Natural Fallow Research Articles

Response of soil water to long-term revegetation, topography, and precipitation on the Chinese Loess Plateau

The Chinese Loess Plateau (CLP) rose to prominence for its fragmented terrain and fragile ecosystems. Large-scale revegetation was applied to control soil and water loss there. However, revegetation resulted in unexpected water shortages. In this study, we investigated the temporal-spatial distribution of soil water in the northern CLP based on 13-year soil water content (SWC) data of four different revegetation types on a loessial slope and 4-year data of a gully system to study the response of soil water to long-term revegetation, topography, and precipitation. Results showed that in the 0–400 cm soil depth under shrub, grass, natural fallow, and millet, soil water storage (SWS) was –102.8, –129.3, 54.9, and 39.3 mm higher after 13-year of restoration, respectively. Although soil water under shrubs- and grasslands became more replenished under high precipitation, planting these water-intensive vegetation types aggravated soil desiccation. The gully intensified soil water spatial heterogeneity, with mean SWS within 0–480 cm soil depth of 902, 712, and 746 mm at the gully bottom, edge, and bank, respectively. The deviation index among the four revegetation types and among gully bottom, edge, and bank were 0.43 and 0.26, respectively, which indicated that revegetation types had a more obvious effect on SWS. Given that more concentrated rainfall under global climate change, both revegetation type and topography should be considered during ecological restoration in semi-arid areas. These findings can deepen our comprehension of the hydrological processes on the CLP and provide a reference for the development of ecological restoration policies under future climate change.

Low-cost agroforestry technologies for climate change mitigation and adaptation in Sub-Saharan Africa: A review

Agroforestry encompasses a large set of techniques and practices that have the potential to improve farm productivity with minimum environmental impacts in the context of climate change mitigation and adaptation (CCMA). In this paper, we discuss the relevance of agroforestry technologies and practices for CCMA in Sub-Saharan Africa (SSA). We recorded 173 scholarly works and and reviewed 62. Our findings indicate that comprehensive and well-developed technologies are used in agroforestry systems in SSA. They can be classified into four main groups (intercropping, improved fallows, mulching and parkland) and seven sub-groups (relay cropping, hedgerow intercropping, rotational woodlots, coppicing fallows, farmer-managed regeneration, on-farm tree domestication through poly-propagation and mulching) based on factors including the origins and uses of the trees and the types of tree-crop association. Our review showed that the maximum positive effect of parkland agroforestry is obtained when tree density ranges from 20 to 40 tree/ha, indicating an increase in crop production of 915.9 kg/ha. Furthermore, overall, the returns to labour of techniques involving fertilizer trees outperform those for natural fallows by 17%. Agroforestry techniques contribute substantially to the REDD+ program, but the best techniques with the highest cost-benefit- ratio and a substantial CCMA effect appear to be the intercropping and improved fallow systems. However, we observed a lack of detailed context-specific economic, social and environmental costs for the different techniques. For effective and rational decision-making by farmers in their adoption of agroforestry, further research should focus on filling in the detailed economic, social and environmental costs of each technology in each specific context.

Exploring Phosphorus Fraction Dynamics in Loess Soils: Impact of Long-Term Nitrogen and Phosphorus Fertilization on Cropland and Fallow Land

