长期施肥对中国亚热带水稻土土壤稳定性和机械属性的影响

Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.     

长期施用牛粪对松嫩平原盐渍化土壤质量的影响

在盐渍化土壤中,普遍存在土壤结构性和养分状况差以及土壤酶活性低等现象.这种现象主要是由于土壤中过量的交换性钠离子和较高的土壤pH所引起.长期施用有机肥(牛粪)是一项提升盐渍化土壤质量的重要措施.本研究依托东北农业大学盐碱土改良长期定位试验站,以腐熟的牛粪为改良材料,依据牛粪施用年限共设置5个处理,采用完全随机区组设计,每处理3次重复,供试作为玉米,各处理分别为:施用牛粪2年、6年、13年和18年,以不施用牛粪的盐渍化土壤作为对照.分别测定各处理的土壤理化指标和酶活性.采用因子分析法与土壤质量指数法评价长期施用有机肥对盐渍化土壤质量的影响.研究结果表明:长期施用有机肥能够改善盐渍化土壤的物理性状、提高土壤养分状况、降低土壤pH和盐分以及增加土壤酶活性.根据特征根>1原则,经因子分析后可提取2个公因子,分别表征"土壤结构性"(因子1)和"土壤盐碱性质"(因子2).与未施用有机肥的土壤相比,施用有机肥13年和18年的土壤具有较好的土壤结构性和较低的盐碱性质,而施用有机肥2年和6年的土壤仅具有较低的盐碱性质.比较土壤质量指数(SOI)可知:盐渍化土壤质量随有机肥施用年限而增加,有机肥施用18年处理的土壤质量最高.总之,土壤结构性差和盐碱性质高是影响松嫩平原盐渍化土壤质量的关键限制因子,其中以土壤结构性差最为主导;土壤容重、pH和盐分的降低是长期有机培肥措施下盐渍化土壤质量得以提升的重要特征,尤其是以土壤容重的降低最为重要.     

Denitrification characteristics of subtropical soils in China affected by soil parent material and land use

Forty‐five soil samples were collected from rice paddy land (R), tea garden land (T), forestland (F), brush land (B), and upland (U) in Jiangxi province, a subtropical region of China. These soils were derived from Quaternary red earth (Q), Tertiary red sandstone (S), and granite (G). Their denitrification capacities were determined after treatment with 200 mg NO₃⁻‐N kg⁻¹ soil by measuring changes in NO₃⁻‐N content during a 28‐day anaerobic incubation under N₂ gas in the headspace, at 30°C. The subtropical soils studied here were characterized by generally small denitrification capacities, ranging from no denitrification capacity to complete disappearance of added NO₃⁻‐N within 11 days of incubation. With few exceptions, NO₃⁻‐N reduction with incubation time followed a first‐order relationship with reaction constants of 0 – 0.271 day⁻¹, but the data could be simulated better by a logarithmic relationship. Thus, denitrification capacity was determined by the reaction constant of the first‐order reaction, the slope of the logarithmic relationship, and the averaged NO₃⁻‐N reduction rate in the first 7 days of anaerobic incubation (ranging from 0 to 28.5 mg kg⁻¹day⁻¹), and was significantly larger in the soils derived from G than from Q and S for all land uses except for rice paddy land. Soil organic carbon and nitrogen availability are the key factors that determine differences in denitrification capacity among the three soil parent materials. Rice cultivation significantly promoted denitrification capacity compared with the other four land uses and masked the effect of soil parent materials on denitrification capacity. This is most likely due to increases in organic carbon and total N content in the soil, which promoted the population and biological activities of microorganisms which are able to respire anaerobically when the rice soil is flooded. Neither the increased pH of upland soil caused by the addition of lime for upland crop production, nor the decreased pH of the tea garden soil by the acidification effect of tea plants altered soil denitrification capacity. Our results suggest that land use and management practices favour soil carbon and/or nitrogen accumulation and anaerobic microorganism activities enhance soil denitrification capacity.     

