Conservation agriculture based sustainable intensification of basmati rice-wheat system in North-West India

Continuous mono-cropping of rice-wheat (RW) system with conventional tillage (CT) based management practices have led to decline in soil health, groundwater table and farmers profit in north-west India. A medium-term (4 years) farmer’s participatory strategic research trial of basmati RW system was conducted to evaluate the effects of conservation agriculture (CA) based management practices on crop yields, water productivity, profitability and soil quality. Six treatments were compared varied in the cropping system, tillage, crop establishment and residue management. CA-based management under zero-till direct seeded rice-wheat-mungbean recorded 36% higher system yield than conventional till rice-wheat system (14.91 Mg ha^?1). CA-based rice-wheat system and rice-wheat-mungbean system saved ~35% irrigation water compared to conventional RW system (2168 mm ha^?1). Total water productivity (WP_I+R) was improved by 67% with CA-based rice-wheat-mungbean system (0.90 kg grain m^?3) over the conventional system. On system basis, 42% higher net return was recorded with CA-based rice-wheat-mungbean system compared to conventional system (USD 2570 ha^?1). Mungbean integration in basmati RW system contributed 29% share in system net returns across the treatments. Soil chemical and biological properties were improved by ~40% and 150%, respectively, with CA-based management system.     

Effect of conservation agriculture on stratification of soil organic matter under cereal-based cropping systems

ABSTRACT

Degradation of soil quality caused by conventional tillage practices is a major concern for the sustainability of rice-wheat cropping systems in South Asian region. Therefore, suitable conservation agriculture (CA) practices are required. This study investigates the stratification and storage of soil organic carbon (SOC) and total nitrogen (TN) as affected by eight years of different CA practices in the North-West Indo-Gangetic Plains of India. There were four treatments: (1) conventionally tilled rice-wheat cropping system, (2) reduced-till CA-based rice-wheat-mungbean system, (3) no-till CA-based rice-wheat-mungbean system, and (4) no-till CA-based maize-wheat-mungbean system. The mean stratification ratio (SR) (i.e. a ratio of the concentrations of SOC and TN in the soil surface to those in a deeper layer) of SOC and TN for 0–5:5–10, 10–15, 15–20, 20–25 and 25–30 cm were found higher (> 2) under CA practices compared to intensive tillage-based conventional agricultural practice (< 2). No-till CA-based rice-wheat-mungbean system stored the highest amount of SOC (25.32 Mg ha^?1) whereas reduced till CA-based rice-wheat-mungbean system stored highest amount of TN (3.21 Mg ha^?1) at 0–30 cm soil depth. This study shows that CA stratifies SOC and TN and helps to enhance SOC sequestration and soil quality.     

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.     

Deforestation and land-use effects on soil degradation and rehabilitation in western Nigeria. I. Soil physical and hydrological properties

