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 859 毫秒
1.
Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO2 emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha−1 in OF and 54·4 Mg ha−1 in CT; and the total nitrogen (TN) stock was 7·1 Mg ha−1 and 5·8 Mg ha−1 for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
Soil organic carbon (SOC) pools are important for maintaining soil productivity and reducing the net CO2 loading of the atmosphere. An 18‐year old long‐term field experiment involving pearl millet‐cluster bean‐castor sequence was conducted on an Entisol in western India to examine the effects of chemical fertilizers and manuring on carbon pools in relation to crop productivity and C sequestration. The data showed that even the addition of 33.5 Mg ha−1 C inputs through crop residues as well as farm yard manure could not compensate the SOC depletion by oxidation and resulted in the net loss of 4.4 Mg C ha−1 in 18 years. The loss of SOC stock in the control was 12 Mg C ha−1. Conjunctive use of chemical fertilizers along with farm yard manure produced higher agronomic yields and reduced the rate of SOC depletion. The higher average seed yields of pearl millet (809 kg ha−1), cluster bean (576), and castor (827) over six cropping seasons were obtained through integrated use of fertilizers and manure. For every Mg increase in profile SOC stock, there was an overall increase of 0.46 Mg of crop yield, comprising increase in individual yield of pearl millet (0.17 Mg ha−1 y−1 Mg−1 SOC), cluster bean (0.14) and castor (0.15). The magnitude of SOC build up was proportional to the C inputs. Carbon pools were significantly correlated with SOC, which increased with application of organic amendments. Threshold C input of 3.3 Mg C ha−1 y−1 was needed to maintain the SOC stock even at the low antecedent level. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

3.
For a quantitative analysis of SOC dynamics it is necessary to trace the origins of the soil organic compounds and the pathways of their transformations. We used the 13C isotope to determine the incorporation of maize residues into the soil organic carbon (SOC), to trace the origin of the dissolved organic carbon (DOC), and to quantify the fraction of the maize C in the soil respiration. The maize‐derived SOC was quantified in soil samples collected to a depth of 65 cm from two plots, one ’︁continuous maize’ and the other ’︁continuous rye’ (reference site) from the long‐term field experiment ’︁Ewiger Roggen’ in Halle. This field trial was established in 1878 and was partly changed to a continuous maize cropping system in 1961. Production rates and δ13C of DOC and CO2 were determined for the Ap horizon in incubation experiments with undisturbed soil columns. After 37 years of continuous maize cropping, 15% of the total SOC in the topsoil originated from maize C. The fraction of the maize‐derived C below the ploughed horizon was only 5 to 3%. The total amount of maize C stored in the profile was 9080 kg ha−1 which was equal to about 31% of the estimated total C input via maize residues (roots and stubble). Total leaching of DOC during the incubation period of 16 weeks was 1.1 g m−2 and one third of the DOC derived from maize C. The specific DOC production rate from the maize‐derived SOC was 2.5 times higher than that from the older humus formed by C3 plants. The total CO2‐C emission for 16 weeks was 18 g m−2. Fifty‐eight percent of the soil respiration originated from maize C. The specific CO2 formation from maize‐derived SOC was 8 times higher than that from the older SOC formed by C3 plants. The ratio of DOC production to CO2‐C production was three times smaller for the young, maize‐derived SOC than for the older humus formed by C3 plants.  相似文献   

4.
This study investigated the potential for visible–near‐infrared (vis–NIR) spectroscopy to predict locally volumetric soil organic carbon (SOC) from spectra recorded from field‐moist soil cores. One hundred cores were collected from a 71‐ha arable field. The vis–NIR spectra were collected every centimetre along the side of the cores to a depth of 0.3 m. Cores were then divided into 0.1‐m increments for laboratory analysis. Reference SOC measurements were used to calibrate three partial least‐squares regression (PLSR) models for bulk density (ρb), gravimetric SOC (SOCg) and volumetric SOC (SOCv). Accurate predictions were obtained from averages of spectra from those 0.1‐m increments for SOCg (ratio of performance to inter‐quartile (RPIQ) = 5.15; root mean square error (RMSE) = 0.38%) and SOCv (RPIQ = 5.25; RMSE = 4.33 kg m?3). The PLSR model for ρb performed least well, but still produced accurate results (RPIQ = 3.76; RMSE = 0.11 Mg m?3). Predictions for ρb and SOCg were combined to compare indirect and direct predictions of SOCv. No statistical difference in accuracy between these approaches was detected, suggesting that the direct prediction of SOCv is possible. The PLSR models calibrated on the 10‐cm depth intervals were also applied to the spectra originally recorded on a 1‐cm depth increment. While a bigger bias was observed for 1‐cm than for 10‐cm predictions (1.13 and 0.19 kg m?3, respectively), the two populations of estimates were not distinguishable statistically. The study showed the potential for using vis–NIR spectroscopy on field‐moist soil cores to predict SOC at high depth resolutions (1 cm) with locally derived calibrations.  相似文献   

