Amount Of Soil Organic Matter Research Articles

Soil health practices have different outcomes depending on local soil conditions

The amount of soil organic matter is a critical indicator of soil health. Applying compost or manure, growing cover crops, reducing tillage, and increasing crop diversity may increase soil organic matter. However, soil organic matter can vary dramatically in different environments, regardless of management practices. This calls for a framework to recommend place-based soil health practices and evaluate their outcomes. We used a new framework that groups soil survey data into seven regions in California's Central Valley and Central Coast. These regions either have performance limitations, such as root restrictive horizons, salinity, and shrink-swell behavior, or have relatively homogeneous, coarse-to-loamy soils ideal for agriculture. These inherent conditions affect a soil's response to practices designed to improve soil health. Looking at vineyards as an example, we find significant soil organic matter contrasts between soil health regions but not among contrasting management approaches within a given region. We also show that conservation practices improve or help maintain soil health in several long-term experiments, but inherent soil properties and types of cropping systems affect outcomes.

Carbon and Nitrogen Stocks and Microbiological Activity Under Forest-Pasture System and Traditional Pasture in Pernambuco

An adequate amount of soil organic matter is considered essential for long-term sustainable agriculture, ensuring good productivity. Therefore, the present study quantified carbon and nitrogen stocks and microbiological activity in soil of three different areas: Forest-pasture System, Pasture System and preserved Caatinga - used as a reference of the experiment - located in a semi-arid region, in Watershed of Pajeú River, state of Pernambuco, Brazil. Eight trenches were opened in each system to collect soil samples at depths of 0 - 10, 20 - 30 and 50 - 60 cm, for chemical and microbiological analysis. In general, attributes of soil showed better results of land use in the following order: preserved Caatinga - Forest-pasture System - Pasture System.

Fractionation of Soil Organic Matter into Labile and Stable Fractions

The present study aims to test and evaluate the efficiency of a new modified method of organic matter evaluation. It allows the assessment of the quality and quantity of the primary soil organic matter and the stable organic fractions separately. The new method was tested in six soil samples of different localities in the Czech Republic. This method is based on observing reaction kinetics during the oxidation of soil organic matter and measuring the cation-exchange capacity of stable organic fractions. The results were compared with classical methods, which rely on the isolation of humic substances, determination of the content of humic acids and fulvic acids and their ratio CHA:CFA, quotient E4/6, and fractionation of soil organic matter according to resistance to oxidation. It turned out that the results of the new modified method are more sensitive in comparison with the results obtained by classical procedures. The linear regression demonstrated the dependence between the amounts of soil organic matter determined by the classical method compared with the modified method. Moreover, the new modified method was found to be faster and not demanding on laboratory equipment. The new method has been improved to be easily repeatable, and some shortcomings of the previous method were eliminated. Based on our results and other recent studies, the modified method may be recommended for the practical evaluation of soil organic matter conditions.

Soil properties and topographic features influence within‐field variation in potato tuber yield in New Brunswick, Canada

AbstractReduced within‐field potato (Solanum tuberosum L.) yield variation may lead to increased productivity and reduced environmental impact. Using soil samples collected from 88 site‐years in commercial fields in New Brunswick, Canada from 2013–2017, this study examined how within‐field variation in potato tuber yield was related to soil properties and topographic features. At each of 774 sampling locations, a wide range of soil physical and chemical properties was measured in the lab and topographic features were assessed using a regional digital elevation model. Principal component (PC) analysis identified three PCs, which accounted for 79.1% of the total variation. The PC1 (41.3% of total variance) was dominated by soil texture (i.e., sand, silt) and the quantity and quality of soil organic matter (i.e., soil organic C, particulate organic matter C, and soil C/N ratio). Under rain‐fed potato production in New Brunswick, finer soil texture and increased soil organic matter pools are expected to enhance soil water availability and thereby improve yield. The PC2 (22.7% of total variance) was related primarily to parameters associated with soil fertility, and PC3 (15.1% of total variance) was related primarily with concave or convex landforms, which may influence yield through drought or excess water. This study demonstrated the value in using multivariate approaches to identify the factors that control within‐field yield variability in the presence of significant regional variation in soil properties and environmental conditions. The findings point to the value of enhancing the quantity and quality of soil organic matter as a key strategy to overcome yield limitations under rain‐fed production.

