Nitrogen Mineralization in West Indian Soils

1971 ◽  
Vol 7 (4) ◽  
pp. 345-349
Author(s):  
I. S. Cornforth

SUMMARYSoil properties influencing N mineralization, and hence the potential N-supplying power of 154 West Indian soils, have been studied. Mineralizable N was correlated with the activity of the soil biomass measured as extractable glucose, with exchangeable bases in base-deficient soils and with total N in soils well supplied with bases, but not with other estimates of the nature of soil organic matter (e.g. extractable chlorophyll or C : N ratio). It is suggested that cation exchange capacity and percentage base saturation may influence the N-supplying power of West Indian soils more than their total N content.

Soil Research ◽  
1994 ◽  
Vol 32 (5) ◽  
pp. 1015
Author(s):  
PW Moody

Krasnozems (Ferrosols) characteristically have high contents of citrate-dithionite extractable Fe and moderate to high contents of clay throughout the profile. They typically have low cation exchange capacity (2-20 cmolc kg-1), high P sorbing ability, and a significant anion exchange capacity at depth. The chemistry of krasnozems is dominated by the variable charge characteristics of the organic matter and the oxy-hydroxides of Fe and Al which occur in the predominantly kaolinitic clay fraction. The effects of surface charge characteristics, organic matter, and extractable iron and aluminium on the cation and anion exchange capacities, P sorbing abilities and pH buffer capacities of Australian krasnozems are reviewed. A selection of reports of nutrient deficiencies and toxicities in these soils is presented and briefly discussed. Published data on the chemical composition of the soil solutions of krasnozems are reviewed. Data from a suite of paired (undeveloped and developed) krasnozem profiles from eastern Australia indicate that exchangeable Ca and Mg, effective cation exchange capacity (ECEC), pH buffer capacity (pHBC) and total N decrease significantly (P < 0.05) in the A horizon following development, while exchangeable K, ECEC and pHBC decrease (P < 0-05) in the B horizon. The decreases in the A horizon are shown to be a direct consequence of the decline in organic matter which occurs following development. Because of the crucial role that organic matter plays in the chemical fertility of krasnozems, they are less likely to maintain their fertility under exploitative conditions than other productive clay soils such as Vertosols. It is concluded that the sustainable use of krasnozems will depend on maintenance or enhancement of organic matter levels, maintenance of surface and subsoil pH by regular application of amendments, minimization of erosion, and replacement of nutrients removed in harvested products.


1999 ◽  
Vol 79 (3) ◽  
pp. 501-504 ◽  
Author(s):  
B. J. Zebarth ◽  
G. H. Neilsen ◽  
E. Hogue ◽  
D. Neilsen

Sandy, infertile soils can benefit from the addition of organic waste amendments. Annual applications of organic wastes for as long as 4 yr increased soil organic matter content, decreased soil bulk density, and increased soil water retention of a coarse-textured soil. However, soil water-holding capacity was not necessarily increased, and there was a limited effect on soil cation exchange capacity. Key words: Cation exchange capacity, water retention, soil pH, soil organic matter, soil bulk density


1976 ◽  
Vol 56 (3) ◽  
pp. 213-221 ◽  
Author(s):  
Y. A. MARTEL ◽  
M. R. LAVERDIERE

The objectives of this work were (1) to determine the relation existing between the organic matter contents of Ap horizons and their respective soil Orders, (Gleysolic and Podzolic), texture, pH and geographic locations in the different thermal regions of Quebec and (2) to determine the role of organic matter and soil texture on the cation exchange properties of the same Ap horizons coming from soils used for forage crops in Quebec. The cation-exchange capacity (CEC), the exchangeable bases and acidity were determined by using 1 N NH4OAC – pH 7. The results showed a variation in the carbon content ranging from 1.4 to 6.9%. The heat units accumulated in each region and the clay contents were correlated with the percentage of carbon and nitrogen. Soil pH and soil Orders (Gleysolic vs. Podzolic) did not seem to affect the organic matter content. The cation-exchange capacity (CEC) ranged from 10.6 to 42.6 meq/100 g soil; 40% of this was attributable to carbon and 32% to clay contents. Simple and multiple regression equations showed that carbon was correlated with the exchangeable acidity, while clay was related to the exchangeable bases. The CEC of organic matter and clay were respectively 161 ± 45 meq/100 g organic matter and 29 ± 6 meq/100 g clay. These values, lower than for Western Canada, reflected the nature of the organic matter that is less developed in Eastern Canada than in the Chernozemic soils; they also showed the effect of the predominant illite mineral found in the clay fractions compared to montmorillonite in Western Canada.