5.
Abstract

Profiles of semi‐arid–zone soils in Punjab, northwest India, were investigated for different forms of zinc (Zn), including total, diethylenetriamine penta‐acetic acid (DTPA)-extractable, soil solution plus exchangeable (Zn), Zn adsorbed onto inorganic sites, Zn bound by organic sites, and Zn adsorbed onto oxide surfaces. Irrespective of the different fractions of Zn present, its content was higher in fine‐textured Alfisols and Inceptisols than in coarse‐textured Entisols. In general, the higher content of Zn was observed in the surface horizon and then decreased in the subsurface horizons. However, none of the forms of Zn exhibited any consistent pattern of distribution. Organic matter and size fractions (clay and silt) had a strong influence on the distribution of different forms of Zn. Based upon the linear coefficient of correlation, the soil solution plus exchangeable Zn, adsorbed onto inorganic sites, and DTPA‐Zn increased with increase in organic carbon but decreased with increase in pH and calcium carbonate content. Total Zn increased with increase in clay and silt content. Among the different forms, Zn bound by organic sites, water soluble plus exchangeable Zn and Zn adsorb onto oxide (amorphous surfaces) were all correlated with DTPA extractable Zn. The uptake of Zn was more in recent floodplain Entisols than very fine textured Alfisols and Inceptisols. Among the different forms soil solution +exchangeable and DTPA‐extractable Zn was positively correlated with total uptake of Zn.  相似文献   

6.
Orchards have a high potential for carbon sequestration. However, little research is available on the spatial variability at catchment scale and on the difference between the tree area and the lanes. We analyzed theik spatial variability of soil organic carbon stock, SOCstock at 90 cm depth in an 8-ha catchment in Southern Spain with olives on a vertic soil. Results showed higher soil organic carbon concentration, SOC, in the tree area as compared to the lane up to 60 cm depth, but its impact on SOCstock was negligible since it was compensated by the higher soil bulk density in the lane. SOC at different depths was correlated with that in the top 0–5 cm. The overall SOCstock of the orchard was 4.14 kg m−2, ranging between 1.8 and 6.0 kg m−2. This SOCstock is in the mid-lower range of values reported for olive orchards, measured at smaller scale, and similar to those other intensive field crops and agroforestry under comparable rainfall conditions. The spatial variability in SOCstock was correlated to several geomorphological variables: elevation, cumulative upstream area, topographic wetness index, sediment transport index, and tillage erosion. Differences in SOC and SOCstock are driven by the sediment redistribution downslope, mainly by tillage erosion, and higher soil water availability in lower areas allowing higher biomass production. These topographic indexes and the correlation between SOC in the topsoil and SOCstock up to 90 cm should be further explored in other typology of olive orchards for facilitating the mapping of SOCstock.  相似文献   

7.
Topsoil samples from a long‐term fertilizer trial on a red earth rice paddy from Jiangxi Province, China, were used to investigate soil organic carbon (SOC) mineralization using aerobic incubation for 58 days at 20 °C and 25 °C. SOC mineralization rates varied between 0.62 and 0.76 mg C/g SOC/h at 20 °C, and between 0.65 and 0.97 mg C/g SOC/h at 25 °C. There was no significant correlation between the mineralization potential and SOC content in treated soil samples. However, a close correlation was found between total C mineralization and the carbon stability index. This suggests that the potential C release from the soil is controlled by C lability rather than by total SOC. The calculated Q10 quotient was negatively correlated with dithionate‐citrate‐bicarbonate‐extracted Fe. It is suggested that the free Fe‐oxyhydrates that are prevalent in red earth paddy soils provide physico‐chemical protection and control biological decomposition rates under warming and these are modified in the long‐term fertilizer treatments. The enhancement of physico‐chemical protection of labile SOC by free Fe‐oxyhydrates is a potential mechanism for soil C stabilization under warming conditions. The interaction with fertilizers in the red earth‐derived paddies of South China deserves further study.  相似文献   

