Effects of Different Organic Materials on Crop Production under a Rice–Corn Cropping Sequence

Soil organic matter (SOM) is an important index of soil quality because of its relationship with crop yield. The application of organic matter to soil is a significant method for increasing SOM. Different organic materials have varying effects in increasing SOM. This study investigates the effects of combining different sources of organic matter (i.e., compost, leguminous green manure, and peat) with a chemical nitrogen (N) fertilizer on the growth and N accumulation in corn and rice plants. This study examines seven treatments, including a no-fertilization check and a conventional chemical fertilizer treatment. Shoots of corn and rice were sampled at the tasseling (panicle initiation for rice) and maturity stages. The biomass yield was measured and the total N was analyzed. At the maturity stage, the soil samples were collected to determine the chemical properties. The results showed that a small percentage of the N in the compost and peat, after their application, was available to the crop during the growth season; the production of biomass and N absorption among rice and corn plants was minimal compared to that treated with chemical N fertilizer. The application of compost and peat resulted in SOM accumulation, particularly with peat. However, the application of compost combined with chemical fertilizer not only produced sufficient nutrients for crop growth but also resulted in an accumulation of SOM, which is vital for enhancing the soil quality. Most of the N in green manure (GM) was mineralized shortly after application, causing excessive growth of rice and corn plants during the early stage, but reducing their reproductive growth and grain yield.     

The contribution of various organic matter fractions to soil–water interactions and structural stability of an agriculturally cultivated soil

The presence and mutual interactions of soil organic matter (SOM) and clay particles are major factors determining soil structural stability. In the scope of agricultural management and environmental sustainability, it remains unclear how various mineral and organic matter (OM) fractions, OM–clay interactions and swelling processes in the interparticle space determine soil–water interactions and thus soil structural stability. To investigate this issue, we isolated the mineral and OM fractions of an agriculturally cultivated silty loam soil by soil density fractionation and assessed their hydration characteristics and effects on soil structural stability combining ¹H‐NMR relaxometry, soil rheology and single wet‐sieving of soil aggregates. The results showed that agricultural management practices, in particular compost and ploughing, as well as various OM–clay interactions significantly affected soil–water interactions and soil structural stability. On the one hand, ploughing reduced soil structural stability by promoting clay swelling as a result of disrupted soil structures and reduced SOM content. On the other hand, compost treatment and reduced tillage increased soil structural stability. In all cases, soil density fractionation showed that compost‐derived particulate organic matter (POM) and mineral‐associated organic matter (MAOM) restricted clay swelling and resulted in a highly porous and mechanically stable soil matrix. In particular, POM increased soil structural stability by acting as nucleus for soil aggregation and by restricting clay swelling via its presence as solid, granular interparticulate material. In contrast, MAOM seemed to restrict clay swelling via clay surface covering and the formation of viscous interparticulate hydrogel structures.     

Aggregation and organic matter in subarctic Andosols under different grassland management

Quantity and quality of soil organic matter (SOM) affect physical, chemical, and biological soil properties, and are pivotal to productive and healthy grasslands. Thus, we analyzed the distribution of soil aggregates and assessed quality, quantity, and distribution of SOM in two unimproved and improved (two organic and two conventional) grasslands in subarctic Iceland, in Haplic and Histic Andosols. We also evaluated principal physicochemical and biological soil properties, which influence soil aggregation and SOM dynamics. Macroaggregates (>250 µm) in topsoils were most prominent in unimproved (62–77%) and organically (58–69%) managed sites, whereas 20–250 µm aggregates were the most prominent in conventionally managed sites (51–53%). Macroaggregate stability in topsoils, measured as mean weight diameter, was approximately twice as high in organically managed (12–20 mm) compared with the conventionally managed (5–8 mm) sites, possibly due to higher organic inputs (e.g., manure, compost, and cattle urine). In unimproved grasslands and one organic site, macroaggregates contributed between 40% and 70% of soil organic carbon (SOC) and nitrogen to bulk soil, whereas in high SOM concentration sites free particulate organic matter contributed up to 70% of the SOC and nitrogen to bulk soil. Aggregate hierarchy in Haplic Andosols was confirmed by different stabilizing mechanisms of micro- and macroaggregates, however, somewhat diminished by oxides (pyrophosphate-, oxalate-, and dithionite-extractable Fe, Al, and Mn) acting as binding agents for macroaggregates. In Histic Andosols, no aggregate hierarchy was observed. The higher macroaggregate stability in organic farming practice compared with conventional farming is of interest due to the importance of macroaggregates in protecting SOM and soils from erosion, which is a prerequisite for soil functions in grasslands that are envisaged for food production in the future.     