Long-term cropping systems require balanced phosphorus (P) management for better yield and environmental sustainability. However, the soil P transformations under fallow rotations with and without long-term nitrogen (N) and P fertilization largely remained unknown. This study evaluated the status of P forms in loess soils in response to varied combined rates of N and P fertilizers, tillage management practices, fallow land systems (natural fallow (NF), and bare fallow (BF)). Four NP treatments (N0P0, control; N0P100, 100 kg P ha−1; N160P0, 160 kg N ha−1; and N160P100), and two treatments with no fertilizer application and crops (NF and BF) were conducted. The treatments N0P100 and N160P100 significantly increased soil total P, inorganic P (Pi), organic P (Po), and Olsen P concentrations compared to the control, NF, and BF treatments. Labile P fractions (NaHCO3-Po and NaHCO3-Pi) were 7.30% and 11.8–12.4% higher in fertilized treatments than in control, NF, and BF treatments. The moderately labile NaOH-Pi was stable in all treatments, but NaOH-Po significantly decreased in the NF (2.60%) and BF (1.40%) treatments compared to the control and fertilized treatments; however, HClD-Pi was 59.1–66.0% higher in NF and BF compared to the control and fertilized treatments. Non-labile P (HClC-Pi and HClc-Po) fractions showed no significant difference between the fertilized and unfertilized treatments. Residual P levels were substantially greater in the P fertilized (N0P100) treatment than in the fallow treatments. The conceptual framework and redundancy (RDA) analysis revealed that the labile (NaHCO3-Pi and NaHCO3-Po) and moderately labile P fractions (NaOH-Po, NaOH-Pi, and HClD-Pi) were substantially associated with Olsen P contents, grain yield, and P uptake. Higher moderate fraction concentrations in fallows and their positive correlation with yield, P uptake, and Olsen P predict the importance of reserved P in these soils upon long-term fertilization, suggesting the utilization of P legacy and optimizing fertilizer applications.

Determination of Weed Control Efficiency of Pre-Rice Cropping Cassava/Legume Intercrops and Different Weed Management Practices in Low Land Rice at Badeggi Central Nigeria

The experiment was conducted at the lowland experimental field of National Cereals Research Institute, Badeggi. (90 45N, 600 7E, Alt, 70.57 m) in the Southern Guinea Savannah Agro-ecological zone of Nigeria in 2020-2022 cropping seasons The study was to evaluate the effect of pre-rice cropping cassava/legume intercrops and different weed management practices on weed control efficiency, growth and productivity of low land rice. The trial was conducted in two stages. The first (preceding intercropping) The treatments consisted of Mucuna puriens, Cowpea, Soybean, Lablab purpureus and Aeschynomene histrix that were intercropped with cassava (IIT 427 variety), sole cassava and natural fallow were also included as treatments. These were laid out in a Randomized Complete Block Design and replicated three times. Cassava/legume intercropping was carried out in January using residual moisture on raised beds that were prepared manually. Plot size used was 12.5 x 5 m with alley way of 0.5 m. Beds were constructed at 2.5 m long, 0.5 m wide and 0.75 m high. Planting of Cassava was done on the top sides of beds in two rows with the intra-row spacing of 0.5 (ten stands per bed) and planting of legumes were 0.5 m x 9.25 inter and intra-row spacing respectively except for soybean which was planted drilled at 5 cm intra row spacing immediately the beds were constructed. The cassava/legume cropping was harvested in August The second trial was the planting of rice on the plots previously cropped with cassava/legume intercrops. The trial was laid out in split plot design. Cassava/legume intercrop systems were allocated to the main plot, while weed management practices:- (i) Application of 4. 0 (propanil at 1.44 kg a.i. ha-1 plus 2,4 D at 0.80 kg a.i ha-1 ( Orizo plusR, at the rate of 2.24 kg a.i ha-1 at 3 weeks after transplanting (WAT) followed by hand weeding at 6 WAT (ii) two hand weedings at 3 and 6 WAT (iii) one hand weeding at 3 WAT, and (iv) weedy check were put into the sub plots with size of 12.5 x 5 m for main plots while and sub plot size was 3 x 5 m three replications. The results of treatments indicated that rice planted after cassava/Mucuna, cassava/Aeschynomene intercrops under two hand weeding and herbicide followed by one hand weeding produced lower density and dry matter. Weed control efficiency was higher in rice planted after cassava/mucuna intercrop. Weed reduction percentage range from 25-45 %, 30-50 % and 45-65 % in rice grown after cassava/legume intercrop compared to rice after fallow in 2011, 2012 and 2013 respectively. Higher rice plant height, higher number of rice tiller/stand were recorded in rice grown after cassava/Mucuna, cassava/Aeschynomene. Rice panicles per m2 and rice grain yield were increased by 72.9%, 83.6% and 84.1% in 2011, 2012 and 2013, respectively, with two hand weeding when compared with zero weeding. Rice planted after natural fallow under zero weeding produced higher weed density which resulted in poor rice performances. Rice planted after cassava Mucuna consistently controlled weed growth while cassava/cowpea and cassava Aeschynomene performed much better in rice production hence should be adopted as cropping systems for farmers

Insights into the impacts of autotoxic allelochemicals from rhizosphere of Atractylodes lancea on soil microenvironments.

