•The 4‰ Initiative aims to increase global soil organic carbon (SOC) at 4‰ yr−1.•SOC data under agroforestry and conservation agriculture in Africa were reviewed.•Published data show very large ...variability in SOC storage rates.•SOC storage rates under fallows and multistrata systems are higher than 4‰ yr−1.•Only rates under full conservation agriculture are higher than 4‰ yr−1.
The 4‰ initiative launched by the French government at COP21 in Paris in December 2015 aspires to increase global soil organic carbon (SOC) stocks at a rate of 0.4% per year. We conducted a systematic literature review on SOC storage under agroforestry and conservation agriculture systems in sub-Saharan Africa, where we reported 66 and 33 cases for both systems respectively. The results showed that SOC storage rates were significantly higher than 4‰ yr−1 in fallows and in multistrata agroforestry systems (P = 0.0001 and 0.0178, respectively), but not in alley cropping and parklands systems. For conservation agriculture, SOC storage rates were only significantly higher than 4‰ yr−1 (P = 0.0438) when all three principles were applied, i.e. no- or minimum tillage combined with crop residue retention and intercropping or rotation. The data showed very large variability in SOC storage rates as the result of various factors, including previous land-use history, experimental set up and approach used to determine SOC storage (diachronic versus synchronic approach), soil type, depth of soil sampling, type of crops and management, and duration of the experiment. SOC storage rates significantly decreased with time in the agroforestry systems (P = 0.0328). However, we were unable to find significant relationships with initial SOC stocks or tree density. Given the limited published data and the high variability in results, no significant relationships between SOC storage rates and site variables were found for conservation agriculture. We argue that there is a potential for SOC storage in agricultural soils of sub-Saharan Africa, as illustrated by SOC gaps observed on smallholder farms. Low SOC levels are, however, to a great extent the result of limited resources of most smallholder farmers. Practices such as agroforestry and conservation agriculture can restore SOC in these soils, but the 4‰ initiative has to be implemented on the grounds of the positive impact on crop productivity rather than on climate change mitigation. The efficiency in doing so will depend on the specific situations and will need economic support to smallholder farmers, including the promotion of good markets for sale of extra produce and for input supply, effective private support and policy, such as credit schemes and subsidies for inputs, and efficient extension services which incentivize farmers to invest in new technologies.
Efficient utilization of rice (Oryza sativa L.) fallow (∼11.6 million hectares) systems can accelerate the growth of Indian agriculture. But, bringing more area under cultivation is an ...energy-demanding process and a source of gaseous emissions in the era of climate change. Hence, development of environmentally sustainable cropping systems require for efficient use of rice-fallow lands for sustainable productivity. Therefore, the present study was conducted with the objective to identify sustainable and environmentally safer cropping systems with low global worming potential (GWP) and low energy requirement for rice fallow land of India. Seven diverse crops (e.g., toria (Brassica campestris var. toria), lentil (Lens culinaris), field pea (Pisum arvense), garden pea (Pisum sativum L.), green gram (Vigna radiata), black gram (Vigna mungo) and maize (Zea mays)) were introduced in rice-fallow system by adopting no-till (NT) production technology to develop sustainable and environmentally cleaner production systems in a subtropical climate of Tripura, India. All these rice-based cropping systems were evaluated on the basis of the energy requirements and system productivity. Results indicated that rice had the highest energy input followed by that for maize and the least for lentil. System productivity regarding equivalent rice yield was the highest in rice–garden pea system. The relative amount of energy input in all cropping systems involved 44–54% for chemical fertilizers, 13–17% for land preparation, 12–15% for diesel and 11–14% for labor. Total energy input of 28,656 MJ per hectare (MJ/ha) was the highest for rice–maize and the lowest of 22,486 MJ/ha for rice–lentil systems. The highest system productivity and the highest energy productivity were obtained for the rice–garden pea system. The GWP was lower for legume-based than that for cereal and oilseed-based cropping systems. The lowest GWP of 7.97 Mg CO2e/ha per yr was observed for the rice-lentil cropping system and the highest GWP of 8.39 Mg CO2e/ha per yr for the rice-maize cropping system. The rice-vegetable pea and rice-lentil cropping systems also had low greenhouse gas emission intensity. The rice–pea and rice–lentil cropping systems are recommended for the region because of their low energy requirement, high energy and system productivity and low GWP. These systems are suited for the efficient utilization of rice fallow lands of eastern India to sustain productivity while adapting and mitigating the climate change.
Display omitted
•Efficient utilization of rice fallow systems can accelerate the growth of Indian agriculture.•The introduction of lentil in rice fallow requires lower energy inputs than other crops.•Chemical fertilizer consumed highest energy input (44–54%) followed by the land preparation (13–17%) and diesel use (12–15%).•The rice-lentil system had the low GWP (7.97 CO2e Mg/ha.yr) and GHGI (0.93 kg CO2 e/kg REY).
