土壤调理剂对日光温室土壤理化性质和蔬菜产量、品质的影响

试验研究了土壤调理剂对日光温室土壤理化性质和蔬菜产量、品质的影响。结果表明,施用土壤调理剂能够明显改善土壤结构,增强土壤保水能力,与对照相比,施用2次调理剂后土壤容重降低6.36%,土壤总孔隙度增加4.97%,田间持水量增加6.75%,渗透系数提高46.28%;调理剂还能增加土壤养分含量,提高土壤保肥能力;调理剂能够提高蔬菜的产量和品质,对番茄品质的改善效果尤为明显;调理剂与秸秆配合施用效果更佳。     

Using soil organic matter fractions as indicators of soil physical quality

The objective of this study was to evaluate the use of chemical and physical fractions of soil organic matter (SOM ), rather than SOM per se , as indicators of soil physical quality (SPQ ) based on their effect on aggregate stability (AS ). Chemically extracted humic and fulvic acids (HA and FA ) were used as chemical fractions, and heavy and light fractions (HF and LF ) obtained by density separation as physical fractions. The analyses were conducted on medium‐textured soils from tropical and temperate regions under cropland and pasture. Results show that soil organic carbon (SOC ), SOM fractions and AS appear to be affected by land use regardless of the origin of the soils. A general separation of structurally stable and unstable soils between samples of large and small SOC content, respectively, was observed. SOM fractions did not show a better relationship with AS than SOC per se . In both geographical regions, soils under cropland showed the smallest content of SOC , HA and carbon concentration in LF and HF , and the largest HF /LF ratio (proportion of the HF and LF in percent by mass of bulk soil). With significant associations between AS and SOC content (0.79**), FA /SOC (r  = −0.83*^*), HA /FA (r  = 0.58*^*), carbon concentration of LF (r  = 0.69*^*) and HF (r  = 0.70*^*) and HF /LF ratio (r  = 0.80*^*), cropland showed lowest AS . These associations indicate that SOM fractions provide information about differences in SOM quality in relation to AS and SPQ of soils from tropical and temperate regions under cropland and pasture.     

Temporal changes of soil physical quality under two residue management systems

Although crop residue management is known to affect near‐surface soil physical quality, little is known about the temporal variability of these indicators over short time intervals. This study evaluates the temporal changes of nine indicators of soil physical quality. These are organic carbon content, structural stability index, bulk density, macroporosity, air capacity, relative field capacity, plant available water capacity, Dexter's S‐index and saturated hydraulic conductivity. A second set of soil physical indicators, based on the distribution of soil pore volume, was also evaluated. The indicators were determined in three different times during the growing cycle of winter durum wheat cultivated within a long‐term field research carrying out in Southern Italy and comparing two types of crop residue management, that is, burning (B) and soil incorporation (I). Only the bulk density changed over time for both treatments, although the air capacity also changed for the incorporation of wheat residues. Residual effects of the autumnal soil tillage and soil compaction were a common source of variability, irrespective of which treatment was used. Based on the existing guidelines for evaluating the physical quality of these agricultural soils, optimal or near‐optimal values were detected in about half of the cases under consideration. This suggests that both B and I create sufficiently good conditions for crop growth during the crop cycle. The comparison between observed and optimal soil pore distribution function was always poor. The pore volume distributions showed lower densities of small pores and relatively higher densities of large pores than the proposed optimal distribution. This study also suggests that the considered optimal or references curves probably cannot be applied successfully to a wide range of agricultural soils.     