Atractylodes lancea suffers from continuous cropping obstacles that have become a major constraint in its cultivation, but there is still little information on the autotoxic allelochemicals and their interaction with soil microorganisms. In this study, we firstly identified the autotoxic allelochemicals from rhizosphere of A. lancea and determined their autotoxicity. Third-year continuous A. lancea cropping soils, i.e., rhizospheric soil and bulk soil, compared with control soil and one-year natural fallow soil were used to determine soil biochemical properties and microbial community. Eight allelochemicals from A. lancea roots were detected and exhibited significant autotoxicity effects on seed germination and seedling growth of A. lancea with the highest content of dibutyl phthalate in rhizospheric soil and lowest IC50 value of 2,4-di-tert-butylphenol inhibiting seed germination. The contents of soil nutrients and organic matter, pH value, and enzyme activity were altered between different soils, and the parameters of fallow soil were close to those of the unplanted soil. The PCoA analysis indicated that the community composition of both bacteria and fungi were differed significantly among the soil samples. Continuous cropping decreased OTUs numbers of bacterial and fungal communities, and natural fallow restored them. The relative abundance of Proteobacteria, Planctomycetes, and Actinobacteria decreased, and that of Acidobacteria and Ascomycota increased after three years cultivation. The LEfSe analysis identified 115 and 49 biomarkers for bacterial and fungal communities, respectively. The results suggested that natural fallow restored the structure of soil microbial community. Overall, our results revealed that autotoxic allelochemicals caused the variations of soil microenvironments and resulted in replantation problem of A. lancea, and natural fallow alleviated the soil deterioration by remodeling the rhizospheric microbial community and restoring soil biochemical properties. These findings provide important insights and clues for solving the continuous cropping problems and guiding the management of sustainable farmland.

Dynamics of the Soil Macrofauna Influenced by Improved Fallows With Andropogon gayanus in Hydromorphic Soil at Bondoukuy (Western Burkina Faso)

In western Burkina Faso, in the Bondoukuy cotton zone, on silty-clay soils, the rarefaction of the perennial grass Andropogon gayanus, characteristic of old fallows, is noticed. This grass is known to restore the structural stability of the soil rather quickly, due to a stimulation of biological activity, while the storage of organic matter in the soil remains slow. The biological aspect has been prospected through the study of invertebrate populations in 3 sites, all of which present 4 situations: 30-year-old fallows, 5-year-old natural fallows, and 5-year-old A. gayanus improved fallows and 10-year-old permanent crop fields.
 
 The results show that invertebrate populations are very diverse. A total of 172 morphotypes were recorded, including 115 species of insects (24 species of social insects), 31 species of Chelicerata, 8 Myriapoda and 5 earthworms. In the fields, earthworms and Diplopoda populations are less important than in old fallows. On the other hand, the fields have the highest species diversity, 50 species on average. The most abundant population is found in natural fallows, with a density of 835 individuals/m² and 43 species represented. Improved fallows with A. gayanus have a lower stand density and species richness than natural fallows (less than 50% and 43 species). In old fallows, stands are stable with a richness limited to 30 species, while earthworms and myriapods have significantly reduced densities.
 
 Soil invertebrate communities thus recover rapidly after crop abandonment and are fully active during the most intense phase of recovery in the first 5 years. Trees do not appear to have a significant effect on the conservation and stimulation of macrofauna except for Coleoptera.
 
 Our results show that the cropping system adopted in the region allows for minimal conservation of soil macrofauna and that the macrofauna recovers rapidly during the fallow. Improved fallows with A. gayanus differ from natural fallows in limiting Termite density, while old fallows and fields are of comparable density.