Long‐lasting impact of biowaste‐compost application in agriculture on soil‐quality parameters in three different crop‐rotation systems

Soil‐quality parameters, such as soil organic matter (SOM) and plant‐available nutrient contents, microbial properties, aggregate stability, and the amounts of heavy metals were carried out in arable soils of different rotation schedules applied with a total of 50 Mg dry mass ha^–1 biowaste compost relative to an untreated control. This was investigated during a 10 y period from 1994 to 2004. Overall, soil‐quality parameters studied appeared to be promoted by biowaste‐compost application. This was evidenced for example by a remarkable increase of SOM and total N content of ≈ 15%–20% relative to the control. Subsequently, amounts of soil microbial biomass and alkaline phosphatase activity were significantly increased as well. In addition, biowaste‐compost application revealed an increase of plant‐available P and K contents and aggregate stability in soil. There was, however, no treatment effect for net N‐mineralization rates. Moreover, in soils of maize and sugar beet rotation schedule a slight decrease was found. Heavy‐metal contents of Pb and Zn were significantly increased in all compost‐treated soils, whereas no significant increase of Cd and Cu contents was measured. However, the investigated amounts were far below of the limits of the German Biowaste Ordinance. It is finally recommended, that biowaste compost may sustain and improve soil quality in agriculture when N nutrition will be considered.     

The effects of compost in a rice–wheat cropping system on aggregate size,carbon and nitrogen content of the size–density fraction and chemical composition of soil organic matter,as shown by 13C CP NMR spectroscopy

We investigated whether the long‐term application of compost from agricultural waste improved soil physical structure, fertility and soil organic matter (SOM) storage. In 2006, we began a long‐term field experiment based on a rice–wheat rotation cropping system, having a control without fertilizer (NF) and three treatments: chemical fertilizers (CF), pig manure compost (PMC) and a prilled mixture of PMC and inorganic fertilizers (OICF). Following the harvest of wheat in 2010, the mean‐weight diameter (MWD) of water‐stable aggregates and the concentration of C and N in bulk soil (0–20 cm; <2 mm fraction) were significantly greater (P < 0.05) in PMC and NF plots than in CF or OICF plots. Pig manure compost significantly increased the proportion of >5‐mm aggregates, whereas CF significantly increased the proportion of 0.45‐ to 1‐mm aggregates. The C and N contents of all density fractions were greater in PMC than in other treatments with levels decreasing in the following order: free particulate organic matter (fPOM) >occluded particulate organic matter (oPOM) > mineral‐combined SOM (mineral–SOM). Solid‐state ¹³C CPMAS NMR spectra showed that alkyl C/O‐alkyl C ratios and aromatic component levels of SOM were smaller in PMC and OICF plots than in CF plots, suggesting that SOM in PMC and OICF plots was less degraded than that in CF plots. Nevertheless, yields of wheat in PMC and NF plots were smaller than those in CF and OICF plots, indicating that conditions for producing large grain yields did not maintain soil fertility.     

