首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
Soil surface evaporation processes under mulches of different sized gravel   总被引：1，自引：0，他引：1  
To reduce water loss from soil surface evaporation is important in agricultural and environmental practices, especially in arid and semi-arid regions. Gravel mulch has long been practiced to reduce soil surface evaporation. In this study, a series of simulation experiments were conducted to study the effects of gravel mulches of different sizes on evaporation process from soil surface. Four mulch treatment levels were used: diameter 0.5 cm (A), diameter 2.5 cm (B), diameter 4.5 cm (C), and bare soil (CK), with three replicates. It was found that the gravel mulches dramatically reduced the evaporation from bare soil surface, particularly when soil water contents were at high levels. Under the same soil water content, the evaporation reduction rates under gravel mulches were negatively correlated with gravel sizes. The evaporation processes under gravel mulches were much more stable as compared with that from bare soil surface. The ratio of the soil surface evaporation to the atmospheric evaporation (Ess/Esa) and soil water contents with no mulch decreased rapidly with time. Soil water contents decreased slowly with time under mulches while the Ess/Esa values maintained at the more or less stable levels. During the successive evaporation process of 41 days, the cumulative soil surface evaporation under mulches was linearly correlated with time but that from bare soil surface was logarithmically correlated with time.  相似文献   

2.
Mulching the soil surface with a layer of plant residue is considered an effective method of conserving water and soil because it increases water infiltration into the soil, reduces surface runoff and the soil erosion, and reduces flow velocity and the sediment carrying capacity of overland flow. However, application of plant residues increases operational costs and so optimal levels of mulch in order to prevent soil and/or water losses should be used according to the soil type and rainfall and slope conditions. In this study, the effect of wheat straw mulch rate on the total runoff and total soil losses from 60-mm simulated rainstorms was assessed for two intensive rainfalls (90 and 180 mm h−1) on three slope gradients typical conditions on the Loess Plateau of China and elsewhere. For short slopes (1 m), the optimal mulch rate to save water for a silt loam and a loam soil was 0.4 kg m−2. However, for a clay loam soil the mulch rate of 0.4 kg m−2 would be optimal only under the 90 mm h−1 rainfall; 0.8 kg m−2 was required for the 180 mm h−1. In order to save soil, a mulch rate of 0.2 kg m−2 on the silt loam slopes prevented 60%–80% of the soil losses. For the loam soil, mulch at the rate of 0.4 kg m−2 was essential in most cases in order to reduce soil losses substantially. For the clay loam, 0.4 kg m−2 may be optimal under the 90 mm h−1 rain, but 0.8 kg m−2 may be required for the 180 mm h−1 rainstorm. These optimal values would also need to be considered alongside other factors since the mulch may have value if used elsewhere. Hence doubling the optimal mulch rate for the silt loam soil from 0.2 kg m−2 or the clay loam soil under 90 mm h−1 rainfall from 0.4 kg m−2 in order to achieve a further 10% reduction in soil loss needs to be assessed in that context. Therefore, Optimal mulch rate can be an effective approach to virtually reduce costs or to maximize the area that can be treated. Meantime, soil conservationist should be aware that levels of mulch for short slopes might not be suitable for long slopes.  相似文献   