施用禽畜粪对两种土壤As、Cu和Zn有效性的影响

在水稻土和赤红壤中分别以2%和4%(w/w)比例施入含As、Cu和Zn的鸡粪和猪粪,以不施肥为对照进行苋菜盆栽试验,研究施入粪肥对土壤As、Cu和Zn有效性的影响。结果表明,与对照相比,施用粪肥均提高苋菜生物量,但几乎均显著降低苋菜As、Cu和Zn含量。试验前,赤红壤As、Cu和Zn总含量及有效含量明显低于水稻土,但赤红壤中施用粪肥处理的苋菜As、Cu和Zn含量及As和Zn吸收量均极显著高于水稻土的。苋菜收获后,各处理的土壤As总含量和有效含量均较试验前下降,施用高量鸡粪和猪粪处理的土壤总Cu、总Zn及有效Cu、有效Zn均出现累积。与对照比较,施用粪肥提高了土壤As、Cu和Zn的总含量、有效含量及有效含量占各自总量的百分数。如以土壤重金属有效含量增量及有效百分数增加来衡量粪肥提高土壤重金属有效性作用大小,则鸡粪提高土壤As有效性的作用较猪粪大,但其提高Cu、Zn有效性的作用不如猪粪,且高量粪肥处理较低量处理作用明显,粪肥在赤红壤中提高As、Cu和Zn有效性的作用大于在水稻土中。     

我国中亚热带丘陵地区红壤的肥力恢复

There are about 1.27 million ha of upland red soils derived from Quaternary red clay facing the degradation in the low-hilly region of the middle subtropical China. From the aspects of chemistry, physics and microbiology, the processes of soil fertility restoration in the surface layer (0~20 cm) under three types of land use patterns (i.e. citrus orchard, tea garden and upland) in two provinces were studied in this work. Results showed that the reclamation of eroded waste land improved most of soil properties. Soil organic matter, total N and P, available P and K, and exchangeable Ca and Mg increased, but soil total K and exchangeable Al decreased. Soil pH decreased by 0.5 unit in the pure tea plantation for 20 years. Soil reclamation increased the percentage of soil microaggregates (<0.25 mm), especially those with a diameter of 0.02~0.002 mm. Soil total porosity increased in the cultivated lands with the increase of soil aeration and capillary porosity. The number of soil microorganisms increased with reclamation caused mainly by the huge increase of the total amount of bacteria. With the cultivation, the activity of soil urease and acid phosphatase increased, but that of invertase dropped.     

施用钾肥和有机肥对小麦产量、品质的影响

利用布置在河北玉田县的一个钾肥定位试验,研究了在施用氮磷化肥的基础上,施用钾肥和有机肥对小麦子粒产量、17种氨基酸、粗蛋白和粗淀粉含量的影响。结果表明,施用钾肥明显提高了小麦子粒产量,同时提高了天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量;施用有机肥明显提高了蛋氨酸、赖氨酸和脯氨酸的含量;钾肥和有机肥配合施用明显提高了产量、天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量,对上述氨基酸的提高幅度均在10%以上。施用钾肥和(或)有机肥提高了小麦子粒的氨基酸总量、粗蛋白含量,但降低了粗淀粉含量。     

Erosion rates and nutrient losses affected by composted cattle manure application in vineyard soils of NE Spain

