A note on ringed fields

Stocks (1983) suggested four reasons which motivate the planting of South American tropical forest swidden crops in concentric rings. His third proposal, that of protection from insect pests, is examined in the light of recent fieldwork with the Bari, and reformulated to suggest that protection from mammalian pests may be a more accurate explanation of the value of this type of field architecture.     

Restoration of degraded lands through bioenergy plantations

Land degradation has become a worldwide problem. Increasing population, the conversion of forest land into cropland, and its gradual degradation due to unsustainable agricultural practices have led to this prevailing scenario. Unsustainable agriculture practices like use of chemical fertilizers for increasing crop productivity (recorded 281.75 lakh tonnes in the year 2010–2011) also leads to degradation of land. A total of 4.1 million hectares of culturable wasteland was recorded in the same year. Also, crude oil consumption is increasing at a rate of 1.7% which prompts for massive input of crude oil. Thus, biofuel plantations have recently attracted a lot of attention because of several advantages that they present. The genetically engineered bioenergy crops can help in land restoration by increasing the soil fertility, growing in stress conditions, and they also lead to the production of fuels through their various parts. The use of genetically engineered bioenergy crops will not only help in the prevention of degraded land but also yield biofuel as a product and enhance soil fertility and health for further sustainable agricultural practices.     

Farmers’ Perspectives on Vital Soil-related Ecosystem Services in Intensive Swidden Farming Systems in the Peruvian Amazon

A growing dilemma is how to conserve Amazonian forest while allowing local people to secure their livelihoods. Small-scale swidden farming in Amazonia is entirely dependent on the continued provision of ecosystem services (ES) that generate the conditions for agriculture. This study identified soil-related ES needed for, and enhanced by, productive swidden systems from the farmer’s perspective. Workshops in six farming communities in northeastern Peru discussed various land uses, swidden systems that continue to be productive, and swidden systems on degraded land. The participating farmers noted changes in their production systems and described the ES (or lack thereof) in terms of soil quality, crop production quantity and quality, burning practices, forest regeneration, and farming skill. The central elements described in farmers’ own strategies for managing soil-related ES were fallow management for biomass production and crop diversity, factors identified as central to future ES management work in established agricultural areas in Amazonia.     

The Contribution of Paraserianthes (Albizia) falcataria to Sustainable Swidden Management Practices among The Baduy of West Java

There is a prohibition on the use of modern external inputs, such as chemical fertilizers, in Baduy swidden farming. Ordinarily, the consequence of this in a situation of acute forest pressure would be a decrease in fallow times, and an inevitable depletion of soil fertility. The Baduy (particularly Outer Baduy) have several ways of alleviating this problem, one of which is the introduction of Paraserianthes (Albizia) falcataria. By alternating this commercially valuable perennial leguminous tree with rice, soil fertility is maintained and the socio-economic position of the Baduy improved. As a result, swidden farming, which is considered by the Baduy to be central to their cultural identity, continues to be viable, despite increasing population density and the continuing depletion of mature forest.     

Short–rotation woody crops: A prospective method for phytoremediation of agricultural land at risk of salinisation in southern Australia?

Growing short–rotation woody crops (SRWC) in rotation with conventional agriculture (phase farming with trees) is a prospective method for ameliorating degraded soils, particularly those at risk from salinisation. This work details changes in soil water storage and crop and pasture growth in the first 2 years after harvesting SRWCs at two sites in Western Australia between 2002 and 2004.This trial has demonstrated that where the roots of SRWCs can penetrate deeply into the subsoil, it is possible to develop soil water deficits large enough to subsequently allow several decades of conventional agriculture before groundwater recharge is resumed. At one site, Eucalyptus polybractea dried the soil to 10 m, creating a soil water deficit of 1350 mm within 6 years of planting. It is estimated that annual crops and pasture could be grown at this site for 68 years before the soil again reaches field capacity. Further work is required to determine where in the landscape SRWCs can develop these large soil water deficits.Reduced soil fertility limited crop and pasture growth in the first year after the SRWC at one site, while reduced plant–available water limited crop and pasture growth for 2 years after the SRWC at the other. Monitoring is continuing to determine longer-term changes in soil water content and crop and pasture productivity.     