Continuous cropping legumes in semi-arid Southern Africa: Legume productivity and soil health implications

Abstract Legume agronomic research in Southern Africa has often focused on integrating legumes into smallholder cereal cropping systems, but there is limited information available on the feasibility and soil health implications of continuous cropping legumes in the region. Continuous legumes may be suitable in areas with large livestock populations where a premium is placed on high-quality forage, or where efforts are underway to reclaim degraded cropland. Our objectives in this study were to (i) evaluate the performance of diverse legumes under continuous cropping and conservation tillage management with no fertility inputs and (ii) assess the response of soil health parameters to continuous legumes in a semi-arid environment. A 4-year study was conducted in Limpopo, South Africa beginning in the 2011–2012 growing season in which 10 legume and fallow treatments were imposed in the same plots for 4 growing seasons. All legumes responded negatively in varying degrees to continuous cropping in terms of biomass and nutrient accumulation. Lablab (Lablab purpureus L.) was the top-performing legume in the study and accumulated 4.5–13 Mg ha−1 of biomass and 153–345, 11–34, and 75–286 kg ha−1 of N, P, and K, respectively. Lablab often outperformed natural fallow, while other legumes generally performed as well as or inferior to natural fallow, depending on species and growing season. Cowpea (Vigna unguiculata Walp) was especially incompatible with continuous cropping and averaged less than 252 kg ha−1 and 2.1 Mg ha−1 of grain and biomass, respectively, from 2012–2013 to 2014–2015. Continuous cropping did not lead to sustained improvements in soil health. By 2014–2015, soil organic matter for all treatments had either declined or resembled baseline values. Rates of potentially mineralizable N in cowpea, lablab, vining mucuna (Mucuna pruriens var. Utilis), natural fallow, and bare ground plots fell by 70–96% during the study. There was also evidence for lower recovery of leached K by legumes compared to natural fallow species. In conclusion, legumes, such as lablab, should be considered as continuous forages on marginal land in areas where high-quality forage is in demand, but continuous cropping legumes without fertility inputs are not an effective strategy for improving soil health on degraded cropland in this semi-arid region of Southern Africa. Future research efforts may focus on the grazing strategies and baling frequencies required to optimize annual biomass accumulation of continuous lablab to meet livestock demand and support smallholder livelihoods.

Soil moisture and electrical conductivity relationships under typical Loess Plateau land covers

AbstractVegetation changes that are driven by soil conservation measures significantly affect subsurface water flow patterns and soil water status. Much research on water consumption and sustainability of newly introduced vegetation types at the plot scale has been done in the Loess Plateau of China (LPC), typically using local scale measurements of soil water content (SWC). However, information collected at the plot scale cannot readily be up‐scaled. Geophysical methods such as electromagnetic induction (EMI) offer large spatial coverage and, therefore, could bridge between the scales. A noninvasive, multicoil, frequency domain, EMI instrument was used to measure the apparent soil electrical conductivity (σa) from six effective depths under four typical land‐covers (shrub, pasture, natural fallow, and crop) in the north of the LPC. Concurrently, SWC was monitored to a depth of 4 m using an array of 44 neutron probes distributed along the plots. The measurements of σa for six effective depths and the integrated SWC over these depths, show consistent behavior. High variability of σa under shrub cover, in particular, is consistent with long term variability of SWC, highlighting the potential unsustainability of this land cover. Linear relationships between SWC and σa were established using cumulative sensitivity forward models. The conductivity–SWC model parameters show clear variation with depth despite lack of appreciable textural variation. This is likely related to the combined effect of elevated pore water conductivity as was illustrated by the simulations obtained with water flow and solute transport models. The results of the study highlight the potential for the implementation of the EMI method for investigations of water distribution in the vadose zone of the LPC, and in particular for qualitative mapping of the vulnerability to excessive vegetation demands and hence, unsustainable land cover.

Native hymenopteran parasitoids associated with fruit‐infesting flies in three plant formations and prospects for biological control in Western Burkina Faso, West Africa

Abstract In Western Burkina Faso, fruit flies (Diptera: Tephritidae) cause economic impacts. Damage on a mango can reach 100% in late varieties, and on shea fruits, the average attack rate is 66.5%. Parasitoids offer natural biocontrol services, but the potential for this in Burkina Faso remains unknown. We performed a survey (2017–2019) in three plant formations (natural fallows n = 6; agroforestry parks n = 6 and mango orchards n = 6) to determine the levels of parasitism of tephritid fruit fly pests. For this purpose, fruits from cultivated and wild fruit fly host plant species were sampled in these plant formations and incubated for insects' emergence. In total, 1822 adults belonging to 7 parasitoid species were found. Fopius caudatus (Szépligeti) and Psyttalia concolor (Szépligeti) with 51.47% and 30.60% of the total of parasitoid adults emerged, respectively, were the most predominant. Parasitism rate varied according to host fruit species. Pupae recorded from Sarcocephalus latifolius and Vitellaria paradoxa were most parasitized (27.22% ± 3.96%) and (17.08% ± 2.37%), respectively, while those obtained from mangoes were the less parasitized (3.73% ± 0.91%). Mass rearing of F. caudatus and P. concolor, as well as habitat management, will contribute to the promotion of both, augmentation and conservation biological control.

