Fallow Duration Research Articles

Impact of Vineyard Fallow Practices on Reducing Meloidogyne hapla Population Densities

The northern root-knot nematode (Meloidogyne hapla) is a common plant-parasitic nematode in northern grape production regions. This nematode induces small galls on roots, which restricts water and nutrient uptake, resulting in poor vine establishment or exacerbated decline in stressed vines. A study was conducted to explore the impacts of site management practices on M. hapla population densities following removal of wine grape (Vitis vinifera) vineyards in Washington State. Soil was collected from 38 fields, M. hapla second-stage juvenile densities in soil were determined, and to assist in identifying M. hapla in potentially low-population density samples, an eight week-long tomato (Solanum lycopersicum) bioassay was conducted. Vineyard managers also provided information on site management techniques. Of the 20 total management techniques and combinations explored (e.g., fallow duration, cover crops, mowing, irrigation, herbicide applications), only one component resulted in lower M. hapla population densities: duration of vine-free period. A duration of at least one-year post vineyard removal showed a decline in M. hapla population densities in the sampled former vineyard sites. These results suggest that a fallow period could be useful as a non-chemical management tool for M. hapla in vineyard replant soils. However, consideration of additional site management factors such as weed management, soil series and amendments, interim crop planting, and irrigation or accumulated rainfall that may support M. hapla development is necessary.

Influence of agroforestry systems on earthworm diversity and soil properties in a Sudano-Sahelian landscape

Agroforestry systems promote a range of ecological base management to support sustainable agriculture. However, the influence of agroforestry management on soil biodiversity is still poorly investigated in Sudano-Sahelian landscapes. This study aims to guide sustainable management for soil biodiversity conservation in agroforestry systems by determining the drivers of earthworm diversity with their abundance and corresponding soil properties. Nested sampling following three management systems (agroforestry fallow, agroforestry intercropping, agroforestry grazing) and the protected area as a baseline, were designed for data collection in a Sudano-Sahelian landscape. Earthworm inventory and soil sampling (0–10 cm), coupled with a survey focusing on the cropping and fallowing duration with other agricultural practices (herbicide use, soil tillage), were conducted on the farm. The soil analysis included soil texture, bulk density and a suite of chemical analyses (pHKCl, C and N, available macro and micronutrients). The data were analyzed using generalized linear models (GLMs) and ANCOVA to determine the effects of agroforestry systems on earthworm abundance and soil properties. A Principal Component Analysis (PCA) was performed to determine the relationship between the species richness of earthworms, agroforestry systems and soil properties. The results showed a diversity of five species belonging to the endogeic and epigeic ecological groups numbered at 7 ± 3 to 22 ± 10 individuals m−2 (mean ± standard deviation). In agroforestry fallow systems, earthworm diversity and abundance were both highest, and the abundance increased with the fallow duration. The prolongation of cropping duration coupled with herbicide use in agroforestry intercropping systems decreased significantly the abundance of earthworms. Agroforestry grazing systems increased significantly soil C, N and available nutrients, but the abundance of earthworms and species richness were the lowest likely due to soil destructuration by trampling. Overall, soil texture controlled the species richness of earthworms. Fallow management and agricultural practices with fewer herbicide use and soil destructuration, are essential to improve earthworm abundance and diversity.

Characterization of shifting cultivation, trends, and diversification of livelihood patterns: A case study from forest villages in Barak valley, Assam, Northeast India

