Contrasting development of soil microbial community structure under no-tilled perennial and tilled cropping during early pedogenesis of a Mollisol

A range of agricultural practices influence soil microbial communities, such as tillage and organic C inputs, however such effects are largely unknown at the initial stage of soil formation. Using an eight-year field experiment established on exposed parent material (PM) of a Mollisol, our objectives were to: (1) to determine the effects of field management and soil depth on soil microbial community structure; (2) to elucidate shifts in microbial community structure in relation to PM, compared to an arable Mollisol (MO) without organic amendment; and (3) to identify the controlling factors of such changes in microbial community structure. The treatments included two no-tilled soils supporting perennial crops, and four tilled soils under the same cropping system, with or without chemical fertilization and crop residue amendment. Principal component (PC) analysis of phospholipid fatty acid (PLFA) profiles demonstrated that microbial community structures were affected by tillage and/or organic and inorganic inputs via PC1 and by land use and/or soil depth via PC2. All the field treatments were separated by PM into two groups via PC1, the tilled and the no-tilled soils, with the tilled soils more developed towards MO. The tilled soils were separated with respect to MO via PC1 associated with the differences in mineral fertilization and the quality of organic amendments, with the soils without organic amendment being more similar to MO. The separations via PC1 were principally driven by bacteria and associated with soil pH and soil C, N and P. The separations via PC2 were driven by fungi, actinomycetes and Gram (−) bacteria, and associated with soil bulk density. The separations via both PC1 and PC2 were associated with soil aggregate stability and exchangeable K, indicating the effects of weathering and soil aggregation. The results suggest that in spite of the importance of mineral fertilization and organic amendments, tillage and land-use type play a significant role in determining the nature of the development of associated soil microbial community structures at the initial stages of soil formation.     

联合施用不同植物物质和鸡粪对土壤碳氮含量和蔬菜产量的影响

The use of plant materials as soil amendments is an uncommon practice amongst major farming communities in Ghana, although it is necessary for soil fertility improvement. An examination of the effects of soil amendments is necessary to encourage the use of under-utilized organic resources in Ghana. Thus, a field experiment was conducted using 8 different tropical plant materials mixed with chicken manure as soil amendments for growth of tomato as a test crop. The plant materials included Leucaena leucocephala, Centrosema pubescens, Sesbania sesban, Gliricidia sepium, Mucuna pruriens, Pueraria phaseoloides, Azadirachta indica, and Theobroma cacao. There were two other treatments: one with equivalent amounts of chemical fertilizers and the other with no-fertilizer input (control). Plant materials were mixed with chicken manure to obtain a uniform carbon-to-nitrogen (C:N) ratio of 5:1. Except the no-fertilizer control, all treatments received the same amount of nitrogen (N). To clarify the decomposition pattern of the plant materials in soil, an incubation experiment was conducted using only the plant materials before the field experiment. The Gliricidia treatment released significantly more mineral N than the other plant materials in the incubation experiment. However, the tomato fruit yield was not enhanced in the Gliricidia treatment in the field experiment. The known quality parameters of the tested plant materials, such as total N, total carbon (C), C:N ratio, and total polyphenols, had minimal effects on their mineralization dynamics. Azadirachta showed the best synergistic effect with chicken manure through significantly increasing soil microbial biomass and fruit yield of tomato. This result provides insights into the possible adoption of Azadirachta in combination with chicken manure as a soil amendment in small-scale agricultural holdings.     

Influence of inorganic fertilizers and organic amendments on soil organic matter and soil microbial properties under tropical conditions

 Soil organic matter level, mineralizable C and N, microbial biomass C and dehydrogenase, urease and alkaline phosphatase activities were studied in soils from a field experiment under a pearl millet-wheat cropping sequence receiving inorganic fertilizers and a combination of inorganic fertilizers and organic amendments for the last 11 years. The amounts of soil organic matter and mineralizable C and N increased with the application of inorganic fertilizers. However, there were greater increases of these parameters when farmyard manure, wheat straw or Sesbania bispinosa green manure was applied along with inorganic fertilizers. Microbial biomass C increased from 147 mg kg^–1 soil in unfertilized soil to 423 mg kg^–1 soil in soil amended with wheat straw and inorganic fertilizers. The urease and alkaline phosphatase activities of soils increased significantly with a combination of inorganic fertilizers and organic amendments. The results indicate that soil organic matter level and soil microbial activities, vital for the nutrient turnover and long-term productivity of the soil, are enhanced by use of organic amendments along with inorganic fertilizers. Received: 6 May 1998     