Biochar and leguminous cover crops as an alternative to summer fallowing for soil organic carbon and nutrient management in the wheat-maize-wheat cropping system under semiarid climate

Cereal-based cropping systems under arid and semiarid climates have typically low soil organic matter and fertility, and natural fallowing during summer gap could have negative effects on soil quality and health. We tested an alternative approach of using biochar and leguminous cover crops to replace natural summer fallowing of about 75 days in the wheat-maize-wheat cropping systems with a view of studying the effects on legume productivity, soil organic carbon (C), and soil nutrients over the 2-year experiments. The two-factor completely randomized block experimental design consisted of biochar, developed from acacia tree biowaste and applied at 0, 5, and 10 t ha−1 rate, and leguminous cover crops (cowpea, mungbean, and sesbania) with natural fallow were used to test soil fertility and crop productivity. Treatments were laid out following completely randomized block design and each treatment had three replicates leading to 36 experimental plots in total. Pearson’s correlation coefficients were calculated to find the relationships between plant and soil variables. Regression analysis was performed to study correlations of total organic C with soil available N, P, and K contents. Results from the 2-year experiment indicated that plant height, pods plant−1, grains pod−1, 1000-grain weight, fresh and dry biomass, and grain yield were higher at 10 t ha−1 biochar rate; however, the nodule density plant−1 of cowpea and sesbania was the highest at 5 t ha−1 biochar. Integrating legumes with biochar further conserved and improved soil C which significantly positively correlated with soil fertility indicators. Despite linear positive changes in soil pH and electrical conductivity (EC) with biochar rate, increase was minor and was never significant. We observed significant positive relationships of biochar rate with soil organic C contents and soil N and K contents whereas soil P contents were higher at 5 t ha−1 biochar rate. However, not always significant difference between 5 and 10 t ha−1 biochar rates for legume and soil productivity suggested flexibility of choosing the biochar application rate. Our study emphasized that adopting integrative biochar-leguminous cover crop fallowing to replace natural summer fallowing could yield beneficial effects in terms of conserving soil organic carbon, sustaining soil fertility, and improving soil quality. In addition to positive supplementary effects on the succeeding crops, this approach also allows at utilizing and recycling on-farm biowaste more efficiently and environment friendly.

Maize grain and straw yields over 14 consecutive years in burned and mulched Mucuna pruriens var. utilis and Pueraria phaseoloides relay cropping systems

AbstractThe cover crops Mucuna pruriens var. utilis and Pueraria phaseoloides were introduced to African farmers to improve crop production on degraded soils, yet they appear not to be adopted at scale. In the humid forest zone of West and Central Africa, the dominant Acrisols and Nitisols are inherently poor even when not degraded through agriculture. In this zone, sole maize cropping and vegetable production systems are gaining importance, yet both suffer from nutrient deficiencies. Cover crops were often introduced along with a system change, requiring biomass retention, mainly for nutrient retention reasons. Farmers in the zone commonly use slash and burn systems due to added weed control and ease of operations on clean fields. This study evaluated mucuna and pueraria with and without burning the fallow biomass in an annual sole maize crop relay system against the burned and retained natural fallow. Over 14 consecutive years, biomass burning did not cause lower maize grain yields in any of the fallow types, on the contrary, the economically important marketable cob yields were higher when biomass was burned (mulched 2.10 cobs m−2 vs. 2.26 cobs m−2 when burned, p < 0.07). After cover crop fallow, maize grain yields were significantly higher than after natural fallow (1.92 Mg ha−1) over the 14 years, with maize yields in the pueraria treatment (2.63 Mg ha−1) out yielding those in the mucuna treatment (2.28 Mg ha−1). Maize produced 1.92 cobs m−2 in natural fallow, significantly less than in the mucuna (2.23 m−2, p < 0.013) and the pueraria (2.39 m−2, p < 0.001) fallow. Introducing mucuna or pueraria cover crops into slash and burn systems appears as a suitable measure to increase yields without changing the land preparation approach.