Shifting cultivation is a traditional agricultural system and predominant land use in the mountainous regions of many parts of the world. Recently, there has been a change in traditional shifting cultivation practice. The purpose of the current study is to map the spatial distribution of shifting cultivation plots in forest villages of Barak Valley, Assam, Northeast India, document the socio-economic profile of cultivators, and examine how traditional shifting cultivation is transitioning towards other agricultural systems, leading to livelihood diversification. The study included both primary and secondary data. The shifting cultivation plots were digitized using Sentinel 2 image of 2022. A total of 146 respondents from nine forest villages were interviewed using a structured questionnaire. The plots were concentrated in the southern part of Barak Valley and sparsely distributed in the Northern part. The average plot size was 1.35±0.02 ha. A positive correlation was observed between family size and size of jhum plot. The villages were located in remote areas with little access to basic amenities such as metalled roads and schools. The duration of fallow was lesser in villages located nearer to the market, as it was easier for them to sell their produce. Diversification of livelihoods among the younger members was observed, who were engaged in activities other than cultivation. The reason cited by respondents for this was earning additional income. Shifting cultivation combined with commercial farming on fallow land was the most common form of livelihood. The fallow period ranged between 2 to10 years. Weed infestation and loss of fertility were cited as major reasons by all respondents for leaving jhum plots fallow. Species such as Citrus sinensis (L.) Osbeck (Orange), Musa sp (Banana), Piper betle L. (Betel Leaf), Parkia timoriana (DC.) Merr. (Tree bean), Thysanolaena latifolia (Roxb. ex Hornem.) Honda (Asian Broom Grass) and other economically important species were cultivated in the fallow lands. This has increased the pressure on remaining forest lands that are being converted into shifting cultivation areas. Although conversion of fallow for monoculture and agroforestry may not be the solution to every problem, it holds promise for both ecological and economical sustainability, if managed judiciously. However, transition to other livelihood systems must occur with minimal degradation of ecosystem services.

Direct sowing of onion (Allium cepa) over cover crops with different lengths of the chemical fallow

The objective of this work was to evaluate the effect of cover crops and fallow duration on the onion crop planted in direct sowing in trials carried out for three years. In the year 2013, two field trials were carried out in two sites. Two cover crops (oats and millet) and one uncovered control were evaluated at three planting dates. The studied variables were crop establishment and dry matter of the cover. In the field trials performed in 2014 and 2015 the effect of the length of the chemical fallow of oats on the establishment of onion was evaluated. The effect of the duration of the chemical fallow of oats was also evaluated in laboratory in 2015 in Petri dishes. In 2013, the greatest establishment was obtained in the treatments without cover in both sites. In 2014 the greater the duration was of the chemical fallow of the cover, the greater the onion establishment. In the field trial in 2015, no effects of fallow duration on crop establishment were observed, a result attributable to the intense rainfall recorded. In the laboratory, germination was higher in treatments with longer fallow periods. Based on the results, evidence was obtained of the negative effect of the cover crops in the establishment of the onion crop. These effects were inversely related to the duration of chemical fallow and may be attributable to allelopathic effects.

Sustainable Agroforestry Crop Rotation System for the Tropics: A Theoretical Exposition

Population pressure is the key reason that has been reducing the duration of fallow in shifting cultivation. In many places, it has changed to bush fallow and subsequently is going towards the need to use available arable lands continuously. As a result, soil productivity is declining since long fallow is required for its regeneration after land is planted for a few years. An agroforestry tree crop/arable crop rotation system was proposed to mimic the natural fallow system and improve nutrient recycling through litter drops, which will improve soil organic matter. As soil organic matter improves the soil structure in addition to the ability of the soil to retain nutrients and water, the land becomes suitable for continuous crop production with appropriate fertilization regimes. The proposed tree crop/arable crop rotation will therefore result in continuous generation of income from harvestable produce in the rotation system year in year out. The paper, equally elucidated on other benefits of rotating tree crops with arable crops on the same land towards achieving maximum land productivity and obtaining benefits from the land without subjecting the land to the traditional fallowing system. This intervention will reduce abject poverty (SDG1), reduce acute hunger (SDG2), promote sustainable economic activities and growth, increase employment and decent work (SDG8) and promote sustainable industrialization and foster innovation (SDG9). The paper also identified the challenges associated with this type of rotation system and proffered suggestions on how to ameliorate such challenges.

Dry bolls and their association withAnthonomus grandis grandisBoheman (Coleoptera: Curculionidae) survival through cotton fallow periods

AbstractThe boll weevil,Anthonomus grandis grandisBoheman (Coleoptera: Curculionidae), can remain inside dry and deformed reproductive structures of cotton,Gossypium hirsutumLinnaeus (Malvaceae), known as dry bolls, during the cotton fallow to infest the next cotton crop. In this study, the influence of cotton cultivars and sowing densities on the formation of dry bolls was evaluated. In addition, dry bolls were dissected and internal structures that were related to boll weevil development were estimated. Finally, the presence and survival of boll weevils inside dry bolls were evaluated. The results indicate that the number of dry bolls, empty pupal cells, and emergence holes was influenced by cultivar and not by sowing density. Almost one-quarter (22.53%) of adult boll weevils examined was found alive inside the dry bolls after 10 weeks, which is slightly longer than the duration of cotton fallow in Brazil’s main cotton-producing regions. Therefore, remaining inside the dry bolls is an important survival strategy for boll weevils during the cotton fallow period, and cotton cultivars with a greater propensity for the formation of dry bolls might favour survival of the pest during this period.