Soil microbial activity and crop sustainability in a long-term experiment with three soil-tillage and two crop-rotation systems

Reduction in soil disturbance can stimulate soil microbial biomass and improve its metabolic efficiency, resulting in better soil quality, which in turn, can increase crop productivity. In this study we evaluated microbial biomass of C (MB-C) by the fumigation-extraction (FE) or fumigation-incubation (FI) method; microbial biomass of N (MB-N); basal respiration (BR) induced or not with sucrose; metabolic quotient (obtained by the ratio BR/MB-C) induced (qCO₂(S)), or not with sucrose (qCO₂); and crop productivity in a 14-year experiment in the state of Paraná, southern Brazil. The experiment consisted of three soil-tillage systems [no-tillage (NT), conventional tillage (CT) and no-tillage using a field cultivator every 3 years (FC)] and two cropping systems [a soybean–wheat-crop sequence (CS), and a soybean–wheat–white lupin–maize–black oat–radish crop rotation (CR)]. There were six samplings in the 14th year, starting at the end of the winter crop (wheat in the CS and lupin in the CR plots) and finishing at full flowering of the summer crop (soybean in the CS and maize in the CR). Differences in microbiological parameters were greater than those detected in the total C (TCS) and total N (TNS) contents of the soil organic matter (SOM). Major differences were attributed to tillage, and on average NT was higher than the CT in the following parameters: TCS (19%), TNS (21%), MB-C evaluated by FE (74%) and FI (107%), and MB-N (142%). The sensibility of the microbial community and processes to soil disturbance in the tropics was highlighted, as even a moderate soil disturbance every 3 years (FC) affected microbial parameters but not SOM. The BR was the parameter that most promptly responded to soil disturbance, and strong differences were perceived by the ratio of qCO₂ evaluated with samples induced and non-induced with sucrose. At plowing, the qCO₂(S):qCO₂ was five times higher under CT, indicating a C-starving low-effective microbial population in the C-usage. In general, crop rotation had no effect on microbial parameters or SOM. Grain yield was affected by tillage and N was identified as a limiting nutrient. Linear regressions between grain yields and microbial parameters showed that soybean was benefited from improvements in the microbial biomass and metabolic efficiency, but with no significant effects observed for the maize crop. The results also indicate that the turnover of C and N in microbial communities in tropical soils is rapid, reinforcing the need to minimize soil disturbance and to balance inputs of N and C.     

Microbiological parameters as indicators of soil quality under various soil management and crop rotation systems in southern Brazil

The objective of this work was to identify soil parameters potentially useful to monitor soil quality under different soil management and crop rotation systems. Microbiological and chemical parameters were evaluated in a field experiment in the State of Paraná, southern Brazil, in response to soil management [no-tillage (NT) and conventional tillage (CT)] and crop rotation [including grain (soybean, S; maize, M; wheat, W) and legume (lupin, L.) and non-legume (oat, O) covers] systems. Three crop rotation systems were evaluated: (1) (O/M/O/S/W/S/L/M/O/S), (2) (O/S/L/M/O/S/W/S/L/M), and (3) (O/S/W/S/L/M/O/M/W/M), and soil parameters were monitored after the fifth year. Before ploughing, CO₂-emission rates were similar in NT and CT soils, but plough increased it by an average of 57%. Carbon dioxide emission was 13% higher with lupin residues than with wheat straw; decomposition rates were rapid with both soil management systems. Amounts of microbial biomass carbon and nitrogen (MB-C and MB-N, respectively) were 80 and 104% higher in NT than in CT, respectively; however, in general these parameters were not affected by crop rotation. Efficiency of the microbial community was significantly higher in NT: metabolic quotient (qCO₂) was 55% lower than in CT. Soluble C and N levels were 37 and 24% greater in NT than in CT, respectively, with no effects of crop rotation. Furthermore, ratios of soluble C and N contents to MB-C and MB-N were consistently lower in NT, indicating higher immobilization of C and N per unit of MB. The decrease in qCO₂ and the increase in MB-C under NT allowed enhancements in soil C stocks, such that in the 0–40 cm profile, a gain of 2500 kg of C ha⁻¹ was observed in relation to CT. Carbon stocks also varied with crop rotation, with net changes at 0–40 cm of 726, 1167 and −394 kg C ha⁻¹ year, in rotations 1, 2 and 3, respectively. Similar results were obtained for the N stocks, with 410 kg N ha⁻¹ gained in NT, while crop rotations 1, 2 and 3 accumulated 71, 137 and 37 kg of N ha⁻¹ year⁻¹, respectively. On average, microbial biomass corresponded to 2.4 and 1.7% of the total soil C, and 5.2 and 3.2% of the N in NT and CT systems, respectively. Soil management was the main factor affecting soil C and N levels, but enhancement also resulted from the ratios of legumes and non-legumes in the rotations. The results emphasize the importance of microorganisms as reservoirs of C and N in tropical soils. Furthermore, the parameters associated with microbiological activity were more responsive to soil management and crop rotation effects than were total stocks of C and N, demonstrating their usefulness as indicators of soil quality in the tropics.     

