Gliricidia sepium Carbon Inputs and Soil Carbon Pools in a Costa Rican Alley Cropping System

Alternative land management practices, including agroforestry, help to maintain levels of soil organic matter (SOM) and can facilitate soil carbon (C) sequestration for mitigating atmospheric CO₂ emissions. This study quantified C inputs and determined the changes of the soil C pool in a 19-year-old Gliricidia sepium alley cropping system, studied at two fertiliser levels (tree prunings only [? N], and tree prunings plus chicken manure [+ N]), and was compared to a sole crop system. Carbon input from tree prunings ranged from 455 to 457 g C m^{? 2} y^{? 1}, whereas C inputs from crop residues were similar between alley- and sole crops ranging from 121 to 159 g C m^{? 2}y^{? 1}. The soil organic C (SOC) pool in the alley crop was 16–23% higher than the sole crop. In the 19th year of alley farming, SOC was significantly higher (p < 0.05) in the alley crop (3.2%) compared to the sole crop (2.4%), and was also greater compared to that at the time of establishment of the agroforestry system (2.8%). Gross SOC turnover to a 20-cm depth ranged from 12 to 14 years in the + N and ?N alley crops compared to 49 and 50 years in the + N and ?N treatments for the sole crops. Residue stabilisation efficiency in the alley crops was 39% and 55% in + N and ?N treatments respectively.     

Improving China’s food and environmental security with conservation agriculture†

China has achieved impressive increases in agricultural output in recent decades. Yet, past approaches centred on a growing use of fertilizers, pesticides, fuel and water are not likely to achieve the required 30–50% additional increases in food production by mid-century. We show that efficiencies of production are falling and the costs of environmental harm are increasing. Agricultural innovations that improve natural capital are urgently needed. Conservation agriculture (CA) is now practised on >8?Mha in China and is offering promising prospects of both enhanced yields and environmental services. Our meta-analysis of 60 papers with 395 observations in China shows notable benefits from CA. Mean yield increase was 4.5% or 263?kg?ha^?1 for wheat, 8.3% or 424?kg?ha^?1 for maize, and 1.65% or 250?kg?ha^?1 for rice. In 34 datasets from 22 published papers (experimental duration: 2–17 years), 26 datasets (76.5%) show that CA increased yield and soil organic carbon (mean SOC increase of >3?g.kg^?1 in 0–10?cm soil depth) when compared with traditional tillage. Key priorities for the spread of more sustainable forms of agriculture in China are national policy and financial support, better coordination across agencies, and better extension for farmers.     

Reduced tillage and nitrogen effects on soil water dynamics and maize (Zea mays L.) yield under semi-arid conditions

Soil water and nutrients are critical drivers of crop production for smallholders of southern Africa. A three-year study was conducted to assess the effect of integrating single and double ploughing, ripping and planting basins with nitrogen fertilizer (0, 10 and 20?kg?N?ha^–1) on soil water dynamics and maize (Zea mays L.) yields. The experimental design was factorial with four tillage methods and three nitrogen levels as treatment factors. The study was conducted under semi-arid conditions of Zimbabwe. Tillage methods had similar soil water patterns in the profile and no tillage?×?N interaction effects were observed on soil water dynamics. Soil water penetrated deeper into the profile under ripper and basin methods than conventionally ploughed treatments. Nitrogen increased maize yields (14–96%) and rainwater-use efficiency (20–92%) regardless of tillage methods and growing season quality. However, more studies are required to explore complementary techniques that can improve rainwater capture and prolong soil water storage, and improve soil fertility.     

Integration of conservation agriculture in smallholder farming systems of southern Africa: identification of key entry points

A component-omission experiment based on the principle of conservation agriculture (CA) was established on smallholder farms for three seasons in Murehwa and Hwedza districts, Zimbabwe; Barue district in Mozambique; Balaka district and Chitedze Research Station in Malawi, and Monze district in Zambia to identify strategies for improving crop productivity and livelihoods for smallholder farmers. The objective of the experiment was to evaluate the effect of tillage, residue retention, fertiliser application and weed control on maize yield. In addition, the study analysed possible combinations of these factors that could provide a sustainable entry point for intensification through CA. Results showed that fertilisation had the strongest effect on crop yield in both tillage systems; adequate fertilisation is therefore key to success in CA. Retention of crop harvest residues increased yield in no-tillage systems; no-tillage without residues depressed yield by 50% when compared with yields of conventional tillage. A step-wise integration of CA into the smallholder farming systems is proposed as a possible strategy to avoid new constraints on smallholder farms. If resources are limiting, farmers may apply all principles on small areas to overcome the initial demand in resources (labour, fertiliser and residues), and once productivity is raised, they can expand.     