Land preparation for mechanisation in vineyards of the Anoia–Alt Penedès region, NE Spain, has required major soil movements, which has enormous environmental implications not only due to changes in the landscape morphology but also due to soil degradation. The resulting cultivated soils are very poor in organic matter and highly susceptible to erosion, which reduces the possibilities of water intake as most of the rain is lost as runoff. In order to improve soil conditions, the application of organic wastes has been generalised in the area, not only before plantation but also every 3–4 years at rates of 30–50 Mg ha^− 1 mixed in the upper 30 cm.These organic materials are important sources of nutrients (N and P) and other elements, which could reduce further fertilisation cost. However, due to the high susceptibility to sealing of these soils, erosion rates are relatively high, so a higher nutrient concentration on the soil surface increases non-point pollution sources due to runoff.The aim of this study is to analyse the influence of applied composted cattle manure on infiltration, runoff and soil losses and on nutrients transported by runoff in vineyards of the Alt Penedès–Anoia region, NE Spain. In the two plots selected for the analysis, composted cattle manure had been applied in alternate rows 1 year previous to the study. In each plot soil surface samples (0–25 cm) were taken and compared to those of plots without manure application. The study was carried out at laboratory scale using simulated rainfall. Infiltration rates were calculated from the difference between rainfall intensity and runoff rates, and the sediment and total nitrogen and phosphorus were measured for each simulation. In addition, the influence of compost was investigated in the field under natural rainfall conditions by analysing the nutrient concentration in runoff samples collected in the field (in the same plots) after seven rainfall events, which amount different total precipitation and had different erosive character.Compost application increases infiltration rates by up to 26% and also increases the time when runoff starts. Sediment concentration in runoff was lower in treated (13.4 on average mg L^− 1) than in untreated soils (ranging from 16.8 to 23.4 mg L^− 1). However, the higher nutrient concentration in soils produces a higher mobilisation of N (7–17 mg L^− 1 in untreated soils and 20–26 mg L^− 1 in treated soils) and P (6–7 mg L^− 1 in untreated soils and 13–19 mg L^− 1 in treated soils). A major part of the P mobilised was attached to soil particles (about 90% on average) and only 10% was dissolved. Under natural conditions, higher nutrient concentrations were always recorded in treated vs. untreated soils in both plots, and the total amount of N and P mobilised by runoff was higher in treated soils, although without significant differences. Nutrient concentrations in runoff depend on rainfall erosivity but the average value in treated soils was twice that in untreated soils for both plots.     

Erosion rates and nutrient losses affected by composted cattle manure application in vineyard soils of NE Spain

Land preparation for mechanisation in vineyards of the Anoia–Alt Penedès region, NE Spain, has required major soil movements, which has enormous environmental implications not only due to changes in the landscape morphology but also due to soil degradation. The resulting cultivated soils are very poor in organic matter and highly susceptible to erosion, which reduces the possibilities of water intake as most of the rain is lost as runoff. In order to improve soil conditions, the application of organic wastes has been generalised in the area, not only before plantation but also every 3–4 years at rates of 30–50 Mg ha^− 1 mixed in the upper 30 cm.These organic materials are important sources of nutrients (N and P) and other elements, which could reduce further fertilisation cost. However, due to the high susceptibility to sealing of these soils, erosion rates are relatively high, so a higher nutrient concentration on the soil surface increases non-point pollution sources due to runoff.The aim of this study is to analyse the influence of applied composted cattle manure on infiltration, runoff and soil losses and on nutrients transported by runoff in vineyards of the Alt Penedès–Anoia region, NE Spain. In the two plots selected for the analysis, composted cattle manure had been applied in alternate rows 1 year previous to the study. In each plot soil surface samples (0–25 cm) were taken and compared to those of plots without manure application. The study was carried out at laboratory scale using simulated rainfall. Infiltration rates were calculated from the difference between rainfall intensity and runoff rates, and the sediment and total nitrogen and phosphorus were measured for each simulation. In addition, the influence of compost was investigated in the field under natural rainfall conditions by analysing the nutrient concentration in runoff samples collected in the field (in the same plots) after seven rainfall events, which amount different total precipitation and had different erosive character.Compost application increases infiltration rates by up to 26% and also increases the time when runoff starts. Sediment concentration in runoff was lower in treated (13.4 on average mg L^− 1) than in untreated soils (ranging from 16.8 to 23.4 mg L^− 1). However, the higher nutrient concentration in soils produces a higher mobilisation of N (7–17 mg L^− 1 in untreated soils and 20–26 mg L^− 1 in treated soils) and P (6–7 mg L^− 1 in untreated soils and 13–19 mg L^− 1 in treated soils). A major part of the P mobilised was attached to soil particles (about 90% on average) and only 10% was dissolved. Under natural conditions, higher nutrient concentrations were always recorded in treated vs. untreated soils in both plots, and the total amount of N and P mobilised by runoff was higher in treated soils, although without significant differences. Nutrient concentrations in runoff depend on rainfall erosivity but the average value in treated soils was twice that in untreated soils for both plots.     