English

The effects of cassava/legume intercrop-rice relay and weed management practices on weed infestation, growth and yield of rice were investigated at Badeggi, Southern Guinea Savanna of Nigeria in 2011 to 2013 cropping seasons. The treatments consisted of factorial combination of cassava (IIT 427) intercrop with: Mucuna or Velvet bean [Mucuna pruriens (L.) DC.], Cowpea [Vigna unguiculata (L.) Walp.], Soybean [Glycine max (L.) Merr.], Hyacinth bean [Lablab purpureus (L.) Sweet.] and Porcupine Jointvetch (Aeschynomene histrix Poir.) and weed management practices: (i) application of propanil at 1.44 kg a.i ha-1 plus 2,4-D at 0.80 kg a.i ha-1 (Orizo Plus®) at the rate of 2.24 kg a.i ha-1 at three weeks after transplanting (WAT) rice followed by hoeing at 6 WAT, (ii) two hoeing at 3 and 6 WAT, (iii) one hoeing at 3 WAT, and (iv) weedy check with sole cassava and natural fallow as control laid in a split plot arranged in a randomized complete block with three replications. Across cassava/legumes intercrops, cassava/mucuna had lower weed density and dry matter, cassava/Aeschynomene and cassava/cowpea produced comparable taller rice plants, more rice panicles and paddy yield, and cassava/Aeschynomene produced greater number of rice tillers. Irrespective of the weed management practices, two hoeing at 3 and 6 WAT gave better weed control, taller rice plants, greater number of tillers and panicles, and higher paddy yield comparable to application of Orizo Plus® at 3 WAT followed by one hoeing at 6 WAT. This study suggests that sustainable weed control with Mucuna intercrop and rice productivity with Aeschynomene and cowpea intercrops can be achieved with two hoeing at 3 and 6 WAT or application of Orizo Plus® at 3 WAT followed by hoeing at 6 WAT in this agro-ecology of Nigeria. Key words: Intercrops, legumes, Oryza sativa L., paddy yield, weed suppression. &nbsp

Land use and management effects on volcanic soils in West Sumatra, Indonesia

In this study, we aimed to assess the influence of land use and management on the fertility characteristics and pedogenic indicators of volcanic soils. Our study area was a mountainous area located in West Sumatra, Indonesia, where local farmers intensively cultivate vegetables by applying high amounts of chemical fertilizers and agrochemicals. Some negative impacts of conventional management were observed in the vegetable fields: soil acidification and loss of organic matter, with descended soil pH and increased acidity as well as decreased contents of exchangeable bases and with decreased amount of organic C. These impacts were not effectively mitigated by positive factors such as increased P availability and decreased capacity for P fixation. Continued cultivation over the years compounded the effects of these changes. Organic farming was advantageous in terms of soil fertility maintenance as it alleviated negative impacts compared to conventional farming. Natural fallow was effective in replenishing soil fertility as indicated by a significant increase in organic C, total N, and exchangeable Ca and Mg contents compared to the vegetable fields. The degree of replenishment was enhanced with a longer period under fallow; however, the natural fallow decreased P availability and increased P fixation capacity. Calliandra calothyrsus fallow further accelerated soil acidification, regardless of the rapid increase in the organic C and exchangeable bases contents. The adverse effects of Calliandra fallow were associated with the formation of humus–aluminum complexes to an extent that it changed from Sil-andic to Alu-andic Andosols.

Seasonal Abundance and Diversity of Fruit Flies (Diptera: Tephritidae) in Three Types of Plant Formations in Western Burkina Faso, West Africa

Abstract 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 288 Tephri Trap 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 cosyra Walker (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.