Marginal Abatement Cost Curves for UK Agricultural Greenhouse Gas Emissions

This article addresses the challenge of developing a ‘bottom‐up’ marginal abatement cost curve (MACC) for greenhouse gas (GHG) emissions from UK agriculture. An MACC illustrates the costs of specific crop, soil and livestock abatement measures against a ‘business as usual’ scenario. The results indicate that in 2022 under a specific policy scenario, around 5.38 Mt CO₂ equivalent (e) could be abated at negative or zero cost. A further 17% of agricultural GHG emissions (7.85 Mt CO₂e) could be abated at a lower unit cost than the UK Government’s 2022 shadow price of carbon [£34 (tCO₂e)^?1]. The article discusses a range of methodological hurdles that complicate cost‐effectiveness appraisal of abatement in agriculture relative to other sectors.     

Long-term effects of crop residues and fertility management on carbon sequestration and agronomic productivity of groundnut–finger millet rotation on an Alfisol in southern India

The data from long-term management and cropping systems experiments are needed to assess changes in soil quality, organic carbon pool, and agronomic sustainability. Thus, a 13-year-old soil fertility management experiment was used to assess the impact of crop residues carbon (C) inputs on SOC stock in a rainfed groundnut (Arachis hypogeae L.)–fingermillet (Eleusine coracana (L.) Gaertn) rotation in semiarid alfisol. The application of farmyard manure (FYM) alone or in a combination with chemical fertilizers contributed to higher amounts of C inputs and subsequently to build up a higher SOC pool. Application of 10?Mg?ha^?1 of FYM and a recommended dose of chemical fertilizer (25:21.8:20.7 and 50:21.8:20.7?kg?N, P, K ha^?1 for groundnut and fingermillet, respectively) increased soil SOC pool by 41.2% to 73.0?Mg?ha^?1 with an increase of 9.3?Mg?ha^?1 over 13 years. Both SOC pool and rates of its sequestration were positively correlated with cumulative C input and sustainable yield index. A minimal input of 1.62?Mg?C?ha^?1?yr^?1 is needed to maintain SOC pool at the antecedent level. Balanced application of NPK fertilizers is needed to reduce and reverse the depletion of SOC pool.     

The assessment of the impact of oil palm and rubber plantations on the biotic and abiotic properties of tropical peat swamp soil in Indonesia

Current intensification of agricultural activities in Indonesia has led to increased use of tropical peat swamp forests for agriculture. Ideally, peat swamp ecosystems should not be disturbed as they provide essential services such as soil erosion control, ecosystem stabilization and moderation of climate and energy fluxes as well as reducing carbon emission and conserving biodiversity. In this study, agricultural land from Giam Siak Kecil–Bukit Batu Biosphere Reserve in Indonesia was evaluated to assess the impact of oil palm (burning and without burning) and rubber (5–10 and >40 years old) plantations on soil properties through comparisons with soils from a natural forest (NF). Substantial changes in the physico-chemical properties of soils from both plantations were observed including significant reductions in soil organic matter (4–18%) and water holding capacity (22–53%), but an increase in bulk density (ρb) (0.08–0.17?g?cm^?3). A significant increase in bacterial biomass was also observed following conversion of the NF to plantation (p<0.05). However, the oil palm plantation (OPP) (without burning) showed reduced microbial activities and the lowest Shannon diversity values (2.90) compared to other samples. Community-level physiological profiling showed impaired community function only in soils from the OPP but higher CO₂ exchange rates in most plantation soils. Soils from the rubber plantation (RP) were less impaired in terms of their natural function and therefore RPs appeared to be more suitable for sustainable agricultural use than OPP.     