铵、钾同时存在时, 土壤对铵的优先吸附

The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studied. The results showed that the water stability of soil aggregates declined with increasing size, especially for the low organic matter soils. Organic matter plays a key role in the formation of water-stable soil aggregates. The larger the soil aggregate size, the greater the impact of organic matter on the water stability of soil aggregates. Removal of organic matter markedly disintegrated the large water-stable aggregates (> 2.0 mm) and increased the small ones (< 0.25-0.5mm) to some extent, whereas removal of free iron(aluminium) oxides considerably destroyed aggregates of all sizes, especially the < 0.25-0.5 mm classes. The contents of organic matter in water-stable aggregates increased with aggregate sizes. It is concluded from this study that small water-stable aggregates (< 0.25-0.5 mm) were chiefly cemented by Fe and Al oxides whilst the large ones (> 2.0 mm) were mainly glued up by organic matter. Both free oxides and organic matter contribute to the formation and water stability of aggregates in red soils.     

长期施肥黑土微生物区系及功能多样性的变化

Black soil （Mollisol） is one of the main soil types in northeastern China. Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis （PCR-DGGE） methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin, Heilongjiang Province. Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer＋manure treatments. The metabolic ability of the bacterial community in the manure treatment was similar to the control. DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments, suggesting that microorganisms with those bands were stable and not influenced by fertilization. However, chemical fertilizer increased the diversity of soil bacterial community. Principal com- ponent analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments, suggesting that the application of manure increased the soil microbial population, but had no effect on the bacterial community structure. Catabolic function was similar in the chemical fertilizer and chemical fertilizer＋manure treatments, but the composition structure of the soil microbes differed between them. The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.     

Bacterial communities in paddy soils changed by milk vetch as green manure: A study conducted across six provinces in South China

The use of green manures contributes to sustainable soil and nutrient management in agriculture; however, the responses of soil microbial communities to different fertilization regimes at the regional scale are uncertain. A study was undertaken across multiple sites and years in Hunan, Jiangxi, Anhui, Henan, Hubei, and Fujian provinces of South China to investigate the effects of green manuring on the structure and function of soil bacterial communities in rice-green manure cropping systems. The study included four treatments:winter fallow with no chemical fertilizer as a control (NF), milk vetch as green manure without chemical fertilizer (GM), winter fallow and chemical fertilizer (CF), and a combination of chemical fertilizer and milk vetch (GMCF). Significant differences were found in the responses of soil microbial communities at different sites, with sampling sites explaining 72.33% (F=36.59, P=0.001) of the community composition variation. The bacterial communities in the soils from Anhui, Henan, and Hubei were broadly similar, while those from Hunan were distinctly different from other locations. The analysis of Weighted UniFrac distances showed that milk vetch changed soil microbial communities compared with winter fallow. Proteobacteria and Chloroflexi predominated in these paddy soils; however, the application of green manures increased the relative abundance of Actinobacteria. There was evidence showing that the functional microbes which play important roles in the cycling of soil carbon, nitrogen (N), and sulfur (S) changed after several years of milk vetch utilization (linear discriminant analysis score > 2). The abundance of methane-oxidizing bacteria and S-reducing bacteria increased, and microbes involved in N fixation, nitrification, and denitrification also increased in some provinces. We concluded that the application of milk vetch changed the bacterial community structure and affected the functional groups related to nutrient transformation in soils at a regional scale.     

Carbon mineralization in soils of different textures as affected by water-soluble organic carbon extracted from composted dairy manure

The water-soluble organic C in composted manure contains a portion of labile C which can stimulate soil microbial activity. The objective of this experiment was to evaluate the effects of water-soluble organic C extracted from composted dairy manure on C mineralization in soil with different textures. Three soils with textures varying from 3 to 54% clay were amended with 0 to 80 mg water-soluble organic C kg^–1 soil extracted from a composted dairy manure and incubated for 16 weeks at 23°C. The total amount of C mineralized was greater than the amount of C added in the three soils. Differences in mineralizable C with and without added water-soluble organic C were approximately 13–16 times, 4.8–8 times, and 7.5–8 times greater than the amount of C added to clay, loam, and sand soils, respectively. The results of this experiment suggest that immediately following composted manure applications, C mineralization rates increase, and that most of the C mineralized comes mainly from the indigenous soil organic C pool.CLBRR contribution No. 94-71     