Effects of compost on the chemical composition of SOM in density and aggregate fractions from rice–wheat cropping systems as shown by solid‐state 13C‐NMR spectroscopy

The 4‐year application of pig‐manure compost (PMC) to crop fields in Jiangsu significantly increased organic‐C and total N concentrations compared to chemical fertilization and control treatment. To identify the soil processes that led to these changes, ¹³C cross‐polarization magic‐angle spinning nuclear‐magnetic resonance (¹³C CPMAS NMR) and dipolar‐dephasing nuclear‐magnetic‐resonance spectroscopy (DD NMR) were conducted on soil organic matter (SOM) fractions separated by wet‐sieving and density fractionation procedures. This allowed characterization of the SOM quality under three contrasting fertilizer regimes. The results indicate that PMC application can alter the distribution of functional groups and improve alkyl C‐to‐O‐alkyl C ratios compared to chemical‐fertilizer treatment (CF). Alkyl C contents were increased from macroaggregate fractions (> 2 mm) to microaggregate fractions (0.05–0.25 mm) for all treatments, suggesting that recalcitrant material accumulates in the microaggregate fractions. The O‐alkyl C contents were decreased from macroaggregate fractions (> 2 mm) to microaggregate fractions (0.05–0.25 mm) under CF and PMC treatments, while no consistent trend was found for the control (NF) treatment. The alkyl C‐to‐O‐alkyl C ratios in macroaggregates were lower than those in microaggregates, indicating that the degrees of SOM decomposition were lower in macroaggregates compared to microaggregates. In all aggregate‐size classes, the amount of organic matter appeared to depend on the fertilization regime. This study provides useful information regarding the buildup of organic material in soil from long‐term manure‐compost enrichment.     

Compost Changed Soil Organic Matter Molecular Composition: A Py-GC/MS and Py-FIMS Study

Changes in the molecular composition of soil organic matter (SOM) resulting from compost application are not sufficiently known at the molecular scale even though this is a major issue for soil fertility and soil carbon sequestration. Therefore, the present study investigated effects of long-term compost application in comparison to mineral fertilizer on the molecular composition of SOM in a 34-year-old experiment. Soil samples were taken after 19 and 34 years of constant management and analyzed by Curie point Pyrolysis-Gas Chromatography/Mass Spectrometry (Cp Py-GC/MS) and Pyrolysis-Field Ionization Mass Spectrometry (Py-FIMS). In general, compost application increased the organic carbon (C) content. The Cp PyGC/MS revealed larger relative intensities of alkylphenols/lignin monomers at the expense of carbohydrates in the compost treatments. Py-FIMS indicated higher proportions of labile n-fatty acids, lipids and sterols in the compost than in the mineral fertilizer treatment. Permanent cropping of grass between years 19 and 34 revealed similar signal patterns, which is also maintained after conversion of soil from permanent grass to arable use. Thermograms of volatilization indicated enrichments of stable (compounds volatilized in between 370°C and 570°C) phenols/lignin monomers, lipids and alkylaromatics between years 19 and 34 in compost fertilized soils. This was a result of enhanced losses of compounds that are considered easily metabolized by microorganisms (e.g. carbohydrates) after compost addition as derived from Py-GC/MS and Py-FIMS. In summary, long-term application of mature compost was shown to have a positive, long lasting effect on the organic carbon sequestration in agricultural soils.     

Farming Methods Effects on the Soil Fertility and Crop Production Under a Rice-Vegetables Cropping Sequences

This study conducted a long-term field trial to evaluate the effects of three farming methods (i.e., conventional farming, organic farming, and intermediate farming) on soil fertility and plant growth under a crop rotation of vegetables, sweet corn, and rice. The nitrogen (N) uptake of crops grown with chemical fertilizers (CFs) and organic fertilizers was also compared carefully over 7 consecutive years. The results revealed that only a fraction of the nitrogen N in chicken manure compost was available to crops immediately following application. Therefore, the fresh weight production and absorption of N by amaranth, water convolvulus, and sprouting broccoli plants were relatively minimal compared to those grown with chemical N fertilizers. However, the amount of N from the chicken manure compost met the nutrient requirements of rice and sweet corn. Application of chicken manure compost increased the accumulation of soil organic matter (SOM) and available phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) content, which is essential for enhancing soil quality. Because of the rapid decomposition of rapeseed seed meal (RSM), most of the N in RSM was mineralized immediately following application, which induced the rapid growth of leafy vegetables and increased yields. Application of compost with chemical fertilizers not only results in yields as high as those from pure chemical fertilizer treatment, but also improves SOM accumulation and soil fertility.     