Assessments of the effects of deforestation, post-clearance tillage methods and farming systems treatments on soil properties were made from 1978 through 1987 on agricultural watersheds near Ibadan, southwestern Nigeria. These experiments were conducted in two phases: Phase I from 1978 through 1981 and Phase II from 1983 to 1987, with 1 year (1982) as a transition phase when all plots were sown with mucuna (Mucuna utilis). There were six treatments in Phase I involving combinations of land clearing and tillage methods: (1) manual clearing with no-till (MC-NT); (2) manual clearing with plough-till (MC-PT); (3) shear-blade clearing with no-till (SB-NT); (4) tree-pusher/root rake clearing with no-till (TP-NT); (5) tree-pusher/root-rake clearing with plough-till (TP-PT); (6) traditional farming (TF). The six treatments were replicated twice in a completely randomized design. The traditional treatment of Phase I was discontinued during Phase II. The five farming systems studied during Phase II with a no-till system in all treatments were: (1) alley cropping with Leucaena leucocephala established on the contour at 4-m intervals; (2) and (3) fallowing with Mucuna utilis on severely degraded and moderately degraded watersheds, respectively, for 1 year followed by maize-cowpea rotation for another; (4) and (5) ley farming involving establishment of pasture in the first year on severely and moderately degraded plots, respectively, controlled grazing in the second year, and growing maize (Zea mays)-cowpea (Vigna unguiculata) in the third year. All treatments, imposed on watersheds of 2–4 ha each, were replicated twice. The soil properties analyzed were particle size distribution, total aggregation and mean weight diameter of aggregates, soil bulk density, penetrometer resistance, water retention characteristics, infiltration capacity and saturated hydraulic conductivity. These properties were measured under the forest cover in 1978, and once every year during the dry season thereafter during Phases I and II. Prior to deforestation, mean soil bulk density was 0·72 Mg m⁻³ and 1·30 Mg m⁻³, soil penetration resistance was 32·4 KPa and 90·7 KPa, and mean weight diameter of aggregates was 3·7 mm and 3·2 mm for 0–5 cm and 5–10 cm depths, respectively. The infiltration rate was excessive (54–334 cm hr⁻¹) and saturated hydraulic conductivity was rapid (166–499 cm hr⁻¹) under the forest cover. Furthermore, water transmission properties varied significantly even over short distances of about 1 m. Deforestation and cultivation increased soil bulk density and penetration resistance but decreased mean weight diameter of aggregates. One year after deforestation in 1980, mean soil bulk density was 1·41 Mg m⁻³ for 0–5 cm depth and 1·58 Mg m⁻³ for 5–10 cm depth. Soil bulk density and penetration resistance were generally higher for NT than for PT methods, and the penetration resistance was extremely high in all treatments by 1985. During Phase II, soil bulk density was high during the grazing cycle of the ley farming treatment. Sand content at 0–5 cm depth increased and clay content decreased with cultivation duration. Soon after deforestation, saturated hydraulic conductivity and equilibrium infiltration rate in cleared and cultivated land declined to only 20–30 per cent of that under forest. Mean saturated hydraulic conductivity following deforestation was 46·0 cm hr⁻¹ for 0–5 cm depth and 53·7 cm hr⁻¹ for 5–10 cm depth. Further, infiltration rate declined with deforestation and cultivation duration in all cropping systems treatments. During Phase I, mean infiltration rate was 115·8 cm hr⁻¹ under forest cover in 1978, 20·9 cm hr⁻¹ in 1979, 17·4 cm hr⁻¹ in 1980 and 20·9 cm hr⁻¹ in 1981. During Phase II, mean infiltration rate was 8·5 cm hr⁻¹ in 1982, 11·9 cm hr⁻¹ in 1983, 11·0 cm hr⁻¹ in 1984, 11·3 cm hr⁻¹ in 1985 and 5·3 cm hr⁻¹ in 1986. Infiltration rate was generally high in ley farming and mucuna fallowing treatments. Natural fallowing drastically improved the infiltration rate from 19·2 cm hr⁻¹ in 1982 to 193·2 cm hr⁻¹ in 1986, a ten-fold increase within 5 years of fallowing. High-energy soil water retention characteristics in Phase I were affected by those treatments that caused soil compaction by mechanized clearing and no-till systems. Soil water retention at 0·01 MPa potential in 1979 was 19·2 per cent (gravimetrics) for SB, 17·9 per cent for TP, 15·9 per cent for MC and 17·8 per cent for TF methods. With regards to tillage, soil water retention was 17·8 per cent for NT compared with 16·8 per cent for PT. During Phase II, water retention characteristics were not affected by the farming system treatments. Mean soil water retention (average of 4 years' data from 1982 to 1986) at 0·01 MPa for 0–5 cm depth was 16·6 per cent for alley cropping, 16·7 per cent for mucuna fallowing and 16·8 per cent for ley farming. Mean soil water retention for 1·5 MPa suction was 9·3 per cent for alley cropping, 8·7 per cent for mucuna fallowing, and 9·3 per cent for ley farming. Water retention at 1·5 MPa suction correlated with the clay and soil organic carbon content.     

