CF Soils Research Articles

Biochar produced at high temperature mitigates N2O emission and promotes nitrogen retention in subtropical forest soils

AbstractBiochar is produced by burning biomass under oxygen‐limited conditions, and it has been widely used as a soil amendment to improve soil functions such as nutrient retention. However, whether the impact of biochar application on soil nitrogen (N) transformation and N2O emission varies with the pyrolysis temperature remains unclear, especially in different forest types in subtropical regions. In this study, a 60‐day laboratory incubation experiment was conducted to evaluate the impact of biochar with different pyrolysis temperatures (300°C [BC300], 500°C [BC500], and 800°C [BC800]) on net N transformation rates and N2O emission in soils collected from Castanopsis kawakamii dominated natural forest (NF) and Chinese fir (Cunninghamia lanceolate, CF) plantation in subtropical China. The results showed that the application of biochar significantly increased soil ammonium (NH4+) content (p < 0.001) but reduced nitrate (NO3−) content (p < 0.001) compared with the control. The soil NH4+ content of the BC800 treatment was significantly higher than that of other treatments (p < 0.001). Biochar application significantly reduced soil net N mineralization (NRmin) and nitrification (NRnit) rate (p < 0.001), but increased net ammonification (NRamm) rate (p < 0.001). The application of biochar led to a remarkable decrease in cumulative N2O emission compared to the control (p < 0.001). In particular, soils treated with high‐temperature biochar emitted significantly lower N2O compared to other treatments (p < 0.001). The partial least squares path model demonstrated that biochar influenced N2O emission through a direct effect in NF soil and an indirect effect in CF soil. This study highlights the distinct role of biochar, particularly that produced under high pyrolysis temperatures as a soil amendment to mitigate N2O emission and promote N retention in both subtropical natural and planted forests.

Soil quality and microbial communities in subtropical slope lands under different agricultural management practices.

Land degradation is a major threat to ecosystem. Long-term conventional farming practices can lead to severe soil degradation and a decline in crop productivity, which are challenging for both local and global communities. This study was conducted to clarify the responses on soil physicochemical properties and microbial communities to changes in farming practices. Slope land orchards under three agricultural management practices-conventional farming (CF), organic farming (OF), and ecofriendly farming (EFF)-were included in this study. We found that soil carbon stock increased by 3.6 and 5.1 times in surface soils (0-30 cm) under EFF and OF treatments, respectively. EFF and OF significantly increased the contents of total nitrogen by 0.33-0.46 g/kg, ammonia-N by 3.0-7.3 g/kg, and microbial biomass carbon by 0.56-1.04 g/kg but reduced those of pH by 0.6 units at least, and available phosphorous by 104-114 mg/kg. The application of phosphorous-containing herbicides and chemical fertilizers might increase the contents of phosphorous and nitrate in CF soil. High abundances of Acidobacteria and Actinobacteria were observed in EFF and OF soils, likely because of phosphorous deficiency in these soils. The abundance of fungi in OF soil indicated that plants' demand for available soil phosphorous induced the fungus-mediated mineralization of organic phosphorous. High abundances of Gammaproteobacteria, Planctomycetes, Firmicutes, and Nitrospirae were observed in CF soil, possibly because of the regular use of herbicides containing phosphorous and chemical fertilizers containing high total nitrogen contents.

Effects of cattle manure compost application on crop growth and soil-to-crop transfer of cesium in a physically radionuclide-decontaminated field