Does carbon farming provide a cost‐effective option to mitigate GHG emissions? Evidence from China

In this study, we apply a whole farm bioeconomic analysis to explore the changes in land use, farm practices and on‐farm greenhouse gas (GHG) emission under varying levels of agricultural greenhouse gas abatement incentives in the form of a carbon tax for a semi‐arid crop‐livestock farming system in China's Loess Plateau. Our results show that the optimised agricultural enterprises move towards being cropping‐dominated reducing on‐farm emission since livestock perform is the major source of emission. Farmers employ less oats‐based and rapeseed‐based rotations but more dry pea‐based rotations in the optimal enterprise mix. A substantial reduction in on‐farm greenhouse gas emission can be achieved at low cost with a small increase in carbon incentives. Our estimates indicate that crop‐livestock farmers in China's Loess Plateau may reduce their on‐farm GHG emission between 16.6 and 33 per cent with marginal abatement costs <￥100/t CO₂e and ￥150/t CO₂e in 2015 Chinese Yuan. The analysis implies that reducing greenhouse gas emission in China's semi‐arid crop‐livestock agriculture is potentially a low‐cost option.     

氮肥减量及秸秆替代过量氮肥下冬小麦/夏玉米轮作体系氮素淋失风险研究

针对过量施用氮肥和地下水硝酸盐超标的现状,探索减量施氮、秸秆替代过量氮肥下土壤氮素的淋失风险,以期为降低氮素淋失风险提供科学依据。通过在河北省徐水县进行连续4年的冬小麦—夏玉米轮作体系田间定位试验,分析耕作(少耕和常规耕作)、施氮量(无机氮0、200和300 kg/hm~2)和秸秆(还田、不还田)等措施对作物收获后土壤无机氮累积、土壤—作物体系氮平衡状况以及冬小麦和夏玉米产量的影响。结果表明,小麦收获后,过量施氮处理0~100 cm土壤硝态氮累积量显著高于其它处理,高达221 kg/hm~2,过高的土壤残留硝态氮增加玉米高温多雨季氮素淋洗风险。3年氮平衡累积量比较显示,过量施氮、少耕/常规耕作减量施氮秸秆还田3处理的氮平衡值无显著性差异,以少耕减量施氮秸秆还田最低,为236 kg/hm~2,过量施氮处理最高,为281 kg/hm~2,三者均显著高于少耕/常规耕作减量施氮秸秆不还田处理。冬小麦—夏玉米轮作体系氮平衡值与0~100 cm土层的土壤无机氮、土壤硝态氮累积量呈显著正相关,说明氮素大量盈余会导致0~100 cm土壤剖面无机氮大量累积,尤其是硝态氮大量累积。少耕和常规耕作减量施氮秸秆还田处理的冬小麦、夏玉米产量与过量施氮无显著差异。综合考虑土壤无机氮累积量、氮平衡值和作物产量,少耕或者常规耕作下,可以利用秸秆氮替代过量无机氮,降低氮素淋洗风险。     

Apparent Gains,Hidden Costs: Examining Adoption Drivers,Yield, and Profitability Outcomes of Rotavator Tillage in Wheat Systems in Nepal

The ‘high speed’ rotavator is used for shallow tillage to create a fine tilth and incorporate crop residues, often with a single tractor pass. Rotavator tillage has spread quickly in many parts of South Asia, despite short-term experimental trials suggesting deteriorating soil quality and crop yield penalties. Evidence of rotavator impacts on farmer fields across soil gradients and time is largely absent. From a farm household survey conducted among wheat farmers in Nepal, we estimate wheat yield and profitability outcomes for rotavator adopters and non-adopters using propensity score matching. We find that rotavator adoption leads to inferior outcomes, despite significant cost savings for land preparation (US$ 11–15 per hectare). With rotavator adoption, farmers lose about 284–309 kg of wheat grain and about US$ 93–101 of profits on average per hectare per season, and these penalties increase with longer-term use of the technology. Adoption of rotavator appears to be driven by the cost and time savings for land preparation. Against this backdrop, new policy and extension efforts are required that discourage rotavator use and favour more sustainable tillage technologies.     

