Changes In Soil Chemical Properties Research Articles

Multi-element mapping of anthropogenically modified soils and sediments at the Bronze to Iron Ages site of Tel Burna in the southern Levant

Human settlement activities have caused changes in soil chemical properties that might remain preserved in the soil archive for a very long time. These traces might be close to irreversible on the timescale of known civilizations. Our study explores the potential of an extensive mapping of the multi-elemental composition of soil and buried sediments by a portable XRF spectrometer, using the Tel Burna site in the southern Levant as a case study. The tell, dating from the 3rd to the 1st millennium BCE, is known as a Bronze Age Canaanite settlement, and later in the Iron Age as a stronghold on the historic border between the Kingdom of Judah and Philistia. We compared the results of our geochemical survey conducted on the surface layer of contemporary soil with the data acquired by the same method from the archaeological stratigraphy exposed during excavations of the site. We found that handheld XRF spectrometry can reveal archaeologically meaningful patterns of the multi-elemental composition of soils and sediments in the horizontal plane, as well as in vertical profiles. Such patterns correspond to areas and loci of ancient settlement activities, dated to millennia ago. This methodology, if used critically, provides a rapid and cost-effective analysis of soil chemical composition that can significantly enhance our understanding of archaeological sites in arid environments.

Residual effect of surface-applied lime on soil acidity properties in a long-term experiment under no-till in a Southern Brazilian sandy Ultisol

The changes in soil chemical properties caused by surface lime application depend on the application dose, reaction time, and are limited to the top few centimeters of the soil profile. The present study aimed to monitor and to interpret the impacts of surface lime re-application at different rates and splitting rates on the amelioration of soil acidity and its distribution and migration through soil profile in a sandy Ultisol from Southern Brazil under long-term no-tillage (NT) system. The experiment was installed in an area where the conventional tillage (CT) was practiced till 1988 when the soil was limed (3.1Mgha−1) and then the area was maintained under NT. In October 1994, the soil was sampled and lime was reapplied at four rates: 0, 3.6, 5.4, and 6.0Mgha−1. The full dose to raise soil pH to 6.0 was applied in 1994 once. The rate of 5.4Mgha−1 was split in three times, applying 1.8Mglimeha−1 in 1994, 1995, and 1999, and the rate of 6.0Mgha−1 was split in five times, applying 1.2Mglimeha−1 in 1994, 1995, 1996, 1999, and 2000. The experimental design was randomized blocks with five replications. In October 2006 and 2012, i.e. after 18 and 24years of the start of NT or 12 and 18years after lime re-application (beginning of the experiment), soil samples were taken at each 1cm depth up to 10cm layer, each 2.5cm depth up to 10 to 25cm layer, and each 5cm depth from 25 to 60cm layer. Soil acidity attributes including active acidity (pH-H2O), aluminum (Al) saturation, exchangeable Al, exchangeable calcium (Ca), exchangeable magnesium (Mg) and base saturation were also evaluated. Results show that the re-acidification of the soil is extremely slow. Even after 24years without re-application of lime, the re-acidification process resulted in only 20% of the original potential acidity observed in the area under natural grassland. The surface application of lime in a re-acidified soil under NT promoted the formation of an alkalizing front by statistically modifying the soil acidity attributes up to 60cm. However, it was much less deeper (<35cm) when considering the agronomic interpretation of the soil acidity properties. Nevertheless, for both interpretations, the lime migration and its residual behavior were proportional to the lime application rate and its split application.