Resuming crop production in physically decontaminated fields affected by radiocesium (134Cs and 137Cs) releases is crucial for restoring impacted areas. However, surface soil excavation to reduce radiocesium may lead to lower crop yield due to the loss of fertile topsoil. This study aimed to assess the effects of cattle manure compost (CMC) application on soil properties, crop growth, and 137Cs soil-to-crop transfer in a physically decontaminated field and pot experiment. Field trials were conducted during 2018–2022, with CMC (1 and 2 kg m−2 year−1) applied alongside conventional fertilization (CMC1 and CMC2 plots, respectively) in 2018–2019 and conventional fertilization alone in 2020–2022. Additionally, a pot experiment was used to evaluate the impact of CMC application in soil (1 kg m−2 year−1 for 5 years) on 137Cs transfer. In the field trial during 2018–2019, CMC1 and CMC2 plots exhibited higher soybean shoot dry weight (DW) compared with plots receiving conventional fertilization and additional K fertilizer (+K2O). CMC application also improved soil nutrient content. The transfer factor of 137Cs (TF-137Cs: plant 137Cs activity concentration/soil 137Cs activity concentration) followed the order CMC2 < CMC1 ≈ +K2O < conventional fertilization only (CF) and was negatively correlated with soil exchangeable K (Ex-K). During 2020–2022, when all plots received conventional fertilization alone, grain yields were higher in CMC1 and CMC2 plots than in the +K2O plot, with the lowest TF-137Cs in CMC2 plot followed by CMC1, +K2O, and CF plots. The pot experiment confirmed that CMC soil had a lower TF-137Cs and higher plant DW compared with CF soil with the same Ex-K level. Additionally, the soil exchangeable 137Cs (Ex-137Cs) level was significantly lower in CMC soil than CF soil. These findings demonstrate the potential of CMC application to improve crop growth and reduce 137Cs transfer in physically decontaminated fields.

Environmental Geochemistry and Bioavailability and Health Effects of Chromium in Topsoil and Cauliflower Plant in Kirkuk, Northern Iraq

The content of chromium in the surface soil as well as its content in cauliflower plants in Kirkuk was studied to investigate the environmental geochemistry of this element. 30 samples of surface soil were collected from inside the study area at a depth of 0-20 cm. Eight samples of cauliflower were collected from the same study area, soil and plant sampling sites were determined using a GPS device . Using ICP-MS technology we were able to analyze these samples. The results of ICP-MS showed that the average concentration of chromium in the soil samples was 78.59 mg/kg and its highest concentration was in the sample A12 (93.4 mg/kg), the increase in the concentration of chromium in the soil is due to agricultural fertilizers, irrigation with sewage water, the impact of traffic, commercial activities and industrial workshop. The mean of its concentration cauliflower samples was 3.81 mg/kg, and the highest concentration was 4.7 mg/kg in sample AQ10, the increase in the concentration of chromium in the plant is due to pollution in the soil, and the difference in these concentrations is due to the location of the sample and the properties of the soil. The plant absorbs it through the roots, then the stems, leaves,and fruits. Bioaccumulation factor value for chromium ranged with an average of 0.047 for all cauliflower samples. CF soil samples that the surface soil for this area is within a level (low pollution, CF &lt;1) indicating the presence of pollution at a very low level, and the potential ecological risk index PRI found that all surface soil samples in the study area have (low risk level, PLI≤50), and Igeo indicates that there is no pollution (practically uncontaminated, Igeo ≤ 0). It was found that the value of THQnc for both groups of adults and children in the study area was greater than 1. The CRcancer values for both groups were greater than 1*10-4.

Effects of different fertilizer application practices on newly reclaimed soil structure and its nutrient content

Effects of organic fertilizer practice (OF), organic fertilizer combined with chemical fertilizer practice (OC), and conventional fertilization practice (CF) on soil structure were evaluated by combining micro and macro analyses in newly reclaimed cultivated land. Soil organic matter (SOM), cation exchange capacity (CEC), soil bulk density (BD), soil moisture content (SMC), and aggregate stability were also analyzed. The CF soil structure was mainly composed of moderately separated block and angular structures with the minimum SOM (7.08 g/kg) and the highest BD (1.40 g/cm3), and the pore type was mainly simple surface cracks. Compared with CF, OF and OC significantly increased SOM content by 59.3 and 29.6% (p &lt; 0.05) and CEC by 13.5 and 5.2%, respectively. The newly reclaimed soil structure was improved to a moderately separated clump structure and a well-developed aggregated structure, and the number of composite accumulation pores gradually increased. Moreover, OF and OC were associated with higher mean weight diameter (MWD), geometric mean diameter (GMD) values, and lower BD and fractal dimension (D) values. The water-stable macroaggregates (R0.25) and the aggregate stability of newly reclaimed soil were significantly increased, with a stronger improvement observed under OF. These results confirm the benefits of OC and OF practices on the structural stability, water and fertilizer retention characteristics of newly reclaimed cultivated land, and will be conductive to improving the soil quality and achieving sustainable soil development. Bangladesh J. Bot. 50(3): 781-794, 2021 (September) Special