田间原位试验分析长期机械作业下稻麦轮作地块土壤入渗性能

田间原位不同深度入渗试验是表达土壤分层状态、展示土层物理分异以及定量土壤剖面水功能变化的关键。为了探究不同深度水稻土的入渗能力及保水作用,该研究以华东稻麦轮作区小农户长期机械化耕整模式下代表地块的土层分异为目标,设计田间原位不同深度入渗试验。在试验地块内开挖7个不同深度的入渗坑并在坑底进行入渗试验,然后渗透48 h分层测取土壤含水率,研究不同坑底深度（坑深）土壤的入渗能力和入渗后各土层含水率的变化。结果表明,不同深度入渗试验准确表达了不同坑深土壤的水分入渗及土层持水分异,同时也能清晰地鉴别出犁底层所在位置和厚度,犁底层始于15 cm深,且耕作层与犁底层分异明显,耕作层平均紧实度为1 005.79 kPa,犁底层平均紧实度为1 910.73 kPa;土壤剖面分析表明,耕作层土壤形态疏松,根系分布稠密,犁底层土壤容重大,孔隙度小,透水性差,心土层土壤铁锰斑点较多,结构性差;土壤入渗参数随坑深的增加而减少,其中0～15 cm坑深范围内平均的平均入渗速率和累计入渗量分别为>20～30 cm的17.04倍和18.06倍;通过对比初始含水率和渗透48 h后含水率,得到坑深在15 cm范围内的...     

废水灌溉对芦苇地土壤水文特征的影响

为研究造纸废水灌溉对黄河三角洲内陆盐碱芦苇地土壤水文特征的影响,通过设置芦苇地不同废水灌溉次数下的随机区组试验,采用田间测量土壤入渗过程和实验室内测定水文物理参数相结合的方法,分析造纸废水灌溉前后土壤pH值、含盐率及土壤水文物理参数的变化。结果表明：1）废水灌溉后,土壤pH均值降低6.0%;废水灌溉1～2次,土壤含盐率降低11.7%,废水灌溉3～4次后,增壤含盐率增加12.6%。2）废水灌溉后土壤体积质量均值减小6.5%,总孔隙度均值增大18.1%;随着废水灌溉次数的增多,土壤体积质量和总孔隙度分别有减小和增大的趋势。3）Horton模型比较适合描述废水灌溉后芦苇群落的土壤入渗过程,废水灌溉降低了初渗率,但随着废水灌溉次数的增多,稳渗率增加明显。4）废水灌溉增强了土壤贮蓄水分的能力,废水灌溉3次吸持贮水量达到最高（90.15 mm）,灌水4次滞留贮水量达到最高（4.51 mm）。与未灌溉相比,废水灌溉具有明显的压碱抑盐、改良土壤水文物理性状、提高土壤入渗和贮水能力的作用,但不同灌溉次数处理间差异性显著。该研究为黄河三角洲内陆盐碱地区芦苇群落在造纸废水灌溉下的适宜灌溉次数和灌溉水量的确定提供了科学依据,有利于造纸废水资源的合理化开发利用。     

Influence of basin‐based conservation agriculture on selected soil quality parameters under smallholder farming in Zimbabwe

The research was carried out to determine the effect of basin‐based conservation agriculture (CA) on selected soil quality parameters. Paired plots (0.01 ha) of CA and conventional tillage based on the animal‐drawn mouldboard plough (CONV) were established between 2004 and 2007 on farm fields on soils with either low (12–18% – sandy loams and sandy clay loams) or high clay levels (>18–46% – sandy clays and clays) as part of an ongoing project promoting CA in six districts in the smallholder farming areas of Zimbabwe. We hypothesized that CA would improve soil organic carbon (SOC), bulk density, aggregate stability, soil moisture retention and infiltration rate. Soil samples for SOC and aggregate stability were taken from 0 to 15 cm depth and for bulk density and soil moisture retention from 0 to 5, 5 to 10 and 10 to 15 cm depths in 2011 from maize plots. Larger SOC contents, SOC stocks and improved aggregate stability, decreased bulk density, increased pore volume and moisture retention were observed in CA treatments. Results were consistent with the hypothesis, and we conclude that CA improves soil quality under smallholder farming. Benefits were, however, greater in high clay soils, which is relevant to the targeting of practices on smallholder farming areas of sub‐Saharan Africa.     