8.
Studies relating macro‐ and microscopic aspects of impacts of long‐term contaminative practices on soils are scarce. We performed such an approach by assessing the fate of metal pollutants in an area close to Paris, where sandy Luvisols were irrigated for 100 years with urban waste water. As a result, these soils display strong accumulation of organic matter, dissolved salts and metal pollutants in surface horizons, but also migration of metals to depth. We examined soil development and metal distribution patterns in two irrigated soils, in comparison with a non‐irrigated reference soil. Soil macromorphological characteristics were studied in the field. Soil micromorphology and micro‐scale metal distributions were both studied in situ in thin sections, the latter by synchrotron X‐ray mapping. Microscopic study focussed on characteristic parts of the Ap and Bt horizons, mainly involved in metal retention. For Ap horizons, both large and diffuse metal concentrations were revealed, mainly associated with organic matter and dissolved components added by irrigation water. For Bt horizons, zinc accumulation was detected on clay‐iron coatings. Our results suggest that with time, a double metal‐filtering capacity has developed in these sandy Luvisols: in the Ap horizon, an anthropogenic filter resulted from input of metal pollutants together with highly reactive organic matter, carbonates and phosphates, thus favouring metal immobilization and limiting migration to depth. In the Bt horizon, the evidence is of a second, natural filter. However, this filtering capacity is endangered by clay destruction due to ferrolysis, as revealed by micromorphology. Ferrolysis, here initiated by intensive irrigation practices, leads to a reduction of the natural filtering potential and an increasing risk of metal transfer towards the groundwater.  相似文献   

9.
The impacts of tillage and cropping sequences on soil organic matter and nutrients have been frequently reported to affect the uppermost soil layers, but there is little published information concerning effects at greater depth. This article reports results on the distribution of soil organic carbon (SOC), active carbon (AC), N, Olsen‐P and extractable K within 100 cm in short (4 yr) and long (16 yr) term experiments under different tillage systems. Short (TT4) and long (TT16) traditional tillage are compared with conservation tillage, reduced (RT16) and non‐tillage (NT4). The results show more accumulation of SOC in the near‐surface under RT16 and NT4 in both experiments compared with traditional tillage. Moreover, greater C content occurs to 40 cm depth in the long‐term experiment. The results demonstrate the importance of time on C accumulation, not only in near‐surface layers but also at greater depths. Active C is an indicator of the increase in soil quality in the long‐term experiment. This trend is only apparent for the first 10 cm in the short‐term experiment. Patterns in N, Olsen‐P and extractable K are similar to that of SOC. However, only extractable K is significantly greater in soil under conservation tillage (RT16 and NT4) after short and long periods. Potassium availability is a good indicator of the changes caused by tillage. Our results indicate that studies of soils at depth could be very useful in long‐term experiments to demonstrate the effect of conservation tillage on C and nutrient distribution.  相似文献   

10.
Short‐rotation forestry (SRF) on arable soils has high potentials for biomass production and leads to long‐term no‐tillage management. In the present study, the vertical distributions of soil chemical and microbial properties after 15 y of SRF with willows and poplar (Salix and Populus spp.) in 3‐ and 6‐year rotations on an arable soil were measured and compared to a pertinent tilled arable site. Two transects at different positions in the relief (upper and lower slope; transect 1 and 2) were investigated. Short‐rotation forestry caused significant changes in the vertical distribution of all investigated soil properties (organic and microbial C, total and microbial N, soil enzyme activities), however, the dimension and location (horizons) of significant effects varied. The rotation periods affected the vertical distribution of the soil properties within the SRF significantly. In transect 1, SRF had higher organic‐C concentrations in the subsoil (Bv horizon), whereas in transect 2, the organic‐C concentrations were increased predominantly in the topsoil (Ah horizon). Sufficient plant supply of P and K in combination with decreased concentrations of these elements in the subsoil under SRF pointed to an effective nutrient mobilization and transfer from the deeper soil horizons even in the long term. In transect 1, the microbial‐C concentrations were higher in the B and C horizons and in transect 2 in the A horizons under SRF than under arable use. The activities of β‐glucosidases and acid phosphatases in the soil were predominantly lower under SRF than under arable use in the topsoil and subsoil. We conclude, that long‐term SRF on arable sites can contribute to increased C sequestration and changes in the vertical distribution of soil microbial biomass and soil enzyme activities in the topsoil and also in the subsoil.  相似文献   