Changes in Nutrient Contents of Soil across Different Land Uses in a Forest Reserve

In order to assess the changes in soil chemical properties’ resulting from conversion of forest to other agricultural land uses a study was conducted in Okomu Forest Reserve (Nigeria). Five soil samples collected from top and sub soils of marked points within the undisturbed forest, farmland, cocoa plantation, oil palm plantation and rubber plantation were analyzed for pH, organic carbon, total nitrogen, available phosphorus, exchangeable acidity, sodium, potassium, calcium and magnesium. The results showed variations in all chemical parameters across the land use types with soil depths (top and sub soils). Soil pH ranged from 4.88 (in the cocoa plantation subsoil) to 6.75 (in the forest top soil). Soils (top and sub soils) of the rubber plantation, forest and cocoa plantation had the highest stock of soil organic carbon (SOC), N and exchangeable Na respectively. Available P was highest in the top soil of the rubber plantation and sub soil of the farmland. Exchangeable Ca and Mg were highest in the top soil of the forest and sub soil of the rubber plantation. Exchangeable K and C:N was highest in the farmland top soil and cocoa plantation sub soil. Relationship among the chemical parameters varied with soil depth. Conversion of forest and cocoa plantation resulted in the highest decline (55.78% and 44.40%) in soil N. There is the need to regulate the conversion of natural forests to agricultural lands and plantations as conserve the nutrient cycling processes.

Elevated ozone level affects micronutrients bioavailability in soil and their concentrations in wheat tissues

To investigate the bioavailability of essential micronutrients (Fe, Mn, Cu, Zn) in soil-plant system, sequential scheme of weak acid soluble (WAS), reducible (RED) and oxidizable (OXI) fractions was used to evaluate the bioavailability of micronutrients in different soil depths. The results revealed that at the tillering stage elevated O&lt;sub&gt;3&lt;/sub&gt; concentration significantly increased WAS-Fe at 0–5 cm and 10–15 cm soils by 69.11% and 59.72%, respectively. At the ripening stage, both WAS-Cu and RED-Cu were significantly increased in elevated O&lt;sub&gt;3&lt;/sub&gt; treatment compared to control, while WAS-Mn only showed significant in 0–5 cm soil. In bulk soil, WAS-Zn and RED-Zn concentrations were generally greater than those in control, which was more evident at 10–15 cm soil. Besides, O&lt;sub&gt;3&lt;/sub&gt; decreased the whole plant biomass by 14.63% and increased the root to shoot ratio. Elevated O&lt;sub&gt;3&lt;/sub&gt; significantly increased grain Fe, Mn and Cu concentrations by 9.37, 36.68 and 48.18%, respectively, while it decreased Zn by 17.09%. It can be inferred that altered micronutrients bioavailability in soil and nutrients uptake in plants are likely associated with the changed soil chemical properties and plant physiology in response to the rising O&lt;sub&gt;3&lt;/sub&gt; level.

Comparison of Heat Transfer and Soil Impacts of Air Curtain Burner Burning and Slash Pile Burning

We measured soil heating and subsequent changes in soil properties between two forest residue disposal methods: slash pile burning (SPB) and air curtain burner (ACB). The ACB consumes fuels more efficiently and safely via blowing air into a burning container. Five burning trials with different fuel sizes were implemented in northern California, USA. Soil temperature was measured at 1, 2, 3, 4, 6, and 8 cm depth. Immediately after burning, soil samples from two depths (0–10 and 10–20 cm) and ash samples were collected for analyzing organic matter; carbon and nitrogen content; and calcium, magnesium, and potassium concentrations. The highest temperature observed was 389 °C at 1 cm depth under the SPB. Mean peak temperatures were 133.2 °C and 162.2 °C for ACB and SPB, respectively. However, there were no significant differences in peak temperatures and duration of lethal soil temperatures (total minutes over 60 °C) between ACB and SPB. Heat transfer decreased rapidly as the soil depth increased. There is little evidence that any subsequent changes in soil chemical properties occurred, concluding that these small-scale burns had few negative impacts at our study site. Therefore, given the lack of extreme soil heating and more efficient and safer woody residue reduction, the ACB may be more effective than open SPB, especially where fire escape or long-term fire damage to soils are of concern.

Plant-soil feedbacks in declining forests: implications for species coexistence.