Soil carbon sequestration on a maize-mung bean field with rice straw mulch, no-tillage, and chemical fertilizer application in Thailand from 2011 to 2015

ABSTRACT Increasing soil organic carbon (SOC) content in agricultural fields is one of the strategies for mitigating climate change through carbon (C) sequestration, and could improve soil fertility. However, only a few field experimental studies have been conducted to determine the SOC stock changes in tropical areas. A field experiment was conducted under various soil management approaches in a maize-mung bean double cropping system in Lopburi, Thailand, from 2011 to 2015. The following treatment combinations were applied: 1) rice straw mulch (RS) and no organic matter application (NoOM); 2) tillage (Till) and no-tillage (NoTill); and 3) chemical fertilizer application (CF) and no chemical fertilizer application (NoCF). Soil samples were obtained at 0–15 cm depths before plowing and after maize harvest. SOC stock change was higher in RS than in NoOM. These results were attributable to the high organic C input with rice straw in the soil, although the conversion rate of total organic C input to SOC stock change with rice straw mulch did not increase. SOC stock change in NoTill did not differ from that in Till, which might be caused by no increase in the conversion rate of total organic C to SOC stock change in NoTill in this field. In addition, SOC stock change in CF was not significantly different from the stock change in NoCF. Although a large amount of organic C was supplied to the CF soil, the conversion rate of organic C to SOC decreased. The results of this study could contribute to clarifying SOC stock changes in upland crop fields in tropical monsoon conditions.

Accumulation of gallium (Ga) and indium (In) in rice grains in Ga- and In-contaminated paddy soils

To understand the risk of two emerging contaminants, gallium (Ga) and indium (In) to humans via rice consumption, effects of soil properties and concentrations of spiked Ga/In on the accumulation of Ga and In in rice grains were investigated. A pot experiment was conducted, and paddy rice was grown in three soils with different pH values and Al availabilities (i.e., Pc, TWz and Cf), which were spiked with various Ga and In concentrations. The growth index and concentrations of Ga, In, and Al in plant tissues and soil pore water were measured. Results revealed that the concentrations of Ga and In in soil pore water increase with the spiking of Ga or In in all of the tested soils, but the biomass of roots and shoots does not significantly decrease. The accumulation of Ga in shoots and brown rice was significantly reduced in high available Al acidic soils (Pc soils), but this accumulation was significantly increased in low available Al acidic soils (TWz soils), which can be explained by the competitive uptake between Ga and Al by rice plants. The extent of competitive effects between In and Al was less than that between Ga and Al because of the lower solubility and translocation capability of In than those of Ga in soil–rice systems. However, significant differences in the concentrations of Ga and In in brown rice in neutral soils (Cf soils) among the Ga or In treatment were not observed. In addition, the iron plaque formed on the root surface can serve as a barrier to reduce the accumulation of Ga in rice plants. This study suggested that the risk of accumulation of Ga and In in rice grains should be of concern when paddy rice is grown in acidic Ga- or In-contaminated soils with low Al availability.