11.
The maintenance and accumulation of soil organic carbon (SOC) in agricultural systems is critical to food security and climate change, but information about the dynamic trend and efficiency of SOC sequestration is still limited, particularly under long‐term fertilizations. In a typical Purpli‐Udic Cambosols soil under subtropical monsoon climate in southwestern China this study thus estimated the dynamic, trend and efficiency of SOC sequestration after 22‐year (1991–2013) long‐term inorganic and/or organic fertilizations. Nine fertilizations under a rice–wheat system were examined: control (no fertilization), N, NP, NK, PK, NPK, NPKM (NPK plus manure), NPKS (NPK plus straw), and 1.5NPKS (150% NPK plus straw). Averagely, after 22‐years SOC contents were significantly increased by 4.2–25.3% and 10.2–32.5% under these fertilizations than under control conditions with the greatest increase under NPKS. The simulation of SOC dynamic change with an exponential growth equation to maximum over the whole fertilization period predicted the SOC level in a steady state as 18.1 g kg?1 for NPKS, 17.4 g kg?1 for 1.5NPKS, and 14.5–14.9 g kg?1 for NK, NP, NPK, and NPKM, respectively. Either inorganic, organic or their combined fertilization significantly increased crop productivity and C inputs that were incorporated into soil ranging from 0.91 to 4.63 t (ha · y)?1. The C sequestration efficiency was lower under NPKM, NPKS, and 1.5NPKS (13.2%, 9.0%, and 10.1%) than under NP and NPK (17.0% and 14.4%). The increase of SOC was asymptotical to a maximum with increasing C inputs that were variedly enhanced by different fertilizations, indicating an existence of SOC saturation and a declined marginal efficiency of SOC sequestration. Taken all these results together, the combined NPK plus straw return is a suitable fertilizer management strategy to simultaneously achieve high crop productivity and soil C sequestration potential particularly in crop rotation systems.  相似文献   

12.
In this paper we address total glomalin‐related soil protein (T‐GRSP) as a possible indicator of differences in forest soils related to reactive nitrogen and forest composition. We focused especially on the relationship between T‐GRSP (g kg−1), soil organic carbon (SOC), and reactive nitrogen (Nr) availability among different categories of temperate forests and different horizons. Our study included 105 sampling sites divided into 5 categories, which vary in elevation and tree species composition (coniferous, deciduous, mixed). We detected significantly higher T‐GRSP and SOC in the F+H horizon under conifers. We assume that this observation might be attributed to suppression of decomposition of T‐GRSP and SOC by nature of coniferous litter. The lack of significant differences in T‐GRSP/SOC among the categories and the positive correlations between T‐GRSP and SOC in most of the categories confirmed the strong relationship of T‐GRSP with SOC. We found a significantly higher content of T‐GRSP in the F+H horizon for all studied forest categories. However, the contribution of T‐GRSP to SOC is significantly higher in the A horizon, which might be caused by stabilization of glomalin by mineral fraction, including clay minerals or by the belowground origin of glomalin. We found the increase of SOC with increasing Nr in the A horizon for most categories of forest. T‐GRSP follows this trend in the case of deciduous forests (decid), mixed forest (mixed), and mountain forests (mount). On the other hand, we detected a decrease of T‐GRSP with increasing Nr in the F+H horizon of coniferous forests (conif). Moreover the T‐GRSP/SOC decreases with the increase of Nr in the A horizon of conif, mixed and mount, which points to the higher sensitivity of forest with prevalence of coniferous trees. Our observations have confirmed an ecosystem‐specific relationship between T‐GRSP, SOC and Nr. We concluded that T‐GRSP in combination with T‐GRSP/SOC has the potential to reveal qualitative changes in soil organic matter (SOM) connected with increasing Nr.  相似文献   