Improved genotypes and fertilizers, not fallow duration, increase cassava yields without compromising arbuscular mycorrhizal fungus richness or diversity

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in agroecosystems, but their role in mediatingagricultural yield remains contested. Field experiments testing effects of realistic agronomic practices ofintensification on AM fungus composition and yields are scarce, especially in the low-input systems ofsub-Saharan Africa. A large, full-factorial field experiment was conducted in South-Kivu (DR Congo),testing effects of fallow duration (6 vs. 12 months), genotype (landrace vs. improved), and fertilizermanagement (control vs. five combinations omitting N, P, K, and/or secondary macro- andmicronutrients) on yields of cassava, an important staple crop strongly colonized by AMF. Furthermore,we used DNA-metabarcoding to evaluate effects of these agronomic practices on the AM fungalcommunities on the roots. The shorter fallow duration strongly increased diversity and richness of AMF,but this did not correspond with increased yields. Cassava yield was mainly determined by genotype,being largest for the improved genotype, which coincided with a significantly higher sum of AM fungalsequences. Effects of fertilizer or genotype on community composition were minor to absent. We foundno evidence that increased AMF richness and diversity enhanced cassava yields. In contrast, the use ofthe improved genotype and mineral fertilizers strongly benefitted yields, without compromising richnessor diversity of AMF. Cassava-AMF associations in this work appear robust to fertilizer amendments andmodern genotype improvement.

Optimal and sustainable management of a soilborne banana pest

In this paper we propose an eco-friendly optimization of banana or plantain yield by the control of the pest burrowing nematode Radopholus similis. This control relies on fallow deployment, with greater respect for the environment than chemical methods. The optimization is based on a multi-seasonal model in which fallow periods follow cropping seasons. The aim is to find the best way, in terms of profit, to allocate the durations of fallow periods between the cropping seasons, over a fixed time horizon spanning several seasons. The existence of an optimal allocation is proven and an adaptive random search algorithm is proposed to solve the optimization problem. For a relatively long time horizon, deploying one season less than the maximum possible number of cropping seasons allows to increase the fallow period durations and results in a better multi-seasonal profit. For regular fallow durations, the profit is lower than the optimal solution, but the final soil infestation is also lower.

Modelling and control of a banana soilborne pest in a multi-seasonal framework

We study the infestation dynamics of banana or plantain plants by Radopholus similis, a plant-parasitic nematode that causes severe damages. Two control strategies are implemented in our model: pesticides, which are widely used, and fallows, which are more environmentally friendly. To represent the host-parasite dynamics, two semi-discrete models are proposed. During each cropping season, free nematodes enter the plant roots, on which they feed and reproduce. At the end of the cropping season, fruits are harvested. In the first model, the parent plant is cut down to be replaced by one of its suckers and pesticides are applied. In the second model, the parent plant is uprooted and a fallow period is introduced, inducing the decay of the free pest populations; at the beginning of the next cropping season, a pest-free vitroplant is planted. For both models, the effective reproduction number of pests is computed, assuming that the infestation dynamics are fast compared to the other processes, which leads to the model order reduction. Conditions on the pesticide load or the fallow duration are then derived to ensure the stability of the periodic pest free solution. Finally, numerical simulations illustrate these theoretical results.

Effect of Fallow Duration on Growth of Paddy Rice Seedlings and Mineralized Nitrogen in Organic Fertilizer-amended Soil

Effect of Fallow Duration on Growth of Paddy Rice Seedlings and Mineralized Nitrogen in Organic Fertilizer-amended Soil

Impact of different fallow durations on soil aggregate structure and humus status parameters