Plant-soil feedbacks (PSFs) play a relevant role as drivers of species abundance, coexistence, and succession in plant communities. However, the potential contribution of PSFs to community dynamics in changing forest ecosystems affected by global change drivers is still largely unexplored. We measured the direction, strength and nature (biological vs. chemical) of PSFs experienced by coexisting tree species in two types of declining Quercus suber forests of southwestern Spain (open woodland vs. closed forest) invaded by the exotic soil pathogen Phytophthora cinnamomi. To test PSFs in a realistic community context, we focused not only on individual PSFs (i.e., comparing the growth of a tree species on conspecific vs. heterospecific soil) but also calculated net-pairwise PSFs by comparing performance of coexisting tree species on their own and each other's soils. We hypothesized that the decline and death of Q.suber would alter the direction and strength of individual and net-pairwise PSFs due to the associated changes in soil nutrients and microbial communities, with implications for recruitment dynamics and species coexistence. In support of our hypothesis, we found that the decline of Q.suber translated into substantial alterations of individual and net-pairwise PSFs, which shifted from mostly neutral to significantly positive or negative, depending on the forest type. In both cases however the identified PSFs benefited other species more than Q.suber (i.e., heterospecific positive PSF in the open woodland, conspecific negative PSF in the closed forest). Our results supported PSFs driven by changes in chemical soil properties (mainly phosphorus) and arbuscular mycorrhizal fungi, but not in pathogen abundance. Overall, our study suggests that PSFs might reinforce the loss of dominance of Q.suber in declining forests invaded by P.cinnamomi by promoting the relative performance of non-declining coexisting species. More generally, our results indicate an increase in the strength of net PSFs as natural forests become disturbed by global change drivers (e.g., invasive species), suggesting an increasingly important role of PSFs in forest community dynamics in the near future.

Combined effects of climate, restoration measures and slope position in change in soil chemical properties and nutrient loss across lands affected by the Wenchuan Earthquake in China

The MS 8.0Wenchuan Earthquake in 2008 caused huge damage to land cover in the northwest of China's Sichuan province. In order to determine the nutrient loss and short term characteristics of change in soil chemical properties, we established an experiment with three treatments (‘undestroyed’, ‘destroyed and treated’, and ‘destroyed and untreated’), two climate types (semi-arid hot climate and subtropical monsoon climate), and three slope positions (upslope, mid-slope, and bottom-slope) in 2011. Ten soil properties—including pH, organic carbon, total nitrogen, total phosphorus, total potassium, Ca2+, Mg2+, alkaline hydrolysable nitrogen, available phosphorus, and available potassium—were measured in surface soil samples in December 2014. Analyses were performed to compare the characteristics of 3-year change in soil chemical properties in two climate zones.This study revealed that soil organic carbon, total nitrogen, Ca2+ content, alkaline hydrolysable nitrogen, available phosphorus, and available potassium were significantly higher in subtropical monsoon climate zones than in semi-arid hot climate zones. However, subtropical monsoon climate zones had a higher decrease in soil organic carbon, total nitrogen, total phosphorus, total potassium, and alkaline hydrolysable nitrogen in ‘destroyed and untreated’ sites than in semi-arid hot climate zones. Most soil chemical properties exhibited significant interactions, indicating that they may degrade or develop concomitantly. ‘Destroyed and treated’ sites in both climate types had lower C:P and N:P ratios than ‘destroyed and untreated’ sites. Principal component analysis (PCA) showed that the first, second, and third principal components explained 76.53% of the variation and might be interpreted as structural integrity, nutrient supply availability, and efficiency of soil; the difference of soil parent material; as well as weathering and leaching effects.Our study indicated that the characteristics of short term change in soil properties were affected by climate types and treatments, but not slope positions. Our results provide useful information for the selection of restoration countermeasures in different climate types to facilitate ecological restoration and reconstruction strategies in earthquake-affected areas.