3.
Improved information on water‐extractable soil P (Pw) and its distribution in various forms is needed to assess its bioavailability and environmental impact. This study investigated Pw in a fluvo‐aquic soil solution in relation to the continuous application of inorganic fertilizer (NPK) and wheat straw–soybean‐based compost for 15 y. Phosphatase‐hydrolysis techniques were used to fractionate organic P (Po) in water extracts of soil into phosphomonoester (Pom) and phosphodiester (Pod). In comparison with the noncomposted treatments, compost application significantly increased the levels of inorganic P (Pi) and Po. Pom was the main form in water‐extractable soil Po (71%–88%), in which sugar phosphate (Pos) occupied 48%–75%, inositol hexakisphosphate (Pop) comprised 13%–23%, and Pod only accounted for a small percentage (11%–26%). Long‐term compost application significantly increased the content of Pom, Pos, and Pod, but decreased the Pop content; the ratio of Pom to Po increased significantly in compost‐treated soil, but the ratio of Pop to Po and Pod to Po significantly decreased. Thus, the equilibrium of phosphatase involved P transformations shifted to Pi in compost‐treated soil. The phosphomonoesterase and phosphodiesterase activities were significantly higher in compost‐treated soil, which favored the transformations of Pod into Pom and Pom into Pi. The ratio of Po to Pw in water extracts of compost‐treated soil was similar to that of control soils with no fertilizer input (CK), but was significantly lower than in NPK treatment, which demonstrated that a larger increase occurred for soil Pi in water extracts of compost‐treated soil. Long‐term compost application in the fluvo‐aquic soil changed the composition of Pw, promoted the rate of P transformations in soil solution, and significantly increased soil P bioavailability.  相似文献   

4.
Changes in soil properties and yield response in relation to tillage and residue management treatments in an irrigated groundnut (Arachis hypogea L.)—wheat (Triticum aestivum, L.) rotation on a sandy soil (1972–1974) and on a sandy loam soil (1974–1976) were evaluated. Tillage treatments (T1 and T2) did not cause significant changes in soil properties. Incorporation of crop residues (5 t residue per ha per crop, T3) caused a substantial increase in organic C, available N, and NaHCO3 -extractable P contents in the top 15 cm of both soils. Residue management treatments (T3, T4 and T5) showed no significant effect on soil bulk density and exchangeable K. Crop yields under no-tillage (T1) and conventional tillage (control, T2) were comparable on sandy soil but on the sandy loam soil, no-tillage yielded significantly lower than conventional tillage. Compared with the control, incorporation of crop residues (T3) caused higher yields on sandy soil for groundnut and wheat by 34.1 and 47.4%, respectively, and on sandy loam by 17.1 and 7.2%, respectively. Mulching with crop residues conserved soil moisture and reduced maximum soil temperature (1.5–5.3°C in groundnut and 1.5–2.9°C in wheat) but other measured soil properties were not significantly affected. Significant yield increase due to residue mulching (T4) was observed in sandy soil but it was significantly less than when total crop residue was incorporated (T3). Increased wheat root-weight density in the top 15 cm soil with residue mulching was not reflected in grain yield. Compared with the incorporation of the total amount of crop residue (T3), incorporation of half the amount and application of the other half as mulch (T5) caused lower yields — on sandy soil for groundnut and wheat by 31.5 and 15.7%, respectively, and on sandy loam by 4.8 and 3.6%, respectively.  相似文献   

5.
Abstract

This study was undertaken to assess the mineralization of sulfur (S) in laboratory conditions of three rice soils (Joydebpur, Faridpur, and Thakurgaon), receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), and 3) pea vine (Pisum sativum L.). The organic residue (25 mg g‐1) was added and mixed with soil and glass beads (1:1, soil to bead ratio) and placed into a Pyrex leaching tube. The soils were flooded and incubated at 35°C, after which they were leached with deionized water at 1, 2,4, 8, and 12 weeks for analysis of SO4 and other chemical properties in the leachates. Potentially mineralizable S (So) and C (Co) pools and first‐order rate constants (Ks for S and Kc for C) in soils amended with rice straw and pea vine under flooded conditions were estimated using an exponential equation. The So and Ks varied considerably among the soils and types of added organic residues, and their values in rice straw and pea vine ranged from 8.70 to 29.55 and 0.124 to 0.732 mg S kg‐1 wk‐1, respectively. Except for the Thakurgaon soil, the So and Ks values in Joydebpur and Faridpur soils were higher in the unamended treatments. Higher So values in the unamended soils were probably due to less microbial activity to mineralize organic S from organic residues. The results indicate that the amount of SO4 in flooded soils amended with organic residues are dependent on soil type, nature of organic residues, and time of incubation. The Co and Kc values under flooded incubation were higher in residue amended soils than in unamended soils. Pea vine treated soils had higher Co and Kc values than the soils treated with rice straw.  相似文献   