Nitrogen and phosphorus fluxes in three soils fertigated with decentralised wastewater treatment effluent to field capacity

Abstract The Decentralised Wastewater Treatment System (DEWATS) provides low cost onsite sanitation to residents living in informal settlements. Wastewater management through agriculture prevents environmental pollution and promotes sustainable agriculture. This study investigated the effects of fertigation with DEWATS effluent to field capacity in three South African soils under a banana crop. The experiment was conducted as a complete randomised design in a greenhouse with two irrigation water treatments (DEWATS effluent vs municipal tap water irrigation + fertiliser) × three soil types (Ia, Cf and Se) and four replicates over 728 days. Data were collected on crop growth, nitrogen (N) and phosphorus (P) uptake and dynamics in the soil. The DEWATS effluent significantly (p &amp;lt; 0.05) increased N and P uptake and soil NH+4-N and extractable P concentrations. Furthermore, DEWATS effluent fertigation significantly (p &amp;lt; 0.05) increased N leaching from the Ia soil and P leaching from the Cf soil. Nitrogen and phosphorus leaching from DEWATS was lower than the tap water irrigation + fertiliser treatment. There was, however, excess N and P accumulation from the DEWATS than the irrigation + fertiliser treatment, which would cause environmental concerns from runoff and leaching losses in the medium to long term.

Arsenic phytotoxicity and accumulation in rice seedlings grown in arsenic‐contaminated soils as influenced by the characteristics of organic matter amendments and soils

AbstractOrganic matter (OM) application into soils is a common agricultural practice. Previous studies have shown that in arsenic (As)‐contaminated paddy soils, OM has the potential to alter the behavior of As and affects the growth and As accumulation of rice plants. In this study, pot experiments were conducted to investigate the differences in the amounts of As released into soil solutions, its toxicity, and accumulation in rice seedlings caused by application of three different OM amendments [soybean meal (SB), sugarcane dreg compost (SC), and cattle‐dung compost (CD)]. These OM amendments were each applied to three As‐contaminated soils, Guandu (Gd), Pinchen (Pc), and Chengchung (Cf), which have different characteristics. The results indicate that after addition of two easily decomposable OMs (SB and SC), the As toxicity and concentrations increased in rice plants, especially in As‐spiked Cf soils which had low As retention capacity. This was the result of elevated As concentration in soil solutions due to a decrease in soil redox potential and competition between dissolved organic carbon (DOC) and As for sorption sites, as well as the formation of As–DOC complexes. However, there were no significant effects on plant growth and As accumulation in rice seedlings after treatments with CD (not easily decomposable OM). Another important finding was that the amount of iron plaque on the surface of rice roots increased with OM amendments in the Gd soils rich in iron oxides and hydroxides, thus reducing the As uptake by rice plants. These results suggest that the characteristics of OM and soils should be considered when OM amendments are applied to As‐contaminated soils.

Response of phosphorus fractions to land-use change followed by long-term fertilization in a sub-alpine humid soil of Qinghai–Tibet plateau

Identification of phosphorus (P) species is essential to understand the transformation and availability of P in soil. However, P species as affected by land use change along with fertilization has received little attention in a sub-alpine humid soil of Tibet plateau. In this study, we investigated the changes in P species using Hedley sequential fractionation and liquid-state 31P-NMR spectroscopy in soils under meadow (M) and under cropland with (CF) or without (CNF) long-term fertilization for 26 years in a sub-alpine cold-humid region in Qinghai–Tibet plateau. Land-use change and long-term fertilization affected the status and fractions of P. A strong mineralization of organic P (OP) was induced by losing protection of soil organic matter (SOM) and Fe and Al oxides during land-use change and resulted in an increase of orthophosphate (from 56.49 mg kg−1 in M soils to 130.07 mg kg−1 in CNF soils) and great decreases of orthophosphate diesters (diester-P, from 23.35 mg kg−1 in M soils to 10.68 mg kg−1 in CNF soils) and monoesters (from 336.04 mg kg−1 in M soils to 73.26 mg kg−1 in CNF soils). Long-term fertilization boosted P supply but failed to reclaim soil diester-P (from 10.68 mg kg−1 in CNF soils to 7.79 mg kg−1 in CF soils). This may be due to the fragile protection from the combination of SOM with diester-P when long-term fertilization had only improved SOM in a slight extent. These results suggest that SOM plays an important role in the soil P cycling and prevents OP mineralization and losses from soil. It is recommended that optimization of soil nutrient management integrated with SOM was required to improve the P use efficiency for the development of sustainable agriculture.