Water infiltration and soil structure related to organic matter and its stratification with depth

Soil organic matter is a key attribute of soil quality that impacts soil aggregation and water infiltration. Two soils (Typic Kanhapludults), one under long-term management of conventional tillage (CT) and one under long-term management of no tillage (NT), were sampled to a depth of 12 cm. Soil cores (15 cm diameter) were either left intact or sieved and repacked to differentiate between short-term (sieving) and long-term (tillage management) effects of soil disturbance on water infiltration, penetration resistance, soil bulk density, macroaggregate stability, and soil organic carbon (SOC). Mean weekly water infiltration was not different between sieved and intact cores from long-term CT (22 cm h⁻¹), but was significantly greater in intact (72 cm h⁻¹) than in sieved (28 cm h⁻¹) soil from long-term NT. The stratification ratio of SOC (i.e., of 0–3 cm depth divided by that of 6–12 cm depth) was predictive of water infiltration rate, irrespective of short- or long-term history of disturbance. Although tillage is used to increase soil porosity, it is a short-term solution that has negative consequences on surface soil structural stability, surface residue accumulation, and surface-SOC, which are critical features that control water infiltration and subsequent water transmission and storage in soil. The stratification ratio of SOC could be used as a simple diagnostic tool to identify land management strategies that improve soil water properties (e.g., infiltration, water-holding capacity, and plant-available water).     

Evaluation of precision land leveling and double zero-till systems in the rice–wheat rotation: Water use, productivity, profitability and soil physical properties

In recent years conventional production technologies in the rice–wheat (RW) system have been leading to deterioration of soil health and declining farm profitability due to high inputs of water and labour. Conservation agriculture (CA)-based resource-conserving technologies (RCTs) vis-à-vis zero-till (ZT), raised-bed planting and direct-seeded rice (DSR) have shown promise as alternatives to conventional production technologies to overcome these problems. The integration of CA-based RCTs with precision agriculture (PA)-based technologies in a systems perspective could provide a better option for sustainable RW production systems. In this study we attempted to evaluate conservation and precision agriculture (CPA)-based RCTs as a double-ZT system integrated with laser-assisted precision land leveling (PLL) in the RW system. A field experiment was conducted in the western IGP for 2 years to evaluate various tillage and crop establishment methods under PLL and traditional land leveling (TLL) practices to improve water productivity, economic profitability and soil physical quality. Irrespective of tillage and crop establishment methods (TCE), PLL improved RW system productivity by 7.4% in year 2 as compared to traditional land leveling. Total irrigation water savings under PLL versus TLL were 12–14% in rice and 10–13% in wheat. PLL improved RW system profitability by US$113 ha⁻¹ (year 1) to $175 ha⁻¹ (year 2). Yields were higher in conventionally transplanted rice followed by direct-drill-seeded rice after ZT. In wheat, yields were higher in ZT when followed by DSR than in the conventional-till (CT) system. RW system productivity under double ZT was equivalent to that of the conventional method. Among different TCE, conventional puddled-transplanted rice-CT wheat required 12–33% more water than other TCE techniques. Compared with CT systems, double ZT consumed 12–20% less water with almost equal system productivity and demonstrated higher water productivity. The CT system had higher bulk density and penetration resistance in 10–15 and 15–20 cm soil layers due to compaction caused by the repeated wet tillage in rice. The steady-state infiltration rate and soil aggregation (>0.25 mm) were higher under permanent beds and double ZT and lower in the CT system. Under CT, soil aggregation was static across seasons, whereas it improved under double no-till and permanent beds. Similarly, mean weight diameter of aggregates was higher under double ZT and permanent beds and increased over time. The study reveals that to sustain the RW system, CPA-based RCTs could be more viable options: however, the long-term effects of these alternative technologies need to be studied under varying agro-ecologies.     

Agronomic productivity,nitrogen fertilizer savings and soil organic carbon in conservation agriculture: efficient nitrogen and weed management in maize-wheat system