6.
The management of crop residues coupled with external nutrient inputs is important for improving and conserving soil fertility and productivity. We assessed the long-term effects of three wheat residue management options (RMO) (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on phosphorus (P) fractions and adsorption behavior of a Vertisol under soybean–wheat system. Wheat residue incorporation and retention improved the labile inorganic P [sodium bicarbonate (NaHCO3-Pi)] by 3.2 and 5.0 mg kg?1 and the labile organic P (NaHCO3-Po) by 2.4 and 4.2 mg kg?1, respectively, as compared to residue burning. The soils under residue incorporation and retention had 38 and 26% more moderately labile organic P [sodium hydroxide (NaOH-Po)], respectively, than the soil under residue burning. The SNI either as fertilizer or FYM further enhanced NaHCO3-Pi, NaHCO3-Po, and NaOH-Po. In contrast, less labile P fractions [hydrochloric acid (HCl)-P and residual-P] remained unaffected by RMO and SNI treatments. Residue retention or incorporation decreased P adsorption over the residue burning for all the three nutrient inputs. The P-adsorption data fitted well to the Langmuir equation (R2 ranged from 0.970 to 0.994). The P-adsorption maximum (b), bonding energy constant (k), differential P-buffering capacity (DPBC), and standard P requirement (SPR) were lower with residue incorporation or surface retention than with residue burning. The SPR followed the order residue burning > incorporation > retention for RMOs and control > fertilizer > FYM for SNI treatments. The NaHCO3-Pi, NaHCO3-P0, and NaOH-Po had negative correlation with P-adsorption parameters and showed positive correlation with soybean P uptake. Wheat residue incorporation or retention plus FYM could be an effective strategy for enhancing the P fertility of Vertisols under a soybean–wheat system.  相似文献   

7.
  相似文献   

8.
Abstract

A Typic Ustochrept sandy loam was dried under constant evaporation (Eo) of 4, 8, and 16 mm/day. The soil dried more uniformly with depth under lower than under higher Eo. Downward movement of isohydral fronts could be adequately described by equations of the type, D = a + b t0.5 (where ‘D’ is the depth of isohydral front in cm, Y is the drying time in days and ‘a’ and ‘b’ are constants). Rates of their advance were influenced by the Eo and water content of the front. Higher Eo caused earlier deviation of the cumulative evaporation (CE) from the cumulative Eo. Equations of the type, CE = m tn (where ‘t’ is the drying time in days and ‘m’ and ‘n’ are constants), gave an excellent fit for all the three Eo's. Falling‐rate stage evaporation rates were sensitive to Eo during its earlier stages.  相似文献   

9.
Two soils, one a sandy loam and the other of relatively high clay content, were incubated with [14C(U)]gtucose and [15N](NH4)2SO4 for 101 days, either under continuously moist conditions, or with intermittent drying of soils. Rates of evolution of 14CO2, decline in residual organic 14C, and net immobilization and mineralization of N and 15N in the sandy loam soil were more rapid than in the clay soil. First order decay rates for the decomposition of residual 14C, after 10 days, were consistently twice as fast in the sandy loam soil. By contrast, the efficiency with which glucose was utilized within the first few days, and the amounts of C, 14C, N and 15N present as soil biomass throughout the incubation, were greater in the clay soil than in the sandy loam. Biomass 14C as a percentage of residual organic 14C, was consistently 1.5 times greater in the clay soil. Compared with soils held continuously moist, soils which were intermittently dried and remoistened contained smaller amounts of isotope-labelled biomass C and N, but overall similar amounts of total residual organic 14C and 15N. Remoistening of dried soils caused a temporary (4 days) flush in C and N mineralization rates.A simulation model describes C and N behaviour in the two soils. Three features of the model are proposed to expain short-term differences between soils in the rates of C and N turnover, viz. the clay soil (a) has a greater capacity to preserve biomass C and N (b) holds a higher proportion of microbial decay products in the near vicinity of surviving cells, and, to a lesser extent, (c) utilizes glucose and metabolic products more efficiently for biosynthetic reactions.  相似文献   