长期施肥对红壤不同形态碳的影响

长期定位施肥对红壤不同形态有效碳的影响试验研究结果表明,与对照相比,长期施肥后红壤不同形态有效碳均有不同程度提高,且全C、矿化碳的变化为厩肥>绿肥>稻草秸秆肥>本田还田>对照,易氧化碳、C库管理指数(CPMI)、C素有效率的变化为绿肥>稻草秸秆肥>厩肥>本田还田>对照,微生物生物量C变化为绿肥>厩肥>稻草秸秆肥>本田还田>对照,绿肥和稻草秸秆肥可有效改善土壤肥力及理化性状。C库管理指数与土壤养分因子量相关或极相关关系,反映了农业生产措施对土壤C库的影响,可运用其评估土壤C库的变化。     

Accumulation and availability of copper in citrus grove soils as affected by fungicide application

Purpose  

Copper is a trace element of environmental concern. Repeated applications of Cu-containing fungicides have resulted in a large scale of Cu contamination in agricultural soils. However, limited information is available regarding Cu accumulation and availability in soils under citrus production in the Indian River Area, South Florida, which has received increasing amounts of Cu fungicides to control canker and other diseases. The purpose of this study was to investigate Cu transformation, availability, and mobility in soils as affected by external Cu loading and soil properties.     

Glycosidases in soils as affected by cropping systems

Glycosidases are a group of soil enzymes that play a major role in degradation of carbohydrates. This study was conducted to assess the impact of crop rotation and N fertilization on the activities of α‐ and β‐glucosidases and α‐ and β‐galactosidases in plots of two long‐term field experiments at the Clarion‐Webster Research Center (CWRC) and Northeast Research Center (NERC) in Iowa. Surface‐soil (0–15 cm) samples were taken in 1996 and 1997 in corn (Zea mays L.), soybean (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) plots that received 0 or 180 kg N ha^–1, applied as urea before corn, and an annual application of 20 kg P ha^–1 and 56 kg K ha^–1. Activities of the four glycosidases were significantly affected by crop rotations in both years at the two sites but not by nitrogen application. In general, higher activities were observed in plots under meadow or oat and the lowest in continuous corn (CWRC) and soybean (NERC). Four‐year rotation showed the highest activity, followed by 2‐year rotation and monocropping systems. Linear‐regression analyses indicated that, in general, the activities of the glycosidases were significantly correlated with microbial‐biomass C (r > 0.302, p ≤ 0.05) and microbial‐biomass N (r > 0.321, p ≤ 0.05), organic‐C (r > 0.332, p ≤ 0.05) and organic‐N (r > 0.399, p ≤ 0.01) contents of the soils. Results of this work suggest that multicropping stimulated the activities of the glycosidases. The specific activities of the glycosidases in soils of the two sites studied, expressed as g p‐nitrophenol released per kg of organic C, differed among the four enzymes. The lowest values were obtained for β‐galactosidase and α‐glucosidase, followed by α‐galactosidase and β‐glucosidase.     

中国亚热带红壤团聚体稳定性与土壤化学性质的关系

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates, especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm. In addition, aggregate stability was positively and often significantly correlated with Fe_d, Al_d, Fe_o and clay content, but significantly and negatively correlated to SOC.     

长期有机无机肥配施对土壤水稳性团聚体酶活性的影响

The activities of invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase in different fractions of waterstable aggregates (WSA) were examined in long-term (26 years) fertilised soils. The long-term application of organic manure (OM) with chemical fertiliser (CF) significantly increased macroaggregate and decreased microaggregate percentages, enhanced the mean weight diameter, and significantly increased soil total carbon (TC) and total nitrogen (TN) contents of WSA in different size fractions. Combined fertilisation with OM and CF also increased invertase, protease, urease, acid phosphomonoesterase, dehydrogenase, and catalase activities of WSA in different size fractions. Enzyme activities were higher in macroaggregates than in microaggregates. The distribution of enzyme activities generally followed the distribution of TC and TN in WSA. The geometric mean of the enzyme activities in different WSA of OM-treated soils was significantly higher than that in soils treated with 100% CF or no fertiliser. The results indicated that the long-term combined application of OM with CF increased the aggregate stability and enzyme activity of different WSA sizes, and consequently, improved soil physical structure and increased soil microbial activity.     