An inverse dielectric mixing model at 50 MHz that considers soil organic carbon

Abstract. The prevalent soil moisture probe algorithms are based on a polynomial function that does not account for the variability in soil organic matter. Users are expected to choose a model before application: either a model for mineral soil or a model for organic soil. Both approaches inevitably suffer from limitations with respect to estimating the volumetric soil water content in soils with a wide range of organic matter content. In this study, we propose a new algorithm based on the idea that the amount of soil organic matter (SOM) is related to major uncertainties in the in situ soil moisture data obtained using soil probe instruments. To test this theory, we derived a multiphase inversion algorithm from a physically based dielectric mixing model capable of using the SOM amount, performed a selection process from the multiphase model outcomes, and tested whether this new approach improves the accuracy of soil moisture (SM) data probes. The validation of the proposed new soil probe algorithm was performed using both gravimetric and dielectric data from the Soil Moisture Active Passive Validation Experiment in 2012 (SMAPVEX12). The new algorithm is more accurate than the previous soil-probe algorithm, resulting in a slightly improved correlation (0.824 to 0.848), 12 % lower root mean square error (RMSE; 0.0824 to 0.0727 cm3 cm−3), and 95 % less bias (−0.0042 to 0.0001 cm3 cm−3). These results suggest that applying the new dielectric mixing model together with global SOM estimates will result in more reliable soil moisture reference data for weather and climate models and satellite validation.

Characterizing porous microaggregates and soil organic matter sequestered in allophanic paleosols on Holocene tephras using synchrotron-based X-ray microscopy and spectroscopy

Allophanic tephra-derived soils can sequester sizable quantities of soil organic matter (SOM). However, no studies have visualized the fine internal porous structure of allophanic soil microaggregates, nor studied the carbon structure preserved in such soils or paleosols. We used synchrotron radiation-based transmission X-ray microscopy (TXM) to perform 3D-tomography of the internal porous structure of dominantly allophanic soil microaggregates, and carbon near-edge X-ray absorption fine-structure (C NEXAFS) spectroscopy to characterize SOM in ≤ 12,000-year-old tephra-derived allophane-rich (with minor ferrihydrite) paleosols. The TXM tomography showed a vast network of internal, tortuous nano-pores within an allophanic microaggregate comprising nanoaggregates. SOM in the allophanic paleosols at four sites was dominated by carboxylic/carbonyl functional groups with subordinate quinonic, aromatic, and aliphatic groups. All samples exhibited similar compositions despite differences between the sites. That the SOM does not comprise specific types of functional groups through time implies that the functional groups are relict. The SOM originated at the land/soil surface: ongoing tephra deposition (intermittently or abruptly) then caused the land-surface to rise so that the once-surface horizons were buried more deeply and hence became increasingly isolated from inputs by the surficial/modern organic cycle. The presence of quinonic carbon, from biological processes but vulnerable to oxygen and light, indicates the exceptional protection of SOM and bio-signals in allophanic paleosols, attributable both to the porous allophane (with ferrihydrite) aggregates that occlude the relict SOM from degradation, and to rapid burial by successive tephra-fallout, as well as strong Al-organic chemical bonding. TXM and C NEXAFS spectroscopy help to unravel the fine structure of soils and SOM and are of great potential for soil science studies.

Conversion of Brazilian savannah to agricultural land affects quantity and quality of labile soil organic matter