Changes in Soil Chemical Properties of Organic Paddy Field with Azolla Application

The use of high organic fertilizer in the organic farming system is one of the obstacles in the implementation of organic farming in Indonesia. It is necessary to find alternative materials to substitute or meet the shortage of existing organic fertilizer. This study aims to determine the effect of Azolla ( Azolla mycrophylla . L) on some soil chemical properties on organic paddy field. The The field experiments used factorial complete randomized block design of three factors, namely Azolla (0 and 2 tons / ha), Manure (0 and 10 tons / ha) and Rice Varieties ( Mira1, Mentik Wangi and Merah Putih), with three times replication. Azolla 2 tons / ha is able to increase soil total N 18%; available P 87,5 %; organic C 3,78% CEC 8,03 % and soil pH 1,00%; compared to control (without Azolla). Compared with manure 10 tonss / ha, giving Azolla 2 tonss / ha was able to increase only on soil available P about 50 %, but lower on soil total N, organic C, CEC and soil pH 1,9% ; 9,27% ; 9,40% and 0,67%. Azolla can be used as a substitute or complement of manure on organic paddy field.

Land-use types and soil chemical properties influence soil microbial communities in the semiarid Loess Plateau region in China

Similar land-use types usually have similar soil properties, and, most likely, similar microbial communities. Here, we assessed whether land-use types or soil chemical properties are the primary drivers of soil microbial community composition, and how changes in one part of the ecosystem affect another. We applied Ion Torrent sequencing to the bacterial and fungal communities of five different land-use (vegetation) types in the Loess Plateau of China. We found that the overall trend of soil quality was natural forest > plantation > bare land. Dominant bacterial phyla consisted of Proteobacteria (42.35%), Actinobacteria (15.61%), Acidobacteria (13.32%), Bacteroidetes (8.43%), and Gemmatimonadetes (6.0%). The dominant fungi phyla were Ascomycota (40.39%), Basidiomycota (38.01%), and Zygomycota (16.86%). The results of Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA) based on land-use types displayed groups according to the land-use types. Furthermore, the bacterial communities were mainly organized by soil organic carbon (SOC). The fungal communities were mainly related to available phosphorus (P). The results suggested that the changes of land use type generated changes in soil chemical properties, controlling the composition of microbial community in the semiarid Loess Plateau region. The microbial community could be an indicator for soil quality with respect to ecological restoration.

Impact of pyrochar and hydrochar on soybean (Glycine max L.) root nodulation and biological nitrogen fixation

AbstractThe aim of this study was to identify effects of carbonized organic material (“biochar”) on soybean growth, root nodulation and biological nitrogen fixation, and to elucidate possible underlying mechanisms.Soybean (Glycine max L.) was grown in four arable soils amended with carbonized organic material produced from wood or maize as feedstocks, by pyrolysis (“pyrochar”) or hydrothermal carbonization (“hydrochar”). Nodulation by Bradyrhizobium, biological nitrogen fixation (BNF) assessed by 15N techniques, plant growth, nutrient uptake and changes in chemical soil properties after soil amendment were determined. Data were analyzed by means of a three way ANOVA on the factors soil, carbonization technique and feedstock. It turned out that soybean root nodulation and BNF was influenced by the carbonization technique used to prepare the soil amendment. Hydrochar, in average and across all soils, increased nodule dry matter and BNF by factors of 3.4 and 2.3, respectively, considerably more than pyrochar, which led to 1.8 and 1.2 fold increases, respectively. Nodule dry matter and BNF correlated positively with available soil sulfur and negatively with available soil nitrogen. Hydrochars provided more available sulfur than pyrochars, and hydrochars caused a decrease in nitrogen availability in the soil solution, thereby exerting a positive influence on nodulation and BNF. Pyrochar amendment increased soil pH but had no effect on nodulation and BNF. Plant growth was affected by the soil and by the feedstock used for the “biochar”, and increased slightly more in treatments with pyrochar and hydrochar made from maize, which was richer in nitrogen and potassium.The results show that carbonized organic materials, and specifically hydrochar, have the capacity to increase BNF in soils. We suggest that this enhancement in BNF in response to soil amendments with carbonized organic materials is due to an increase in available sulfur and a reduction of available soil nitrogen.