Linking process capability analysis and least limiting water range for assessing soil physical quality

In the process of evaluating the physical quality of soil for crop production, measurable sources of stress that the soil imposes on growing crops must be identified. Approaches for monitoring or evaluating soil physical quality should then be based on properties or processes that relate to these stresses and must be measured against definable standards. We hypothesized that process capability analysis applied to measurements of soil water content and the least limiting water range (LLWR) would meet these requirements and could be used to evaluate the physical quality of soils for crop growth. Previously published data obtained over 3 years in a field with a variable landscape planted to corn under no-till were used to test the hypothesis. The temporal variability of soil water content was regarded as a process which aims to generate individual values for soil water content inside the limits specified by the LLWR. Process capability analysis successfully linked the temporal variability of soil water content in relation to the LLWR. The main process capability parameter, i.e. distance to nearest specification (DNS) varied by a factor of three across the landscape and was related to clay and organic carbon contents. Values of DNS were strongly correlated with shoot growth (R² = 0.97) suggesting that DNS effectively characterized the spatial variability in stresses imposed on plant growth by soil and described changes in the soil physical quality for crop growth across the site. The results supported our hypothesis.     

Mulching with branches of an indigenous shrub (Guiera senegalensis) and yield of millet in semi-arid Niger

Crop residues from millet production in southwest Niger are limited for their utilization as mulch because of many other uses. Thus, branches of an indigenous shrub (Guiera senegalensis J.F. Gmel.) were tested with a randomised block design for their effect on millet (Pennisetum glaucum L.) yield. Pearl millet was planted in 1995 and 1996 on a luvic Arenosol in southwest Niger. Three treatments were applied: control, 1000 kg ha⁻¹ dry matter Guiera-mulch and 2000 kg ha⁻¹ dry matter Guiera-mulch. Mulched plots had 68–94% higher millet yields compared to the control. Differences in soil properties before the treatments were applied, explained a high variability within the treatments. Significant differences of soil properties between blocks led to a distinction of infertile and fertile blocks. In infertile plots with 1000 kg ha⁻¹ Guiera-mulch, millet yield was higher than in plots with 2000 kg ha⁻¹ Guiera-mulch. Due to the many uses of Guiera senegalensis by the local farmers, an application of 1000 kg ha⁻¹ Guiera-mulch, at least on infertile soils, seems a good possibility to increase millet production.     

氟 对玉米产量品质及土壤性质的影响

适量氟对动物和人类健康有益, 而过量氟对动物和人类健康有害。为研究氟对玉米产量品质及土壤性质的影响, 采用盆栽试验研究了添加0、100 mg·kg^-1、200 mg·kg^-1、500 mg·kg^-1、1 000 mg·kg^-1 和1 500 mg·kg^-1 氟(NaF)对玉米产量、粗蛋白和淀粉含量及土壤pH、水溶性钙和微生物数量的影响。结果表明: 随氟处理浓度的增加玉米产量显著降低, 减产9.9%~85.4%; 玉米籽粒蛋白质含量显著增加, 从91.8 g·kg^-1 增加到108.8 g·kg^-1。加入氟100 mg·kg^-1 和200 mg·kg^-1 时, 淀粉含量表现为下降趋势,而当加入氟500 mg·kg^-1、1 000 mg·kg^-1 和1 500 mg·kg^-1 时, 淀粉含量表现为上升趋势。玉米不同部位氟含量基本上随氟浓度的增加而增加, 玉米根部和籽粒含氟量与氟添加量的相关性达极显著水平, 相关系数分别为r_根=0.998^**和r_粒=0.915^**; 叶含氟量与氟添加量的相关性达显著水平, r_叶=0.852^*; 玉米不同部位氟含量的大小顺序为根>叶>叶鞘>茎>籽粒。氟浓度在200 mg·kg^-1 时, 籽粒含氟量已超过无公害农产品标准1.0 mg·kg^-1。石灰性土壤添加氟后, 可使土壤pH 增加,从8.05 增加到8.70; 水溶性钙含量显著下降, 由2.71 g·kg^-1 下降到1.02 g·kg^-1。随氟浓度的增加土壤放线菌数量显著降低, 与对照相比, 降低0.92%~65.22%; 低浓度的氟可以促进土壤细菌、真菌的生长, 而高浓度的氟可以抑制细菌、真菌的生长。     

Integrated tillage-water-nutrient management effects on selected soil physical properties in a rice-wheat system in the Indian subcontinent