Seventeenth century organic agriculture in China: I. Cropping systems in Jiaxing region

The cropping systems of seventeenth century traditional organic agriculture in the Jiaxing region of eastern China required about 2000 hr of labor per hectare for rice production. Rice and related grain crops were produced employing only human power. The input was about 200 times that for most mechanized grain production today. The charcoal or fossil energy input to produce simple hand tools accounted for only 1–2% total energy in the crop systems. Organic wastes including manures, pond sediments, and green manure crops supplied most of the nutrients. Rice yields, ranging as high as 6700–8400 kg/ha, were similar to some of the highest yields today. The energy output/input ratio ranged from 9 for compost-fertilized rice to 12 for green manure-fertilized rice production. These ratios were 2–10 times higher than most mechanized rice production systems of today. Knowledge of the crop and soil system enabled the early Chinese farms to maintain high crop yields and sustain highly productive soils.     

Ecological aspects of swidden cultivation among the Andoke and Witoto Indians of the Colombian Amazon

The investigation of crop and soil-crop conditions among Andoke and Witoto cultivators in southeast Colombia is used as a basis for assessing Geertz' (1963) model of swidden cultivation. In this respect, the extent to which maniocdominated swiddens in the study area simulate the structure and composition of the forest climax community is questioned. As Geertz (1963) indicates, an initial nutrient boost for crop cultivation results from the preliminary burning of forest debris, but weed competition, rather than progressive loss of soil fertility, is reported to be the primary cause of abandoning manioc cultivation after 2–3 years. While the Andoke and Witoto crop system remains adaptive at the individual field level, particularly in its constituent species, its fundamental adaptation is considered to be its integration into the broader field and fallow system that juxtaposes crop production with extended periods of forest regeneration.     

Nutrient levels in corn and competing weed species in a first year milpa,Indian church,Belize, C.A.

Summary Grain production in two 1/4 hectare plots gave 2971 and 1380 kg/ha for an average yield of 2175 kg/ha. Average yield for local farmers was 1700 kg/ha. Weed biomass accounted for 50% of total bioomass in the hydric Site 4, but held 64–83% of the total nutrients. In the mesic Site 1, values were 5% and 3–29% respectively.Canna edulis was the most abundant weed species. Soil nutrient levels neither increased or decreased significantly between clearing and harvesting. Any decline in future crop production would be due to increased weed competition and not a decline in soil fertility. Weevil (Sitophilus zeamais) infestation is a serious problem in hybrid corn not encountered with local varieties.     

Effects of length of forest fallow on fertility dynamics in a Mexican ultisol

Changes with time in the fertility of a Mexican ultisol were evaluated from analyses of soil samples from fields representing 50 years of pineapple slash-and-burn agriculture. Sixteen fields with similar soil profile charactersitics representing eight ages of forest fallow were sampled. The fields, within an area of 5 km² of nearly level tropical forest, had been cleared by hand, initially intercropped with corn and manioc, followed with 3 to 4 y of pineapple, and then abandoned. The surface soils contained relatively high levels of C and N (5% and 0.3% respectively), were strongly acid (pH 5 to 5.5), and supplied very low levels of available P and K. Soil contents of both C and N declined rapidly after clearing to levels approximately 20% lower at 10y, then increased steadily during the fallow period to values not different from their initial levels. Since little of the N released was utilized by the low-yielding, P-deficient crops, this loss of C, N and accompanying cations is a most serious consequence of this rotation. Both the exchangeable and reserve K levels of these ultisols are low. Thus, K is identified as second to P as a growth limiting factor and the most difficult fertility management problem.     

Consequences of Swidden Transitions for Crop and Fallow Biodiversity in Southeast Asia

Swidden agriculture, once the dominant form of land use throughout the uplands and much of the lowlands of Southeast Asia, is being replaced by other land uses. While change and adaptation are inherent to swiddening, the current rapid and widespread transitions are unprecedented. In this paper we review some recent findings on changes in biodiversity, especially plant diversity at various scales, as swidden farming is replaced by other land uses. We focus particularly on two areas of Southeast Asia: northern Thailand and West Kalimantan. We examine actual and potential changes in the diversity of crops that characterize regional swidden systems, as well as that of the spontaneously occurring plants that appear in swidden fields and fallows. Severe declines in plant diversity have been observed in most areas and at most spatial scales when swidden is replaced by permanent land use systems. However, shifts away from swidden agriculture do not invariably result in drastic declines or losses of biological diversity, but may maintain or even enhance it, particularly at finer spatial scales. We suggest that further research is necessary to understand the effects of swidden transitions on biodiversity.     