Growth inhibition of rice (Oryza sativa L.) seedlings in Ga- and In-contaminated acidic soils is respectively caused by Al and Al + In toxicity

Limited information exists on the effects of emerging contaminants gallium (Ga) and indium (In) on rice plant growth. This study investigated the effects on growth and uptake of Ga and In by rice plants grown in soils with different properties. Pot experiment was conducted and the rice seedlings were grown in two soils of different pH (Pc and Cf) spiked with various Ga and In concentrations. The results showed concentrations of Ga, In, and Al in soil pore water increased with Ga- or In-spiking in acidic Pc soils, significantly decreasing growth indices. According to the dose-response curve, we observed that the EC50 value for Ga and In treatments were 271 and 390mgkg−1 in Pc soils, respectively. The context of previous hydroponic studies suggests that growth inhibition of rice seedlings in Ga-spiked Pc soils is mainly due to Al toxicity resulting from enhanced Al release through competitive adsorption of Ga, rather than from Ga toxicity. In-spiked Pc soils, both In and Al toxicity resulted in growth inhibition, while no such effect was found in Cf soils due to the low availability of Ga, In and Al under neutral pH conditions.

Rhizobacterial community structure differences among sorghum cultivars in different growth stages and soils

Plant genotype selects the rhizosphere microbiome. The success of plant-microbe interactions is dependent on factors that directly or indirectly influence the plant rhizosphere microbial composition. We investigated the rhizosphere bacterial community composition of seven different sorghum cultivars in two different soil types (abandoned (CF) and agricultural (VD)). The rhizosphere bacterial community was evaluated at four different plant growth stages: emergence of the second (day 10) and third leaves (day 20), the transition between the vegetative and reproductive stages (day 35), and the emergence of the last visible leaf (day 50). At early stages (days 10 and 20), the sorghum rhizosphere bacterial community composition was mainly driven by soil type, whereas at late stages (days 35 and 50), the bacterial community composition was also affected by the sorghum genotype. Although this effect of sorghum genotype was small, different sorghum cultivars assembled significantly different bacterial community compositions. In CF soil, the striga-resistant cultivar had significantly higher relative abundances of Acidobacteria GP1, Burkholderia, Cupriavidus (Burkholderiaceae), Acidovorax and Albidiferax (Comamonadaceae) than the other six cultivars. This study is the first to simultaneously investigate the contributions of plant genotype, plant growth stage and soil type in shaping sorghum rhizosphere bacterial community composition.

Evaluation of the mixing of sands into soils on nitrification potential from different land-use systems

Quartz sand is often mixed with soil to enable leaching in studies where nitrate leaching is simulated. However, the addition of sand may also have an effect on the N transformations dynamics but this aspect has never been studied so far. A15N tracer experiment was conducted to investigate this effect on coniferous forest soil (CF), rice-rice rotation soil (RR), rice-wheat rotation soil (RW) and maize-wheat rotation soil (MW). Results showed that the addition of quartz sand into the three agricultural soils (RR, RW and MW) reduced the net production of NO3−-N, but the mechanisms involved in the reduction among the three soils were different. In the RR soil, the addition of quartz sand had no effect on gross NO3−-N production (autotrophic nitrification + heterotrophic nitrification), but enhanced gross NO3−-N consumption (NO3−-N immobilization + dissimilatory NO3− reduction to NH4+), resulting in reduced NO3−-N built-up. In the RW soil, the addition of quartz sand significantly inhibited gross autotrophic nitrification rates and stimulated gross NO3−-N immobilization rate. In the MW soil, only dissimilatory NO3− reduction to NH4+ (DNRA) rate was stimulated by the addition of quartz sand. In contrast, in the CF soil sand addition did not have an effect on the gross N transformation rates. Our results show that sand additions will alter N transformations dynamics in an unforeseeable manner and should be considered with the utmost caution.