We studied few soil physical indicators after eighth cropping cycle of rice-wheat. The experiment was laid out in split-split plot design with two tillage (rice: puddling vs. non-puddling; wheat: conventional tillage vs. no-tillage), three water management (rice: submergence vs. drainage; wheat: five/three/two irrigations) and nine nutrient (N) management treatments (inorganic vs. integrated nutrient management). The bulk density (t m^?3) in non-puddled soil (1.33) was significantly less than puddled soil (1.59); while mean weight diameter (0.55 mm) and saturated hydraulic conductivity (0.43 cm h^?1) were higher in the former treatment. Irrigation after 3-days of drainage was found to enhance soil aggregation (0.54 mm) and moisture retention (71.6%) during rice. No-tillage in wheat had overall positive impact. Organic sources of nutrients increased soil water retention (biofertilizer for rice), water conductivity and aggregate stability (combined organics for rice and wheat). Interactions between (tillage × N), (water × N), (tillage × water) revealed crop-wise variations. The saturated hydraulic conductivity and soil aggregation for rice; and bulk density, water retention and saturated hydraulic conductivity for wheat were identified as sensitive soil physical indicators. We suggest an effective combination of no tillage and intermittent irrigation with integrated nutrient management for sustaining soil physical quality in rice-wheat rotation.     

伊朗东北部的农业和牧场土壤孔隙大小分布作为土壤物理质量指标

Assessment of soil quality is important for optimum production and natural resources conservation. Agricultural and pasture soil qualities of Deh-Sorkh region located at south of Mashhad, northeastern Iran were assessed using the integrated quality index (IQI) and Nemero quality index (NQI) models in combination with two datasets, i.e., total data set (TDS) and minimum data set (MDS). In this study 6 soil properties considered as MDS were selected out of 18 properties as TDS using principle component analysis. Soil samples were divided into 3 groups based on optimum ranges of 8 soil physical quality indicators. Soil samples with the most indicators at optimum range were selected as group 1 and the samples having fewer indicators at optimum range were located in groups 2 and 3. Optimum ranges of soil pore size distribution functions were also determined as soil physical quality indices based on 8 soil physical quality indicators. Pore size distribution curves of group 1 were considered as the optimum pore size functions. The results showed that relatively high organic carbon contents could improve pore size distribution. Mean comparisons of soil physical quality indicators demonstrated that mean weight diameter of wet aggregates, structural stability index, the slope of moisture retention curve at inflection point, and plant available water content in agricultural land use decreased significantly in relation to pasture land use. In addition, the results demonstrated that the studied MDS could be a suitable representative of TDS. 78% of pasture soils had the optimum pore size distribution functions, while this parameter for agricultural soils was only 13%. In general, the soils of the studied region showed high limitations for plant growth according to the studied indicators.     

土壤质量评价方法述评

 为全面总结土壤质量评价方法的研究进展,从指数法、模型法及GIS的参与等方面综述当前一些定量评价土壤质量的方法。指数法计算方法较简单、实用;模型法具有较强的逻辑性和系统性;应用GIS评价土壤质量客观且潜力大,对土壤进行时空动态监测以实现土壤持续经营管理。在土壤质量评价工作中将定量与定性评价结合起来,选择适宜的土壤质量评价指标,不断完善现有的评价方法,发挥信息技术的优势,为合理开发利用土壤提供依据。     

Applications of S‐theory in the study of soil physical degradation and its consequences

The S‐theory for soil physical quality is introduced. It is shown how values of S can be determined from the water retention characteristic curve. It is also explained how, when experimental data are not available, pedotransfer functions can be used to obtain estimates of S. Although S was first introduced as an index of soil physical quality, it is being increasingly found that it is a useful numerical quantity that can be used in equations for prediction of a range of soil physical properties. Its use is illustrated with examples for hydraulic conductivity, friability, tillage, compaction, penetrometer resistance, plant‐available water, root growth and readily dispersible clay. The main merit of S derives from the fact that given values of S have the same meaning and consequences in different soils. It is described how S can be used to identify areas of land where physical degradation or amelioration are taking place, and to evaluate management practices that will give sustainable land use. Copyright © 2007 John Wiley & Sons, Ltd.     