Short-term improved fallows of Tephrosia vogelii and Cajanus cajan enhanced maize productivity and soil chemical properties of a degraded fallow land in Southwestern Ethiopia

An improved fallow experiment was established in 2013 to examine the contribution of shrub legume species, Tephrosia vogelii and Cajanus cajan, in improving the productivity of a degraded tropical soil and crop yields compared with traditional fallow. The study was conducted on five farmers’ fields in southwestern Ethiopia laid out in randomized complete block design with farmers as replicates. After 2 years, the amount of aboveground biomass produced was 5–8 t ha−1 for Tephrosia and 3–5 t ha−1 for Cajanus. Maize grain yield was 80% higher for Tephrosia and 41% for Cajanus compared with the traditional fallow. The legume species significantly increased soil pH, organic carbon and total nitrogen levels compared with the natural fallow but there was no significant effect for available phosphorus. The magnitude of fallow benefit from Tephrosia in terms of yield advantage and nitrogen availability could be related to its high biomass production capacity compared to Cajanus. Fallowing with Tephrosia has the potential for improving productivity of degraded tropical soils. Farmers’ responses to the improved fallows were in general positive and their preference was Tephrosia fallow. Farmers can therefore use Tephrosia to enhance soil fertility by increasing N-levels, soil pH and organic matter of the soil. However, phosphate fertilizer is required as basal application to enhance N-fixation by legumes.

Comparative assessment of temporal changes in soil degradation under four contrasting land‐use options along a tropical toposequence

AbstractAssessment of land‐use types has conventionally been on spatial rather than temporal scales, thus limiting the inference on relative potential of land‐use types against soil degradation, needed to validate their allotment to ecosystems on agricultural watersheds. The study assessed the changes in key indices of soil degradation among four land‐use systems of West African 'watershed' agroforestry development over about a decade (1999–2011) along a toposequence in Central Ghana. The land‐use systems were grass‐dominated natural fallow (Fallow), cocoa plantation (CPT), traditional rice farm (TRF), and Sawah ecotechnology for wet inland valley rice farm (Sawah), with sampled land areas covering 2,000, 1,500, 4,500, and 6400 m2, respectively. In 1999 and 2011, soil samples were taken from 0–20, 20–40, and 40–60‐cm depths. Samples were collected from about the same spots in both years. The samples were analyzed for selected physicochemical parameters and, for each land‐use option and depth, comparison made between 1999 and 2011. A mean‐weighted decadal change in degradation status was used to rank the land‐use options. Most of the decadal changes in soil properties (including available micronutrients) were negative, with about two‐third of the significant changes in the top (0–20 cm) soils. For instance, soil pH tended to decrease in 2011 compared with 1999; the decreases (14.51%) were significant in the topsoils under Sawah where no other index showed significant decline. Topsoil total carbon decreased under TRF (49.08%) and CPT (32.80%). Available phosphorus marginally increased only under Sawah. The overall aggregate scores for the mean‐weighted decadal change in degradation status showed that the land‐use options differed in their potential to resist degradation: Sawah (slight), Fallow (mild), and TRF/CPT (moderate). Our findings highlight the extent of temporal changes in soil degradation under different topo‐positions in tropical African ecosystems while pointing to the superiority of Sawah ecotechnology. Increased use of this soil‐and‐water management system in lowland rice farming could, therefore, have some soil conservation benefits.

Responses of weed community, soil nutrients, and microbes to different weed management practices in a fallow field in Northern China.

The long-term use of herbicides to remove weeds in fallow croplands can impair soil biodiversity, affect the quality of agricultural products, and threaten human health. Consequently, the identification of methods that can effectively limit the weed seed bank and maintain fallow soil fertility without causing soil pollution for the next planting is a critical task. In this study, four weeding treatments were established based on different degrees of disturbance to the topsoil: natural fallow (N), physical clearance (C), deep tillage (D), and sprayed herbicide (H). The changes in the soil weed seed banks, soil nutrients, and soil microbial biomass were carefully investigated. During the fallow period, the C treatment decreased the annual and biennial weed seed bank by 34% against pretreatment, whereas the H treatment did not effectively reduce the weed seed bank. The D treatment had positive effects on the soil fertility, increasing the available nitrogen 108% over that found in the N soil. In addition, a pre-winter deep tillage interfered with the rhizome propagation of perennial weeds. The total biomass of soil bacterial, fungal, and actinomycete in H treatment was the lowest among the four treatments. The biomass of arbuscular mycorrhizal fungi in the N treatment was respectively 42%, 35%, and 91%, higher than that in the C, D, and H treatments. An ecological weeding strategy was proposed based on our findings, which called for exhausting seed banks, blocking seed transmission, and taking advantage of natural opportunities to prevent weed growth for fallow lands. This study could provide a theoretical basis for weed management in fallow fields and organic farming systems.