Climate change impacts on rain-fed and irrigated rice yield in Malawi

There is extensive scientific evidence on climate impacts and adaptation in rice (Oryza sativa L.), but the majority relates to production in South Asia and China. Only a handful of studies have been conducted in Sub-Saharan Africa and none in Malawi. In this paper, the climate impacts on rain-fed and irrigated rice yield have been assessed by combining the downscaled outputs from an ensemble of general circulation models (GCM) (HADCM3, INCM3 and IPCM4) with data from the LARS-WG weather generator to drive the CERES-Rice crop model. This was calibrated and validated using 10 years (2001–2010) field data from three rice schemes to simulate the baseline (1961–1990) yield (t?ha^?1) and then model future yield changes for selected (B1 and A2) emissions’ scenarios for the 2050s. Although relatively small increases in average yield were projected (+8% and +5% for rain-fed and irrigated rice, respectively), there was large uncertainty (?10% to +20% yield change) when considering different GCMs and emission scenario. Farmer responses to cope with the projected impacts include both autonomous and planned adaptation strategies, such as modifying planting dates to maximize crop growth calendars and available soil moisture, increased use of on-farm water conservation measures and land levelling to improve water efficiency in rice schemes dependent on surface irrigation.     

基于多源遥感数据融合的运城盆地夏玉米估产研究

[目的]准确估算区域尺度作物产量是确保粮食安全,发展生态、安全农业的关键。[方法]文章以山西省重要的粮食产区——运城盆地为例,利用2020年空间分辨率为10m的Sentinel-2A数据和时间分辨率为1d的MODIS数据,采用STNLFFM (Spatial and Temporal Nonlocal Filter based Fusion Model)算法并结合光能利用率模型进行夏玉米NPP (Net Primary Production)模拟和产量估测。[结果]（1）融合后的NDVI数据能较好地继承Sentinel-2A NDVI数据的空间细节,同时能够较好地表达较小地物之间空间差异;（2）STNLFFM NDVI时序曲线能准确地反映夏玉米种植时期的NDVI变化趋势和局部突变信息,比MODIS NDVI时序曲线更符合夏玉米实际生长状况。（3）运城盆地夏玉米种植区累积NPP均值为667.42 gC/m2,其中西北部的涑水河冲湖积平原,受人类活动影响显著,灌溉条件较好,NPP累积量较高,为700～900 gC/m2。（4）东北部山区和北部台塬区受地形破碎程度较高影响,NPP累积量小于5...     

The impact of conservation tillage on maize yield and input demand: the case of smallholder farmers in north‐west Ethiopia

This study analyses the economics of conservation tillage (CT) with respect to its effect on maize yield and chemical fertiliser, herbicide, and female and male labour demand. We estimate production and input demand functions using seemingly unrelated regressions on plot‐level cross‐sectional farm household data collected in the north‐west of Ethiopia. A two‐step control function is applied to address potential endogeneity bias due to the inclusion of the CT adoption decision as an explanatory variable. Our results show that CT increases maize yield and chemical fertiliser demand. Additionally, the results show that the adoption of CT reduces female and male labour required for crop production. However, this is achieved through the increased use of herbicides, which might have an undesirable health and environmental effects.     

Characterisation and Diagnosis of Rural—Urban Interface Farming in the Tu Liem and Thanh Tri Districts of Hanoi City,Vietnam

A research project was carried out in two areas in the outskirts of Hanoi city using a combination of qualitative and quantitative methods. The objective was to study interactions among the vegetable farming systems and the peri-urban context within which they are situated. The farms studied were characterised as small-scale farms that use high inputs of soil amendments and pesticides for diversified crop rotation systems. The main source of irrigation water and nutrients for vegetable farming in southern Hanoi is wastewater from the To Lich River. In northern Hanoi, irrigation water is obtained directly from the Red River and nutrients are supplied through high fertiliser inputs. The concentrations of COD (144–287 mg l^?1), N-NH₄ ⁺ (1–25 mg l^?1), PO₄ ^3? (0.5–4 mg l^?1) and coliform (525 × 10³?28 × 10⁶ MPN 100 ml^?1) along the To Lich River was much higher than the limits specified in the Vietnamese standard for water used in agriculture. A higher Cu content in soil in Phuc Ly seems to be linked to the high input of chicken manure at the site. However, the contents of heavy metals in irrigation water, in vegetables and in the soil surface layer at the two sites were lower than the Vietnamese maximum permissible levels.     