13.
The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass‐C input and its biodiversity under no‐till (NT) drives soil restoration of degraded agro‐ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow‐based conventional tillage (CT) on soil organic carbon (SOC) stock vis‐à‐vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0·58 and 0·67 Mg C ha−1 y−1 in the 0‐ to 20‐cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0·59 for the PG site and ranged from 0·48 to 1·30 Mg C ha−1 y−1 for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14·2% at the PG site and ~20·5% at the LRV site. The SOC resilience index ranged from 0·29 to 0·79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
Long‐term no‐tillage management and crop residue amendments to soil were identified as an effective measure to increase soil organic carbon (SOC). The SOC content, SOC stock (SOCs), soil carbon sequestration rate (CSR), and carbon pool management index (CPMI) were measured. A stable isotopic approach was used to evaluate the contributions of wheat and maize residues to SOC at a long‐term experimental site. We hypothesized that under no‐tillage conditions, straw retention quantity would affect soil carbon sequestration differently in surface and deep soil, and the contribution of C3 and C4 crops to soil carbon sequestration would be different. This study involved four maize straw returning treatments, which included no maize straw returning (NT‐0), 0.5 m (from the soil surface) maize straw returning (NT‐0.5), 1 m maize straw returning (NT‐1), and whole maize straw returning (NT‐W). The results showed that in the 0–20 cm soil layer, the SOC content, SOCs, CSR and CPMI of the NT‐W were highest after 14 years of no‐tillage management, and there were obvious differences among the four treatments. However, the SOC, SOCs, and CSR of the NT‐0.5 and NT‐W were the highest and lowest in 20–100 cm, respectively. The value of δ13C showed an obviously vertical variability that ranged from –22.01‰ (NT‐1) in the 0–20 cm layer to –18.27‰ (NT‐0.5) in the 60–80 cm layer, with enriched δ13C in the 60–80 cm (NT‐0.5 and NT‐1) and 80–100 cm (NT‐0 and NT‐W) layers. The contributions of the wheat and maize‐derived SOC of the NT‐0.5, NT‐1 and NT‐W increased by 11.4, 29.5 and 56.3% and by 10.7, 15.1 and 40.1%, relative to those in the NT‐0 treatment in the 0–20 cm soil layer, respectively. In conclusion, there was no apparent difference in total SOC sequestration between the NT‐0.5, NT‐1, and NT‐W treatments in the 0–100 cm soil layer. The contribution of wheat‐derived SOC was higher than that of maize‐derived SOC.  相似文献   

15.
Because of the important role of soil organic carbon (SOC) in nutrient cycling and global climate changes, there has been an interest in understanding how different fertilizer practices affect the SOC preservation and promotion. The results from this study showed that long‐term application of manure (21 years) could increase significantly the content of SOC, total nitrogen (N) and soil pH in the red soil of southern China. The chemical structure of SOC was characterized by using solid‐state cross‐polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy, and the aromatic C, ratio of alkyl C : O‐alkyl C, aromaticity and hydrophobicity of mineral fertilizers N, P and K plus organic manure (NPKM) and organic manure (M) treatments were less than those of mineral fertilizer nitrogen (N) and mineral fertilizers N, P and K (NPK) treatments. Both poorly crystalline (Feo) and organically complexed (Fep) iron contents were influenced significantly (P < 0.05) by different fertilizers, and it was observed that NPKM and M treatments increased the non‐crystalline Fe (Feo‐Fep) content. There was a significant (P < 0.01) positive correlation between soil organic C and non‐crystalline Fe in both the surface (0–20 cm) and subsurface (20–40 cm) soils. The results suggested that non‐crystalline Fe played an important role in the increase of SOC by long‐term application of organic manure (NPKM and M) in the red soil of southern China.  相似文献   