Ecosystem Services and Biodiversity in a Rapidly Transforming Landscape in Northern Borneo

Because industrial agriculture keeps expanding in Southeast Asia at the expense of natural forests and traditional swidden systems, comparing biodiversity and ecosystem services in the traditional forest–swidden agriculture system vs. monocultures is needed to guide decision making on land-use planning. Focusing on tree diversity, soil erosion control, and climate change mitigation through carbon storage, we surveyed vegetation and monitored soil loss in various land-use areas in a northern Bornean agricultural landscape shaped by swidden agriculture, rubber tapping, and logging, where various levels and types of disturbance have created a fine mosaic of vegetation from food crop fields to natural forest. Tree species diversity and ecosystem service production were highest in natural forests. Logged-over forests produced services similar to those of natural forests. Land uses related to the swidden agriculture system largely outperformed oil palm or rubber monocultures in terms of tree species diversity and service production. Natural and logged-over forests should be maintained or managed as integral parts of the swidden system, and landscape multifunctionality should be sustained. Because natural forests host a unique diversity of trees and produce high levels of ecosystem services, targeting carbon stock protection, e.g. through financial mechanisms such as Reducing Emissions from Deforestation and Forest Degradation (REDD+), will synergistically provide benefits for biodiversity and a wide range of other services. However, the way such mechanisms could benefit communities must be carefully evaluated to counter the high opportunity cost of conversion to monocultures that might generate greater income, but would be detrimental to the production of multiple ecosystem services.     

Tree species selection and soil tillage in alley cropping systems with Phaseolus vulgaris L. in a humid premontane climate: biomass production,nutrient cycling and crop responses

The development of alley cropping systems is based on the assumption that leguminous trees planted in hedgerows influence the yield of associated crops favourably by means of the additional nutrient pool applied to the soil through tree prunings. An on-station field study (split-plot design in a randomised block design) was conducted on an Eutric Cambisol under humid premontane climate conditions in Costa Rica in order to evaluate the ability of Erythrina poeppigiana, Calliandra calothyrsus and Gliricidia sepium to increase bean (Phaseolus vulgaris) yields compared to sole cropping. Soil tillage was applied as a sub-treatment in order to evaluate if soil preparation would additionally alter soil fertility and bean yield. After seven years with pruning twice per year, the size of both the total N and P pool in the pruned tree material was about three times higher for Erythrina prunings than for Calliandra and Gliricidia prunings. Two and five weeks after mulch application 50–150% higher inorganic N pools were measured in the soil from Erythrina plots, the bean shoot biomass at harvest was increased by 65–100% and the bean yield was 15–50% higher than in plots with beans alone. Hence, of the three tree species, Erythrina was the best choice for alley cropping systems in the pedoclimatic environment studied. Soil tillage reduced bean yield, soil organic matter, total soil N content and soil microbial biomass N in the top soil and is not recommended for similar soils in humid premontane climates.     

Assessing long-term impacts of cover crops on soil organic carbon in the central US Midwestern agroecosystems

Cover crops have been reported as one of the most effective practices to increase soil organic carbon (SOC) for agroecosystems. Impacts of cover crops on SOC change vary depending on soil properties, climate, and management practices, but it remains unclear how these control factors affect SOC benefits from cover crops, as well as which management practices can maximize SOC benefits. To address these questions, we used an advanced process-based agroecosystem model, ecosys, to assess the impacts of winter cover cropping on SOC accumulation under different environmental and management conditions. We aimed to answer the following questions: (1) To what extent do cover crops benefit SOC accumulation, and how do SOC benefits from cover crops vary with different factors (i.e., initial soil properties, cover crop types, climate during the cover crop growth period, and cover crop planting and terminating time)? (2) How can we enhance SOC benefits from cover crops under different cover crop management options? Specifically, we first calibrated and validated the ecosys model at two long-term field experiment sites with SOC measurements in Illinois. We then applied the ecosys model to six cover crop field experiment sites spanning across Illinois to assess the impacts of different factors on SOC accumulation. Our modeling results revealed the following findings: (1) Growing cover crops can bring SOC benefits by 0.33 ± 0.06 MgC ha⁻¹ year⁻¹ in six cover crop field experiment sites across Illinois, and the SOC benefits are species specific to legume and non-legume cover crops. (2) Initial SOC stocks and clay contents had overall small influences on SOC benefits from cover crops. During the cover crop growth period (i.e., winter and spring in the US Midwest), high temperature increased SOC benefits from cover crops, while the impacts from larger precipitation on SOC benefits varied field by field. (3) The SOC benefits from cover crops can be maximized by optimizing cover crop management practices (e.g., selecting cover crop types and controlling cover crop growth period) for the US Midwestern maize–soybean rotation system. Finally, we discussed the economic and policy implications of adopting cover crops in the US Midwest, including that current economic incentives to grow cover crops may not be sufficient to cover costs. This study systematically assessed cover crop impacts for SOC change in the US Midwest context, while also demonstrating that the ecosys model, with rigorous validation using field experiment data, can be an effective tool to guide the adaptive management of cover crops and quantify SOC benefits from cover crops. The study thus provides practical tools and insights for practitioners and policy-makers to design cover crop related government agricultural policies and incentive programs for farmers and agri-food related industries.     