Most studies assessing land-use change (LUC) and management impacts on the soil organic carbon (SOC) budget mainly focused on total soil organic matter (SOM), neglecting its functional fractions such as water-extractable organic matter (WEOM). This may limit a better understanding of SOC dynamics along the soil profile as WEOM plays a key role in several soil and microbial processes. Here, we aimed to obtain a quantitative and qualitative assessment of WEOM dynamics to 1 m depth in areas after native vegetation conversion to long-term agriculture in Brazil. For this purpose, cropland areas under no-tillage (NT; ∼ 23 years old) and native vegetation (NV; i.e., Cerrado vegetation) were evaluated across a transect of 1000 km within Brazil’s new agricultural frontier – the so-called MATOPIBA region. We combined spectroscopic analyses (UV–Vis and DRIFT spectroscopies), C and nitrogen (N) determination in different SOM pools (i.e., bulk SOM, WEOM, and microbial biomass), and microbial measurements [e.g., microbial biomass C (MBC) and N (MBN), and β-glucosidase activity] to better understand changes in WEOM dynamics induced by LUC. We observed that although SOC decreased along the soil profile after NV (4.2–20.7 g kg−1) conversion to NT (3.8–14.2 g kg−1), water-extractable organic C levels (3.6–79.3 mg L−1) were similar between land uses. On the other hand, an increase in water-extractable total N was observed after NV (0.4–4.6 mg L−1) conversion to NT (0.5–19.3 mg L−1). Although MBC and MBN levels decreased for most study sites, β-glucosidase activity increased after LUC indicating intensive microbial processing of SOM. As a result, WEOM had lower aromaticity and molecular weight (i.e., low values of SUVA254 and A2/A3) in NT than NV; and a relative decomposition of aliphatic and polysaccharides over aromatic and amine/amide was observed after LUC through DRIFT spectroscopy. Our study indicates that LUC had stronger impacts on WEOM quality than its quantity, with agricultural areas having more biochemical changes in WEOM than NV.

The Role of Cover Crop Types and Residue Incorporation in Improving Soil Chemical Properties

Soil chemical properties can be improved by incorporating crop residues in soil and letting it decompose. This study explored the use of incorporating residues of cover crops for improvements in soil chemical properties including soil organic matter (SOM), soil pH, and the selected soil macro- and micronutrients in greenhouse and field trials. Factors of interest included (i) cover crops and their combinations and (ii) methods of crop termination and incorporation in soil (disc, mow + disc, glyphosate, roller crimper). The greenhouse trial showed up to a 20% higher amount of SOM accumulated in soils incorporated with crop residues. Buckwheat (3.12%) and phacelia (3.12%) produced significantly different and larger SOM than that of the control treatment that received no crop residues (p ≤ 0.05). The soil pH of the brown mustard treatment was also significantly affected by the experimental treatments (p ≤ 0.05). The incorporation of crop residues did not affect soil phosphorous (P) or potassium (K) concentrations, except for brown mustard, with significantly higher values of P and K than the control treatment. Calcium (Ca) was significantly higher in the soil of phacelia + pea treatment (p ≤ 0.05). Buckwheat + pea produced a higher concentration of Ca (1028 mg/kg) followed by buckwheat alone (1006 mg/kg). Analysis of variance (ANOVA) calculated on the results of the field trial showed that the mix treatment that had a mixture of four cover crops significantly increased the SOM content. Buckwheat produced the highest (2.95%) SOM, then brown mustard and timothy. This study concludes that, irrespective of the tillage incorporation methods, the residues from cover crops are a potential source of improvement in soil health, and this practice may promote sustainable agriculture in conditions similar to those in this study.

Evolution of soil organic matter qualitative composition under different land-use types in the Yaroslavl oblast (European Russia) over longstanding period

The paper describes the postagrogenic transformation of soil organic matter (SOM). For this purpose, the results of chemodestructive fractionation (CDF), the content of chlorophylls a and b, pheophetins and carotenoids were used for the first time. To assess the state of soil algae, Margalef’s pigment index (PI) was calculated. Soils humus horizons of arable lands and fallow ones of the Poshekhonsky district of the Yaroslavl oblast of the Russian Federation were selected as objects of research. The objects were grouped into two groups that differ in the type of land use. In one of them the soil for 30–40 years remained arable (arable-arable group), other soils arable land over the same time period were transferred to the fallow (arable-fallow group). It was found that the conversation of arable soils to fallows led to: improving the state of soil algocenosis (a value of Margalef’s PI decreased), increasing of both total organic carbon and amount of soil organic matter (SOM) easily oxidized fraction, strengthening of hydrolytic processes that reduced content of carotenoids and chlorins (in particular, pheophetins and chlorophylls a and b) in SOM. When the content of total organic carbon did not exceed 1%, the conversion of arable soils to the fallows did not cause a noticeable change in the studied characteristics of soil organic matter qualitative composition.