Dynamics of Chemical and Biological Properties of Organically Amended Petroleum Hydrocarbon Polluted Soil as Affected by Incubation Periods

A study was conducted in the Screen house of the Department of Crop, Soil and Pest Management, FUTA Akure to examine the time dynamic trends in soil chemical properties as affected by contamination with petroleum hydrocarbon compounds (PHC) in a 6 months incubation period as affected by organic amendments. The petroleum hydrocarbon compounds used were spent engine oil (SEO), bitumen (BIT) and crude oil (CRO). The organic amendments used were poultry manure and mycorrhizal fungi (Glomus mossae) spores. The respective petroleum hydrocarbon compounds (spent engine oil SEO, bitumen BIT and crude oil CRO) were applied at 2 rates of 0 and 455 ml per pot and 3 levels of organic amendments followed by incubation for six (6) months. Soil samples were collected from each treatment at 0, 2, 4 and 6 months after treatment application for the determination of some chemical properties (pH, organic carbon, N, P, K, Ca and Mg). The time changes in elemental concentrations of soil contamination with petroleum hydrocarbon compounds (SEO, BIT and CRO) showed declining trends in the values of pH, organic carbon and Mg while N-Total, Ca and available P and K rose with time. In general, the nature of the trends (polynomial function as best fit) indicated that the observed responses were not uni-function of a factor but suggest interaction among factors responsible for the breakdown of petroleum hydrocarbon compounds and hence its toxicity to soil chemical properties. The time course of changes in soil chemical properties as affected by petroleum hydrocarbon compounds (PHCs) contamination in soil differed among the PHCs evaluated. The values of the measured soil parameters recorded at the commencement of the experiment and at 2, 4, 6 months after the application of the petroleum hydrocarbon compounds showed declining trends in the values of pH, organic carbon and Mg were obtained. Increasing trends in N-total and available P with time up till the end of the experiment while SEO recording the highest values at 6 months of incubation. Trends of the mean values (highest and lowest values) with respect to treatment showed that CRO had the highest soil pH at 2 and SEO had the lowest at 6 month. SOC increased across treatments with SEO recording the highest value at 2 months of incubation, which was followed by general decline in values with time across the PHCs. The results indicated that PHCs adversely affect soil chemical properties and that addition of organic substances improved chemical properties of the soil following pollution with petroleum hydrocarbon compounds compared with the un-amended soils. Poultry manure in particular performed better compared with mycorrhizal inoculum with respect to improvement of soil chemical properties.

Caracterização da fertilidade do solo em um povoamento de &lt;em&gt;Eucalyptus dunnii&lt;/em&gt; Maiden no bioma Pampa do Rio Grande do Sul

O monitoramento da qualidade do solo, como das propriedades químicas, pode fornecer subsídios para o manejo silvicultural e conservação do solo, visando à manutenção da produtividade de sítios florestais. O presente trabalho teve como objetivo avaliar as mudanças nos atributos químicos do solo em um povoamento de Eucalyptus dunnii, aos dois e aos cinco anos de idade, no bioma Pampa do Rio Grande do Sul. Para tanto, foram coletadas amostras de solo em cinco profundidades (0-20, 20-40, 40-60, 60-80 e 80-100 cm), com posterior determinação de atributos físicos, além de pH, matéria orgânica, teores de alumínio, cálcio, magnésio, potássio e fósforo, bem como CTC potencial e efetiva, saturação por bases e por alumínio. Aplicou-se o teste t (α = 5 %) para detecção de diferenças significativas nas propriedades do solo, em função do tempo. A análise química do solo revelou que, em ambas ocasiões, houveram baixos teores de nutrientes, matéria orgânica, bem como pH ácido, além de alta saturação por alumínio. Após três anos de crescimento das árvores de Eucalyptus dunnii o pH reduziu em todas as profundidades do solo, o cálcio e potássio reduziram em 20-40 cm e 0-20 cm, respectivamente. Já o teor de alumínio aumentou em todas as profundidades, assim como o fósforo e a matéria orgânica de 40 até 100 cm do solo. Após três anos da primeira avaliação do solo, verificou-se alteração da fertilidade do mesmo, principalmente no pH, matéria orgânica e teores de potássio e fósforo.