Soil gross nitrogen transformations along a secondary succession transect in the north subtropical forest ecosystem of southwest China

Soil nitrogen (N) transformations in forest soils play a vital role in plant N availability. However, the effect on soil N dynamics of forest succession remains largely unknown. A 15N tracing study was conducted in situ to investigate gross N transformation rates along a secondary succession transect (grassland GL, coniferous forest CF, coniferous-broad-leaved mixed forest CBF, broad-leaved forest BF, natural broad-leaved forest NF) under a north subtropical monsoon climate. Gross N mineralization and NH4+ immobilization rates were significantly higher in the BF soil than in the NF, CBF, GL and CF soils, although no significant differences were found among the latter four soils. Gross NO3− immobilization rates in the GL and CF soils were negligible, and were significantly lower than those in the three late succession stage soils. In all soils, NO3− was produced almost exclusively by heterotrophic nitrification. The ratio of the gross NO3− immobilization rate to the gross nitrification rate was significantly lower in the GL and CF soils than in the other three soils, indicating a higher NO3− retention capacity in the three late successional stage soils. The combination of higher gross N mineralization, NH4+ and NO3− immobilization turnover and higher NO3− retention promotes a faster N turnover, resulting in greater N availability and N retention capacity in the late successional stages. Such results also suggested that during succession, internal N cycles adapt and develop mechanisms (i.e. increasing soil organic C and N concentration) in response to soil–plant interactions that enhance the soil N supply and N retention.

Conversion of a natural evergreen broadleaved forest into coniferous plantations in a subtropical area: effects on composition of soil microbial communities and soil respiration

In this study, we examined how the conversion of native broadleaved forests into plantations of more productive forest species for timber use affects soil microbial community composition at 0–10-cm depth and soil respiration by comparing two 36-year-old plantation forests of Chinese fir (Cunninghamia lanceolata, CF) and Pinus massoniana (PM) with an adjacent relict natural forest of Castanopsis carlesii (NF, ~200 years old) in Sanming, Fujian, China. The soil microbial community composition was determined by phospholipid fatty acid (PLFA) analysis. The monthly in situ soil respiration rate was measured from October 2010 to September 2012. Results showed that the abundance of Gram-negative bacterial PLFAs, actinomycetal PLFAs, and total PLFAs did not vary significantly with forest conversion. The CF soil was characterized by higher abundance of fungal PLFA and lower abundance of Gram-positive bacterial PLFA compared with NF and PM soils. Redundancy analysis (RDA) indicated that the significant change in the composition of soil microbial community was mainly due to fine root biomass and soil pH. Annual soil respiration rate averaged 161.7 mg C m−2 h−1 in NF, 95.1 mg C m−2 h−1 in CF, and 103.2 mg C m−2 h−1 in PM. The NF showed significantly higher mean annual soil CO2 flux (1421 g C m−2 year−1) than CF (837 g C m−2 year−1) and PM (907 g C m−2 year−1). After forest conversion, the apparent temperature sensitivity of soil respiration (Q 10) increased from 1.75 in NF to 2.04 and 1.98 in CF and PM, respectively. The mean annual soil respiration was significantly correlated with soil organic C (SOC) content and abundances of microbial PLFAs except for abundance of fungal PLFA, but not significantly correlated with fine root biomass (<2 mm in diameter) across the different forest soils. The latter behavior may be due to the higher fine root biomass in the CF than in the NF and PM. Our results suggest that studies incorporating the microbial community composition with soil respiration may enhance our understanding of the mechanisms of soil C dynamics.