Soil aggregate structure and soil organic matter are closely interrelated and commonly considered as key indicators of soil quality. The aim of this study was to evaluate the effects of different fallow durations on indices of soil structure and humus status indicators. Studies were conducted on abandoned agricultural fields (15, 20 and, 35 years after abandonment). As a reference site, we used a cultivated field in the area. The experimental soil fields are classified as Gleyic Cambisols. Soil macroaggregates were separated with the sieve (dry sieve) to seven aggregate size fractions, i.e.> 10, 10–5, 5–2, 2–1, 1–0.5, 0.5–0.25 and < 0.25 mm. The humus status parameters of soils included the following indicators: soil organic carbon (C<sub>org</sub>), humus reserves (Q<sub>H</sub>), the degree of humification of organic matter (SOM<sub>dh</sub>), fractions of humic acids (HA) (free and bound with monovalent cations and Al<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub>, bound with Са<sup>2+</sup> which forms humates, bound with clay minerals), fulvic acids (FA) (free aggressive) and ratio of HA to FA (C<sub>HA</sub><sub> </sub>: C<sub>FA</sub>). After a fallow period of more than 20 years on the surface formation of a sod layer. A long-term fallow period had an impact on the mean weight diameter of the aggregates (MWD) and agronomically valuable aggregates (AVA). Fallow soils have a significantly better structure than soils under a cultivated field. Long-term cultivation leads to the deterioration of soil structure and the formation of large aggregates (>10 mm). The C<sub>org</sub> content remains at the level of the background content when the soils are left fallow for less than 15 years and increases over time. The C<sub>org</sub> in the upper 0–20 cm soil layer has been shown to increase from 3.55 to 8.74% on arable land that has been fallow for 35 years and has been largely associated with significant accumulation of organic matter within the plant root mass. Mature sites are characterized by an increase of fulvic acids in the humus composition in comparison with their arable analogues. The abandonment of soil agricultural use and the cessation of mechanical tillage results in the restoration of the natural structure of soils and the improvement of their agrophysical properties. Such studies have not been previously conducted in the Primorsky region of the Russian Far East.

Temporal Bacterial Surveillance of Salmon Aquaculture Sites Indicates a Long Lasting Benthic Impact With Minimal Recovery.

Coastal aquaculture has experienced substantial growth in the last few decades and associated impacts on natural environments are of increasing importance. Understanding both the effects of aquaculture on marine ecosystems and the processes of recovery during fallowing periods is crucial for the development of a more environmentally sustainable industry. Because bacteria are sensitive to environmental change, surveying fluctuations in bacterial communities is a promising tool for monitoring the status of benthic environments. Here, we used 16S rRNA gene high-throughput sequencing to characterize bacterial communities in flocculent matter samples collected over a period of 3 years and at various distances from cages (0–200 meters) at production and fallow (3–35 months) salmon aquaculture sites in southern Newfoundland to evaluate the environmental impact of aquaculture on predominantly hard-bottom substrates. Bacterial composition analysis revealed four clusters, three of which (defined as “recently disturbed,” “intermediate impact,” and “high impact”) differed markedly from a fourth “low impact” cluster that contained far-field samples collected >500 m from cages. Samples within the high impact group were most often collected directly under cages, whereas those in the intermediate impact group were mainly sampled from 20 to 40 m from cages. Large scale phylum shifts (increases of Bacteroidetes, Firmicutes, Spirochaetes, and decreases in Proteobacteria and Epsilonbacteraeota) and a decline in bacterial diversity were observed in the high impact cluster, indicating significant ecological change. Samples from sites of different fallow duration were found in the high impact cluster, indicating a lack of recovery, even after 35 months of fallowing. Finally, we identified 28 genera as bacterial biomarkers, specific to one or more clusters, including genera associated with organically enriched environments and previously reported in the context of aquaculture impacts. Tracking the relative abundance of biomarkers in relation to different lengths of fallowing in the three more impacted clusters showed that these markers remained significantly above low impact cluster levels at all times, further pointing toward incomplete recovery. Our results suggest that coastal aquaculture on hard-bottom substrates is prone to long lasting impacts on bacterial communities, especially below cages, and that effects can be accurately tracked using bacterial community profiles or specific biomarkers.