秸秆还田施氮调节碳氮比对土壤无机氮、 酶活性及作物产量的影响

秸秆的质量,特别是C/N是影响秸秆分解速率和养分释放的重要因素。在秸秆还田条件下,如何科学合理地施用氮肥是秸秆利用和优化施肥研究的关键问题。本研究以秸秆还田施入碳氮的C/N为切入点,于2012—2013年通过田间试验(设秸秆不还田不施肥、秸秆还田不施氮、秸秆还田施用无机氮肥调节C/N为10∶1、16∶1和25∶1以及秸秆还田施用有机氮肥调节C/N为25∶1处理),研究秸秆还田不同氮输入对小麦-玉米轮作田土壤无机氮、土壤微生物量氮、酶活性以及作物产量的影响。结果表明:1)在C/N为25∶1下,施用有机氮肥和无机氮肥对土壤无机氮含量无显著影响;在施用无机氮肥的情况下,C/N越低土壤无机氮含量越高。2)秸秆还田施氮提高了土壤微生物量氮含量,但是各秸秆还田施氮处理之间差异不显著;秸秆还田不同施氮处理对脲酶活性无显著影响;秸秆还田施氮提高了FDA水解酶活性,并随C/N降低呈升高趋势,施用无机氮肥的效果强于施用有机氮肥的。3)秸秆还田施用无机氮肥显著提高了小麦和玉米地上部生物量,施用无机氮肥调节C/N为10∶1和16∶1相比于C/N为25∶1提高了小麦和玉米的苗期和成熟期地上部生物量;施用有机氮肥调节C/N为25∶1相比秸秆还田不施氮对地上部生物量无显著影响。秸秆还田施用无机氮肥提高了作物产量,施用无机氮肥调节C/N为16∶1产量最高,而施用有机氮肥调节C/N为25∶1有降低作物产量的趋势。综合以上结果来看,施用无机氮肥调节C/N为16∶1较为合理。     

稻田系统管理措施对微生物生物量C、N、P的长期影响

A 12-year field experiment was conducted to investigate the effect of different tillage methods and fertil-ization systems on microbial biomass C,N and P of a gray fluvo-aguic soil in rice-based cropping system .Five fertilization treatments were designed under conventional tillae(CT) or on tillage(NT) system:no fertilizer(CK) ; chemical fertilizer only(CF) ; combining chemical fertilizer with pig manure(PM); combining chemical fertilizer with crop straw (CS) and fallow (F). The results showed that biomass C,N and P were enriched in the surface layer of no-tilled soil,whereas they distributed relatively evenly in the tilled soil,which might result from enrichment of crop resdue,organic manure and mineral fertilzer,and surficial developent of root systems under NT.Under the cultivation system NT had slightly greater biomass C,N and P at 0-5 cm depth ,significantly less biomass C,N and P at 5-15 cm depth ,less microbial biomass C,N and equivalent biomass P at 15-30 cm depth as compared to CT,indicating hat tillage was beneficial for the multiplication of organims in the plowed layer of soil.Under the fallow system,biomass C,N and P in the surface layer were significantly greater for NT than CT while their differences between the two tillage methods were neligible in the deeper layers.In the surface layer,biomass C,N and P in the soils amended with oranic manure combined with mineral fertilizers were significantly greater than those of the treatments only with mineral fertilizers and the control.Soils without fertilzer had the least biomass nutrient contents among the five fertilization treatments.Obviously,the long-term application of organic manure could maintain the higher activity of microorganisms in soils.The amounts of biomass C,N and P in the fallowed soils varied with the tillage methods;they were much greater under NT than under CT,especially in the surface layer,suggesting that the frequent plowing could decrease the content of organic matter in the surface layer of the fallowed soil.     