10.
The concern for groundwater pollution by agrichemicals through solute movement within the soil is widespread. Zeolite is a type of soil amendment that is utilized to improve physical properties of soil and ameliorate polluted soil. The high negative charge of the zeolite and its open space structure allows adsorption and access of heavy metals and other cations and anions. The objectives of this research were (i) to determine the effects of different application rates of zeolite (0, 2, 4, and 8 g kg?1) on the immobile water content and mass exchange coefficient in a loam soil and then (ii) to determine the effects of optimum application rate of zeolite on the immobile water content and mass exchange coefficient of sandy loam and clay loam soils in saturated conditions by a mobile and immobile (MIM) model. In a disturbed soil column, a method was proposed for determination of MIM model parameters, that is, immobile water content (θim), mass exchange coefficient (α), and hydrodynamic dispersion coefficient (Dh). Breakthrough curves were obtained for different soil textures with different zeolite applications in three replicates, by miscible displacement of chloride (Cl?1) in disturbed soil column. Cl?1 breakthrough curves were evaluated in terms of the MIM model. The results showed that the pore water velocity calculated based on the total soil volumetric water content (θim+ θm) and real pore water velocity calculated based on the mobile water content (θm) increased in the loam soil with an increase in zeolite application rate, so that, between these different rates of zeolite application, the maximum value of pore water velocity and real pore water velocity occurred at zeolite application rates of 8.6 and 11.5 g kg?1, which are indicated as the optimum application rates. However, the comparison between different soils showed that the zeolite application rate of 8 g kg?1 could increase pore water velocity of sandy loam and loam soils by 31% more than that of clay loam soil. The immobile water content and mass exchange coefficient of loam soil were correlated with the zeolite application rate and reduced with an increase in the rate of applied zeolite. In a comparison between different soils at zeolite application rate of 8 g kg?1, the immobile water contents of the zeolite-treated soil decreased by 57%, 60%, and 39% on sandy loam, loam, and clay loam soils, respectively, compared with the untreated soil. Furthermore, zeolite application could reduce mass exchange coefficient by 9%, 43%, and 21% on sandy loam, loam, and clay loam soils, respectively. A positive linear relationship was found between θim and α. Zeolite application increased real pore water velocity of sandy loam soil by 39% and 46% compared with loam and clay loam soils, respectively. In other studies there was a decrease in ammonium and nitrate leaching due to the zeolite application, and therefore, an increase in real pore water velocity due to zeolite application in sandy loam soil, as compared with the loam and clay loam soils, may not show more rapid movement of solute and agrichemicals to the groundwater.  相似文献   

11.
Crop residue mulch reduces evaporation, but residue production by dryland crops may be inadequate to reduce evaporation effectively. An alternative material is waste paper for which disposal on agricultural land is being considered. A laboratory study compared evaporation from soil with paper-pellet or crop-residue mulch in two trials, each conducted for 21 days. In Trial I, small (4.8-mm diameter) and large (9.5-mm diameter) waste-paper pellets provided full cover or half that amount (on a weight basis). Large pellets at full cover reduced evaporation more than other treatments during most of the trial. Evaporation was reduced most on Day 4 when it was 0.52 of that with bare soil. Both half-cover treatments resulted in similar evaporation. At full cover, evaporation tended to be greater with small than with large pellets. In Trial II, evaporation with small and large pellets at full cover, wheat (Triticum aestivum L.) straw at 0.60 kg m?2, grain sorghum [Sorghum bicolor (L.) Moench] stover at 1.20 kg m?2, and bare soil were compared. Except with small pellets after Day 11, evaporation was significantly lower with mulch than with bare soil. Evaporation tended to be greater with small than with large pellets, similar for large pellets and wheat straw, and lower with sorghum than with other treatments on most days. Maximum evaporation reduction occurred on Day 1 with sorghum stover when it was 0.28 of that with bare soil. Use of paper-pellet mulch can reduce evaporation and thus increase water conservation. Technology improvements underway should make paper-pellet use on cropland practical. Waste paper use on cropland will require close attention to soil nutrient relations.  相似文献   

