direction of responses to added nutrients was consistent among sites and between forest ages. We conclude that in these organic horizons limitation by N promotes mineralization of C from SOC, whereas limitation by P constrains mineralization of C from new organic inputs. We also suggest that N suppresses respiration in these organic horizons either by relieving the N limitation of microbial biomass synthesis, or by slowing turnover of C through the microbial pool; concurrent measures of microbial growth and turnover are needed to resolve this question. 相似文献
The scarcity of non-renewable resources such as soils and fertilizers and the consequences of climate change can dramatically influence the food security of future generations. Mutualistic root microorganisms such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can improve plant fitness. We tested the growth response of wheat (Triticum aestivum [L.]), rice (Oriza sativa [L.]) and black gram (Vigna mungo [L.], Hepper) to an inoculation of AMF and PGPR alone or in combination over two years at seven locations in a region extending from the Himalayan foothills to the Indo-Gangetic plain. The AMF applied consisted of a consortium of different strains, the PGPR of two fluorescent Pseudomonas strains (Pseudomonas jessenii, R62; Pseudomonas synxantha, R81), derived from wheat rhizosphere from one test region. We found that dual inoculation of wheat with PGPR and AMF increased grain yield by 41% as compared to un-inoculated controls. Yield responses to the inoculants were highest at locations with previously low yields. AMF or PGPR alone augmented wheat grain yield by 29% and 31%, respectively. The bio-inoculants were effective both at Zero and at farmers’ practice fertilization level (70 kg N ha−1, 11 kg P ha−1 in mineral form to wheat crop). Also raw protein (nitrogen × 5.7) and mineral nutrient concentration of wheat grains (phosphorus, potassium, copper, iron, zinc, manganese) were higher after inoculation (+6% to +53%). Phosphorus use efficiency of wheat grains [kg P grain kg−1 P fertilizer] was increased by 95%. AMF and PGPR application also improved soil quality as indicated by increased soil enzyme activities of alkaline and acid phosphatase, urease and dehydrogenase. Effects on rice and black gram yields were far less pronounced over two cropping seasons, suggesting that AMF and PGPR isolated from the target crop were more efficient. We conclude that mutualistic root microorganisms have a high potential for contributing to food security and for improving nutrition status in southern countries, while safeguarding natural resources such as P stocks. 相似文献