Effect of pH on nitrogen immobilization in two California soils

Abstract

It has now been weil established through tracer experiments that nitrogen fertilizers applied to soils may be rapidly incorporated into the organic fraction and rendered temporarily unavailable for the growth of plants (Broadbent and Tyler t Stewart et al 7). The rate of incorporation or immobilization is dependent primarily on the supply of readily decomposable organic matter in relation to the quantity of available nitrogen present, commonly expressed in terms of carbon/nitrogen ratios. When the C/N ratio is greater than a certain critical value, usually in the vicinity of 30/1, net immobilization may be expected to occur.The rate and quantity of nitrogen immobilized in a given situation are also iniluenced by other soil factors, including temperature, pH, and chemical form of available nitrogen. Quantitative information on the influence of these other factors is quite limited. In 1931 N o rm an 5 measured nitrogen immobilization in decomposing straw percolated with solutions containing ammonium nitrogen and adj usted to various pH values. He found that under slightly alkaline conditions immobilization was more rapid than in either neutral or slightly acid conditions, and ultimately more nitrogen was retained. He'attributed the observed effects to differences in character of the active microflora induced by changes in pH.In soil systems the problem of evaluating nitrogen immobilization as a function of pH is complicated by the fact that ammonium sources of nitrogen are utilized perferentially by the heterotrophic popnlation (Jansson et al.4), but an ammonium source cannot be

Non-adaptive measurement-based quantum computation and multi-party Bell inequalities

“…Although the connection between MQC and Bell inequalities is recently made, there is a long tradition of viewing Bell inequalities as information theoretic tasks, for example, in the context of quantum games [16,17]. This approach is to frame the Bell inequality experiment in terms of the achievement of a certain task by a set of players, who are given certain resources and who must abide by certain rules.…”

“…We show here that a broad class of natural multi-party generalisations of the CHSH inequality, where measurements are restricted to two settings and two outcomes, can be cast (as computational non-locality "games") directly in the NMQC ⊕ framework. Doing this immediately provides new structures for the classification of Bell inequalities, and allows us to derive general properties of n-party families of Bell inequalities true for all n.Although the connection between MQC and Bell inequalities is recently made, there is a long tradition of viewing Bell inequalities as information theoretic tasks, for example, in the context of quantum games [16,17]. This approach is to frame the Bell inequality experiment in terms of the achievement of a certain task by a set of players, who are given certain resources and who must abide by certain rules.…”

Imobilização de nitrogênio da uréia e do sulfato de amônio aplicado em pré-semeadura ou cobertura na cultura de milho, no sistema plantio direto

“…A ocorrência favorável à mineralização ou imobilização é influenciada por diversos fatores, como: temperatura, umidade, presença de O 2 , biomassa de solo e os conteúdos de C e N do material orgânico adicionado ao solo (Lopes et al, 2004). Na imobilização, o NH 4 + é preferencialmente utilizado pela biomassa de solo (Jansson et al, 1955;Broadbent & Tyler, 1965;Recous et al, 1988), em detrimento do NO 3 -. O aumento de pH no solo favorece maior imobilização de N-NH 4 + (Broadbent & Tyler, 1965).…”

“…Na imobilização, o NH 4 + é preferencialmente utilizado pela biomassa de solo (Jansson et al, 1955;Broadbent & Tyler, 1965;Recous et al, 1988), em detrimento do NO 3 -. O aumento de pH no solo favorece maior imobilização de N-NH 4 + (Broadbent & Tyler, 1965). A imobilização ocorre quando a relação C:N excede valores de 20:1 a 25:1 (Sims, 1990;Burgess et al, 2002;Lopes et al, 2004).…”

Fixed Ammonium in Nigerian Soils

“…The rate of immobilization is dependent primarily on the C/N ratio and other soil factors such as temperature, pH and chemical form of available nitrogen (Broadbent and Tyler, 1965;Norman, 1931;Stewart, Porter, and Johnson, 1963).…”