English

Tree planted fallow is an agroforestry system that may restore degraded soils and protect them from erosion. In this study, sandy soils properties of Acacia senegal planted fallows (AF) were assessed and compared to those from the continuous cropped system (CC) in 3 sites from Northern Cameroon in order to determine its suitability to restore soil fertility and sustain crop productivity. Soil samples were collected from the topsoil (0 to 20 cm) and the subsoil (20 to 40 cm) and subjected to physicochemical analyses. The trials were established for 2 consecutive years, respectively with sorghum (Sorghum bicolor) and cowpea (Vigna unguiculata). Results confirmed the sandy (more than 80% of sand) and acidic (4.42 ≤ pH ≤ 6.59) soil characters. In every site, topsoil from AF was relatively more fertile than from CC. Globally, nutrients content were influenced by tree density and fallow duration. The more improved elements were organic matter, nitrogen and pH. Sorghum and cowpea yields were quite variable depending on fallow duration, tree density and conversion form. The highest crop yields (3.4 tha-1 for sorghum and 2.4 tha-1 for cowpea) were obtained in 19 years old AF converted by partial clear-felling. The intercropping process by partial clear-felling of trees was the best conversion form. Overall findings indicated that fallowing with A. senegal can reduce soil acidity, restore nutrients and therefore it constitutes a suitable agroforestry system that may sustain annual crops productivity. However, researches have to determine the best tree density for intercropping and the tools for their sustainable management.   Key words: Acacia senegal fallow, agroforestry, sandy soils, continuous cropping, North Cameroon. &nbsp

Degradation of soil nutrients and slow recovery of biomass following shifting cultivation in the heath forests of Sarawak, Malaysia

Heath forests which are tropical forests on sandy soils are widely distributed in Borneo and provide many ecosystem services, such as carbon storage and non-timber forest products. Over the past several decades, such forests have been disturbed by non-traditional shifting cultivation, which is usually conducted in unsuitable land with short fallow duration. Anthropogenic disturbances in forests growing on sandy soils that have low nutrient retention capacities may promote further reductions in soil fertility. Long-term monitoring of soil nutrients and biomass accumulation is rare in degraded tropical rainforests growing on sandy soils despite the known negative effects of non-traditional shifting cultivation practices on soil fertility, vegetation and biomass recovery, and the growth of trees planted to rehabilitate forests. The objective of the current study was therefore to elucidate changes in soil fertility and biomass recovery potential in degraded forests on sandy soils in Borneo. We monitored soil nutrients and chemical properties in fifty-four 12 × 12 m plots located on different topographical positions along upper and lower slopes. Samples were collected in plots aged 7 and 14 years after abandonment of shifting cultivation. The biomass of secondary forest trees in all plots 12 years after the abandonment was also measured to determine the relationship between biomass accumulation and changes in soil nutrients. We found that soil pH and cation exchange capacity, and the concentrations of most nutrients, including nitrogen, magnesium, and phosphorus, had decreased significantly 7–14 years after abandonment; biomass accumulation in the plots was also limited 12 years after abandonment (<0.8 Mg ha−1 year−1). These changes in soil traits within the study plots were similar regardless of topographical position, and the changes were not related to the amount of biomass. Soil nutrients in the plots may have leached out as a result of removal of thick root mats in the surface soil, high sand content, and large amounts of rainfall in the area rather than uptake by recovering trees. These results indicate that it may be difficult to recover soil fertility on steep slopes in sandy soil conditions because of high leaching rates and erosion when the soil surface layer is destroyed by shifting cultivation. It is therefore important to carefully manage shifting cultivation practices in tropical forests on sandy soils in Borneo.

Ecosystem recovery indicators as decision criteria on potential reduction of fallow periods in swidden systems of Northern Thailand