12.
Effect of tillage and residue management on enzyme activities in soils   总被引：14，自引：3，他引：14  
Recent interest in soil tillage and residue management has focused on low-input sustainable agriculture. In this study we investigated the effect of three tillage systems (no-till, chisel plow, and moldboard plow) and four residue placements (bare, normal, mulch, and double mulch) on the activities of four amidohydrolases (amidase, L-asparaginase, L-glutaminase, and urease) in soils from four replicated field-plots. Correlation coefficients (r) for linear regressions between the activities of each of the enzymes and organic C or pH and between all possible paired amidohydrolases were also calculated. The results showed that the effects of tillage and residue management on pH in the 28 surface soil (0–15 cm) samples were not significant. The organic C content, however, was affected significantly by the different tillage and residue-management practices studied, being the greatest in soils with notill/double mulch treatment, and the least with no-till/bare and moldboard/normal treatments. Within the same tillage system, mulch treatment resulted in greater organic C content compared with normal or bare treatment. The activities of the amidohydrolases studied were generally greater in mulch-treated plots than in non-treated plots, and were significantly correlated with organic C contents of soils, with r values ranging from 0.70*** to 0.90***. Linear regression analyses of enzyme activities on pH values (in 0.01 M CaCl2) of the 28 surface soils showed significant correlations for L-asparaginase, L-glutaminase, and urease, with r values of 0.74***, 0.77***, and 0.72***, respectively, but not for amidase (r=0.24). The activities of the four amidohydrolases studied in the 40 soil samples tested were significantly intercorrelated, with r values ranging from 0.72*** to 0.92***. The activities of the four amidohydrolases decreased with increasing soil depth of the plow layer, and were accompanied by a decrease in organic C content.  相似文献   

13.
潜水蒸发条件下不同质地剖面的土壤水盐运动   总被引：13，自引：6，他引：13       下载免费PDF全文
刘福汉  王遵亲 《土壤学报》1993,30(2):173-181
  相似文献   

14.
Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO2) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine the influence of calcium carbonate (CaCO3) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to obtain an electrical conductivity (EC) of 1.0 dS?m?1 in a 1:5 soil/water extract. Powdered CaCO3 at rates of 0%, 0.5%, 1.0%, 2.5%, 5.0% and 10.0% (w/w) and 0.25-2 mm mature wheat residue at 0% and 2% (w/w) were then added. Cumulative CO2-C emission from the salt amended and unamended soils was not affected by CaCO3 addition. To investigate the effect of EC on microbial activity, soil respiration was measured after amending a sandy loam (18.8% clay) and a silt loam (22.5% clay) with varying amount of NaCl to obtain an EC1:5 of 1.0–8.0 dS?m?1 and 2.5 g glucose C?kg?1 soil. Soil respiration was reduced by more than 50% at EC1:5?≥?5.0 dS?m?1. In a further experiment, salinity up to an EC1:5 of 5.0 dS?m?1 was developed in the silt loam with NaCl or CaCl2. No differences in respiration at a given EC were obtained between the two salts, indicating that Na and Ca did not differ in toxicity to microbial activity. The effect of different addition rates (0.25–2.0%) of mature wheat residue on the response of respiration to salinity was investigated by adding NaCl to the silt loam to obtain an EC1:5 of 2.0 and 4.0 dS?m?1. The clearest difference between salinity levels was with 2% residue rate. At a given salinity level, the modelled decomposition constant ‘k’ increased with increasing residue addition rate up to 1% and then remained constant. Particulate organic carbon left after decomposition from the added wheat residues was negatively correlated with cumulative respiration but positively correlated with EC. Inorganic N (NH 4 + -N and NO 3 ? -N) and resin P significantly decreased with increasing salinity. Resin P was significantly decreased by addition of CaCl2 and CaCO3.  相似文献   