Rapid assessment of soil water repellency indices using Vis-NIR spectroscopy and pedo-transfer functions

Soil water repellency (SWR) is an important soil physical property that may restrict water infiltration and soil water retention. Common laboratory and field techniques for assessing SWR are laborious, time-consuming, and costly. Meanwhile, Visible–Near-Infrared (Vis-NIR) spectroscopy has been reported as a rapid, cost-effective, and alternative technique to estimate several soil properties. To investigate the efficacy of this technique for predicting SWR indices [soil water repellency index (RI) and soil–water contact angle (β)] at dry condition, 100 soil samples collected from farmlands, orchards, rangelands and forests of Zrêbar lake watershed in Kurdistan province, Iran, were measured by Vis-NIR spectroscopy within the 350–2500 nm range. The Savitzky–Golay first derivative method was applied for denoising the spectral data. The RI and β were measured by the intrinsic sorptivity method (using water and ethanol as absorbing liquids). The other basic soil properties were also measured by standard laboratory methods. Stepwise multiple linear regression (SMLR) and partial least squares regression (PLSR) were utilized to establish pedo-transfer functions (PTFs) and spectro-transfer functions (STFs) using basic soil properties and spectral absorbance data, respectively, to estimate soil organic matter (SOM) content and SWR indices. We obtained good predictions for SOM with R2 = 0.67 and RPIQ (the ratio of performance to interquartile range) = 1.92 using the PLSR-based STF. The results also revealed that although the SMLR-based STFs achieved slightly better estimates of the SWR indices (RI and β) than the SMLR-based PTFs (R2 values of 0.28 to 0.39 vs. 0.19 to 0.23, respectively); but, overall, none of these transfer functions for estimating these indices showed acceptable predictive capability. However, the PLSR-based STFs could provide a reasonable prediction for the studied SWR indices (R2 > 0.52 and RPIQ > 2.27). The majority of important adsorption bands in the Vis-NIR PLSR models for the SWR prediction was related to both the quantity and quality of SOM. Overall, the results demonstrated that the Vis-NIR PLSR could be applied to predict SOM and SWR indices rapidly, non-destructively, and with fair accuracy.

Soil organic carbon, physical fractions of the macro-organic matter, and soil stability relationship in lacustrine soils under banana crop.

Banana is a staple food and a major export commodity in the tropics. However, banana production systems are affected by the plant-soil relationships, where properties such as quality and quantity of soil organic matter play an important role in the dynamics of soil physical properties. In order to evaluate the effect of the soil organic carbon (SOC) content and its distribution in the water-stable of soil aggregates (WAS), and the physical fractions of the macro-organic matter, a study was conducted in lacustrine soils under Banana cv. 'Grand Nain' in Venezuela. Soil sampling was carried out in two batches differentiated by their textural class and crop production. A completely randomized design under a directed random sampling technique was carried out. In each condition, 12 composite samples were taken at depths 0-5 and 5-10 cm, respectively. WAS were separated into micro (< 250 μm) and macroaggregates (> 250 μm). Also, physical fractionation by size-density of the macro-organic matter into light (LF), intermediate (IF), and heavy (HF) fraction using a silica gel solution, and SOC, were determined and correlated with banana yield and other agronomic traits. A major proportion of aggregates > 250 μm were found in both conditions and depths. Organic Carbon within soil aggregates ranged between 29.7 and 35.3 g kg-1. The HF was superior to IF and LF; however, its C content was higher in the LF. The results allow inferring that the stability conferred to these soils is primarily associated with the presence of the snail, which shares the same size as the aggregates studied. High yields are associated with high C content in stable aggregates, as well as in the most labile fractions of macro-organic matter. These results highlight the importance of the use of organic fertilizers less recalcitrant as a strategy for sustainable management of banana cultivation.