16.
Sequestration of soil organic carbon (SOC) is an important strategy to improve soil quality and to mitigate climate change. To investigate changes in SOC under conservation agriculture (CA), we measured SOC concentrations after seven years of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotations in the eastern Indo‐Gangetic Plains (IGP) of India under various combinations of tillage and crop establishment methods. The six treatments were as follows: conventional till transplanted rice followed by conventional till wheat (CTR‐CTW), CTR followed by zero‐till wheat (CTR‐ZTW), ZT direct‐seeded rice followed by CTW (ZTDSR‐CTW), ZTDSR followed by ZT wheat both on permanent raised beds with residue (PBDSR‐PBW+R), and ZTDSR followed by ZTW both with (ZTDSR‐ZTW+R) and without residues (ZTDSR‐ZTW). We hypothesized that CA systems (i.e. ZT with residue retention) would sequester more carbon (C) than CT. After seven years, ZTDSR‐ZTW+R and PBDSR‐PBW+R increased SOC at 0–0.6 m depth by 4.7 and 3.0 t C/ha, respectively, whereas the CTR‐CTW system resulted in a decrease in SOC of 0.9 t C/ha. Over the same soil depth, ZT without residue retention (ZTDSR‐ZTW) only increased SOC by 1.1 t C/ha. There was no increase in SOC where ZT in either rice or wheat was followed by CT in the next crop (i.e. CTR‐ZTW and ZTDSR‐CTW), most likely because the benefit of ZT is lost when followed by tillage. Tillage and crop establishment methods had no significant effect on the SOC stock below the 0.15‐m soil layer. Over the seven years, the total carbon input from above‐ground residues was ca. 14.5 t/ha in ZTDSR‐ZTW+R and PBDSR‐PBW+R, almost sixfold greater than in the other systems. Our findings suggest that the increased biomass production achieved through a combination of ZT and partial residue retention offers an opportunity to increase SOC whilst allowing residues to be used for other purposes.  相似文献   

17.
Soil organic matter (SOM) is considered an important indicator of soil quality, which can be impacted by crop production practices such as tillage. In this study, two long‐term tillage regimes (conventional tillage [CT] and no tillage [NT], conducted for 36 years) were compared in continuous sorghum production in a sub‐tropical environment in southeast Texas. The positive effects of long‐term NT practice were more conspicuous at the soil surface compared with the deeper soil profiles. The SOC was greater (1.5 t C ha?1 greater) in the NT system compared with the CT system. Results from an incubation study indicate that the rate of C‐min at 0–5 cm soil depth was significantly greater (164 μg of CO2–C g?1 of soil greater) in NT than that of CT, but this trend was reversed at 10–20 cm depth wherein the C‐min rates were 106 μg of CO2–C g?1 of soil greater in CT compared with NT, which is likely because of soil disturbance during the study. Soil cumulative CO2‐C emissions were greater in the CT system (7.28 g m?2) than in the NT system (5.19 g m?2), which is primarily attributed to high soil temperature conditions in the CT system. Sorghum grain yield however was not influenced by the differences in SOC content in this long‐term experiment. Overall, the present study found that long‐term conservation tillage improved SOC stock and reduced carbon loss, thus had a positive impact on soil health and sustainability.  相似文献   

18.
Enrichment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO2 in agricultural soils is important because of its impacts on adaptation to and mitigation of climate change while also improving crop productivity and sustainability. In a long‐term fertility experiment carried out over 27 y under semiarid climatic condition, we evaluated the impact of crop‐residue C inputs through rainfed fingermillet (Eleusine coracana [L.] Gaertn.) cropping, fertilization, and manuring on crop yield sustainability and SOC sequestration in a Alfisol soil profile up to a depth of 1 m and also derived the critical value of C inputs for maintenance of SOC. Five treatments, viz., control, farmyard manure (FYM) 10 Mg ha–1, recommended dose of NPK (50 : 50 : 25 kg N, P2O5, K2O ha–1), FYM 10 Mg ha–1 + 50% recommended dose of NPK, and FYM 10 Mg ha–1 + 100% recommended dose of NPK imposed in a randomized block design replicated four times. Application of FYM alone or together with mineral fertilizer resulted in a higher C input and consequently built up a higher C stock. After 27 y, higher profile SOC stock (85.7 Mg ha–1), C build up (35.0%), and C sequestration (15.4 Mg C ha–1) was observed with the application of 10 Mg FYM ha–1 along with recommended dose of mineral fertilizer and these were positively correlated with cumulative C input and well reflected in sustainable yield index (SYI). For sustenance of SOC level (zero change due to cropping) a minimum quantity of 1.13 Mg C is required to be added per hectare per annum as inputs. While the control lost C, the application of mineral fertilizer served to maintain the priori C stock. Thus, the application of FYM increased the C stock, an effect which was even enhanced by additional amendment of mineral fertilizer. We conclude that organic amendments contribute to C sequestration counteracting climate change and at the same time improve soil fertility in the semiarid regions of India resulting in higher and more stable yields.  相似文献   