15.
Abstract

The Cushman and Barber mechanistic model was used to help elucidate the mechanisms that govern the uptake of sulfur (S) by plants. Sulfur uptake predicted by the model was compared to measured S uptake by cotton, (Gossypium hirsutum [L]) grown on Mhoon silty clay loam (Typic Fluvaquent) and a Norwood silt loam (Typic Udifluvent) under glasshouse conditions. Predicted S uptake was significantly correlated with observed uptake r2=0.71. However, the model overpredicted S uptake by a factor of 3.5. The assumption that the maximun ion Influx rate (I max) for roots growing in soils is the same as the Imax measured in solution cultures experiments may not be appropriate. Better agreement between observed and predicted S uptake values was achieved by using an estimated Imax obtained from soil studies (Is) with the method of Warncke and Barber. Using I, predicted vs observed S uptake had a slope of 1.00 and r2=0.93. The model predicted that S concentration in soil solution (Clo) at the root surface (ro) increased with time for soils with initial S concentration in solution of lmM or higher. This high Clo, will trigger a higher Is of about 4 nmol/m2sec, while plants grown on soils with low S content will show a lower Is, suggesting that S uptake by cotton plants is biphasic and depends on Clo at ro.  相似文献   

16.
Background : Potassium (K) availability in soil and plant uptake is restrained by the dynamic interactions among the different pools of K. Aims : To understand these interactions, a study was undertaken to assess the quantity–intensity (Q/I) and buffering characteristics of rainfed maize (Zea mays L.) growing soils. Ten contrasting soils were evaluated for K partitioning changes in exchangeable K (ΔEK) and non‐exchangeable K (ΔNEK) pools in the soil‐solution phase and buffering characteristics using a modified version of Q/I approach. Results : The partitioned Q/I isotherms showed strong adsorption with the increase in K concentration ratio (CRK) and the changes due to ΔEK were higher than changes due to ΔNEK. Total buffering capacity (PBCK) significantly correlated (r = 0.92, p <0.01) with clay content with a major share contributed by buffering capacity owing to non‐exchangeable K ( PBC Δ NEK K ) rather than exchangeable K ( PBC Δ EK K ). The fixation capacity (β) factor, the magnitude of added K converted into a non‐exchangeable pool, ranged from 41 to 63%, whereas release (α) factor, the magnitude of added K converted to the exchangeable pool, ranged from 19 to 36%. Both threshold solution K (CKr) and threshold exchangeable K (EKr) values were found to be high in Satran clay loam (S2) and lower in Doon silty clay loam (S3) soils. The equilibrium exchangeable K (EKo) was found close to minimum exchangeable K (Emin) in Doon silty clay loam (S3) and Babaweyl sandy clay loam (S1) soils and overall Emin constituted about 8.94 to 0.57% of the EKo. Conclusion : It may be concluded that K Q/I isotherm partitioning provides a valuable insight to assess the dynamic relations. The ratio of α/β (K recharge index) could be used to evaluate the K enrichment capacity of soil to K additions while EKr and Emin can be potentially useful in the elucidation of exchangeable K as K fertility index especially in soils with poor K fertilizer management.  相似文献   

17.