Crop rotations in today’s swidden systems of Northern Thailand typically include five to ten years of fallow. Regarding ecosystem functions, these systems are relatively close to secondary forests when compared to modern agricultural systems; but they are under pressure for intensification, i.e. shortened fallow periods. In general, criteria are needed to decide whether fallow duration can be reduced, safeguarding ecosystem restoration and provision of food and income for farmers. Acknowledging that a comprehensive assessment would cover multiple aspects, our study focuses on the role of fallow duration on tree structural and biodiversity related variables.We studied recovery indicators of tree communities at two potential broad-leaved forest climax sites that differ in soils, forest type and agricultural intensification: An intensive system of one-year upland rice, then one- to two-year maize cultivation with synthetic inputs followed by six years fallow; and an extensive system with one-year upland rice cultivation without agrochemicals and ten years fallow. Contrasting systems were chosen to test the applicability of our indicators, not to compare their management practices. From 2010 to 2011, eight variables related to stand structure and tree diversity were either monitored or surveyed in chronosequence plots of 6 × 50 m representing different fallow ages. For each variable, means per fallow year were compared by least squares means (LS-means), and quadratic regressions from mixed models were fitted. Significant differences between LS-means and optima of regressions served to distinguish fallow stages and served as indicators of recovery and system stability. Stepwise multiple regressions confirmed fallow age as main determinant for most variables.Numbers of tree species and diversity index recovered to levels of the previous rotation within the respective fallow time, but in both systems were far from climax communities, probably due to seed-bank depletion and shift toward resprouting species. While species dominance changed over time in the extensive system, the intensive system was dominated by a single species.In the extensive system only tree density passed a peak during the fallow period, while biomass-related variables approached plateaus. In combination with the replacement of early fallow species, this points to the onset of competition and transition between successional stages. For the intensive system, no structural variable passed a maximum. With only one of eight indicators on the extensive site fulfilling the statistical criterion of passing a peak during the prevailing fallow time, reducing fallow periods is not recommended for our cases.Generally, combining LS-means and quadratic regression allowed assessing fallow duration based on distinct successional stages at different sites. The approach should include various relevant site-specific indicators, in our case representing biomass and carbon storage, species and structural diversity, considered crucial for both sites.

Correlation between soil physicochemical properties and vegetation parameters in secondary tropical forest in Sabal, Sarawak, Malaysia

The tree growth is influenced by soil morphological and physicochemical properties in the site. The purpose of this study was to describe correlation between soil properties under various stage secondary forests and vegetation parameters, such as floristic structure parameters and floristic diversity indices. The vegetation surveys were conducted in 5, 10, and 20 years old at secondary tropical forests in Sarawak, Malaysia. Nine sub plots sized 20 m × 20 m were established within each study site. The Pearson analysis showed that soil physicochemical properties were significantly correlated to floristic structure parameters and floristic diversity indices. The result of PCA clarified the correlation among most important soil properties, floristic structure parameters, and floristic diversity indices. The PC1 represented cation retention capacity and soil texture which were little affected by the fallow age and its also were correlated by floristic structure and diversity. The PC2 was linked to the levels of soil acidity. This property reflected the remnant effects of ash addition and fallow duration, and the significant correlation were showed among pH (H2O), floristic structure and diversity. The PC3 represented the soil compactness. The soil hardness could be influenced by fallow period and it was also correlated by floristic structure.

Study of the Effects of Two Crop Systems and Best Management Practices on Soil and Water Conservation in Tunisian Semi-arid Area

In Tunisia, water erosion is one of the most important processes affecting around 25% of arable land, generating a potential loss of soil productivity due to a decrease of hydraulically and chemical stocks. To control water erosion on lands of average slopes (less than 10%) best management practices (crop rotation, organic fertilization, etc.) have to be developed especially in Tunisian semiarid area, where rainfall irregularity and aggressivity enhance water erosion. Thus, conservative techniques for soil and water protection are required and have to be implemented at the level of the agricultural parcel to maintain or improve the productive potential of soils on average slopes in rain-fed lands, located in Tunisian semi arid area. In this context the article is presented. It is a synthesis of some experimental works on plots of 1 to 4 m2 in the experimental field station of the ESA Mograne, for the study of the effects of different kinds of crop-rotation (fallow long duration- chick pea) and organic fertilizers (row olive mills waste water) on the fertility of the soil and its potential yield. Results showed that long fallow-chickpea rotation and use of 50 m3/ha of row olive mills waste water improve soil fertility (water retention and C/N). This improvement in water and soil chemical properties increases the components of performance of chickpea (rate of dry matter) and weight of 1000 grains and plant biodiversity for 50 m3/ha spreading of row olive mills waste water. These results can be valued for the development of strips crops on average slope lands in Tunisian semiarid area for soil and water conservation.