Soil fauna and organic amendment interactions affect soil carbon and crop performance in semi-arid West Africa

A field experiment was conducted at Kaibo in southern Burkina Faso on an Eutric Cambisol during the 2000 rainy season to assess the interaction of organic amendment quality and soil fauna, affecting soil organic carbon and sorghum (Sorghum bicolor L. Moench) performance. Plots were treated with the pesticides Dursban and Endosulfan to exclude soil fauna or left untreated. Sub-treatments consisted of surface-placed maize straw (C/N ratio = 58), Andropogon straw (C/N ratio = 153), cattle dung (C/N ratio = 40), sheep dung (C/N ratio = 17) or compost (C/N ratio = 10) and the control. Organic amendments were applied at a dose equivalent to the application of 40 kg N ha⁻¹. The presence of soil fauna increased soil total carbon by 32% and grain yield production by 50%. The interaction between high C/N ratio organic amendment, Andropogon straw (SA), and soil fauna reduced soil carbon build-up. We suggest that this is due to a priming effect of SA on soil organic matter in the presence of soil fauna. We also suggest that the interaction between soil fauna and easily decomposable organic amendment led to the smallest decrease in soil carbon build-up. It is concluded that in semi-arid West Africa, in the presence of soil fauna, soil carbon build-up is more affected by the quality of organic amendments than the quantity of carbon inputs. Sorghum grain yield production was significantly reduced in the absence of soil fauna. High C/N ratio organic amendment interacted negatively with soil fauna in its effects on crop performance. We propose that the effect of soil fauna on soil carbon build-up and crop performance can be optimised by using high quality organic matter or supplementing low-quality organic matter with inorganic nitrogen in semi-arid West Africa.     

不同有机物料接种蚯蚓对设施菜地土壤 培肥及作物生长的影响

设施蔬菜栽培长期施用过量化肥,往往导致土壤质量退化及作物产量降低等问题。因此,采用生态友好的农业生产方式已成为农业可持续发展的趋势。本研究在野外调控试验的第3年采集作物和土壤,研究了施用不同有机物料条件下,接种赤子爱胜蚓(Eisenia foetida)对设施菜地土壤性质和作物生长的影响。结果表明,在不同有机物料施用下接种赤子爱胜蚓均显著地提高了黄瓜和菠菜的产量,其中在施用腐熟牛粪+食用菌渣条件下接种赤子爱胜蚓效果最显著。此外,在腐熟牛粪和腐熟牛粪+食用菌渣施用条件下,接种赤子爱胜蚓显著地提高土壤的硝态氮(NO3–-N)、团聚体平均重量直径(MWD)、微生物生物量碳(MBC)、微生物生物量氮(MBN)和代谢熵(q CO2),而在施用商品有机肥的处理中,接种赤子爱胜蚓仅显著地提高了土壤NO3–-N和q CO2。本研究促进了对蚯蚓在设施农业生态系统中服务功能的理解,并为设施农业生产提供了理论基础。     

不同节水稻作模式对土壤微生物数量和微生物量碳氮的影响

针对南方丘陵区季节性干旱这一区域问题,以节水稻作模式为研究对象,以常规稻作模式为对照,通过田间定位试验,研究了稻基农田土壤微生物数量和土壤微生物量碳氮的变化规律.结果表明,与该区常规稻作模式相比,节水稻作模式的土壤微生物数量和土壤微生物量碳氮差异显著;节水稻作模式有利于土壤细菌和放线菌的增殖,但抑制了真菌的增殖;土壤微生物量碳和微生物量氮的显著增加,以水旱轮作双季稻模式最佳,说明采用节水稻作模式可有效提升土壤细菌数量、放线菌数量、微生物量碳和微生物量氮含量.因此,在南方丘陵季节性干旱区,采用节水稻作模式,可促进稻田生态系统健康持续发展.     