19.
Soil provides many of the requirements needed for terrestrial plant growth, including an adequate supply of water. Because the proportion of plant roots is usually greatest in the top 10 to 15 cm of soil, the soil moisture content in the Ap horizon is particularly important for plant growth and crop yields. Uncertainties in estimates of plant available water in the Ap horizon (AWAp) often arise from variabilities in field, laboratory and geospatial data at a farm scale. The objectives of this study were to quantify and compare AWAp estimates across the 147-ha Cornell University Willsboro research farm using four different approaches: a) AWAp calculated from values reported in the SSURGO database for available water capacity (AWC) and Ap thickness for the soil map units (SMUs) present on the farm, b) AWAp estimated from soil texture data reported for the SSURGO SMUs, c) AWAp estimated from soil texture data determined from soil cores taken across the farm that were then averaged within each SMU, and d) spatially interpolating the AWAp values predicted from soil cores across the entire farm irrespective of SMU boundaries. Available water in the Ap horizon varied with soil order in the general trend of Alfisols > Inceptisols > Entisols regardless of the estimation approach used. Field measurement-based estimates of AWAp were lower, in general than the reported SSURGO values and estimates based on reported texture in the SSURGO database. The higher abundance of coarse fragments in the Ap horizon of the soil cores collected on the farm partially explains the lower field measurement-based AWAp estimates. In the SSURGO database, values reported for AWC are frequently obtained from a selected pedon from a “type location” and not from the actual study location. These “type locations” can be located far from study sites and even in different states. Although collecting detailed field data may not always be possible due to the high costs of field and laboratory measurements, it is important to understand the potential benefits and limitations of making field-scale and regional AW estimates using the SSURGO database.  相似文献   

20.
Oxisols cover ≈ 23% of the land surface in the tropics and are utilized extensively for agricultural purposes in the tropical countries. Under the variable input types of agricultural systems practiced locally, some of these soils still appear to have problems in terms of proper soil classification and subsequently hinder attempts to implement sustainable agro‐management protocols. The definition for Oxisols in Soil Survey Staff (1999) indicates that additional input is still required to refine the definition in order to resolve some of the outstanding classification problems. Therefore, the objective of this study is to examine the properties of some Oxisols and closely related soils in order to evaluate the classification of these soils. Soils from Brazil, several countries in Africa, and Malaysia were used in this study. Field observations provided the first indication that some of the presently classified kandi‐Alfisols and kandi‐Ultisols were closer to Oxisols in terms of their properties. Water‐retention differences and apparent CEC of the subsurface horizons also supported this idea. The types of extractable Fe oxides and external specific surface areas of the clay fractions showed that many kandic horizons have surface properties that are similar to the oxic horizons. Micromorphology indicated that the genetic transition from the argillic to the oxic involves a diminishing expression of the argillic. Properties, such as CEC, become dominant. The kandic horizon is therefore inferred as a transition to the oxic horizon. It is proposed that the Oxisols be keyed out based only on the presence of an oxic horizon and an iso–soil temperature regime. The presence of a kandic horizon will be reflected at lower levels in Oxisols. The Oxisols will now be exclusive to the intertropical belt with an iso–soil temperature regime. The geographic extend of the Oxisols would increase and that of kandi‐Alfisols and Ultisols would decrease. A few kandi‐Alfisols and Ultisols in the intertropical area will have low CEC which would fail the weatherable mineral contents. The kandic subgroups of some Alfisols and Ultisols will be transitional between the low (< 16 cmolc [kg clay]–1)‐ and high (> 24 cmolc [kg clay]–1)‐activity clay soils. The proposed changes to classification will contribute to a better differentiation of the landscape units in the field. Testing of the proposed classification on some Malaysian soils showed that the new definition for Oxisols provides a better basis for the classification of the local soils and the development of meaningful soil‐management groups for plantations.  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