Conservation agriculture (CA) practice increases agronomic productivity and soil fertility, yet CA stimulate nitrogen (N) immobilization and weed interference during the early periods of implementation. This study focuses on efficient N management by soil testing and optical sensor (GreenSeeker^TM) information; and weed management using brown manuring (Sesbania aculeata co-culture) and herbicide mixtures under CA-based maize (Zea mays L.) – wheat (Triticum aestivum L. emend Fiori & Paol) system in the Indo-Gangetic Plains. Fertilizer N application guided by the optical sensor increased grain yields of maize and wheat up to 20 and 14% (average of two years), respectively, compared to whole N application at sowing. Weed management using brown manuring in maize and herbicide mixtures in wheat increased the grain yields up to 10 and 21%, respectively, over the weedy check. The optical sensor-based N management saved up to 45 and 30 kg N ha^–1 of the optimized N fertilizer rate in maize and wheat, respectively, over whole N application. Fertilizer N management coupled with brown manuring resulted in 5 and 4% higher soil organic carbon accumulation. Implementing efficient N fertilizer and weed management in the early years of CA can improve agronomic yield, fertilizer savings, and soil organic carbon content.     

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.     

Tillage systems and soil properties in Latin America

A review of tillage systems in Latin America revealed that considerable research on this topics has been done and much is currently in progress. Results of most of this tillage research, however, have not been published in international refereed journals, thus making it difficult to assess the current state of the art on this topic. A high percentage of tillage research results has not been published at all. In general, conservation tillage practices, that is, those commonly referred to as no-till and minimum till, had higher bulk densities in the surface soil, but lower macroporosities, infiltration rates and crop yields as compared with conventional tillage, which was typically disk plowing. Chisel plowing and subsoiling, deep tillage practices whose action extends below the usual depth of disk plowing, usually decreased mechanical impedance, improved root penetration and increased crop yields. Soil loss from cropped land was usually greatest under conventional tillage unless mulch was applied to the soil surface. We believe that some form of tillage practice that mixes the surface soil layer will have to be incorporated from time to time into any tillage system to maintain soil conditions adequate for sustained continuous cropping.     

Soil nutrient concentrations and stoichiometry under different tree-cropping systems in a purple hillslope in southwestern China

Agroforestry systems strongly impact soil properties, yet their effects on the stoichiometry of soil nutrients remain unclear. This study aimed to determine the tree-cropping systems effects on soil C, N, P and K concentrations and their stoichiometry in 0–10 and 10–20 cm soil depths in a purple hillslope of southwestern China. Five typical agroforestry systems, including Citrus sinensis (L.) Osbeck system (CO), CO and Ipomoea batatas (L.) system (CI), CO and Arachis hypogaea (L.) system (CA), CO and Zea mays (L.) system (CZ), and CO and Solanum melongena (L.) system (CS), were investigated. Tree-cropping systems (i.e. CI, CA, CZ and CS) showed significantly higher soil C, N, P and K concentrations and clay percentage, and lower bulk density than CO system. Nutrient ratios altered inconsistently among five agroforestry systems. Soil depth differed N concentration, N:K ratio, bulk density and total porosity. Soil nutrient concentrations and stoichiometry showed significant correlations with physical properties. N:P ratio was 69.78 and 78.55% lower than the Chinese and World averages in the 0–10 cm soil depth, indicating that severe N limitation occurred in the agroforestry systems. Rational N fertilization and allocation of tree-cropping systems are urgently needed for sustainable development of agroforestry.     