Soil management effects on entomopathogenic fungi during the transition to organic agriculture in a feed grain rotation

The growing demand for organic products creates opportunities for farmers. Information on the consequences of management practices can help farmers transition to organic and take advantage of these prospects. We examined the interaction between soil disturbance and initial cover crop on naturally occurring entomopathogenic fungi (EPF) during the 3-year transition to organic production in a feed grain rotation in central Pennsylvania. Our experiment included four systems comprised of a factorial combination of two levels of primary tillage (full vs. reduced) and two types of initial cover crop (timothy/clover vs. rye/vetch). The cropping sequence consisted of an initial cover crop, followed by soybean, and finally, maize. The entire experiment was replicated in time, with the initiation lagged by 1 year. We detected four species of EPF (Metarhizium anisopliae, Beauveria bassiana, Isaria fumosorosea, and Isaria farinosa) by bioassay of soil samples collected four times during each field season. The latter three species were detected infrequently; therefore, we focused statistical analysis on M. anisopliae. Detection of M. anisopliae varied across sampling date, year in crop sequence, and experimental start, with no consistent trend across the 3-year transition period. M. anisopliae was isolated more frequently in the systems initiated with timothy/clover cover crops and utilizing full tillage; however, we only observed a tillage effect in one temporal replicate. M. anisopliae detection was negatively associated with soil moisture, organic matter, and zinc, sulfur, and copper concentrations in the soil. This study helps to inform farmers about management effects on soil function, specifically conservation biological control.     

Habitat Selection by Female Elk During Minnesota's Agricultural Season

Understanding space-use patterns by elk (Cervus canadensis) is essential to alleviating human-elk conflicts, particularly when crop depredation by elk can make it harder to justify to the public the need to restore elk populations to regions with agricultural landscapes. In 2016–2017, we used global positioning system data from 20 female elk to investigate their selection for agricultural cover during the agricultural season (1 May–31 Oct) in northwestern Minnesota, USA. We estimated resource selection functions with resource availability defined at the home range scale. Elk space use was primarily determined by distance to forest cover in areas proximate to agricultural fields. During diurnal periods, elk selected areas with forest cover near agricultural fields planted with legumes and cereal. During nocturnal periods, elk selected for agricultural fields with little to no canopy and that were planted with legumes. We suggest that management of elk in northwestern Minnesota will require practices that discourage the use of agriculture by elk while improving natural habitats within areas managed for elk restoration. We suggest that forestry practices (i.e., thinning and burning) could improve cover and forage openings for elk in restoration areas. Furthermore, managers could work with agricultural producers where elk occur to plant crops favored by elk (i.e., legumes) outside known home ranges and plant fields within home ranges with crops that elk avoided (i.e., hay). Collectively, these practices may shift the ranges of elk herds into restoration areas and lower conflict between the public and elk restoration efforts. © 2020 The Wildlife Society.     

Monoculture,polyculture, and polyvariety in tropical forest Swidden cultivation

A number of researchers have suggested that polyculture is characteristic of native tropical forest swiddens and have adduced theory from community ecology to account for its adaptiveness. Ye'kwana and Yanomamö swidden cultivation is examined, and it is shown that polyculture is not practiced to any significant degree. Instead, the concept of polyvariety is introduced along with a number of other cultivation practices that more simply account for the adaptiveness of Ye'kwana and Yanomamö gardening. In addition, comparative data from other parts of the tropical world indicate that polyculture is no more common than monoculture and recent advances in ecological research indicate that the diversity-stability hypothesis that underpins adaptive arguments of polyculture is in need of drastic revision.     