Identifying Controlling Factors of Bioaccumulation of Selected Metal(loid)s in Various Soil–Cereal Crop Systems within Cultivated Fluvisols

The paired Fluvisol and cereal samples in both the field screening and controlled experiments are reported to elucidate the soil–crop relationship for As, Cd, and Pb in relation to changing contamination levels. Significant varietal differences in plant uptake were observed for crop type (barley, triticale) and the harvested part of the crop (oat shoots and grain). When parametrizing the stepwise regression models, the inclusion of soil properties often improved the performance of soil–crop models but diverse critical soil parameters were retained in the model for individual metal(loid)s. The pH value was often a statistically significant variable for Cd uptake. For As and Pb, the more successful model fit was achieved using the indicators of quantity or quality of soil organic matter, but always with lower inherent model reliability compared to Cd. Further, a single correlation analysis was used to investigate the relationship between extractable metal concentrations in soil solution and their crop accumulation. For Cd, there were strong intercorrelations among single extractions, the NH4NO3 extraction stood out with perfect correlation with plant uptake in both experiments. For As and Pb, the CaCl2 and Na2EDTA solutions outperformed other single extractions and were the better choice for the assessment of depositional fluvial substrates.

English

Farmers can play an important role in climate change mitigation through sustainable soil management practices. Semi-structured interviews were conducted in the Atwima Nwabiagya municipality of Ashanti region, Ghana, to explore farmers' knowledge and perceptions of their soils, soil fertility, applied management practices, and climate change on soil organic carbon. The interviews included topics related to farmers’ access to training and its impact in adopting and changes in management strategies. Summary for interviews was prepared based on notes and recordings and analyzed with the Qualitative Content Analysis (QCAmap) software using emergent codes. Results show that farmers had a lot of knowledge on soil organic matter (SOM) and how it affects climate and the relationship between SOM and soil fertility. They also acknowledged that their management practices affect quantities of SOM in topsoil and subsoil and soil fertility. The adoption of current and new management practices including, the use of organic and inorganic fertilizers, manure, mulching, and shade management, is a reflection of their newly acquired knowledge and understanding of fertility sustaining processes. The study highlights the relationship between farmers' training and changes in their adopted practices and how management practices affect SOC influencing climate change and soil fertility. Key words: soil organic carbon, cocoa farmers, perception, soil management, soil fertility and climate change.

Influence of humic acid structure on the accumulation of oxyfluorfen in tropical soils of mountain agroecosystems

Herbicide application is a practice commonly used in agricultural systems because it is an efficient method of weed control. An inherent characteristic of some herbicides used in mountain agriculture, such as oxyfluorfen, is high adsorption to soil organic matter (SOM). Thus, intensive management that changes the quantity and quality of SOM, such as soil tillage and the massive application of organic fertilizers such as poultry litter, may favor soil contamination by this herbicide and alter its dynamics in the environment. Therefore, this study aimed to characterize the structures of humic substances (HSs) in the soil of forest areas and areas with intensive production of vegetables, relating them to the accumulation of the herbicide oxyfluorfen in tropical mountain agroecosystems. Organic carbon content was quantified in HSs, humic acid (HAs) were structurally characterized by CP/MAS 13C-NMR spectroscopy, and the oxyfluorfen molecule was detected and quantified using the QuEChERS residue detection method with subsequent analysis by LC-MS/MS. Oxyfluorfen was not detected in the forest areas, but it was detected in the vegetable growing areas at points with the lowest slope and high contents of organic matter and clay, with values of up to 0.13 mg kg−1. The intensification in the SOM mineralization process, promoted by the intensive management adopted in the vegetable growing areas, resulted in a 16.46% reduction in COT, a 58.84% reduction in the carbon content in the form of SH and a reduction in the structures that give recalcitrance to the HA molecule (CAlkyl-H,R, CCOO–H,R, CAromatic-H,R, and CAromatic-O) when compared to those values in the forest area, presenting HAs with more aliphatic and labile properties. Thus, due to the structural characteristics of the HAs in the vegetable production areas, the herbicide oxyfluorfen showed a close relationship with the more aliphatic oxygenated structures, namely, CAlkyl-O,N, CAlkyl-O and CAlkyl-di-O.

Long-term geochemical monitoring of the soil cover in the impact zone of diamond mining enterprises: a case study in the Nakyn kimberlite field, Russia.

