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Green manure applications in alley cropping systems often include twigs despite their potential to absorb (immobilize) nitrogen (N). To assess the impact of twigs on net N mineralization or immobilization from hedge row cuttings, we separated cuttings fromCalliandra calothyrsus andGliricidia sepium into leaf-only, twig-only, and mixed (leaf + twig) fractions and incubated them with moist soil in the laboratory. Soil extractable inorganic N did no differ among treatments after two weeks, but after four and eight weeks was greatest in leaf-only, and least in twig-only treatments. After two weeks, extractable N from the leaf-only treatment rose steadily, while that from the twig-only and mixed treatments was variable due to periods of net mineralization and net immobilization. The pattern of variation in mixed treatments paralleled that of twig-only, indicating that net immobilization in the mixture was largely caused by the presence of twigs. Extractable N from the mixture was somewhat lower than that predicted from the sum of leaf-only and twig-only treatments. We conclude that twigs in green manure reduce short-term N availability to associated crops in agroforestry systems. 相似文献
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F. Laos Patricia Satti Ingrid Walter María Julia Mazzarino Susana Moyano 《Biology and Fertility of Soils》2000,31(6):462-469
The main objectives of this study were to determine: (1) the agronomic value of composted and noncomposted residues originated
in the Andean-Patagonian region (APR), and (2) whether aerobic incubations provide a reliable index of nutrient availability
to estimate application rates. A Xeric Mollisol of the transitional zone between the APR and the Patagonian steppe, amended
with composted and noncomposted residues, was employed in laboratory incubations without plants and in a 5-month greenhouse
trial with ryegrass. Noncomposted residues were biosolids and fish wastes (FW) collected under farming cages. Composts were
obtained from fish offal and biosolids mixed with sawdust, woodshavings and yard trimmings. A commercial compost was also
included. In laboratory incubations at similar rates of application (10 g kg–1), net N mineralization (Nmin) was about two-fold higher with the noncomposted (17–23%) than with the composted residues (0–12%) and P release was very
high with the FW. Ryegrass yields were closely related to the total Kjeldahl N and mineralized N of the organic residues and
weakly related to their P contents (total or extractable). Yields were increased even in the case of composts which exhibited
very low values of Nmin (and slight N immobilization) during laboratory incubation, suggesting that the presence of plants enhanced Nmin at rates of 10–20 g kg–1. Soil residual extractable P after ryegrass removal was high for fish-derived amendments and the commercial product, suggesting
a potential risk of P pollution when these are applied according to N requirements. Aerobic incubations provided a relatively
good index with which to assess adequate rates of application.
Received: 17 July 1999 相似文献
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科技中小企业的快速成长不仅需要完善的孵化服务,还必须不断的创新孵化模式。该文以福州市高新技术产业创业服务中心发展为例,着重从创新孵化模式、完善服务功能、吸引和促进中小型科技企业创业创新等方面总结了创新孵化模式促进企业发展的方法。 相似文献
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Many techniques such as the acid hydrolysis – incubation (AHI) method have been developed with the aim of elucidating the inherent complexity of soil organic carbon (SOC). While the utility of the AHI method has been demonstrated, there is no standardized protocol developed for conducting the long-term incubation component of the method. In the current study we evaluated the effects of chamber venting and mechanical headspace mixing on soil CO2 flux rates and the resultant size and mean residence time of three operationally defined pools of SOC obtained via the AHI method. Continuous chamber venting resulted in an estimate of the readily mineralized carbon pool that was 2.3 times larger and turned over 2.9 times slower than the same pool estimated using periodically vented chambers. These differences were primarily attributed to the suppression of CO2 flux in periodically vented chambers as a result of high internal CO2 concentrations, and a concomitantly reduced diffusivity gradient. Prior to venting the periodically-vented chambers, CO2 flux rates averaged 2.3 μg C (g soil)−1 d−1, while CO2 flux rates following venting averaged 222.6 μg C (g soil)−1 d−1. We did not detect internal stratification of CO2 suggesting that mechanical headspace mixing is unnecessary in incubation chambers ranging from 1 to 2 L. A standardized protocol is called for that isolates SOC fractions that are useful in hypothesis testing, while simultaneously seeking to minimize laboratory artifacts. 相似文献
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This study aimed to experimentally determine adequate temperature functions for the rate coefficients of net N mineralization in sandy arable soils from NW Germany. Long‐term laboratory incubations were carried out in seven sandy arable soils at 3°C, 10°C, 19°C, 28°C, and 35°C in order to derive the rate coefficients of a simultaneous two‐pool first‐order kinetic equation. Thereby we differentiated between a small, fast mineralizable N pool, comprising mainly fresh residues, and a larger, slowly mineralizable N pool of old, humified organic matter. The rate coefficients were plotted against temperature, and fits of several different functions were tested: Arrhenius, Q10, and multiple non‐mechanistic equations. The two derived rate coefficients showed very different temperature functions. Especially in critical temperature ranges (<5/10°C, >30/35°C) common Q10 functions failed to fit well, and, only below 10°C, the Arrhenius functions were in agreement with mean measured rate coefficients. Over the studied temperature range, only relatively complex, multiple equations could adequately account for the observed patterns. In addition, temperature functions that have been derived earlier from loess soils from NW Germany were found not to be transferable to the sandy arable soils studied. Thus, the results strongly question the use of the same Arrhenius or Q10 function or the same rate modifying factor for different N pools as well as for different soils as is generally done in models. Evaluations with field measurements of net N mineralization in part II of the paper (Heumann and Böttcher, 2004) will show which functions perform best in the field. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(15-20):2833-2840
Abstract The importance of different soil phosphorus (P) compounds and their transformation influenced by several soil and other factors is well established. However, the dynamics of short‐term processes taking part in the long‐term changes of soil P including immobilization and mobilization is still not completely documented. Laboratory incubation experiments were carried out at 10°C and 40°C for studying the influence of incubation on the availability of residual and freshly applied P in samples of a long‐term fertilization field trial conducted on a brown forest soil (U.S. taxonomy: Orthic Eutrochrept; FAO taxonomy: Eutric Cambisol). Samples showing three levels of P resulting from 10 years of intensive P fertilization (referred as P0, P1 and P2, respectively), were collected 30 years after fertilization ceased. Available P contents of soil samples were determined using three approaches: in water (modified Murphy–Riley method), sodium bicarbonate (Olsen, pH=8.5), and ammonium lactate (AL, pH=3.7) extract. Changes in the amounts of P were determined after 2 and 60 days of incubation in four freshly applied new treatments with increasing additions of P: 0, 100, 500, and 1000 mg of P2O5 per kg of soil, representing agronomic and extreme P rates. From the results of our experiments, it was suggested that after 2 days of incubation, at 10°C, both agronomic and extreme P rates resulted in significant increases in P content in each extract. On the other hand, after 60 days, even higher values were obtained. Decreases found in water‐P values after 60 days of incubation were considerable compared to either the Olsen‐P or the AL‐P values, indicating the decline of water‐soluble P forms and further evidence of immobilization with increasing incubation time and temperature. Correlation between water‐P, Olsen‐P, and AL‐P values were significant at both temperatures. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(15-16):2270-2281
Routine use of the Shoemaker, McLean, and Pratt (SMP) lime buffer method resulted in chronic problems with electrode reference junction degradation, stability of readings relative to contact time, and generation of hazardous waste. During method recalibration, the Mehlich buffer was chosen for parallel evaluation with SMP, with the goal of improving method performance and eliminating of hazardous waste. The Mehlich buffer was modified by substituting calcium (Ca) for barium (Ba). The modified Mehlich (MM) buffer was found to be identical to the original with respect to buffering power and linearity over an extended pH range of 3.0–6.6. Seven agronomic soils were incubated with eight rates of calcium carbonate for 90 days. Regression analysis was performed to predict lime requirement (LR) to several target pH levels, based on pH measured in each buffer alone or in both water and buffer. Slightly better predictability was obtained using multiple regressions, with R2>0.95 in all cases. Significant but minor differences occurred between the newly calibrated buffers in extended comparisons. The MM buffer was superior to the SMP during routine usage, with fewer adverse effects on electrodes and the elimination of hazardous waste. 相似文献
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Johan H. Smelt Ariette E. Van De Peppel-Groen Minze Leistra 《Pest management science》1995,44(4):323-334
The transformation of aldicarb sulfoxide and aldicarb sulfone was studied in incubations with water-saturated subsoils under simulated field conditions at 10°C. The subsoils were collected at four locations from beneath the water table at a depth of 2.5 to 3.5 m. In three of the subsoils, the half-life of sulfoxide, incubated at concentrations of 0.14-0.17 mg litre?1, ranged from 0.7 to 2.8 years. At higher concentrations (8-13 mg litre?1), its half-life ranged from 3.4 to 6.4 years. At the lower concentration, a large fraction of sulfoxide was transformed into sulfone. The rates of transformation of the sulfone at the lower concentration in the three subsoils corresponded to half-lives of 3.3 to 8.1 years, but in only one subsoil was a significant transformation rate (half-life 6.7 years) measured at the higher concentration during the 2.3-year incubation period. The half-lives at the lower concentrations were more like those in field studies, and perhaps would still underestimate transformation rates under field conditions. After a year, 2.5-15% of the higher sulfoxide and sulfone doses had been trapped as [14C] carbon dioxide. In the fourth subsoil, with more anaerobic conditions, the half-life of sulfoxide at both concentrations was less than 0.02 year and that of sulfone was about 0.04 year. Four or five radio-labelled transformation products could be traced in this subsoil and about half of the dose of both compounds was trapped as [14C] carbon dioxide. 相似文献
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