Watershed-scale assessment of soil quality in the loess hills of southwest Iowa

Soil quality is a concept that integrates soil biological, chemical and physical factors into a framework for soil resource evaluation. Conventional tillage practices can result in a loss of soil organic matter and decreased soil quality. The potential for soil quality degradation with tillage may vary depending upon landscape position and the spatial distribution of critical soil properties. Information on how to accurately integrate soil spatial information across fields, landscapes and watersheds is lacking in the literature. The primary objective of this study was to evaluate the long-term effect of conventional and ridge-tillage on soil quality in three small watersheds at the Deep Loess Research Station near the town of Treynor in southwest Iowa. Soil types included Monona silt loams in summit positions, Ida or Dow silt loams in backslope positions, and Napier or Kennebec silt loams in footslope positions. We removed surface soil cores from transects placed along topographic gradients in each watershed and quantified total soil organic C (SOC), total soil N (TN), particulate organic matter C (POM-C) and N (POM-N), microbial biomass C (MB-C), N mineralization potential (PMIN-N), nitrate N, extractable P and K, pH, water-stable macroaggregates (WSA), and bulk density (BD). We used terrain analysis methods to group the data into landform element classes to evaluate the effect of topographic position on soil quality. Results indicate that soil quality is higher under long-term ridge-tillage compared with conventional tillage. Soil quality differences were consistently documented among the three watersheds by: (1) quantification of soil indicator variables, (2) calculation of soil quality index values, and (3) comparison of indicator variable and index results with independent assessments of soil function endpoints (i.e. sediment loss, water partitioning at the soil surface, and crop yield). Soil quality differences under ridge-till were found specifically for the backslope and shoulder landform elements, suggesting that soil quality increases on these landform elements are responsible for higher watershed-scale soil quality in the ridge-tilled watershed.     

Mulching effects on soil physical quality of an alfisol in western Nigeria

Degradation of soil physical quality, following deforestation and cultivation, is a major soil‐related constraint to an intensive use of soil for crop production in subhumid regions of subSaharan Africa. Use of crop residue mulch is an important strategy to minimize the risks of soil degradation. Therefore, a three‐year experiment was conducted to study the effects of five rates of mulch application (0, 2, 4, 6 and 8 Mg ha⁻¹ season⁻¹) on soil physical properties and growth and yield of maize (Zea mays). Mulch rate of rice straw significantly increased maize grain and stover yields during the first season, and the stover yield during the second season. In comparison with the control, the grain yield increased by 20 per cent at 2 Mg ha⁻¹ of mulch rate and by 33 per cent at 8 Mg ha⁻¹ of mulch rate. The rate of increase was 0·16 Mg ha⁻¹ for grain yield and 0·38 Mg ha⁻¹ for stover yield for every Mg of mulch applied. The increase in stover yield during the second season was 67 per cent for 8 Mg ha⁻¹ mulch rate compared with the unmulched control. Effects of mulch rate on soil physical properties were confined mostly to the surface 0–5 cm depth. For this depth, mulching decreased bulk density from 1·17 Mg m⁻³ for control to 0·98 Mg m⁻³, and penetration resistance from 1·54 kg cm⁻² to 1·07 kg cm⁻² for 8 Mg ha⁻¹ of mulch rate. Application of mulch up to 16 Mg ha⁻¹ yr⁻¹ for three consecutive years had no effect on soil physical properties below 5 cm depth. Experiments were probably not conducted for a long enough period. For mulch farming to be adopted by farmers of West Africa, it must be an integral part of the improved farming system. Copyright © 2000 John Wiley & Sons, Ltd.     