不同施肥模式对设施菜田土壤微生物量碳、氮的影响

【目的】 本文利用天津日光温室蔬菜不同施肥模式定位试验,研究了不同施肥模式对设施菜田土壤微生物量碳、氮含量的影响,为设施蔬菜高效施肥和菜田土壤可持续利用提供依据。 【方法】 调查在第 9 茬蔬菜 (秋冬茬芹菜) 和第 10 茬蔬菜 (春茬番茄) 进行。定位试验设 8 个处理,分别为:1) 不施氮;2) 全部施用化肥氮 (4/4CN);3) 3/4 化肥氮 + 1/4 猪粪氮 (3/4CN + 1/4PN);4) 2/4 化肥氮 + 2/4 猪粪氮 (2/4CN + 2/4PN);5) 1/4 化肥氮 + 3/4 猪粪氮( 1/4CN + 3/4PN);6) 2/4 化肥氮 + 1/4 猪粪氮 + 1/4 秸秆氮 (2/4CN + 1/4PN + 1/4SN);7) 2/4 化肥氮 + 2/4 秸秆氮 (2/4CN + 2/4SN);8) 农民习惯施肥 (CF),除不施氮肥和农民习惯施肥外,其余处理为等氮磷钾处理。在不同生育时期,采 0—20 cm 土壤样品,测定土壤微生物量碳、氮含量,并分析其与蔬菜产量之间的关系。 【结果】 两茬蔬菜不同施肥模式土壤微生物量碳、氮含量总体上均随生育期的推进呈先增后降的趋势。芹菜季较高土壤微生物量碳含量出现在定植后 90 d,土壤微生物量氮较高含量出现在定植后 60 d;番茄季分别出现在定植后 20～80 d 和 60 d。芹菜季 5 个有机无机肥料配施模式土壤微生物量碳、氮含量分别在 185.0～514.6 和 34.3～79.1 mg/kg 之间,较化肥(4/4CN)模式平均分别增加 15.1%～81.7% 和 24.5%～100.0%,其中以配施秸秆模式土壤微生物量碳、氮含量相对较高,平均分别增加 62.0%～81.7% 和 81.1%～100.0%;番茄季 5 个有机无机肥料配施模式土壤微生物量碳、氮含量分别在 120.7～338.0 和 25.5～68.8 mg/kg 之间,较 4/4CN 模式平均分别增加 16.9%～86.9% 和 12.2%～109.3%,又以配施秸秆模式土壤微生物量碳、氮含量最高,平均分别增加 61.4%～86.9% 和 78.2%～109.3%。两季蔬菜不同生育期土壤微生物量碳、氮含量与当季蔬菜产量和定位试验开始以来蔬菜总产量之间均呈极显著正相关关系。 【结论】 同等养分投入量下,有机无机肥料配合施用提高土壤微生物量碳、氮的效果显著好于单施化肥,又以化肥配施秸秆效果更佳;土壤微生物量碳、氮含量与设施蔬菜产量之间呈极显著正相关关系。证明有机无机肥配施,特别是配施一定量的秸秆可有效提高土壤微生物量碳、氮含量,维持较高的菜田土壤肥力,有利于设施蔬菜的可持续和高效生产。      

土壤点源入渗自动测量系统监测滴头下土壤湿润过程

土壤水运动过程是滴灌系统设计和运行管理的重要内容。该研究采用点源土壤入渗自动测量系统,利用计算机可控数码相机和图像识别技术测量滴灌地表湿润面积和土壤湿润体随时间的变化过程。采用正三棱形有机玻璃土箱,设计一系列点源滴灌室内试验,获得点源滴灌入渗过程随时间的变化过程。试验采用3个流量:2、4及8 L/h处理,每个处理设置了3个重复。用数码相机每4 min拍摄一次地表湿润面积,用于计算地表湿润面积随时间的变化过程。同时,在1、2、3、4、6、8、10、12、20、30、40、50、60、70、80、90、100、120、140、160、180 min时刻,在贴在土箱侧面的透明胶片上,手工记录地表湿润面积和垂直湿润锋面随时间的变化过程。由测量系统根据记录的地表湿润面积随时间的变化过程自动计算得到土壤的入渗过程。通过入渗过程,计算得到滴头下地表土壤的湿润面积,由计算得到的土壤入渗率和计算得到土壤的湿润剖面,将计算结果与实测结果对比,检验测量的精度。结果表明,手工测量得到的地表湿润面积都略大于由土壤入渗自动测量系统计算得到的入渗率计算的地表湿润面积。由计算得到的入渗率预测的土壤入渗深度,略大于实测土壤入渗深度。计算得到前者的相对误差为2%~15%,后者的相对误差为1%~8%。说明土壤入渗自动测量系统,能够准确描述点源滴灌地表湿润过程及土壤入渗过程,并能预测不同流量下垂直入渗深度,测量方法可以为滴灌系统的设计提供相关参数。     

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.     