Changes in soil chemical properties as affected by pyrogenic organic matter amendment with different intensity and frequency

Pyrogenic organic matter (PyOM) has long been used as a soil amendment to improve soil physicochemical properties. However, few studies simultaneously investigated both intensities and frequencies of PyOM addition on soil chemical properties of soil base cations, soil pH buffering capacity (pHBC), and plant available micronutrients. In the main food production area of lower Liaohe River Plain in Northeast China, a field manipulation of PyOM addition was initiated in 2013 to examine how the intensities (0, 1%, 3%, and 5% of 0–20cm soil mass) and frequencies (3% of soil mass applied once versus yearly for 3years) of PyOM amendment affected soil chemical properties. Higher intensity of PyOM addition significantly increased soil exchangeable Mg (by 24.2%), which was caused by increase of soil pH, soil exchangeable surfaces, and soil organic matter. Plant available Fe, Mn, and Cu were significantly decreased with increasing PyOM addition intensity by up to 39.4%, 50.8%, and 30.0%, respectively, especially under the highest amount of PyOM amendment (5%). This was possibly due to removal of micronutrients with plant biomass or irreversible binding of available micronutrients on PyOM which decreased the extraction efficiency. Under the same amount of PyOM addition (3% in total), higher frequency of PyOM amendment significantly increased soil exchangeable Mg, while lower frequency showed no impact as compared to control plots (CK). Higher frequency of PyOM amendment significantly decreased plant available Mn and Cu as compared to both lower frequency and CK treatments. Both the intensity and frequency of PyOM addition significantly increased soil pH but showed no influence on soil pHBC. Our results showed that exchangeable Mg increased but available Mn and Cu decreased with both PyOM amendment intensity and frequency. Even though PyOM amendment could enrich soil base cations, it might cause deficiency of available micronutrients and pose a threat to plant productivity in agroecosystems.

Effectiveness of Organonitrofos Plus Fertilizer on Sweet Corn and Soil Chemical Properties of Ultisols

This study aimed to examine Organonitrofos Plus fertilizer (OP) on sweet corn (Zea mays Saccharata L.) and its effect on changes in soil chemical properties of Ultisols. Organonitrofos Plus fertilizer is an enhancement of Organonitrofos fertilizer enriched with microbes at the beginning of the manufacturing process. Research was conducted in the greenhouse of Integrated Agricultural Laboratory of Lampung University. Treatment applied was a factorial of 4 × 2 × 3 with three replications in a randomized block design. The first factor was the dose of OP fertilizer (0, 10, 20, 30 Mg ha-1), the second factor was the dose of inorganic fertilizers (without inorganic fertilizers, and with inorganic fertilizers, namely Urea 0.44, 0.28 SP-36 and KCl 0.16 Mg ha-1), and the third factor was the dose of biochar (0, 10, 20 Mg ha-1). By a single OP fertilizers, inorganic fertilizers, and the interaction between the OP and the inorganic fertilizers increased the weight of dry stover, cob length, cob diameter, cob with husk and cob without husk of corn. OP fertilizers which are applied in Ultisols can improve soil fertility and increase corn production so that OP fertilizer can lessen the use of inorganic fertilizer and can be used as a substitute for inorganic fertilizer. RAE values were highest in treatment of O4K2B2 (30 Mg OP ha-1, with inorganic fertilizer, 10 Mg biochar ha-1) that was equal to 181%, followed by O2K2B3 (10 Mg OP ha-1, with inorganic fertilizer, 20 Mg biochar ha-1 ) with the difference in RAE value of 0.5%. [How to Cite: Dermiyati, SD Utomo, KF Hidayat, J Lumbanraja, S Triyono, H Ismono, NE Ratna, NT Putri dan R Taisa. 2016. Pengujian Pupuk Organonitrofos Plus pada Jagung Manis (Zea mays Saccharata. L) dan Perubahan Sifat Kimia Tanah Ultisols. J Trop Soils 21: 9-17 Doi: 10. 10.5400/jts.2016.21.1.9]