轮作绿肥对盐碱地土壤性质、后作青贮玉米产量及品质的影响

为明确种植和翻压绿肥改良和培肥盐碱地的效果,采用田间试验研究了种植和翻压毛叶苕子(Vicia villosa Roth.)、田菁(Sesbania cannabina Poir.)、草木樨(Melilotus officinalis L.)、紫花苜蓿(Medicago sativa L.)、箭筈豌豆(Vicia sativa L.)和黑麦草(Lolium perenne L.)6种绿肥对中度苏打盐碱地土壤理化性质、返还土壤的N、P_2O_5和K_2O数量、后作青贮玉米(Zea mays L.)鲜草产量及蛋白质含量的影响。结果表明:与对照(不种植绿肥)相比,绿肥生长后期可显著提高土壤含水量1.0%~6.2%,使pH降低0.03~0.43,EC降低0.12~1.50 mS×cm~(-1);翻压绿肥可返还土壤N 15.6~195.4 kg×hm~(-2)、P_2O_5 5.3~58.8 kg×hm~(-2)和K_2O 34.5~127.9 kg×hm~(-2),使土壤有机质、全氮、碱解氮、速效磷和速效钾分别提高0.42~1.86 g×kg~(-1)、0.05~0.34 g×kg~(-1)、0.5~32.3 mg×kg~(-1)、0.42~4.65 mg×kg~(-1)和3.8~26.1 mg×kg~(-1);与对照相比,青贮玉米的鲜草产量和蛋白质含量分别增加1 294~19 391 kg×hm~(-2)和0.4~23.9 mg×g~(-1)。总体而言,种植和翻压豆科绿肥在保蓄土壤水分,降低土壤pH和EC,提升土壤有机质含量和N、P_2O_5、K_2O养分数量(特别是N素数量),提高青贮玉米鲜草产量与蛋白质等方面的效果均显著优于禾本科绿肥,其中以适应性强、生长快、生物量大的毛叶苕子处理的改良、培肥土壤,生产优质牧草的效果最好;其次是草木樨处理。种植和翻压豆科绿肥可有效改良中度苏打盐碱地,显著提高土壤肥力,提供无机养分替代部分化肥,提高优质牧草的生产,是适合大同盆地中度苏打盐碱地经济、有效和环保的改良模式,对稳定耕地面积、保证粮食安全具有重要意义。     

Effect of biochar application rate on soil physical and hydraulic properties of a sandy loam

Biochar is used as a soil amendment for improving soil quality and enhancing carbon sequestration. In this study, a loamy sand soil was amended at different rates (0%, 25%, 50%, 75%, and 100% v/v) of biochar, and its physical and hydraulic properties were analyzed, including particle density, bulk density, porosity, infiltration, saturated hydraulic conductivity, and volumetric water content. The wilting rate of tomato (Solanum lycopersicum) grown in soil amended with various levels of biochar was evaluated on a scale of 0–10. Statistical analyses were conducted using linear regression. The results showed that bulk density decreased linearly (R² = 0.997) from 1.325 to 0.363 g cm^?3 while the particle density decreased (R² = 0.915) from 2.65 to 1.60 g cm^?3 with increased biochar amendment, with porosity increasing (R² = 0.994) from 0.500 to 0.773 cm³ cm^?3. The mean volumetric water content ranged from 3.90 to 14.00 cm³ cm^?3, while the wilting rate of tomato ranged from 4.67 to 9.50, respectively, for the non-amended soil and 100% biochar-amended soil. These results strongly suggest positive improvement of soil physical and hydraulic properties following addition of biochar amendment.     

Ammonium fertilization increases pearl millet yield by promoting early root growth,higher tillering,and water use during grain filling in a low P Sahelian soil