Crop choice affects biodiversity within fields due to crop-specific characteristics and management practices. However, there is a lack of studies systematically comparing the biodiversity value of ...different crops across multiple taxa. This study empirically compared the diversity of plants, pollinators, predatory arthropods, and multi-taxa diversity between seven crop types and long-term environmental fallows in boreal farmland. The effects of crop production method (organic vs. conventional) on biodiversity were also examined. Biodiversity data were collected in 78 fields in Southern Finland. The studied species groups differed in their preferences for crop types and fallows, but none of them was particularly associated to spring cereal (oat), the dominant arable crop in the boreal farmland. Environmental fallows had the highest plant species richness and butterfly abundance, whereas faba bean and oilseed crop fields attracted high numbers of bumblebees. Carabid beetles were most abundant in winter cereal (rye) fields, and spiders in perennial crop types. Multi-taxa diversity was highest in fallows and lowest in spring cereal (oat), ley and cabbage fields. Organic production increased plant species richness across crop types. Hoverflies responded to the interaction of production method and crop type, being most abundant in organically managed faba bean fields. The other species groups and multi-taxa diversity were not affected by the production method. High arable land cover in the surrounding landscape had negative effect on butterflies, solitary bees and carabid beetles within fields. Our results suggest that diversifying cropping systems to include more insect-pollinated crops, winter cereals and pastures, and increasing the area of environmental fallows while maintaining landscape heterogeneity would enhance resource provision for a variety of organism groups in boreal agricultural landscapes.
•Diversity of multiple taxa was compared between crop types and production methods.•Insect-pollinated crops and fallows attracted the highest numbers of pollinators.•Predatory arthropods were most abundant in winter cereals and perennials.•Multidiversity was highest in fallows and lowest in oat, ley and cabbage fields.•Organic production increased plant species richness across crop types.
•Shifting cultivation had no effects on soil organic carbon (SOC) stocks.•Intensification of shifting cultivation did not affect the active carbon fraction.•Dead root biomass from slashed fallows ...provides a substantial input of C to the soil.•Carbon inputs to deeper layers must be better accounted for in SOC models.•Narratives of shifting cultivation depleting soil carbon stocks must be revisited.
Shifting cultivation systems of Southeast Asia are rapidly intensifying, especially through shortening of the fallow periods. It is typically assumed that intensification will result in a depletion of soil organic carbon (SOC) stocks, but existing estimates of carbon stocks in these systems are variable, and there is little certainty about the carbon outcomes of intensification. We investigated the effects of intensification on SOC stocks of a shifting cultivation system in northern Laos. Volume-specific soil samples were collected from 20 sites representing: i) various rotation intensities (fallow periods of 3–4 years and 7–10 years), ii) various stages of the rotation cycle (fallows and active fields) and iii) reference plots (old regrowth of 25–30 years). Samples were analyzed for SOC, soil texture, pH, Total Nitrogen and permanganate oxidizable carbon (POXC) – an active carbon fraction that has been suggested as an easily measured early indicator of land use induced changes in soil quality and SOC. There were no significant differences between SOC concentrations or stocks of any of the sites under shifting cultivation and the reference sites. However, the SOC stock under fallows in the intensive rotation category was significantly larger than the SOC stock under fallows in the extensive rotation category. This is likely because inputs of dead root biomass from the slashed vegetation provides an important input to the SOC pool. Fallow sites under intensive rotation had significantly higher contents of POXC in the topsoil than the active fields, which suggests that POXC captures the immediate effect of the decreased input of litter to the topsoil during the cultivation period. We conclude that in this study there is no evidence that intensification of shifting cultivation leads to a decline in total soil carbon stock, or to a decline in the more active carbon fraction measured by POXC. Therefore, narratives of shifting cultivation leading to a decline in soil carbon stocks need to be revisited, and land use policies related to the system should not uncritically be based on this incorrect assumption.
In the Indian state of Odisha, rice-based system productivity is poor due to: (i) low rice yield in the monsoon (wet) season (2–4 t ha−1 compared to 6–8 t ha−1 in Punjab or Haryana); and (ii) limited ...cropping during the post-monsoon (dry) season (59% of the wet season rice area is left fallow in the dry season).
Our study identifies strategies for increasing rice-based system productivity through: (i) alternative crop establishment methods in the wet season (Dry-Direct Seeded Rice or DSR, and mechanical puddled transplanted rice or PTR-M) to traditional methods such as broadcasting followed by post-emergence tillage (locally known as beushening) and manual random puddled transplanted rice (PTR-R); (ii) to identify rice-fallow areas suitable for pulse and oilseed cultivation in the dry season; and (iii) to evaluate the performance of short-duration pulses (green gram, Vigna radiata; black gram, Vigna mungo), and oilseeds (Brassica rapa var. toria, Helianthus annuus) in rice-fallow areas in the dry season.