Parameters known to influence mercury (Hg) release from soils include substrate and air Hg concentration, light, atmospheric oxidants, temperature, and soil moisture. However, for low Hg-containing soils, the influence of these parameters has been shown to vary across space and time. Here, we expand upon previous work by investigating whether soil–water evaporative loss, which integrates the influence of multiple parameters, could be applied for predicting Hg flux from soil with low Hg concentrations when bare and planted. To investigate our hypothesis, Hg flux was measured from three soil types (<100 ng Hg g?1). When these soils were saturated, flux was suppressed. Soil moisture evaporative stage was used to partition the parameters most important for controlling Hg flux as the soils dried. Classification and regression tree (CART) analyses showed that soil moisture was the most important parameter predicting Hg flux. Results also showed an important predictor for Hg flux was whether actual evaporation (E a) was equal to potential evaporation (E p) or E a < E p. Depending on evaporative stage, the parameters with the next highest correlation to Hg flux were light, temperature, and soil moisture evaporation rate. The presence of vegetation also influenced flux with lower Hg flux when the plants were transpiring. Results indicate for those developing models that estimate Hg flux from low Hg-containing soils, soil moisture and evaporative stage are useful tools for predicting flux.

  相似文献   

18.
The efficacy of applying plant residues to agricultural soils as a carbon (C) source for microorganisms and C sequestration is dependent on soil physiochemical properties, which can be improved by aggregation using soil conditioners. However, no attempt has been made to assess the effects of soil conditioners such as biochar (BC), biopolymer (BP) or polyacrylamide (PAM) on plant residue decomposition. We assessed the effects of BC, synthesized BP and anionic PAM on the decomposition of 14C‐labelled maize residues and on their stabilization in aggregate fractions in sandy and sandy loam soils. Polyacrylamide and BP were applied at 400 kg ha?1 and BC was applied at 5000 kg ha?1, and the soils were incubated for 80 days at 22°C. The conditioners improved the physical and biological properties of both soils, as shown by a 24% increase in the 1–2 mm aggregates. Biochar and BP accelerated the decomposition of plant residues as indicated by 14CO2 efflux, and resulted in reduced stabilization of residues in both soils relative to that observed in the control and PAM treatments. The reduction in 14C incorporation and C stabilization in the BC‐ and BP‐treated soils was observed mainly in the < 0.25‐mm aggregates. This was confirmed by reduction of activity of hydrolytic enzymes (β‐cellobiosidase and β‐glucosidase). Decomposition of plant residues in sandy soil was more sensitive to BP and PAM application than that in sandy loam soil. Improved soil structure after applying BC and BP increased aeration and decreased the contact between plant residues and mineral soil particles and consequently accelerated plant residue decomposition and reduced C sequestration.  相似文献   

19.
Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha?1 in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton (Gossypium hirsutum L.) residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO2) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level.  相似文献   

20.
Soil degradation affects soil properties such as structure, water retention, porosity, electrical conductivity (EC), sodium adsorption ratio (SAR), and soil flora and fauna. This study was conducted to evaluate the response of contrasting textured soils irrigated with water having different EC:SAR ratios along with amendments: gypsum (G), farm manure (FM), and mulch (M). Water of different qualities viz. EC 0.6 + SAR 6, EC 1.0 + SAR 12, EC 2.0 + SAR 18, and EC 4.0 + SAR 30 was used in different textured soils with G at 100% soil gypsum requirement, FM at 10 Mg ha?1, and M as wheat straw was added on surface soil at 10 Mg ha?1. Results revealed that the applied amendments in soils significantly decreased pHs and electrical conductivity (ECe) of saturated paste and SAR. Four pore volumes of applied water with leaching fraction 0.75, 0.77, and 0.78 removed salts 3008, 4965, and 5048 kg ha?1 in loamy sand, silty clay loam, and sandy clay loam soils, respectively. First four irrigations with LF of 0.82, 0.79, 0.75, and 0.71, removed 5682, 5000, 3967, and 2941 kg ha?1 salts, respectively. The decreasing order for salt removal with amendments was FM > G > M > C with LF = 0.85, 0.84, 0.71, and 0.68, respectively. This study highlights a potential role of soil textures to initiate any mega program for reclamation of saline-sodic soils in the perspective of national development strategies.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号