Effects of Surface Application of MSW Compost On Cotton Production – Soil Properties,Plant Responses,And Nematode Management

Equipment was modified and/or developed for broadcast and banded applications of municipal solid waste (MSW) compost at selected rates to agricultural land for cotton production. Replicated tests were conducted for four years to determine the effects of compost on soil properties, crop yield, and nematode populations. Soil type in the test field was Faceville loamy sand. Broadcast application of compost significantly reduced soil compaction in the top 30 cm of soil in cotton rows and row-middles compared to no compost application. Banded application did not affect compaction in the row middles. Columbia lance nematode densities decreased in all compost-treated plots during all four years of study. Several plots treated with compost had nematode densities comparable to those found in the plots treated with Temik 15G nematicide. Compost application significantly increased the soil organic matter content and soil nitrogen content at six and 14 weeks after planting. However, the compost did not affect the leaf nitrogen content of the cotton plant during the same sampling periods. In 1996, 1997, and 1998, all rates of added compost significantly increased seed cotton yield. Yield increase was proportional to application rate. There were very few carry-over compost effects from each previous year's treatments on either soil organic matter, soil nitrogen, or seed cotton yield.     

Remediation of Cadmium Pollution in Soils by Different Amendments: A Column Study

Abstract

A column study was conducted to determine the effect of city compost, lime, gypsum, and phosphate on cadmium (Cd) mobility in three well‐recognized benchmark soils of India [viz., (Islamnagar) Vertisol, (Amarpur) Inceptisol, and (Khala) Alfisol]. Columns made of PVC were filled with soil treated with different treatment doses [viz., 0.5% city compost, 1% city compost, 2% city compost, 2.5 t lime/ha, 5 t lime/ha, 2.5 t lime/ha+0.5% city compost, 2.5 t gypsum/ha, 2.5 t gypsum/ha+0.5% city compost, and 100 kg P₂O₅/ha as potassium phosphate (KH₂PO₄). The columns were leached with 100 mg L^?1 Cd under saturated condition. The amount of water moving through the soils was measured as the pore volume. A delayed breakthrough curve (BTC) of Cd in the presence of lime has been observed in all the studied benchmark soil series. Among the treatments, lime application reduced the movement of Cd from surface soil to lower depth of soil to a large extent resulted in 9, 25, and 45% more retention of Cd in surface soil of the Islamnagar, Amarpur, and Khala series respectively. Explanation for reduced Cd mobility in limed soil can be derived from pH changes of soils. In comparison to control soil, phosphate application caused 6, 21, and 30% more retention of Cd in surface soil in the Islamnagar, Amarpur, and Khala series, respectively. Combined application of lime and city compost reduced the movement of Cd in the soil profile. It appears that organic matter controls the sorption of Cd in soils. The amount of Cd sorbed increased with increasing organic carbon content, but gypsum application may leach Cd beyond the root‐zone depth. A rapid breakthrough curve was observed under gypsum‐treated soils. Retardation factor revealed that a somewhat lower degree of Cd retention occurred in the Khala series, which might possibly be attributed to less clay content and low pH. Overall, the column study indicated that total Cd accumulation occurred up to depths of 5–7.5 cm, 7.5–10 cm, and 10–15 cm in soils of Islamnagar, Amarpur, and Khala series, respectively.     