Remediation of Abandoned Saline Soils Using Glycyrrhiza glabra: A Study from the Hungry Steppes of Central Asia

Large expansion of the irrigated area in the Aral Sea Basin has exacted a substantial toll on land and water resources in the region. Elevated water tables associated with poor irrigation management and inappropriate drainage infrastructure have resulted in significant secondary salinisation of crop lands resulting in declining cotton and wheat yields and eventual abandonment of lands. Costs associated with the installation of appropriate drainage infrastructure in order to reclaim these areas are prohibitive and hence alternative approaches are required that can be adopted by resource poor farmers. In the current study the potential use of Glycyrrhiza glabra (common name liquorice) to reclaim abandoned saline areas was assessed over a four year period before being returned to a cotton/wheat crop rotation. Two adjacent abandoned fields of 10 and 13 ha respectively were selected for the study on which two treatments were imposed, namely, a control that was maintained as a bare fallow between 1999 and 2003 and a treated plot where liquorice was established over this period. High quality livestock forage with a protein content of 12% was cut from the liquorice plot with dry matter yields ranging from 3.66 (±0.06) to 5.11 (±0.17) t ha^?1. In addition, root dry matter yields of 5.63 (±1.19) to 8.55 (±0.82) t ha^?1 were recorded, this plant component being used in the preparation of herbal medicines and soft drinks. At the end of four years both plots were returned to a wheat and cotton crop rotation. Yields of wheat on the control and treated plots were 0.87 (±0.05) and 2.42 (±0.02) t ha^?1 respectively. Similarly substantial increases in cotton were observed with the control and treated plots yielding 0.31 (±0.01) and 1.89 (±0.18) t ha^?1. These levels of production on the treated plot exceed the district average for wheat and cotton of 1.75 and 1.5 t ha^?1 respectively, clearly showing the positive benefit associated with the growing of liquorice. Water table levels after four years were maintained below the critical level of 2.5 m in the treated plots whilst rising to within 1.99 m from the surface in the control. Salt content of the soil in the treated plot declined over the study while those in the control increased. This preliminary study has clearly demonstrated the ameliorating affect of liquorice in bringing abandoned salt affected soils back into production that is low cost and could be adopted by resource poor farmers.     

A detailed greenhouse gas budget for palm oil production

We have evaluated the global warming impact of palm oil production in a model that simulates the operations of a typical palm oil mill that processes fruit from a nucleus estate and outgrowers. It estimates carbon sequestration in the crop and in mill products and by-products, and balances this against the major sources of greenhouse gases (GHGs), all converted to carbon dioxide equivalents (CO₂-e) over the 25-year lifespan of the crop. The model shows that most carbon sequestration occurs in the standing crop, with smaller amounts in mill products and by-products. Land-use conversion plays a dominant role in the GHG budget, with planting of oil palm after logged forest or rubber leading to a net loss of carbon, and to a net gain following grassland. In the default oil-palm-to-oil-palm case the carbon lost from cleared palms is balanced by sequestration in the current crop. Methane from mill effluent and nitrous oxide from N fertilizers are the next most important emission sources. The default replant case gives net emissions of 0.86t CO₂-e per t crude palm oil, but these can be reduced to very low values, mainly through conversion of methane and surplus fuel in the mill to energy.     

基于DNDC的茶园土壤碳素空间分异及其影响因素——以福建省安溪县为例

[目的]通过探究福建省安溪县茶园土壤碳素储量,揭示各碳素指标的空间分异特征及其关键影响因子,有助于为减少茶园温室气体排放和建设生态茶园提供决策支撑。[方法]文章运用反硝化分解（denitrification decomposition, DNDC）模型和空间统计分析方法对茶园土壤碳素进行模拟和研究。[结果]（1）经过参数率定的DNDC模型对茶园土壤碳素动态循环的模拟具有较好的适用性;（2）安溪茶园土壤有机碳含量丰富,土壤肥力较好。凋落物输入碳是茶园土壤碳素输入的主要来源,平均输入量为505.52 kg/hm2,而通过呼吸作用转化为CO2排放是茶园土壤碳素输出的重要途径,平均CO2排放量为883.78 kg/hm2;(3)茶园SOC10～20cm量、凋落物输入碳量、CH4排放量、CO2排放量均呈现空间聚集分布特征,主要分布在安溪县西部的低山与中低山地区;（4）初始土壤属性中黏粒含量和土壤有机碳含量是影响安溪县茶园土壤碳素空间分异的关键因子,其中土壤黏粒含量对茶园土壤CO2排放量和CH4排放量的影响最强且负向作用效果明显。[结论]安溪县西部等低山和中低山区域土壤肥力较好,但亦应谨慎对待该区...     