Evaluation of nutrient uptake of selected cover crops and biochar on the yield advantage of two taro (Colocasia esculenta) cultivars in Samoa

A study was conducted in three agro ecological zones of Samoa to compare the dry matter yields and nutrient uptake of selected tropical cover crops and biochar application on different Samoan inceptisols. Subsequent improvements in corm yield of the two taro cultivars, (Samoa 1 and Samoa 2), under these fallow systems were also determined. The split-plot arrangement with main plots as cover crops and subplots as the cultivars was used, with four replications. The evaluated cover crops included: a reference – grass fallow treatment (farmers practice), Mucuna pruriens, Erythrina subumbrans, Mucuna pruriens + 200 kg of NPK fertiliser (12-5-20), farmer’s reference practice + 400 kg of NPK fertiliser (12-5-20), and biochar produced from coconut shells. The biomass samples were collected after the six month of fallow duration. Plant tissue analyses revealed that the nitrogen and the phosphorus contents of erythrina was higher than corresponding mucuna cover across all three sites. However, as a result of higher biomass production, Mucuna pruriens showed the highest nutrient accrual over the six month fallow duration. The general yield trend under different fallow practices across all the sites indicates that mucuna with modest supplementation of complete fertilisers can help maintain optimum taro yields. However, it appears that the yield responses of the taro crop to fallow treatments are site-specific.

Effects of Anthropogenic Activities and Eutrophication along River Chanchaga, Minna, Nigeria

River Chanchaga is the major source of drinking water in Minna, Nigeria. This river has been a medium to an increasing pollution loads from contaminated runoff from different land uses degrading aquatic ecosystem and water quality in the river.This paper investigates the threat of anthropogenic influence on river environment and aquatic ecosystem distortion of River Chanchaga, Minna, Nigeria. Field work which include interview and observation methods were used to collect data on effect of anthropogenic and eutrophication along the study area. A total of Two Hundred and Fifty (250) people accounting for 0.5% of the total population were interviewed, making it eight per each community in thirty settlements along the study area. Physical observation of deforestation around sample sites spatially distributed along River Chanchaga depicted in Figure 2 was carried out to study mining activities, farming practice, crop types, and fallow duration to generate the mean and percentages of different anthropogenic activities along the study area. The findings revealed that deforestation is links to high demand for fire wood, lumbering, irrigation farming bank-side mining for sand and gold as depicted in Plat 1 and 2. Eutrophication at the upper course of river is links to high inflow of agricultural wastes and seasonal nature of the river from site A to C evident from Table 4 and constant flow from site C to K as a result of released water from Tagwai Dam that keeps (site C, the confluence of River Chanchaga and River Numui) middle and lower courses of River Chanchaga with sustainable moving water. The result further indicated that continue increase of pollution has a direct relationship to an increasing level of human activities like deforestation, mining activities and agricultural practices along the study area. The result also shows that there is decline in fallow duration as indicated in Table 1 and increase environmental related issues such as soil erosion, water floor (depth) reduction and distortion of river morphology of the study area. It is therefore recommended that the identified anthropogenic activities that lead to pollution and eutrophication such as river-side deforestation, irrigation farming, mining and other related environmental problems should be regulated and discourages to avoid further increase of pollution and distortion of river environment of the study area.

Vegetation of a tropical dry forest in a landscape with chronic disturbance: the case of the indigenous community of San Nicolás Zoyatlan (Guerrero, Mexico)

Background. Tropical dry forests (TDF) provide numerous environmental services to its residents; this has led them to be humanized landscapes subjected to chronic disturbance with a high risk of disappearing.&#x0D; Research question. To establish the relationship of vegetation structure and composition of a chronically disturbed TDF, with some environmental factors and the intensity of agricultural land use.&#x0D; Study site and period of research. Our study was conducted during six months (July through November) in the TDF of the community of San Nicolas Zoyatlan (Guerrero, Mexico); a territory with a history of over 500 years of agricultural use. This use has led to a complex mosaic of vegetation fragments.&#x0D; Methods. A selection of 36 fragments was studied to determine vegetation structure and composition as well as environmental factors. Representative plants from sampled areas were collected. Data gathered was explored with regression and multivariate statistical analysis techniques.&#x0D; Results. 59 families, 178 genera and 279 species were recorded. Species richness varied widely among fragments, in general with a low dominance and high turnover of species. Slope was the only factor that showed a solid relationship with vegetation variables. Three groups of fragments were established and the statistical differences between them were explained by the duration of fallow. The fragments with longer fallow period showed the best conditions in vegetation variables and 66.9% of the species were found in them.&#x0D; Conclusions. Composition and structure of vegetation were related to intensity of agricultural land use. Although there is a process of impoverishment, vegetation dynamics involving species of the Fabaceae, Asteraceae and Burseraceae families show a potential for their use in the environmental restoration of Zoyatlan.