Soil Organic Carbon and Nitrogen Stocks under Tropical Organic and Conventional Cropping Systems in Northeastern Brazil

Soil organic matter (SOM) is an essential ecosystem component whose dynamics are affected by soil management practices. To evaluate the impact of two agricultural systems (organic and conventional) on soil organic carbon (C) and nitrogen (N) stocks in a sandy soil, samples were collected from the Amway Nutrilite Brazil farm and from the Central Pivot Horticultural Farmers Association farm, both situated in the Chapada da Ibiapaba region, Ceará State, Brazil. The first area has a large‐scale Caribbean Cherry fruit production system under organic management, whereas the second represented a conventional soil cultivation condition, characterized by the use of chisel plow and disc plow, mineral fertilization, and herbicides application. Plots with and without green manure fertilization were compared in the organically cultivated systems by using soil samples collected in the rows and between the rows. Areas under native forest were also sampled to determine the steady‐state condition. Total organic C and N contents in the soil (SOC, TN) and in the humic substances were determined at the 0‐ to 5‐, 5‐ to 15‐, 15‐ to 30‐, and 30‐ to 50‐cm soil layers. In addition, oxidizible organic C fractions were measured to calculate the carbon management index (CMI). In general, total SOC levels were low, ranging from 2.5 to 12.6 g kg^?1 in the whole soil profile among the organic systems. In the upper soil layer, SOC and TN stocks were greater in the rows in response to organic fertilization. The conventional system presented lower variation on the SOC contents throughout soil layers when compared to the native forest area, indicating the direct effect of plowing on the downward SOC distribution. The CMI data confirmed the reestablishment of SOM levels in the rows of the organic managed systems in relation to the reference area, whereas the reduction of the CMI in the conventional system suggests a decline in the soil quality and greater potential for increased C losses to the atmosphere.     

Changes in the chemical composition of soil organic matter after application of compost

Is the composition of soil organic matter changed by adding compost? To find out we incubated biowaste composts with agricultural soils and a humus‐free mineral substrate at 5°C and 14°C for 18 months and examined the products. Organic matter composition was characterized by CuO oxidation of lignin, hydrolysis of cellulosic and non‐cellulosic polysaccharides (CPS and NCPS) and ¹³C cross‐polarization magic angle spinning nuclear magnetic resonance (CPMAS ¹³C‐NMR) spectroscopy. The lignin contents in the compost‐amended soils increased because the composts contained more lignin, which altered little even after prolonged decomposition of the composts in soil. A pronounced decrease in lignin occurred in the soils amended with mature compost only. Polysaccharide C accounted for 14–20% of the organic carbon at the beginning of the experiment for both the compost‐amended soils and the controls. During the incubation, the relative contents of total polysaccharides decreased for 9–20% (controls) and for 20–49% (compost‐amended soils). They contributed preferentially to the decomposition as compared with the bulk soil organic matter, that decreased between < 2% and 20%. In the compost‐amended agricultural soils, cellulosic polysaccharides were decomposed in preference to non‐cellulosic ones. The NMR spectra of the compost‐amended soils had more intense signals of O–alkyl and aromatic C than did those of the controls. Incubation for 18 months resulted mainly in a decline of O–alkyl C for all soils. The composition of the soil organic matter after compost amendment changed mainly by increases in the lignin and aromatic C of the composts, and compost‐derived polysaccharides were mineralized preferentially. The results suggest that decomposition of the added composts in soil is as an ongoing humification process of the composts themselves. The different soil materials affected the changes in soil organic matter composition to only a minor degree.     

Relationship between soil neutral sugar composition and the amount of labile soil organic matter in Andisol treated with bark compost or leaf litter

 The effect of short-term bark compost (Ba) and leaf litter (Li) applications on the labile soil organic matter (SOM) status was investigated. The SOM status studied in this paper includes soil microbial biomass, soil available N, hot water extractable C (HwC) and N (HwN) and soil neutral sugar-C composition. The soil microbial biomass C (MBC) and N (MBN), soil available N, HwC and HwN increased upon application of Ba and Li. No quantitative relationship was observed between application of organic material and MBC, MBN or soil available N. A positive linear correlation was observed between MBN and HwC but not between MBN and soil available N. Among the various soil neutral sugar C, xylose C (Xyl) content in Ba plots showed a remarkable increase but mannose C (Man) did not differ among Fer (fertilizer), Ba or Li plots. Soil neutral sugar C had a positive linear correlation with soil available N, MBN and HwC. The proportion of MBN : TN is positively correlated with the Xyl/Man ratio. The increase in the proportion of MBN in SOM seems to occur with the increase of SOM derived from plant debris. Received: 20 October 1997     