Allelopathy as a Tool in the Management of Biotic Resources in Agroecosystems

In modern agriculture, natural plant communities may be replaced by a single crop species. Weeds, some microorganisms, and viruses, as well as some herbivores are organisms that should be eliminated. Pesticides and fertilizers not only affect the pests and crops, but soil, non-pest species, water, food, and humans. In traditional agriculture weeds are components with an important ecological role in the maintenance of the system. Some weeds have been used as tools to control the growth of other weeds in traditional agroecosystems. Researchers on sustainable and organic agriculture get valuable information from traditional agriculture and currently are conducting research on plant breeding, soil fertility and tillage, crop protection, and cropping systems. Allelopathy and chemical ecology are directly involved in each of these fields and can play an important role in crop productivity, conservation of genetic diversity, and maintenance of ecosystems stability. Allelopathy has been shown to be related with problems of chemical interference between crops and weeds, crops and crops, toxicity of crops and weeds residues, and/or crops and weeds exudates. Problems of autotoxicity, orchard replanting, and forest regeneration are also referred as allelopathic. Allelopathy is strongly coupled with other stresses of the environment, including insects and disease, temperature extremes, nutrient and moisture variables, radiation, and herbicides. These stress conditions often enhance allelochemical production and increase the potential for allelopathic interference. Allelopathy offers potential for weed control through the production and release of allelochemicals from plants. Allelochemicals may impact the availability of nutrients through effects on the symbiotic microbes. Destruction and changes in the use of soils in the tropics have decreased biodiversity, bringing about the loss of valuable natural products. Many different types of useful products such as natural pesticides and drugs can arise from allelopathy studies. New methods must be generated for allelopathy as a part of the biotic resources management strategies.     

Comparing forest structure and biodiversity on private and public land: secondary tropical dry forests in Costa Rica

Secondary forests constitute a substantial proportion of tropical forestlands. These forests occur on both public and private lands and different underlying environmental variables and management regimes may affect post‐abandonment successional processes and resultant forest structure and biodiversity. We examined whether differences in ownership led to differences in forest structure, tree diversity, and tree species composition across a gradient of soil fertility and forest age. We collected soil samples and surveyed all trees in 82 public and 66 private 0.1‐ha forest plots arrayed across forest age and soil gradients in Guanacaste, Costa Rica. We found that soil fertility appeared to drive the spatial structure of public vs. private ownership; public conservation lands appeared to be non‐randomly located on areas of lower soil fertility. On private lands, areas of crops/pasture appeared to be non‐randomly located on higher soil fertility areas while forests occupied areas of lower soil fertility. We found that forest structure and tree species diversity did not differ significantly between public and private ownership. However, public and private forests differed in tree species composition: 11 percent were more prevalent in public forest and 7 percent were more prevalent in private forest. Swietenia macrophylla, Cedrela odorata, and Astronium graveolens were more prevalent in public forests likely because public forests provide stronger protection for these highly prized timber species. Guazuma ulmifolia was the most abundant tree in private forests likely because this species is widely consumed and dispersed by cattle. Furthermore, some compositional differences appear to result from soil fertility differences due to non‐random placement of public and private land holdings with respect to soil fertility. Land ownership creates a distinctive species composition signature that is likely the result of differences in soil fertility and management between the ownership types. Both biophysical and social variables should be considered to advance understanding of tropical secondary forest structure and biodiversity.     

Soil nutrient status of hill agro-ecosystems and recovery pattern after slash and burn agriculture (Jhum) in north-eastern India

Summary The present study deals with fertility changes in agro-ecosystems where vegetation is removed by slash and burn procedures, the land is planted to crops (cultivated) for one year, and then left to revegetate naturally for upto 50 years (forested fallow, here after referred to as ‘fallow’) before the entire cycle (locally called ‘Jhum’) is repeated. A comparison has been made between three jhum cycles of 30, 10 and 5 years. Depletion in soil carbon continued throughout the cropping period of one year and extended upto a 5 year fallow. This could be one of the reasons against a short jhum cycle, alongwith a similar pattern in depletion of nitrogen. Available phosphorus build up in the fallows also starded only beyond a 5 year fallow period with rapid increase in 10, 15 and 50 year fallows. Cationic concentration in the soil also rapidly declined in the early phases of regrowth of vegetation. This decline was most pronounced for potassium due to the fact thatDendrocalamus hamiltonii is a heavy accumulator of this nutrient. Since this bamboo species dominates the fallow upto about 20 years, potassium build up in the soil was observable only at this stage. It is suggested that this species plays an important role in conservation of this nutrient. In a 50 year fallow, low levels of calcium and magnesium were maintained with rapid depletion of both with depth which is in contrast to that of potassium and phosphorus. In general, short jhum cycles of 5 year permit only low levels of soil fertility with very poor recovery during the fallow period. The significance of these results are discussed.