Organic matter, microbial biomass and enzyme activity of soils under different crop rotations in the tropics

Soil organic matter level, soil microbial biomass C, ninhydrin-N, C mineralization, and dehydrogenase and alkaline phosphatase activity were studied in soils under different crop rotations for 6 years. Inclusion of a green manure crop of Sesbania aculeata in the rotation improved soil organic matter status and led to an increase in soil microbial biomass, soil enzyme activity and soil respiratory activity. Microbial biomass C increased from 192 mg kg^–1 soil in a pearl millet-wheat-fallow rotation to 256 mg kg^–1 soil in a pearl millet-wheat-green manure rotation. Inclusion of an oilseed crop such as sunflower or mustard led to a decrease in soil microbial biomass, C mineralization and soil enzyme activity. There was a good correlation between microbial biomass C, ninhydrin-N and dehydrogenase activity. The alkaline phosphatase activity of the soil under different crop rotations was little affected. The results indicate the green manuring improved the organic matter status of the soil and soil microbial activity vital for the nutrient turnover and long-term productivity of the soil. Received: 7 January 1996     

Effects of substituting chemical fertilizers with manure on rice yield and soil labile nitrogen in paddy fields of China: A meta-analysis

Substituting chemical fertilizers with manure is an important method for efficient nutrient management in rice cropping systems of China.Labile nitrogen(N) is the most active component of the soil N pool and plays an essential role in soil fertility.However,the effects of manure substitution on soil labile N in rice cropping systems and their relationships with soil properties,fertilization practices,and climatic conditions remain unclear and should be systematically quantified.Here,we investiga...     

Combining Legumes and Compost: A Viable Alternative for Farmers in Conversion to Organic Agriculture

Soil nitrogen (N) availability and crop performance of broccoli (Brassica oleracea var. orion) were observed in a field plot study under different organic amendments addition and chemical fertilizer. The treatments consisted on no amendment; poultry manure based compost, woollypod vetch (Vicia dasycarpa var. lana), a combination of compost with Lana vetch and ammonium sulphate. For almost all sampling dates, the soils treated with vetch (3.6 Mg/ha) combined with compost (9.0 Mg/ha) showed a good performance in replenishing the inorganic N taken up by plants and soil microbes. High yields were achieved with the combination of vetch and compost and moderately high yields were achieved with vetch only and compost only. Yields appeared to be related to quality and N levels in the amendments, and size of existing soil nitrogen pools susceptible to the priming effect.     

Soil organic matter stratification ratio as an indicator of soil quality

Soil quality is a concept based on the premise that management can deteriorate, stabilize, or improve soil ecosystem functions. It is hypothesized that the degree of stratification of soil organic C and N pools with soil depth, expressed as a ratio, could indicate soil quality or soil ecosystem functioning, because surface organic matter is essential to erosion control, water infiltration, and conservation of nutrients. Stratification ratios allow a wide diversity of soils to be compared on the same assessment scale because of an internal normalization procedure that accounts for inherent soil differences. Stratification ratios of soil organic C were 1.1, 1.2 and 1.9 under conventional tillage (CT) and 3.4, 2.0 and 2.1 under no tillage (NT) in Georgia, Texas, and Alberta/British Columbia, respectively. The difference in stratification ratio between conventional and NT within an environment was inversely proportional to the standing stock of soil organic C to a depth of 15–20 cm across environments. Greater stratification of soil C and N pools with the adoption of conservation tillage under inherently low soil organic matter conditions (i.e., warmer climatic regime or coarse-textured soil) suggests that standing stock of soil organic matter alone is a poor indication of soil quality. Stratification of biologically active soil C and N pools (i.e., soil microbial biomass and potential activity) were equally or more sensitive to tillage, cropping intensity, and soil textural variables than stratification of total C and N. High stratification ratios of soil C and N pools could be good indicators of dynamic soil quality, independent of soil type and climatic regime, because ratios >2 would be uncommon under degraded conditions.     