Solid Earth ◽  
2017 ◽  
Vol 8 (4) ◽  
pp. 827-843 ◽  
Author(s):  
Sunday Adenrele Adeniyi ◽  
Willem Petrus de Clercq ◽  
Adriaan van Niekerk

Abstract. Cocoa agroecosystems are a major land-use type in the tropical rainforest belt of West Africa, reportedly associated with several ecological changes, including soil degradation. This study aims to develop a composite soil degradation assessment index (CSDI) for determining the degradation level of cocoa soils under smallholder agroecosystems of southwestern Nigeria. Plots where natural forests have been converted to cocoa agroecosystems of ages 1–10, 11–40, and 41–80 years, respectively representing young cocoa plantations (YCPs), mature cocoa plantations (MCPs), and senescent cocoa plantations (SCPs), were identified to represent the biological cycle of the cocoa tree. Soil samples were collected at a depth of 0 to 20 cm in each plot and analysed in terms of their physical, chemical, and biological properties. Factor analysis of soil data revealed four major interacting soil degradation processes: decline in soil nutrients, loss of soil organic matter, increase in soil acidity, and the breakdown of soil textural characteristics over time. These processes were represented by eight soil properties (extractable zinc, silt, soil organic matter (SOM), cation exchange capacity (CEC), available phosphorus, total porosity, pH, and clay content). These soil properties were subjected to forward stepwise discriminant analysis (STEPDA), and the result showed that four soil properties (extractable zinc, cation exchange capacity, SOM, and clay content) are the most useful in separating the studied soils into YCP, MCP, and SCP. In this way, we have sufficiently eliminated redundancy in the final selection of soil degradation indicators. Based on these four soil parameters, a CSDI was developed and used to classify selected cocoa soils into three different classes of degradation. The results revealed that 65 % of the selected cocoa farms are moderately degraded, while 18 % have a high degradation status. The numerical value of the CSDI as an objective index of soil degradation under cocoa agroecosystems was statistically validated. The results of this study reveal that soil management should promote activities that help to increase organic matter and reduce Zn deficiency over the cocoa growth cycle. Finally, the newly developed CSDI can provide an early warning of soil degradation processes and help farmers and extension officers to implement rehabilitation practices on degraded cocoa soils.


2016 ◽  
Vol 47 (sup1) ◽  
pp. 75-89 ◽  
Author(s):  
Jorge Paz Ferreiro ◽  
Vicente Pereira De Almeida ◽  
Marlene Cristina Alves ◽  
Cleide Aparecida De Abreu ◽  
Sidney R. Vieira ◽  
...  

1991 ◽  
Vol 21 (2) ◽  
pp. 235-241
Author(s):  
J. W. Fyles ◽  
I. H. Fyles ◽  
M. C. Feller

Nitrogen mineralization characteristics of the dominant types of organic matter in the forest floor of slash-burned sites were measured using a 26-week aerobic incubation. Six classes of forest floor material were distinguished on the basis of morphology and N mineralization characteristics. Fermentation layer materials, matted together with fungal hyphae, had a high content of total and potentially mineralizable N (N0) (7804 and 2816 μg/g, respectively) and mineralized the most N during incubation (1605 μg/g). Decayed wood had the lowest level of total N (1816 μg/g) and N0 (195 μg/g) and mineralized the least N (266 μg/g) despite a high inherent mineralization rate (k) (0.16). Humified materials (Hd and Hr) occupied a midrange, with the exception of those from thin residual horizons, which had high N0 values (2246–6009 μg/g) and low k-values (0.005–0.012). The significant differences in N mineralization among organic materials that are morphologically or ecologically distinct in the field suggest that it may be possible to assess site N fertility using intensive forest floor and soil survey data and information on the N characteristics of dominant horizon types.


