Nitrogen mineralization

ABSTRACT An incubation study was conducted to assess the effect of composted tea leaves, coffee waste and kitchen garbage on the kinetics of net nitrogen mineralization and P, K, Ca and Mg availability. NH4-N, NO 3-N, Bray II P, the exchangeable cations, EC and pH were determined after 0, 7, 14, 21, 42 and 63 day. Inorganic N concentration in the amended soils was analyzed by a first-order model. The pH of the soil increased after 14-21 day of incubation and gradually decreased thereafter. EC values showed the following trend: composted tea leaves > kitchen garbage > coffee waste. The composts were highly variable in their N mineralization characteristics, but the peaks for mineralized N content were observed at early incubation times in all the composts, i.e., after 14-21 day because the composts had undergone maturation. Potential respective mineralizable N (N0) content of the composted tea leaves, coffee waste and kitchen garbage was 18.8, 6.30 and 22.4 mg kg-1 dry soil and the respective rate constant (k) was 0.101, 0.199 and 0.255 day-1. Rate of N mineralization for the composted tea leaves, coffee waste and kitchen garbage was 5.25, 9.10 and 38.6%, respectively, of the total N content. Composted kitchen garbage displayed the highest value for N release rate. P, K and Ca showed the following trend: composted tea leaves > kitchen garbage > coffee waste and Mg was composted tea leaves > coffee waste > kitchen garbage.

The mixed oak-pine ecosystems in the southern Appalachians are in decline because of a combination of drought and southern pine-beetle infestation. A commonly applied prescription for restoration of these degraded sites has been to fell all vegetation, allow it to dry, and conduct a site-preparation burn. However, there is little information on the mid- and long-term influences of this prescription

A 3-year field lysimeter experiment was performed to determine transformations of 15N-labeled cauliflower (Brassica oleracea) residues incorporated into lysimeter topsoil in a potato (Solanum tuberosum)/cauliflower rotation. Only the potato crop received 150 kg mineral N ha−1y−1. Cauliflower yields were high (12–13 t fresh matter ha−1), and N returned to the soil represented 51% of the aboveground plant N uptake. The 15N recovery by the potato/cauliflower rotation began at 46%, then decreased sharply to 12 and 6% for the second and third year, respectively. The cumulative 15N leaching rate was only 3%; 63% remained in the soil 3 years after incorporation. Soil N mineralization rates described by a parallel first-order kinetic model predicted 27, 7 and 6% of residual N lost annually during the first, second and third year, respectively. Thus, a potato/cauliflower rotation with moderate N fertilization optimizes N recovery of crop residues and can control leaching loss efficiently.

We investigated litter mass loss and soil nitrogen (N)-transformation rates in oak stands along a 130-km, urban-rural transect originating in New York City to examine the relationship between changes in these parameters and previously documented differences in soil temperature, heavy metal and total salt concentrations, and soil biota. Reference litter from a rural site was placed in litterbags, and rates of mass loss and changes in N concentration in litter residues were measured over a 6-month period. Net N-mineralization and nitrification rates were measured in A horizon soils using laboratory incubations under constant moisture and temperature. Both mass loss (76%) and N release (65%) from litterbags reached their maximum in urban stands, whereas net N-mineralization rates were 2.3-fold higher than in rural A horizon soils. Litter fragmentation by earthworms and higher soil temperatures are potential causes of the higher mass loss rates observed in urban stands. The higher relea...

Extensive forest areas were ameliorated by large-scale liming in the last years in order to prevent proceeding acidification and degradation of forest soils. The hitherto knowledge of liming effects on the function of forest soils still appears insufficient for an unambiguous evaluation. Sorption properties of soils and acidity are favourably affected by liming and the favourable effect is usually manifested in the layer of forest floor humus and in mineral soil within ten years. Reduction of soil acidity stimulates development of a bacterial component of microflora, soil edaphon, and good prerequisites are formed for a release of nutrients from soil organic matter. Improvement of some physical parameters of soils and negative effect of liming on the depth of rooting in spruce, availability of nutrients at some sites and in connection with mechanical soil preparation were also described. A key point of liming effect on forest soils is nitrogen dynamics. Mineralization of nitrogen is...

Global Biogeochemical Cycles includes papers in the broad areas of global change involving the geosphere and biosphere. The journal focuses on research at large geographic scales. Marine, hydrologic, atmospheric, extraterrestrial, geologic, biologic, and human causes of and ...

The role of different plantation tree species in soil nutrient cycling is of great importance for the restoration of degraded lands. The objective of the present study was to evaluate the potential of N-fixing and non-N-fixing tree species to recuperate degraded land in southern China. The soil properties and N transformations in six forest types (two N-fixing plantations, three non-N-fixing plantations and a secondary shrubland) established in 1984 were compared. The N-fixing forests had 40–50% higher soil organic matter and 20–50% higher total nitrogen concentration in the 0–5 cm soils than the non-N-fixing forests. Soil inorganic N was highest under the secondary shrubland. The N-fixing Acacia auriculiformis plantation had the highest soil available P. There were no significant differences in soil N mineralization and nitrification among the forest types, but seasonal variation in these N processes was highly significant. In the rainy season, the rates of N mineralization (7.41–11.3 kg N ha−1 month−1) were similar to values found in regional climax forests, indicating that soil N availability has been well recovered in these forest types. These results suggest that N-fixing species, particularly Acacia mangium, are more efficient in re-establishing the C and N cycling processes in degraded land in southern China. Moreover, the N-fixing species A. auriculiformis performed better than other species in improving soil P availability.

The effects of soil aeration, N fertilizer, and crop residue management on crop performance, soil N supply, organic carbon (C) and nitrogen (N) content were evaluated in two annual double-crop systems for a 2-year period (1994–1995). In the maize-rice (M-R) rotation, maize (Zea mays, L.) was grown in aerated soil in the dry season (DS) followed by rice (Oriza sativa, L.) grown in flooded soil in the wet season (WS). In the continuous rice system (R-R), rice was grown in flooded soil in both the DS and WS. Subplot treatments within cropping-system main plots were N fertilizer rates, including a control without applied N. In the second year, sub-subplot treatments with early or late crop residue incorporation were initiated after the 1995 DS maize or rice crop. Soil N supply and plant N uptake of 1995 WS rice were sensitive to the timing of residue incorporation. Early residue corporation improved the congruence between soil N supply and crop demand although the size of this effect was influenced by the amount and quality of incorporated residue. Grain yields were 13-20% greater with early compared to late residue incorporation in R-R treatments without applied N or with moderate rates of applied N. Although substitution of maize for rice in the DS greatly reduced the amount of time soils remained submerged, the direct effects of crop rotation on plant growth and N uptake in the WS rice crops were small. However, replacement of DS rice by maize caused a reduction in soil C and N sequestration due to a 33–41% increase in the estimated amount of mineralized C and less N input from biological N fixation during the DS maize crop. As a result, there was 11–12% more C sequestration and 5–12% more N accumulation in soils continuously cropped with rice than in the M-R rotation with the greater amounts sequestered in N-fertilized treatments. These results document the capacity of continuous, irrigated rice systems to sequester C and N during relatively short time periods.

... Additional Index Words: N mineralization potential, laboratory in-cubations, sludge recycling. Garau, MA, MT Felipo, and MC Ruiz de Villa. 1986. ... Hydrolyzable-N, g kg-~¶ 30.8 6.4 -- pHH 0 1/5 7.1 7.6 5.5 7.8 ~., Electrical conduct, S m -' 0.44 0.08 20 x 10-4 80 x 10 -4 ...