The most severe disturbance of the earth's surface occurs when the open-cut method of mineral deposits mining is used. The geoecological situation was assessed based on the nature of the soil cover based on the example of an industrial site of a diamond mining and processing plant located in the permafrost zone. During the period from 2007 to 2018, the soil cover of the industrial site is characterized by polyelement contamination. In the surface, soil horizons were an increase in the concentrations of mobile forms of Mn, Zn, Cd, Cr, Co, and Ni. It is identified that AO, ABcr, and CR are the accumulation horizons if the soil profile is preserved. Mobile forms Mn, Zn, Ni, Cr, Co, and As can migrate along with the soil profile to a depth of 40-50cm depending on the amount of soil organic matter, the degree of its decomposition, and the scale of the cryoturbation. Research in 2018 allowed us to localize and confirm the increase in the area of contamination of the industrial site. Areas with an extremely dangerous category of soil cover contamination increased by 3 times compared to 2014. The results obtained are the basis for a more detailed study of the horizons of geochemical accumulation and the creation of artificial geochemical barriers with the development of technologies for the subsequent extraction of useful components.

Organic Matter Decomposition and Nutrient Release from Different Dhaincha (Sesbania spp.) Genotypes

Purpose: An experiment was conducted at Field Laboratory of the Department of Crop Botany, Bangladesh Agricultural University during April to July 2018 to compare the biomass yield potential, decomposition and nutrients release pattern of different dhaincha genotypes.Research Method: Six dhaincha accessions from three Sesbania species, viz. S. bispinosa (accession #05, 71, 77 and 109), S. cannabina (accession #28) and S. sesbsan (accession #81), were used as experimental materials. Dhaincha was cultivated with standard cultivation procedure following a randomized complete block design with three replications and incorporated with soil at 60 days after sowing.Findings: There are wide variations in biomass yield, crude fi bre and crude protein among the accessions. The amount of crude fibre may be used as a descriptor of taxonomic importance. Accession #28 (S. cannabina) produced a significantly higher amount of crude fibre compared to other accessions. Soil organic matter (SOM) and nutrient elements availability increased with the period of time and reached to a peak at 50 days after biomass incorporation (DAI) except K and S. The highest amount of SOM and N was recorded in accession #71 and the lowest in accession #81. The maximum amount of phosphorus and potassium was added by accession #05 and the minimum phosphorus and potassium by accession #28 and #81, respectively. The greatest amount of sulfur showed 5.25 ppm in accession #05 at 20 DAI and the smallest value 2.22 ppm in accession #28 at 60 DAI.Originality: It is evident from results that accession #71 can be recommended for cultivation in the farmer’s field for higher biomass yield and the maximum amount of nutrients release.

Spectral Assessment of Organic Matter with Different Composition Using Reflectance Spectroscopy

Soil surveys are critical for maintaining sustainable use of natural resources while minimizing harmful impacts to the ecosystem. A key soil attribute for many environmental factors, such as CO2 budget, soil fertility and sustainability, is soil organic matter (SOM), as well as its sequestration. Soil spectroscopy is a popular method to assess SOM content rapidly in both field and laboratory domains. However, SOM source composition differs from soil to soil, and the use of spectral-based models for quantifying SOM may present limited accuracy when applying a generic approach to SOM assessment. We therefore examined the extent to which the generic approach can assess SOM contents of different origin using spectral-based models. We created an artificial big dataset composed of pure dune sand as a SOM-free background, which was artificially mixed with increasing amounts of different organic matter (OM) sources obtained from commercial compost of different origins. Dune sand has high albedo and yields optimal conditions for SOM detection. This study combined two methods: partial least squares regression for the prediction of SOM content from reflectance values across the 400–2500 nm region and a soil spectral detection limit (SSDL) to judge the prediction accuracy. Spectral-based models to assess SOM content were evaluated with each OM source as well as with a merged dataset that contained all of the generated samples (generic approach). The latter was concluded to have limitations for assessing low amounts of SOM (&lt;0.6%), even under controlled conditions. Moreover, some of the OM sources were more difficult to monitor than others; accordingly, caution is advised when different SOM sources are present in the examined population.