Compost,Manure and Synthetic Fertilizer Influences Crop Yields,Soil Properties,Nitrate Leaching and Crop Nutrient Content

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input. From 1993 to 1998, red clover (Trifolium pratense L.) and crimson clover (Trifolium incarnatum L.) were used as an annual winter legume cover crop prior to maize production. From 1999 to 2001, hairy vetch (Vicia villosa Roth.) served as the legume green manure nitrogen (N) source for maize. In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production. Vegetables received either compost, manure, or fertilizer N inputs. Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre). This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001. When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 10-24 bu/a). Hairy vetch cover cropping also resulted in a 9-25 % increase in wheat yields in the compost treatments compared to clover cover cropping. Hairy vetch cover crops increased both maize and wheat grain protein contents about 16 to 20% compared to the clover cover crop. Compost was superior to conventional synthetic fertilizer and raw dairy manure in 1) building soil nutrient levels, 2) providing residual nutrient support to wheat production, and 3) reducing nutrient losses to ground and surface waters. After 9 years, soil carbon (C) and soil N remained unchanged or declined slightly in the synthetic fertilizer treatment, but increased with use of compost amendments by 16-27% for C and by 13-16% for N. However, with hairy vetch cover crops, N leaching increased 4 times when compared to clover cover crops. September was the highest month for nitrate leaching, combining high rainfall with a lack of active cash crop or cover crop growth to use residual N. Broiler litter leaf compost (BLLC) showed the lowest nitrate leaching of all the nutrient amendments tested (P= 0.05).     

Soil C balance in a long-term field experiment in relation to the size of the microbial biomass

Soil C balances were calculated in a field experiment started in 1956. Treatments include a fallow and soils receiving different N fertilizers or organic amendments. By assuming the absence of a priming effect, the degree of mineralization of crop residues and organic amendments was calculated. Crop residue mineralization was not affected by a more than 50% decrease in the size of the microbial biomass in soil fertilized with (NH₄)₂SO₄, which had caused the pH of this soil to drop from 6.6 to 4.4. More C had accumulated per unit C input in peat-and sewage sludge-amended soils than in any of the other soils, suggesting that peat and sewage sludge were more resistant to microbial attack. Recalcitrance of substrate C was an adequate explanation for the low ratio of biomass C to soil C in the peat-amended soils, but not in the sewage sludge-amended soil. There was a close linear relationship (r=0.94) between the content of microbial biomass C in the soil measured in 1990 and cumulative C losses from the soil since 1956. Compared to the relationship between soil biomass C and soil organic C concentrations, the linear relationship between microbial C and cumulative C losses suggested that the significantly reduced biomass in the sewage sludge-amended soil was at least partially due to the presence of toxic substances (presumably elevated heavy metal concentrations) in this soil and was probably not affected by the somewhat low pH (5.3) in this soil.     

Long-term tillage and rotation effects on soil microbial biomass,carbon and nitrogen

Summary Three mollisols, typical of the Palouse winter wheat region of eastern Washington and northern Idaho, were analyzed for microbial biomass, total C and total N after 10 years of combined tillage and rotation treatments. Treatments included till, no-till and three different cereal-legume rotations. All crop phases in each rotation were sampled in the same year. Microbial biomass was monitored from April to October, using a respiratory-response method. Microbial biomass, total C and total N were highest under no-till surface soils (0–5 cm), with minimal differences for tillage or depth below 5 cm. Microbial biomass differences among rotations were not large, owing to the relative homogeneity of the treatments. A rotation with two legume crops had the highest total C and N. Microbial biomass was significantly higher in no-till surface soils where the current crop had been preceded by a high-residue crop. The opposite was true for the tilled plots. There was little change in microbial biomass over the seasons until October, when fresh crop residues and rains had a strong stimulatory effect. The seasonal pattern of biomass in no-till surface soils reflected the dry summer/winter rainfall climate of the region. The results of this study show that numerous factors affect soil microbial biomass and that cropping history and seasonal changes must be taken into account when microbial biomass data are compared.Scientific paper no. 7634     

Soil Properties and Maize Growth in Saline and Nonsaline Soils using Cassava‐Industrial Waste Compost and Vermicompost with or Without Earthworms