Relation between the mineral nutrients and the Vitamin C content in camu-camu plants (Myrciria dubia) cultivated on high soils and flood soils of Ucayali, Peru

The use of organic amendments is common under the concept of integrated nutrient management (INM) in Vitis vinifera (Table grape) to improve plant and soil quality. The objective of this study was to evaluate compost (C) and humic substances (HS) mixed with mineral fertilizer (MF) in an INM program of V. vinifera cv Thompson seedless. The chemical, biochemical and microbiological parameters were evaluated in soil on 1-year- old V. vinifera plants growing on Alfisol soil. Five treatments and control were evaluated: (T1) C+MF, (T2) HS+MF, (T3) C, (T4) HS, (T5) MF and (T6) absolute control. The results indicated that the application of C and HS, increased β glucosidase and dehydrogenase activities, reaching values of 90.2 μg p-nitrophenol g-1h-1 and 9.1 μg de TFP g-124h-1, respectively. In addition, pH was similar in all treatments while electrical conductivity increased with application of mineral and organic amendments, reaching 0.41dS m-1 in T2 (HS+MF). Furthermore, yeast concentration increased with organic amendments or mineral. Correlation analysis indicated significant and positive relationships between PO4-P concentration with MF (0.579) and C (0.431) and nitrogen with MF (0.868). These results support that INM, which combines mineral fertilization and organic amendments, improve positive changes in chemical soil properties and C cycling measured in terms of enzymatic activity in V. vinifera.

Chemical Attributes of Soil and Forage Yield of Pasture Recovered with Phosphate Fertilization and Soil Management

ABSTRACTExtensive and semi-extensive pastures are the basis of Brazilian livestock production. However, much of it is degraded or in degradation process, with low stocking rate per area. Even with this problem, this management type is 60% and 50% of Australia’s and the United States’ production costs, respectively. In order to research alternatives for Urochloa decumbens degraded pasture recovery in an Oxisol, Stylosanthes (Stylosanthes spp.) “Campo Grande” cultivar was introduced and phosphate fertilization was applied. The experimental design was of randomized blocks, 7 × 2 × 2 factorial design, with four replicates, involving seven systems to introduction (U. decumbens control; partial desiccation with 1.5 L ha−1 glyphosate, total desiccation with 3.0 L ha−1 glyphosate; direct planting; scarification, harrowing, and plowing + harrowing), phosphate fertilizer presence or absence, and two evaluation periods. “Campo Grande” Stylosanthes legume introduction increased shoot dry weight (SDW) yield, except in direct planting. Phosphorus fertilization increased SDW yield only in the first period, and Stylosanthes introduction in the pasture has not changed soil chemical properties. Phosphorus (P) fertilization also provided available P and exchangeable calcium (Ca2+) content in the soil increase, in addition to sum of bases and cation exchange capacity increase.

Effects of Bio-degradable Mulches on the Yield of Maize and the Density of Soil Microbe

The use of polyethylene film has a problem such as increasing rural environmental contamination, collection costs and farmers’ workload. The objective of this study was to evaluate bio-degradable films in terms of yield of maize and soil environment. Treatments were bio-degradable film A (BDF A), bio-degradable film B (BDF B), high density polyethylene (HDPE), and non-mulched (NM) soil. Daily mean values of soil temperature (10 cm depth) under BDF A, BDF B, and HDPE were higher than in NM soil by 2.2, 2.8, 3.1℃ respectively. In the mulching cultivation of maize, bio-degradable film began to degrade from 50~60days after the planting. The degradation was much progressed in the harvest time and almost decomposed in the following spring. The weight of ear of maize was not shown significantly by mulching treatments. There were little changes of soil chemical properties for the bio-degradable film mulching. After using bio-degradable films, the contents of biomass-C and dehydrogenase activity increased from 92 to 137~147 mg kg -1 , and from 87 to 123~168 mg kg -1 respectively.