Effect of Mixed Liquid Fertilization on Growth Responses of Red peppers and Soil Chemical Properties

We evaluated the effect of mixed liquid fertilizer (MLF) on growth responses of plants and soil chemical properties. A pot experiment with red pepper (Capsicum annuum L.) using loam soil was conducted for 81 days in a temperature-controlled glasshouse, and four N fertilization treatments were laid out in a completely randomized design with three replicates: control (C), chemical fertilizer treatment (CF), and two rates (MLF-0.5 and MLF-1.0) of MLF treatment. Soils were periodically sampled and analyzed for pH, EC(Electrical Conductivity), total N, inorganic N and total C, and some growth characteristics of red peppers were measured. During the experimental periods, the pH of MLF soils was higher than that of CF soils. Soil EC increased right after application of CF or MLF, and the intial increase persisted in CF and MLF soils at the end of experiment. Soil total-N increased right after application of CF or MLF, and this initial increase persisted only in MLF-1.0 soils. Soil inorganic N content initially increased in CF or MLF-1.0 soils, but the initial increase disappeared in 56 days after transplanting. Soil total-C was maintained higher in MLF-1.0 soils and lower in CF soils than in control soils, and the intial increase in MLF-1.0 soils finally disappeared to the level of control soils. Plant height, dry weight of plant organs (shoots, roots and fruit), and the number, diameter and length of red pepper fruits were greatest in CF plants. On the other hand, the effect of MLF-application was different depending on the rate of application. However, no consistent effect of N treatments on some major elements of the organs of red peppers was observed. The amounts of N taken up by plants were 1.3 g for CF, 0.8 g for MLF-1.0, 0.5 g for MLF-0.5 and 0.4 g for control treatments. The results of this study showed that mixed liquid fertilizer (MLF) could appropriately serve as an alternative to chemical N fertilizer in red pepper cultivation.

Effect of Mixed Liquid Fertilization on Growth Responses of Cherry Tomatoes and Soil Chemical Properties

Abstract: We evaluated the effect of mixed liquid fertilizer (MLF) on growth responses of plants and soil chemical properties. To do so, a pot experiment with cherry tomatoes ( Lycopersicon esculentum var. cerasiforme ) using loam soil was conducted for 81 days in a temperature-controlled glasshouse, and four N fertilization treatments were laid out in a completely randomize d design with three replicates: control (C), chemical fertilizer treatment (CF), and two rates (MLF-0.5 and MLF-1.0) of MLF treat ment. Soils were periodically sampled and analyzed for pH, EC, total N, inorganic N and total C, and growth characteristics of cherry tomatoes were measured. During the experimental periods, the pH of MLF soils was higher than that of CF soils. Soil total-N content increased right after CF-application and ultimately decreased to the level of the control (C) soil, while MLF-applicati on slightly increased the level of soil total-N and this level remained unchanged throughout the experiment. The levels of soil in organic N content increased after application of CF or MLF, but the initial increase disappeared in 56 days after transplanting (DAT). The dry weight of shoots and roots increased in CF or MLF plants, while the number of fruit increased only in MLF plants. Whereas soluble solid contents were higher in MLF plants than in the other (C and CF) plants, the titratable acidity was not different among treatments. However, no consistent effect of N treatments on major elements of the organs of cherry tomatoes was found. The amounts of N taken up by plants were 0.91 g for CF, 0.61 g for MLF-1.0, 0.43 g for MLF-0.5, and 0.25 g for control treatments, resulting in greater N efficiency for CF than for MLF.Additional key words:

The effect of irrigation with anaerobic baffled reactor effluent on nutrient availability, soil properties and maize growth