中国农作物碳足迹核算研究概述

[目的]碳足迹核算是对农业温室气体排放的定量评价,开展农作物碳足迹核算理论研究能够为低碳农业建设提供技术支撑。[方法]文章在对我国农资投入变化情况进行简要分析的基础上,从碳足迹概念,碳足迹核算的数据来源、方法,我国农作物碳足迹核算涉及的对象、系统边界以及构成、时空分布特征等方面,系统总结了当前农作物碳足迹核算的研究进展。[结果](1)目前我国已开展碳足迹核算的农作物主要有水稻、玉米、小麦、大豆、油菜、脐橙、苹果、油菜和烟叶等,研究过程中活动水平数据、温室气体排放参数来源和核算包含过程的不尽相同,核算过程有仅针对研究对象生产环节的,也有包含上游环节和生产环节的,部分研究还包括产品加工、运输分销、消费和废弃环节,因此核算结果差异较大。(2)研究表明,肥料尤其是氮肥的施用和灌溉耗电是小麦和玉米生产温室气体排放的主要来源,稻田CH₄排放是水稻最主要的排放源,肥料施用和施肥后田间N₂O排放是棉花、花生、大豆、油菜和水果等的温室气体排放的主要来源。(3)同时,受农资投入、耕作方式和技术手段等影响,农作物的碳足迹是不断变化的。[结论]农作物碳足迹核算研究需...     

Non‐Parametric Modelling of CO2 Emission Quota

Dutch glasshouse firms are facing the introduction of a system of tradable CO₂ emission quotas. This paper employs a non‐parametric method for modelling tradable CO₂ emissions of Dutch glasshouse firms. The method is capable of generating shifts in CO₂ emissions across the sample of firms. Moreover, changes in volumes of outputs produced and inputs used are computed. Results show that firms using a conventional heating technology will be net purchasers of CO₂ emissions, whereas firms using more advanced heating technologies will sell part of their emission quota.     

Improving the productivity of vertisols in the Accra plains of Ghana using leguminous cover crops

The productivity of the Vertisols of the Accra plains is low, in spite of its high potential fertility. This could be attributed to physical constraints and low organic matter content. A study was conducted at the Agricultural Research Centre, Kpong, to assess the suitability of Mucuna pruriens, Mimosa invisa and Stylosanthes guianensis, in short fallows, for improving the fertility, physical properties, moisture conservation and weed control in the case of these soils. Mucuna had the highest biomass of 5.3tha^?1, as opposed to 4.1tha^?1 under natural fallow. The mucuna and stylosanthes biomass had comparatively higher total N values (240.75 and 203.51kgha^?1, respectively) than mimosa and natural fallow (152.46 and 162.74kgha^?1, respectively). Soil organic carbon, one year after the incorporation of cover crops, was found to be relatively higher under the cover crops (mucuna, stylosanthes and mimosa) than it was under natural fallow. Bulk densities were thus lower under the cover crops than they were under natural fallow. Also, soils under the cover crops had higher total porosity, water infiltration rates and moisture storage than they did under natural fallow. Weed cover, 115 days after planting maize, was significantly lower in plots previously under Mucuna pruriens than it was under natural fallow, Stylosanthes guianensis and Mimosa invisa. There was a negative linear correlation between cover crop biomass and weed density (R ² = 0.593–0.805). Grain and stover yields of maize were higher under Mucuna pruriens than they were under natural fallow (138 and 70 per cent higher, respectively). Burning of the natural fallow resulted in greater weed growth than when the material was worked into the soil (41 and 8 per cent, respectively). Grain yield was significantly greater under mucuna than it was under natural fallow (3.1 and 1.3tha^?1, respectively).