Response of Gross Mineralization and Nitrification Rates to Banana Cultivation Sites Converted from Natural Forest in Subtropical China

Evaluations of gross mineralization (MNorg) and nitrification (ONH4) can be used to evaluate the supply capacity of inorganic N, which is crucial in determining appropriate N fertilizer application. However, the relevant research for banana plantations to date is limited. In this study, natural forest and banana plantations with different cultivation ages (3, 7, 10, and 22 y) were chosen in a subtropical region, and the 15N dilution technique was used to determine the gross MNorg and ONH4 rates. The objective was to evaluate the effect of the conversion of natural forests to banana plantations on inorganic N supply capacity (MNorg + ONH4) and other relevant factors. Compared to other natural forests in tropical and subtropical regions reported on by previous studies, the natural forest in this study was characterized by a relatively low MNorg rate and a high ONH4 rate in the soil, resulting in the presence of inorganic N dominated by nitrate. Compared to the natural forest, 3 y banana cultivation increased the MNorg and ONH4 rates and inorganic N availability in the soil, but these rates were significantly reduced with prolonged banana cultivation. Furthermore, the mean residence times of ammonium and nitrate were shorter in the 3 y than in the 7, 10, and 22 y banana plantations, indicating a reduced turnover of ammonium and nitrate in soil subjected to long-term banana cultivation. In addition, the conversion of natural forest to banana plantation reduced the soil organic carbon (SOC), total N and calcium concentrations, as well as water holding capacity (WHC), cation exchangeable capacity (CEC), and pH, more obviously in soils subjected to long-term banana cultivation. The MNorg and ONH4 rates were significantly and positively related to the SOC and TN concentrations, as well as the WHC and CEC, suggesting that the decline in soil quality after long-term banana cultivation could significantly inhibit MNorg and ONH4 rates, thus reducing inorganic N supply and turnover. Increasing the amount of soil organic matter may be an effective measure for stimulating N cycling for long-term banana cultivation.

Importance of Vermicompost in Tomato Plant Cultivation and Improvement of Some Soil Properties

Vermicompost is a material whose popularity is rapidly growing. However, information about the usage amount and mineralization in the soil, and the state of the emergence of plant nutrients is quite limited. In this study, it was aimed to determine the effects of different vermicompost doses at different incubation periods on the soil properties and nutrient concentrations of the tomato plant. For this purpose, increased doses of vermicompost (0, 20, 40, and 60 t ha−1) were mixed into the soil, and effects of them on soil properties at different incubation periods (0, 15, 30, 45, 60 and 90 days) were determined. At the end of the incubation period, the tomato plant was grown. At the end of the cultivation phase, the residual effect of vermicompost on soil properties were determined. Vermicompost doses and the increase in incubation period increased the amount of soil organic matter. With the direct and residual effects of increased vermicompost doses, the total concentration of N, av-P, ex-K, ex-Ca, ex-Mg and av-Zn in the soil increased. Prolongation of the incubation period caused fluctuation of nutrient concentrations. Increased vermicompost doses positively affected the N, P, and K concentrations of the tomato plant, and negatively affected the Ca, Mg, Fe, Zn, and Mn concentrations of it. As a result, it was found that vermicompost improved the chemical properties of the highly calcareous Mediterranean region soils, but it was not sufficient for adequate and balanced feeding in plant production, and it must necessarily be supplemented by chemical feeding.

EVALUATION OF SOIL NUTRIENT STATUS IN APPLE ORCHARDS LOCATED IN DIFFERENT ALTITUDES IN KALIKOT DISTRICT, NEPAL

This study was conducted to assess the fertility status of different altitude of apple orchard and their effect upon soil nutrients and to study the relationship between different altitude and their availability. Seven different orchards located in 2800, 2700 2600, 2500, 2400, 2300 and 2200 at Apple Zone, Raskot, Kalikot were selected as treatments. They were replicated three times in Randomized Complete Block Design. Composite soil samples were collected in each study site from 0-3 ft soil depth in ‘W’ pattern from each plot. Analyses of soil samples were done in regional soil testing laboratory, Surkhet for chemical properties. There was a significant effect (p&lt;0.05) of altitude on soil macronutrients except available potassium level. Maximum amounts of soil organic matter, acidic and soil rich in nitrogen and phosphorus were found in 2800 masl whereas more basic soil , poor soil organic matter and soil poor in nitrogen and phosphorus were found in 2200 masl. Result showed that in altitude of 2200 masl has poor soil nutrients compared to apple orchards in higher altitude. Kalikot is the top producer of apple in Nepal. This assessment will helps apple growers for adopting better nutrient management plan in their orchards according to the altitude in the district. Further, it is recommended to conduct soil nutrient assessments for all other apple growing regions in the country.