The aim of this study was to investigate the effectiveness of compost and vermicompost as soil conditioners in alleviating salt‐affected soils and increasing maize productivity. A greenhouse trial, consisting of seven soil amendment treatments in a completely randomized design with three replications, was carried out at Khon Kaen University, Thailand, during the rainy season of 2011. Plant height and total dry matter of maize increased in treatments with compost and vermicompost application when compared with the control (no fertilizer) in two types of soils (saline and nonsaline) during the growing season. Soil pH and electrical conductivity in saturation paste extracts were decreased by compost and vermicompost amendments with or without earthworms when compared with unamended treatments in the saline soil. Compost and vermicompost amendments improved cation exchange capacity, soil organic carbon, total nitrogen and extractable phosphorus in both soils. These amendments also increased exchangeable K⁺, Ca²⁺ and Mg²⁺ while decreasing exchangeable Na⁺ in the saline soil, which suggested that Ca²⁺ was exchanged for Na⁺, exchangeable Na⁺, then leached out, and soil salinity reduced as a result. Soil microbial activities including microbial C and N and basal soil respiration were improved by the application of compost and vermicompost amendments with or without earthworms when compared with the control in both soils. This experiment showed that the compost and vermicompost were effective in alleviating salinity and improving crop growth. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of cultivation on microbial carbon and nitrogen in dry tropical forest soil

Summary Fifteen- and forty-year-old cropfields developed from a dry tropical forest were examined for soil organic C and total N and soil microbial C and N. The 15-year-old field had never been manured while the 40-year-old field had been fertilized with farmyard manure every year. The native forest soil was also examined. The results indicated that the native forest soil lost about 57% and 62% organic C and total N, respectively, in the 0–10 cm layer after 15 years of cultivation. The microbial C and N contents of the forest soil were greater than those of the cultivated soils. Application of farmyard manure increased the biomass-C and -N levels in the cultivated soil but the values were still markedly lower than in the forest soil. There was an appreciable seasonal variation in biomass C and N, the values being highest in summer and lowest in the rainy season. During an annual cycle, biomass-C contents varied from 180 to 727 g g^–1 and N from 20 to 80 g g^–1 dry soil, and both were linearly related. Microbial biomass C represented 1.6%–3.6% of total soil organic C and microbial biomass N represented 1.7% 1–4.4% of soil organic N.     

Remediation of subsoil compaction and compaction effects on corn N availability by deep tillage and application of poultry manure in a sandy-textured soil

Subsoil compaction may reduce the availability and uptake of water and plant nutrients thereby lowering crop yields. Among the management options for remediating subsoil compaction are deep tillage and the selection of crop rotations with deep-rooted crops, but little is known of the effects of applications of organic amendments on subsoil compaction. The objectives of this study were to determine the effects of subsoil compaction on corn yield and N availability in a sandy-textured soil and to evaluate the use of deep tillage and surface applications of poultry manure to remediate subsoil compaction. A field experiment planted to corn (Zea mays L.) was conducted from 2000 to 2001 on a Reelfoot fine sandy loam (fine-silty, mixed thermic Aquic Argiudolls) formed in silty alluvium located in southeast Missouri near the Mississippi River. Treatments were arranged in a factorial design with three levels of subsoil compaction and subsoiling and four rates (averaging 0, 6, 11 and 18 Mg ha⁻¹) of poultry manure. Subsoil tillage to a depth of 30 cm had multiple effects, including overcoming a natural or tillage-induced dense layer or pan and increasing volumetric soil water content and crop N uptake, especially in the 2001 cropping year with low early season precipitation. N recovery efficiency (NRE) was significantly higher in the subsoil treatment compared to the highest compaction treatment in 2001. No significant interactions between manure rates and compaction and subsoiling treatments were observed for corn grain and silage yields, N uptake and NRE. Average increases in corn grain yields over all manure rates due to subsoil tillage of compacted soil were 2002 kg ha⁻¹ in 2000 and 3504 kg ha⁻¹ in 2001. Application of poultry manure had a consistent positive effect on increasing grain yields and N uptake in 2000 and 2001 but did not significantly alter measured soil physical properties. The results of this study suggest that deep tillage and applications of organic amendments are management tools that may overcome restrictions in both N and soil water availability due to subsoil compaction in sandy-textured soils.