Short-term compost effect on macroaggregation in a sandy soil under low rainfall in the valley of Mexico

Several studies have shown the importance of organic material in the formation and stability of soil aggregates. The organic matter of soil (SOM) is affected among other factors by the application of farmyard waste and compost, as well as tillage and crop rotation. This paper examines the aggregation and stability of a sandy soil (Haplic Fluvisol) in the valley of Mexico when treated with either 40 Mg ha⁻¹ of compost or urea (80 kg ha⁻¹ of N) and sown to amaranth (Amaranthus hypochondriacus L.) under dryland conditions. The application of compost resulted in a significantly larger proportion of aggregates in the fractions >1 mm (1.0–2.0, 2.0–2.3, 2.3–4.7 mm) than in the smaller fraction (<1 mm). However the stability of the macroaggregates >1 mm in the compost treatment was not higher than in contrasting treatments which did not include organic matter. Compost, which was applied under drought conditions, did not increase the aggregate stability of the soil probably because of the restricted transformation of the compost and microorganism activity.     

Increased Levels of Aluminium in Forest Soils: Effects on the Stores of Soil Organic Carbon

Acid atmospheric deposition results in increased levels of mobile aluminium (Al) in forest soils. Laboratory studies suggest that increased binding of Al to soil organic matter (SOM) in the forest floor results in decreased mobility of organic matter in soil water, viz. lower concentrations of dissolved organic carbon (DOC). Other laboratory studies indicate decreased decomposition rates of SOM as a result of Al binding. So far, little field evidence supporting these effects of Al on the lability of SOM have been reported. Here we present a field manipulation experiment in mature Norway spruce forest in Norway, where the content of Al in soil and soil water was increased. Increased Al in the forest floor caused a pronounced decrease in the leaching of DOC. Simultaneously, the decomposition rate of SOM decreased by 30% to 40%. This suggests that elevated Al in the forest floor stimulates accumulation of SOM. In a companion paper we present the effect of increased Al on forest vitality.     

Rice Straw Composting and Its Effect on Soil Properties

In Egypt, recycling rice straw and organic wastes is of great concern as well as improvement of soil properties. Rice straw compost could improve both organic waste recycling and soil quality. The aim of this study was to evaluate the effect of the rice straw compost, with or without water treatment residuals (WTR), on soil chemical properties and dry weight of canola. The results showed that the addition of rice straw compost and WTR decreased soil salinity and increased Ca⁺², K⁺ and organic matter. The addition of compost and WTR (2:1 wet weight ratio) at level of 10 g dry weight kg^?1 dry soil gave the best reduction in soil salinity compared to compost or WTR only or for level 10 g dry weight kg^?1 dry soil. The results also showed that the available P decreased with the application of WTR while it increased with the application of compost. The study demonstrated that the dry weight and relative increase (R.I %) of dry weight of canola plants increased with the application of WTR and compost to soil. Combinations of WTR and compost to soils had a greater effect on increasing yield and improved the efficiency of WTR on soil properties.     

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long‐Term No‐Till Production

Abstract: Soil quality indicators and nematode abundance were characterized in a loessial soil under long‐term conservation tillage to evaluate the effects of no‐till, double‐disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no‐till system amounted to 10887 kg over the 24 years or 454 kg ha^?1 year^?1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha^?1 year^?1) was due to SOM sequestration with no till. No‐till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics.     