A glasshouse study was carried out to assess the availability to maize of nutrients from anaerobic baffled reactor (ABR) effluent. Maize was grown for 6 weeks in pots with three contrasting soils namely a sandy soil (Cartref (Cf), Typic Haplaquept), an organic, acidic soil (Inanda (Ia), Rhodic Hapludox) and a clayey soil (Sepane (Se), Aquic Haplustalf). Fertilizer (N, P and K) was applied at the recommended rate, half the recommended rate and zero fertilizer for each of the soils used. Lime was applied to the Ia following recommendations. Plants were irrigated with either effluent or tap water. Dry matter yields and nutrient concentrations for effluent-irrigated maize were significantly higher (p<0.05) than for all water-irrigated plants. For each soil, the unfertilized, effluent-irrigated plants were not significantly different in most of the above-ground nutrient concentrations from the water-irrigated plants at half fertilization. Phosphorus deficiency was observed in the Ia and Se but not in the Cf, irrespective of fertilizer treatment. Plants grown on the Cf irrigated with effluent and fully fertilized had the highest above-ground dry matter yield (4.90g pot−1) and accumulated more N, P, K, Ca and Mg than all other treatments. After harvest, P in the Cf soil was significantly higher (p<0.05) in the effluent-irrigated than the water-irrigated soils reflecting P input from the effluent. Concurrently, the effect of the effluent was further investigated by planting maize on the Ia with neither lime application nor fertilization. Plants that received effluent irrigation and no lime had significantly higher (p<0.05) dry matter yields (2.67g pot−1) and accumulated more N, P and K than those water-irrigated with no lime as well as the equivalent limed treatments. This suggests an interaction effect between the lime and effluent properties.

Repeated applications of farmyard manure enhance resistance and resilience of soil biological functions against soil disinfection

The effect of repeated application of farmyard manure (FYM) on resistance and resilience of some of soil biological functions was compared between two soils [chemically fertilized soil (CF soil) and chemically and organically amended soil (CF+FYM-soil)]. The impact of chloropicrin and metam sodium disinfection on organic matter (glucose and chitin) decomposition activity and number of ammonia oxidizing bacteria in the soils was measured periodically from just after disinfection to evaluate stability of soil biological functions to soil disinfection. Glucose and chitin decomposition activity and number of ammonia oxidizing bacteria was suppressed by soil disinfection more seriously in the CF soil than in the CF+FYM soil. The decomposition rates recovered in the disinfected CF+FYM soil 2 to 12 weeks after disinfection, but not in the CF soil during 12 weeks incubation. These results demonstrated that soil resistance and resilience of the selected biological functions may be higher in the CF+ FYM soil than in the CF soil. The ratios of fungal and bacterial contribution to glucose decomposition activity were evaluated by the substrate-induced respiration method. Chloropicrin and metam sodium disinfection decreased fungal contribution throughout the incubation period (12 weeks) in the CF soil. A similar tendency was observed in the CF+FYM soil, but the fungal contribution tended to recover more rapidly in the CF+FYM soil than in the CF soil. Repeated applications of FYM may be an effective way to enhance soil functional stability.

Analysis of Proton Generation and Consumption of Forest Surface Soils in Hokkaido, Northern Japan

We determined proton budgets of surface soils in a deciduous forest (Df) and a coniferous forest (Cf) of Volcanogenous Regosols in Tomakomai, Hokkaido of northern Japan. The total H+ source was 12.9 and 11.6 kmolc ha−1 y−1 at Df and Cf respectively, and the external H+ was 1% at Df and 2% at Cf. The primary H+ sources were vegetation uptake of base cations and nitrification, while the major H+ sinks were release of base cations and NO3+ uptake by vegetation. Leaching incubation experiments using A horizon soils including Df and Cf with NH4+ solutions (5.3, 15.9 mg N L−1) showed that H+ from nitrification was generally higher in the Df soil than Cf soil, and nitrification of Tomakomai Df soil was the highest in both treatments. Results of multiple regression analyses suggested that pHkCl and exchangeable Ca2+ contributed to the H+ generation via nitrification. Leaching experiments with dilute HCl (pH 3.3) revealed that cation release (mainly Ca2+) occurred, and the proportion of release by decrease of exchangeable cations was higher than that by mineral weathering. Mineral weathering in the Tomakomai soil was higher than the other soils.