Background : Adaptation of pearl millet [Pennisetum glaucum (L.) R. Br.] to low soil phosphorus (P) at early seedling stages and efficient P fertilizer application are crucial for its survival in the West African Sahel. While addition of ${\mathrm{NH}}_4^{+}\text{-}N$ to P in the microdose technique has been reported to stimulate early growth of pearl millet, there is little information regarding root length (RL) at different timings. Aims : Our study aimed at assessing the effects of added ${\mathrm{NH}}_4^{+}\text{-}N$ and ${\mathrm{NO}}_3^{-}\text{-}N$ to P on (1) pearl millet agronomic traits such as root and shoot growth and (2) the water use dynamics during the cropping cycle. Methods : Twenty‐four “RhizoTubes” filled with P‐deficient soil were used to grow pearl millet under three treatments: (T1) placed P addition alone at 0.4 g per seed hole, P_placed, (T2) P_placed + ${\mathrm{NH}}_4^{+}\text{-}N$, and (T3) P_placed + ${\mathrm{NO}}_3^{-}\text{-}N$. At 2, 3, 4, and 5 weeks after sowing (WAS) we took non‐destructive measurements of RL. Water use (transpiration) was measured from 3.5 to 9 WAS. Results : At early growth, roots in the topsoil of T2 were longer than T3 and T1 roots (at 4 WAS: 129.3 cm for T2, 87.5 cm for T3, and 93.3 cm for T1, p < 0.05). Total RL at 2 WAS correlated positively with seedling height and final grain yield. Fertilization with ${\mathrm{NH}}_4^{+}\text{-}N$ reduced the time to flowering and increased the number of tillers and grain yield, whereas addition of ${\mathrm{NO}}_3^{-}\text{-}N$ increased vegetative dry matter at harvest and water use efficiency. Conclusions : Our findings suggest that fertilization with ${\mathrm{NH}}_4^{+}\text{-}N$ plays a critical root stimulating role at early growth stages, seemingly by increasing lateral root initiation, which carries through to a larger water use during grain filling and higher grain yield.     

Soil degradative effects of slope length and tillage methods on alfisols in western Nigeria. III.Soil physical properties

Effects of six slope lengths, 60 m to 10 m with 10-m increments, on soil physical properties were evaluated for plough-based conventional till and no-till seedbed preparation on field runoff plots for three consecutive years from 1984 to 1987. Soil physical properties measured included texture, bulk density, infiltration capacity, and soil moisture retention characteristics. Conventional till treatment caused a rapid increase in soil bulk density and penetration resistance, and decrease in available water capacity and equilibrium infiltration rate. Gravel content increased with cultivation duration. Soil bulk density of 0–5 cm depth was 1·20 Mg m⁻³ for 1984, 1·39 Mg m⁻³ for 1985 and 1·46 Mg m⁻³ for 1986 for conventional till; and 1·13 Mg m⁻³ for 1984, 1·33 Mg m⁻³ for 1985, and 1·27 Mg m⁻³ for 1986 for the no-till treatment. The penetration resistance of the no-till treatment was relatively low and increased with cultivation duration. Mean penetration resistance for 0–5 cm depth was 2·2 kg cm⁻² in 1984, 2·71 kg cm⁻² in 1985, and 3·79 kg cm⁻² in 1986. The available water capacity decreased in both tillage methods without any consistent trends with regard to slope length. The equilibrium infiltration rate declined drastically for long slopes and conventional till methods. The data support the conclusion that these soils should be managed with short slope lengths and a no-till method of seedbed preparation. © 1997 John Wiley & Sons, Ltd.     

Improvement of the physical fertility of a degraded Alfisol with planted and natural fallows under humid tropical conditions

Abstract. Topsoil (0–15 cm) bulk density, aggregate stability, soil dispersibility, water retention and infiltration were measured between 1989 and 1996 on an Alfisol under rehabilitation in southwestern Nigeria. The planted leguminous species were Pueraria phaseoloides, Senna siamea, Leucaena leucocephala, Acacia leptocarpa and A. auriculiformis. Also, plots with natural fallow and maize/cassava intercropping were included. Level (minimum) and mound tillage with hoes was adopted for the cultivated areas under study after 4 and 6 year fallow periods. Under fallow, the soil bulk density decreased from1.56 to 1.11 t m73.The continuously cropped treatment (level tillage) had significantly higher bulk density than the fallowed subplots after 6 years. Mean soil penetrometer resistance ranged from 75 to 157 kPa for fallowed plots and from 192 to 295 kPa for the continuously cropped (level tillage) subplot. Surface soilwater contentswere similar for all the treatments during the soil strength measurements. Although soil aggregates were generally of low stability and not well formed, they were improved by fallowing.
Soil structural improvement by planted fallows was similar to that by natural fallow, but the trees were more promising for long-term fallow (>6 years) than the herbaceous P. phaseoloides. However, the improvement in soil structure after 4 or 6 year fallow could not be maintained in subsequent cropping. Furthermore, the significant improvement in soil bulk density caused by A. auriculiformis and natural fallow was more rapidly lost on the cultivated subplots compared with other fallow treatments. Thus, soil structure recovery under a fallow does not imply a sustained improvement when stress is applied to this soil. Post-fallow soil management options such as residue incorporation and tillage to ameliorate compaction or soil strength will be necessary to enhance the improvements by fallow species.     