On-farm experiments were conducted between 2017 and 2019 in three districts of Odisha (Bhadrak, Cuttack and Mayurbhanj) to evaluate DSR compared to beushening and PTR-R; and PTR-M compared to PTR-R and manual line puddled transplanted rice (PTR-L) in the wet season. The data from Landsat-8 Operational Land Imager (OLI) and Sentinel-1satellite sensors was used to identify rice-fallow areas, and the daily SMAP (Soil Moisture Active Passive) L-band soil moisture was used for mapping suitable rice-fallow areas for growing pulses and oilseeds. Short duration crops were evaluated in suitable rice-fallow areas.
In the wet season, DSR (range −4 to + 53%) had a significant effect on rice yield over beushening. Similarly, PTR-M consistently increased rice yield by 16–26% over PTR-R, and by 5–23% over PTR-L. In the dry season, pulse crops (green gram and black gram) performed well compared to Indian mustard under rainfed cultivation. However, under irrigated conditions, dry-season rice yield was more productive than the rice equivalent yield of green gram, black gram and sunflower. We found that 1.03 M ha (i.e., ∼50%) of total rice-fallow areas of 2.1 M ha were suitable for growing short duration green gram and black gram in the dry season.
We conclude that system productivity and cropping intensity can be increased by adoption of DSR and PTR-M in the wet season, and growing of green gram and black gram in the dry season.
Odisha state can potentially produce an additional 0.67 million tonnes pulses if suitable rice-fallow areas are brought under green gram and black gram cultivation in the dry the season.
•Rice-based system productivity is poor due to low rice yield in the wet season and limited cropping in the dry season.•Rice yield can be improved by adoption of direct seeded rice and mechanical transplanted rice•Rice-fallow area in Odisha is 2.1 M ha, and 50% (1.03 M ha) of them are suitable for growing short duration crops.•Pulses such as green gram and black gram can be grown in rice-fallow areas in rainfed condition.
Fruit flies are significant insect pests, worldwide. Tephritid species diversity and their seasonal abundance were investigated over 2 yr (May 2017 to May 2019) in Western Burkina Faso. A mass ...trapping experiment consisting of 288TephriTrap types, operating with four types of parapheromones comprising methyl eugenol, terpinyl acetate, trimedlure, and cue lure and an insecticide (Dichlorvos), was used for attracting and killing insects. Plant formations including natural fallows, mango orchards, and agroforestry parks in each of the six study sites were selected for data collection.Twenty-nine tephritid species belonging to 10 genera were identified. Fourteen fruit fly species were identified for the first time in Burkina Faso. The genera Ceratitis MacLeay (Diptera:Tephritidae) and Dacus Fabricius (Diptera:Tephritidae) with, respectively, 14 and 7 species recorded were the most represented. The dominant species caught was the invasive Bactrocera dorsalis Hendel (Diptera: Tephritidae) followed by Ceratitis cosyraWalker (Diptera:Tephritidae) and Ceratitis silvestrii Bezzi (Diptera:Tephritidae).The fruit fly population density was very high during the rainy season, with peaks occurring in June or July.The fruit fly species were generally more abundant during the hot and rainy seasons than during the cold and dry seasons. The highest diversity was recorded in natural fallows, as compared with the mango orchards and agroforestry parks. Tephritid species found refuge in the mango orchards during the dry and cold periods.The results of that investigation may be used for developing a sustainable pest management strategy for commercial orchards.
•Post-milpa fallows reach biomass saturation early during succession.•Pine or alders dominate early stages and oak or cloud forest species late stages.•Limited dispersal, light, and moisture drive ...community dynamics in post-milpa fallows.•β-diversity is high among successional stages, micro-basins, and later stages.•Traditional milpas generate forests with high β-diversity and resilience potential.
The milpa is a millennial agroecosystem commonly practiced in the Mesoamerica mountains. For soil recovery, the milpa depends on the fallows that develop in lands left unsown after the cultivation stage, but their successional dynamics are little known. We studied the successional dynamics of post-milpa fallows in the mountains of Mixteca Baja, north-western Oaxaca, Mexico, where this cropping system is common. We use the chronosequence approach in fallows ranging from ≈20 to 100 years old of three nearby watersheds that differ in their degree of exposure to Pacific Ocean winds, the leading source of rain and moisture. We analyzed information from field plots and unmanned aerial vehicle imagery to detect successional trends in milpa fallows. We find that around two decades after cultivation, the fallows are forests dominated by pines or alders. Plant density, vegetation cover, and diameter at breast height show little change afterward, suggesting that the forests reach a saturating point very early during succession. Subsequently, the main changes are in composition and diversity. Shade-tolerant species may replace pioneer species, species composition is moisture-related, and diversity shows contrasting patterns depending on the watershed. Old-growth vegetation is typically an oak forest in the driest watershed and a tropical montane cloud forest in the most humid. Species dominance tends to decrease with succession. β-diversity is significant and can be ascribed to microclimate and successional processes associated with orography and the milpa practice. Older stands within the same watershed, tend to diverge in composition relative to younger stands, suggesting a lack of convergence towards a climax community. Combining young and old-growth forests might positively impact biodiversity and landscape resilience and helps explain the millennial persistence of milpas in Mesoamerica.
PDF