不同施肥模式对设施秋冬茬芹菜生育期间土壤酶活性的影响

【目的】利用在天津的日光温室蔬菜不同施肥模式定位试验,研究了不同施肥模式对设施菜田土壤酶活性的影响,为设施蔬菜高效施肥和菜田土壤可持续利用提供依据。【方法】取样调查在第9茬蔬菜(秋冬茬芹菜)进行。定位试验设6个处理,在等氮磷钾条件下,分别为1)全部施用化肥氮(4/4CN),2)3/4化肥氮+1/4猪粪氮(3/4CN+1/4PN),3)2/4化肥氮+2/4猪粪氮(2/4CN+2/4PN),4)1/4化肥氮+3/4猪粪氮(1/4CN+3/4PN),5)2/4化肥氮+1/4猪粪氮+1/4秸秆氮(2/4CN+1/4PN+1/4SN),6)2/4化肥氮+2/4秸秆氮(2/4CN+2/4SN)。在芹菜基肥施用前和定植后30、60、90、110天,采取0—20 cm土壤样品,测定土壤α-葡萄苷酶、β-木糖苷酶、β-葡萄苷酶、β-纤维二糖苷酶、几丁质酶、磷酸酶和脲酶的活性,分析其与土壤微生物量碳氮及土壤可溶性有机碳氮含量之间的关系。【结果】芹菜生育期间不同施肥模式土壤α-葡萄苷酶、β-木糖苷酶、β-葡萄苷酶、β-纤维二糖苷酶、几丁质酶和磷酸酶的活性总体上先增后降,较高土壤酶活性均出现在芹菜定植后60~90 d; 土壤脲酶活性总体上呈逐渐升高的趋势。芹菜季有机无机肥料配施模式土壤α-葡萄苷酶、β-木糖苷酶、β-葡萄苷酶、β-纤维二糖苷酶、几丁质酶、磷酸酶和脲酶的活性较4/4CN模式平均分别增加22.9%~92.0%、20.1%~152.4%、23.1%~145.1%、28.7%~273.8%、9.2%~207.8%、13.7%~86.8%和6.5%~56.5%,其中以配施秸秆模式土壤酶活性相对较高,较4/4CN模式平均分别增加59.9%~92.0%、98.9%~152.4%、90.3%~145.1%、171.6%~273.8%、106.4%~207.8%、68.8%~86.8%和30.7%~56.5%。土壤酶活性与土壤微生物量碳氮、可溶性有机碳氮含量及芹菜产量之间总体上呈显著或极显著正相关关系。【结论】同等养分投入量下,设施菜田土壤酶活性表现为有机无机肥料配合显著高于单施化肥,又以配施秸秆效果更佳; 土壤酶活性与土壤微生物量碳氮、可溶性有机碳氮含量和蔬菜产量之间密切相关。说明有机无机肥配施,特别是配施一定的秸秆可有效提高土壤酶活性,维持较高的菜田土壤肥力,有利于设施蔬菜的可持续和高效生产。     

土壤侵蚀因素对紫色丘陵区坡耕地耕层质量影响

土壤侵蚀是导致坡耕地耕层土壤质量退化和土壤生产力不稳定的关键因素。该文以紫色丘陵区坡耕地为例,对坡耕地不同地力等级耕层土壤质量、渗透性能及耕层类型进行聚类分析,讨论了土壤侵蚀对坡耕地耕层厚度影响及合理耕层土体构型。结果表明:(1)紫色土坡耕地耕层土壤质量具有中等程度变异性,有效土层厚度(15~80 cm)和耕层厚度(15~25 cm)变异系数分别为12.18%和37.26%,土壤有效磷变异系数可达94.51%,说明土壤物理指标变异性小于化学指标变化;三级以下地力耕层构型为近似全虚或全实剖面结构,五等地力坡耕地产量下降50%左右。(2)紫色土坡耕地不同坡位、不同垂直深度的耕层土壤物理性质、持水性能及耕作性能差异显著(P0.05),土壤容重为上坡下坡中坡,土壤抗剪强度为上坡中坡下坡,土壤稳定入渗为下坡中坡上坡,土壤贯入阻力表现为中坡上坡下坡;除土壤入渗外,土壤容重、抗剪强度、贯入阻力均表现为底土层心土层耕层;坡耕地0~40 cm土层中蓄存降水可被农作物利用70%左右。(3)中度侵蚀程度坡耕地,年均耕层厚度薄化值为1.04~3.04 mm,坡耕地合理耕层建立可选择有效土层厚度、耕层厚度、土壤容重、土壤抗剪强度、土壤有机质、土壤渗透性为坡耕地合理耕层评价最小数据集,耕层构型总体保持上虚下实型、耕层厚度20~25 cm、有效土层厚度50~60 cm。(4)紫色土坡耕地可分为四种耕层类型,其障碍耕层主要表现为有效土层厚度限制型(第II类)、耕层厚度限制型(第III类)和土壤养分限制型(第IV类),分别占耕层总量30%、10%、3%;紫色土坡耕地合理耕层建立应重点关注有效土层厚度和耕层厚度调控。研究结果可为客观认识土壤侵蚀与紫色土坡耕地耕层退化关系、合理耕层构建提供理论依据和技术参数支持。     