Soil quality degradation processes along a deforestation chronosequence in the Ziwuling area, China

Accelerated erosion caused by deforestation and soil degradation has become the primary factor limiting sustainable utilization of soil resources on the Loess Plateau of Northwestern China. We studied the physical, chemical, and microbiological processes of soil degradation along a chronosequence of deforestation in the Ziwuling area of northwestern Shaanxi province. The results indicated that soil wet aggregate stability, mean aggregate diameter decreased with years following deforestation. Accelerated erosion resulted in soil nutrient loss, and a decrease in soil enzyme activities including notable losses of total soil N, organic C, alkaline phosphatase activity, and invertase activity. During the early time period, the rates of total soil N, organic C, alkaline phosphatase activity, and invertase activity decreasing were rapid and gradually decreased with deforestation years. Increased use of nitrogen fertilizers made determination of soil quality based on measured NO₃–N and NH₄–N inconclusive. The differences in measured parameters between the topsoil and subsoil horizons decreased with time since deforestation, and we concluded that soil erosion was the primary process responsible for the degradation of measured soil physical, chemical, and microbiological properties.     

Amending a loamy sand with three compost types: impact on soil quality

The objective of this study was to investigate the effects of the long‐term addition of three compost types (vegetable, fruit and yard waste compost – VFYW, garden waste compost – GW and spent mushroom compost – SM) on the physical properties of a sandy soil and to quantify any such effects using indicators of soil physical quality. Soil samples were taken from a field with annual compost applications of 30 m³/ha for 10 yr and various physico‐chemical analyses were undertaken. Results show a significant increase in soil organic carbon (21%) with the VFYW and GW compost types. With SM, soil organic carbon increased by 16%. Increased soil macroporosity and water content at saturation with a corresponding decrease in bulk density were observed for all compost types. However, quantification of these improvements using existing soil physical quality indicators such as the ‘S‐index’, soil air capacity and matrix porosity gave mixed results showing that these indices perform poorly when applied to sandy soils. It is concluded that the long‐term application of compost does not significantly improve the physical properties of sandy soils, but the absence of adverse effects suggests that these soils are a viable disposal option for these composts, but new indices of quality are needed for the proper characterization of sandy soils.     

Short-term green manure and tillage management effects on maize yield and soil quality in an Andisol

Andisols are very important land resources supporting high human population density. Maize (Zea mays L.) production on Andisols located in the Purhepecha Region of central Mexico is representative of the highlands conditions of Mexico and Latin America. Farmers struggle with low crop yield and low soil nutrient availability. A 2-year field study was conducted to evaluate the effects of green manures either tilled into the soil (CT) or cut and left on the surface as a mulch (ZT), on maize yield and soil quality. Green manure treatments were: vetch (Vicia sativa L.), oat (Avena sativa L.) and none. No extra N was added to maize. Green manure and tillage had a significant effect on maize grain yield, N uptake and P uptake with CT vetch performing better than ZT oat. Soil organic C and total N were significantly higher under ZT than under CT management. Soils with vetch had higher P concentration. Soil under ZT oat had the highest infiltration rate and penetration resistance compared with other treatments. There appears to be a trade off between soil productivity and intrinsic soil physical properties among soil treatments.