有机无机肥配施对红壤旱地花生生理特性、产量及品质的影响

采用大田试验,研究了有机肥和化肥配合施用对红壤区花生产量、品质及生理特性的影响。结果表明:(1)有机无机肥配施显著影响了花生生理特性,随着有机肥比例的增加,叶片净光合速率(Pn)、气孔导度(Gs)、叶绿素含量Chl(a+b)、超氧化物歧化酶(SOD)、过氧化物酶(POD)等先增加后减少,配施35%和50%有机肥处理显著高于其他处理(p0.05)。(2)有机无机肥配施显著影响花生植株营养生长和产量,有机肥比例越高,植株性状越优良,有机肥比例为65%时,花生在成熟期主茎高、侧枝长较常规施肥分别提高8.01 cm和11.20 cm;而有机肥比例为35%时,荚果产量、籽仁产量、单株结果数及百粒重效果增加最明显,分别较常规施肥提高20.14%、26.92%、27.87%和7.08%。(3)有机无机肥配施对提升花生品质作用明显,配施35%处理的花生籽仁脂肪、蛋白质、可溶性糖含量分别较常规施肥提高3.58%、5.03%及12.16%。总之,在等量N、P、K养分条件下,配施35%~50%猪粪N更有利于红壤地区花生产量、品质及生理特性的改善。     

CH4 oxidation in two temperate arable soils as affected by nitrate and ammonium application

The short-term effect of NaNO₃ or (NH₄)₂SO₄ application on CH₄ oxidation was measured under laboratory conditions with sieved soils collected from the top layer (0–12 cm) of a loamy and a sandy soil. The soils were incubated in sealed flasks and the CH₄ and CO₂ concentrations in headspace were measured periodically. On each gas sampling date the soils were analysed for inorganic N, electro-ultrafiltration organic N, and pH. NH ₄ ⁺ application to the loamy soil inhibited CH₄ oxidation entirely whereas in the untreated control soils CH₄ concentration decreased linearly with a rate of-41 nl CH₄ l^-1 h^-1; NO ₃ ^sup- application to this soil caused a small but significant reduction in CH₄ uptake. The CH₄-oxidizing ability of the sandy soil was low, even in the control. This was mainly a result of the disturbed soil structure after sieving. Both NH ₄ ⁺ and NO ₃ ^sup- treatments completely inhibited CH₄ uptake in this ligh-textured soil. The adverse impact of NH ₄ ⁺ persisted during the entire incubation, although in the loamy soil only 17% of the NH ₄ ⁺ added was recovered after 168 h. The negative effect of NO ₃ ^sup- was probably caused by an increase in osmotic potential. Immediate inhibition of CH₄ oxidation after inorganic N addition was demonstrated in two arable soils, although the effect was directly related only in part to soil N transformations.     

连续施用鸽粪对菜心产量及重金属含量的影响

为提高饲料报酬,养殖业普遍使用微量元素添加剂,致使禽畜粪中重金属残留较高。根据养殖场鸽粪含氮量计算其用量,进行连续4茬菜心施用鸽粪田间试验,探讨其对菜心产量及重金属含量的影响。结果表明,与单施无机肥处理相比,鸽粪单施或与无机肥配施处理均降低第1茬和第3茬菜心产量,显著提高第2茬产量,对第4茬产量则影响不大。各施用鸽粪处理4茬菜心总产量比单施无机肥处理提高4．5％～17．4％。同时,施用鸽粪对菜心不同重金属含量影响不一。与单施无机肥处理相比,施用鸽粪处理提高了菜心As、Cu和Zn含量,降低了Pb、Cr和Cd含量。且菜心As和Pb含量随鸽粪施用茬数的增加而提高,Cd含量则显著下降,不同茬别间Cr、Cu、Zn平均含量则未表现出明显规律。建议在无公害或绿色农产品生产中避免一次性大量施用或连续施用养殖场禽畜粪肥。