Penetration resistance and root growth of oats in tilled and untilled loess soil

Penetration resistance, bulk density, soil water content and root growth of oats were intensively studied in a tilled and an untilled grey brown podzolic loess soil. Bulk density and penetration resistance were higher in the top layer of the untilled soil compared with the tilled soil. In the latter, however, a traffic pan existed in the 25–30 cm soil layer which had higher bulk density and penetration resistance than any layer of the untilled soil. Above the traffic pan, rooting density (cm root length per cm³ of soil) was higher but below the pan it was lower than at the same depth in the untilled soil. Root growth was linearly related to penetration resistance. The limiting penetration resistance for root growth was 3.6 MPa in the tilled Ap-horizon but 4.6-5.1 MPa in the untilled Ap-horizon and in the subsoil of both tillage treatments. This difference in the soil strength-root growth relationship is explained by the build up of a continuous pore system in untilled soil, created by earthworms and the roots from preceding crops. These biopores, which occupy < 1% of the soil volume, can be utilized by roots of subsequent crops as passages of comparatively low soil strength. The channeling of bulk soil may counteract the possible root restricting effect of an increased soil strength which is frequently observed in the zero tillage system.     

Effects of zone-tillage in rotation with no-tillage on soil properties and crop yields in a semi-arid soil from central Spain

A limiting factor to the no-tillage system in arid and semi-arid regions is the possibility of soil densification from lack of tillage. This research examines the extent and duration of the effects of periodic (rotational) zone-tillage over 2 years, on selected soil physical and chemical properties and crop yields. In the first year four tillage treatments were applied: conventional tillage with mouldboard plow (CT), minimum tillage with chisel plow (MT), no-tillage (NT) and zone-tillage subsoiling with a paraplow (ZT). In the second year, the ZT plots were returned to NT to follow the residual effects of ZT. The soil was a loamy sand (Calcic Haploxeralf) from semi-arid Central Spain and the crop rotation was grey pea (Pisum sativum L.)–barley (Hordeum vulgare L.). Crop residues on the soil surface after sowing grey pea were 85% in NT plots, 55% in ZT plots and 15% in MT plots. When comparing NT and ZT, the immediate effects of subsoiling on soil physical properties were significant (P < 0.05). Soil strength as measured by cone index approached 3.0 MPa in NT and was reduced to <1.0 MPa by ZT over 300 mm sampling depth. Soil moisture content and bulk density were improved by ZT. No-till and ZT favoured surface accumulation of soil organic carbon (SOC), total N and available P and K. Stratification ratio of SOC was not different among tillage systems, but soil N stratification ratio followed the order NT > ZT > MT > CT. Grey pea yields were reduced by 3 Mg ha⁻¹ in the NT and MT compared with ZT. Crop residues on the soil surface after barley sowing were 80% in NT, 56% in ZT, and 12% in MT. At the end of the second year, soil strength, soil moisture and bulk density in ZT declined to NT levels at all soil depths. The positive effect of ZT in increasing SOC in the top layer had also disappeared. However, total N, and available P and K concentrations under NT and ZT were still significantly higher than in MT and CT. Stratification ratios of SOC under NT and ZT were >2 and more than two-fold those under MT and CT. Nitrogen stratification ratio under ZT increased and no significant differences between NT and ZT could be reported. Barley yield was 0.6 Mg ha⁻¹ higher in ZT compared with NT. Our results suggest that ZT improved the physical and chemical condition of the soil studied in months following subsoiling. These positive effects, however, diminished with time and only some residual effects on total N and available P and K content in the top-layer were still evident after 2 years.