Soil Research ◽  
1994 ◽  
Vol 32 (5) ◽  
pp. 1015
Author(s):  
PW Moody

Krasnozems (Ferrosols) characteristically have high contents of citrate-dithionite extractable Fe and moderate to high contents of clay throughout the profile. They typically have low cation exchange capacity (2-20 cmolc kg-1), high P sorbing ability, and a significant anion exchange capacity at depth. The chemistry of krasnozems is dominated by the variable charge characteristics of the organic matter and the oxy-hydroxides of Fe and Al which occur in the predominantly kaolinitic clay fraction. The effects of surface charge characteristics, organic matter, and extractable iron and aluminium on the cation and anion exchange capacities, P sorbing abilities and pH buffer capacities of Australian krasnozems are reviewed. A selection of reports of nutrient deficiencies and toxicities in these soils is presented and briefly discussed. Published data on the chemical composition of the soil solutions of krasnozems are reviewed. Data from a suite of paired (undeveloped and developed) krasnozem profiles from eastern Australia indicate that exchangeable Ca and Mg, effective cation exchange capacity (ECEC), pH buffer capacity (pHBC) and total N decrease significantly (P < 0.05) in the A horizon following development, while exchangeable K, ECEC and pHBC decrease (P < 0-05) in the B horizon. The decreases in the A horizon are shown to be a direct consequence of the decline in organic matter which occurs following development. Because of the crucial role that organic matter plays in the chemical fertility of krasnozems, they are less likely to maintain their fertility under exploitative conditions than other productive clay soils such as Vertosols. It is concluded that the sustainable use of krasnozems will depend on maintenance or enhancement of organic matter levels, maintenance of surface and subsoil pH by regular application of amendments, minimization of erosion, and replacement of nutrients removed in harvested products.


PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260933
Author(s):  
Rachel L. Rubin ◽  
Kate A. Ballantine ◽  
Arden Hegberg ◽  
Jason P. Andras

Microbial communities are early responders to wetland degradation, and instrumental players in the reversal of this degradation. However, our understanding of soil microbial community structure and function throughout wetland development remains incomplete. We conducted a survey across cranberry farms, young retired farms, old retired farms, flooded former farms, ecologically restored former farms, and natural reference wetlands with no history of cranberry farming. We investigated the relationship between the microbial community and soil characteristics that restoration intends to maximize, such as soil organic matter, cation exchange capacity and denitrification potential. Among the five treatments considered, flooded and restored sites had the highest prokaryote and microeukaryote community similarity to natural wetlands. In contrast, young retired sites had similar communities to farms, and old retired sites failed to develop wetland microbial communities or functions. Canonical analysis of principal coordinates revealed that soil variables, in particular potassium base saturation, sodium, and denitrification potential, explained 45% of the variation in prokaryote communities and 44% of the variation in microeukaryote communities, segregating soil samples into two clouds in ordination space: farm, old retired and young retired sites on one side and restored, flooded, and natural sites on the other. Heat trees revealed possible prokaryotic (Gemmatimonadetes) and microeukaryotic (Rhizaria) indicators of wetland development, along with a drop in the dominance of Nucletmycea in restored sites, a class that includes suspected mycorrhizal symbionts of the cranberry crop. Flooded sites showed the strongest evidence of wetland development, with triple the soil organic matter accumulation, double the cation exchange capacity, and seventy times the denitrification potential compared to farms. However, given that flooding does not promote any of the watershed or habitat benefits as ecological restoration, we suggest that flooding can be used to stimulate beneficial microbial communities and soil functions during the restoration waiting period, or when restoration is not an option.


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