Cover crops affect the soil chemical properties under no-till system

The purpose of this study was to assess the changes in soil chemical properties affected by the cover crops cultivated in crop rotation in short-term of no-till implementation under Rhodic Hapludox soil. This research was carried out from October 2010 to February 2014. The experiment was set up in completely randomized blocks in a factorial design with eight treatments (cover crops) and three soil depths (0-5, 5-10 and 10-20 cm) with four repetitions. The cover crops were: fall-winter maize (T1), intercropping fall-winter maize with B. ruziziensis (T2), intercropping fall-winter maize with B. brizantha cv. Marandu (T3), intercropping fall-winter maize with Crotalaria spectabilis (T4), B. ruziziensis (T5), B. brizantha cv. Marandu (T6), Pennisetum glaucum L. (T7) and fallow (T8). The T6 and T7 affected exchangeable Mg +2 , it was observed higher exchangeable Mg +2 in T6 (2.39 cmolc dm -3 ) and T7 (2.43 cmolc dm -3 ) in comparison to T1. The phosphorus content showed interactive effect between cover crops and soil depth. In the comparison among the depths, the P contents were higher in 5-10 cm, which showed improvement of 24.6% and 25.2% in comparison to 0-5 and 10-20 cm layers, respectively. The cover crops evaluated in this research affected the exchangeable Mg +2 and K + , as well as Mg +2 and K + saturation. The P content changed in response of cover crops, which was important to observe that this nutrient may increase the content with adoption of cover crops in no-till system. The species used in this research might be recommended to integrate a crop rotation system with the possibility of increasing P availability in topsoil depth in no-till system.

Leucaena leucocephala and adjacent native limestone forest habitats contrast in soil properties on Tinian Island

ABSTRACTAn ex situ germplasm collection of the endangered Cycas micronesica was established in a transition zone between biodiverse native forest and mature stands of the invasive species Leucaena leucocephala. Soil chemical properties were determined for the 2 tree cover types to inform management decisions. Total carbon, total nitrogen, calcium, and net ammonification were greater in native forest cover than in L. leucocephala patches. Net nitrification and net mineralization were greater under L. leucocephala cover. Trace metals also differed between the 2 forest cover types, with chromium, cobalt, and nickel accumulating to greater concentration under L. leucocephala cover and zinc accumulating to greater concentration under native forest cover. The results indicated that L. leucocephala cover generated substantial changes in soil chemical properties when compared with native forest tree cover, illuminating one means by which understory vegetation may be affected by changes in invasive tree cover.

Biochar decreased microbial metabolic quotient and shifted community composition four years after a single incorporation in a slightly acid rice paddy from southwest China

While numerous studies both in laboratory and field have showed short term impacts of biochar on soil microbial community, there have been comparatively few reports addressing its long term impacts particular in field condition. This study investigated the changes of microbial community activity and composition in a rice paddy four years after a single incorporation of biochar at 20 and 40t/ha. The results indicated that biochar amendment after four years increased soil pH, soil organic C (SOC), total N and C/N ratio and decreased bulk density, particularly for the 40t/ha treatment compared to the control (0t/ha). Though no significant difference was observed in soil basal respiration, biochar amendment increased soil microbial biomass C and resulted in a significantly lower metabolic quotient. Besides, dehydrogenase and β-glucosidase activities were significantly decreased under biochar amendment relative to the control. The results of Illumina Miseq sequencing showed that biochar increased α-diversity of bacteria but decreased that of fungi and changed both bacterial and fungal community structures significantly. Biochar did not change the relative abundances of majority of bacteria at phylum level with the exception of a significant reduction of Actinobacteria, but significantly changed most of bacterial groups at genus level, particularly at 40t/ha. In contrast, biochar significantly decreased the relative abundances of Ascomycota and Basidiomycota by 11% and 66% and increased the relative abundances of Zygomycota by 147% at 40t/ha compared to the non-amended soil. Redundancy analysis (RDA) indicated that biochar induced changes in soil chemical properties, such as pH, SOC and C/N, were important factors driving community composition shifts. This study suggested that biochar amendment may increase microbial C use efficiency and reduce some microorganisms that are capable of decomposing more recalcitrant soil C, which may help stabilization of soil organic matter in paddy soil in long term.