Influence of method of residue application and moisture content on water soluble nitrogen in a rhodickandiustalf amended with different fallow plant materials

Use of plant residues as nutrient sources presents a viable option to resource poor farmers who sparsely use mineral fertilizer in crop production. A study was conducted to gain an insight into how different application methods of residues from different fallow management systems under two moisture regimes would affect soluble N release in a Rhodic Kandiustalf. Three residue types viz, elephant grass from a natural fallow (T1) and another as a fallow following a previously fertilized maize (T2) and a fallow legume (T3) were surface applied and incorporated in a Rhodic Kandiustalf at both field capacity (FC) and 60% field capacity over a sixteen-week period. Incorporation of mucuna residues and elephant grass from previously fertilized maize fallow released similar soluble N levels which were higher than levels from the natural elephant grass amendments. At 60% FC, both mucuna and elephant grass from the fertilized maize fields that were surface applied had slower N releases than the grass from the natural fallow, suggesting the elephant grass from the natural fallow field could be used as an N source amidst light watering to avoid leaching in the dry season.

Camponotus japonicus ant mounds indirectly accelerate leaf litter decomposition by altering soil temperature and moisture

As ecosystem engineers, soil-inhabiting ants can influence soil properties in different ways. However, limited attention has been directed toward the role of Camponotus japonicus on litter decomposition in the Loess Plateau. This study quantified the impact of C. japonicus mounds on soil evaporation, temperature and litter decomposition. The distribution and physical properties of C. japonicus mounds in four slopes (61 m × 5 m) under different vegetation types [Korshinsk peashrub (Caragana korshinskii K.), KOP; purple alfalfa (Medicago sativa L.), ALF; natural fallow, NAF; and millet, MIL] were studied. The density of ant mounds in grass and shrublands was considerably higher than that in croplands. Farming activities and intense soil erosion in the crop slope could play a negative role in mound density. On average, half-ellipsoid ant mounds were 2.48 cm in height and 755 cm2 in basal area with 0.75 g/cm3 bulk density. The size distribution of the ant mounds was as follows: 2–3 (6.9%), 1–2 (27.3%), 0.5–1 (16.9%), 0.28–0.5 (18.2%) and <0.28 mm (30.7%). Porous ant mounds that covered the leaf litter of ALF reduced soil evaporation, increased soil temperature and indirectly accelerated leaf litter decomposition. Concentrations of soil organic matter (SOC), total N, ammonium N, nitrate N, available P and available K were higher in soil under ant mounds than those in surrounding soil under KOP, ALF and NAF. High soil moisture and temperature in the leaf litter and enhanced contact area between the soil particles and the leaf litter promoted litter decomposition and contributed to the formation of a ‘fertile island’. These findings may enrich our understanding on the effects of ant activity on soil ecosystems in semiarid areas.

Discrimination of soil aggregates using micro-focus X-ray computed tomography in a five-year-old no-till natural fallow and conventional tillage in South Africa

Soil use and management effect on soil microstructure was quantified. Soil aggregates ∼10 mm diameter were collected from two fields: a five-year-old No-till natural fallow management (NTNF) and continuous cultivation (CC). The aggregate microstructure was determined with X-ray micro-focus computed tomography (X-ray μCT) and image analysis was done using VGstudio MAX 3.0. Aggregate stability was higher in NTNF by ≈ 5.7%. Micro-aggregates constituted ≥80% of the aggregates in both treatments. Total porosity, microstructural pore properties (pore distribution, pore shape proportion) and visualization were similar in NTNF and CC. Despite the similarities, aggregates under NTNF had higher total number of pores. Therefore, managing soil through NTNF improve porosity even when the effect on the overall soil aggregation is not obvious. The study showed that aggregate stability is significantly linked to aggregate microstructure.