Organic matter stabilization in a Xanthic Ferralsol of the central Amazon as affected by single trees: chemical characterization of density,aggregate, and particle size fractions

Not only the amount of organic carbon in soil is important for soil organic matter (SOM) stability, but also its physical and chemical properties. The appropriate technique for the assessment of SOM dynamics can vary between soil types, and information about this is lacking for Ferralsols of the central Amazon basin. First, this work identified SOM pools which are sensitive to land-use changes on the terra firme in the central Amazon. In a second step, the effects of single trees on SOM properties were evaluated in a mixed tree crop plantation in comparison to secondary and primary forest sites. Thus, the processes of organic matter stabilization could be studied in the highly aggregated soils. A combination of aggregate and density fractionation was found to be most suitable for physical SOM characterization. The particulate organic matter (POM, density less than 1.6 Mg m⁻³) varied by one order of magnitude between sites and could be used as a sensitive indicator of land-use changes. Aggregate stability was not related to SOM contents or bulk SOM properties. The incorporation of plant material into stable SOM, however, was enhanced by aggregation. Among aggregate separates, the fraction, 0.25–0.5 mm, showed single-tree effects the most. SOM replenishment was higher under tree species with low quality litter, i.e. high C-to-N and polyphenol-to-N ratios. High quality litter from a leguminous ground cover, however, showed low soil nitrogen and carbon replenishment but increased nitrogen concentrations in light fractions. Litter with a high quality may improve soil nitrogen availability but not amounts of total SOM, which could only be shown for low quality litter. The results indicate the importance of aggregation and POM dynamics for SOM stabilization in the studied Xanthic Ferralsols of the central Amazon basin.     

Effect of Sewage Sludge and Rice Straw Compost on Yield,Micronutrient Availability and Soil Quality under Rice–Wheat System

ABSTRACT

There is a need to improve the way in which crop residues and industrial organic wastes are managed and also to study their potential use in agriculture for improving soil fertility and biological activity. This study evaluated the effects of integrated use of organic (sewage sludge (SS) and rice straw compost (RSC)) and inorganic fertilizers on crop yield, soil enzymes activity, macro- and micro-nutrients availability under rice–wheat cropping system after three consecutive years of cropping in a subtropical semi-arid area. Different combinations of inorganic nitrogen and two doses of organic sources (SS and RSC) were applied to the soil. The results revealed that substitution with 50% N through RSC significantly increased the yield and biochemical properties as compared to inorganic fertilizers (NPK) alone. Micronutrients availability was found increased in treatment having substitution of 50% N through SS @10 t ha^?1. All the enzymatic activities viz. dehydrogenase, fluorescein diacetate (FDA), phosphatase, phytase, and urease) were found to be maximum by substitution of 50% N through RSC. Also, a significant positive correlation was found between soil enzymes (dehydrogenase and FDA) and organic carbon as well as crop yield. Thus, the study demonstrated that substitution of 50% inorganic nitrogen through organic sources will be a better alternative for improving soil quality and productivity.     

Molecular changes in organic matter of a compost-amended soil

The molecular changes of organic matter in a cultivated soil after compost amendments was followed by off-line-pyrolysis-TMAH GC-MS. Thermochemolysis of soil and compost provided a detailed molecular characterization of soil organic matter (SOM) by releasing a large amount of different molecules mainly derived from plant biopolymers such as lignin, waxes and bio-polyesters. No significant differences were found before and after 1 year of cultivation in the pyrolytic products released by control soil, which were mainly fatty acids, oxidized forms of lignins, and minor amounts of microbial bio-products and biopolyesters derivatives. Conversely, significant qualitative and quantitative variations were found in the molecular characteristics of SOM between control and compost-amended soils after 1 year of cultivation. Increasing amounts and diversified components of fatty acids, n -alkanes and various biopolyesters derivatives such as hydroxy-alkanoic and alkandioic acids were found in the compost-amended soil. These results indicate that a significant amount of exogenous compost-derived organic molecules were incorporated into SOM after 1 year of cultivation. The organic structural indexes derived from these results indicated direct inputs of undecomposed lignin residues and hydrocarbon waxes from compost material. When compared with the control soil, small but significant amounts of plant biomarkers, such as cyclic di- and triterpenes derivatives, were found only in the compost-amended soil. These findings suggest that the molecular changes of SOM brought about by amendment with biomass residues can be followed by using thermochemolysis of bulk soil samples.