In a sustainable agriculture system, closed organic materials could help utilize local resources and improve farming efficiency. The purpose of this study was to utilize nearby materials with a high decomposition rate, allowing for the incorporation of well-known residues. Specifically, Tithonia diversifolia and Alnus acuminata biomass were targeted as materials to be mixed with farmyard manure. Different rates of T. diversifolia and A. acuminata biomass + farmyard manure compost materials were assessed with the application of NPK in all the treatments, with two levels of lime (0 and 1.5 t/ha). The compost made by T. diversifolia + farmyard manure increased the dry matter and yield of Irish potato and maize, and lime has contributed to dry matter and yield production. The application of 5 t/ha of manure did not affect much the dry matter yield. 10 t, 15 t, 20 t, 25 t, and 30 t significantly produced good dry biomass compared to the control, but manure rates above 5 t/ha gave similar yields, except for 25 t/ha, which was distinctly higher. Lime application significantly increased the dry matter yield from 3.4 to 3.8 t/ha. All the rates significantly responded well compared to the control on tuber parameters, and the five levels (10 t, 15 t, 20 t, 25 t, and 30 t) with lime belatedly indicated a significant difference with the rate of 5 t/ha on the yield. Both closed biomass sources, farmyard manure from animals, demonstrated strong potential as effective composting materials.

Soil acidity is a limiting factor in legume system during plant growth and microsymbionts process. The aim of this work was to identify and document acid tolerant rhizobium strains and their response to soybean grain yield under low pH. Ninety-one rhizobia isolates were collected from two provinces (Eastern and southern) of Rwanda based on soil acidity in the two regions. Symbiotic nitrogen fixation and yield were determined for three soybean varieties (PK6, SB24 and Sc Squire) inoculated with three acid-tolerant rhizobia strains (BB18S, BB64S and SB88E) across two sites with contrasting soil pH conditions. Interaction of soybean variety and soil amendments significantly revealed differences (p-value <= 0.012), where organic manure increased the number of nodules for two promiscuous varieties (SB24 and Sc Squire). Non-inoculated soybean control produced low N-fixed compared to all inoculated treatments, with high performance recorded for SB88E strain. The total dry matter biomass generated high grain yield, and this resulted from N-fixation due to the interaction between the acid tolerant rhizobia strains, soybean variety and application of N starter, P and K. Interaction of soybean variety and soil amendments revealed significant differences (p-value <= 0.012), with organic manure application increasing the number of nodules for two the promiscuous varieties (SB24 and Sc Squire). The biomass production generated high (p=000) grain yield by significantly (p=000) increasing the pod yields. The N-fixing efficiency of the strains was affected by N, P, and K application and legume isolates, and the grain yield increased when organic manure was applied on PK6 at the site with low pH and increased when lime and organic manure were applied on SB24 and Sc Squire. The study offers a technical solution for addressing soil acidity, nutrient availability, and enhancing soybean yield in Eastern and Southern Rwanda and similar agroecological regions.

AbstractRhizobia diversity in the rhizosphere is one of the key promoters of biological nitrogen fixation between host legumes and microsymbionts, although related complex interaction may depend on various factors. This research was intended to assess the abundance of indigenous rhizobia isolates under various soil conditions, as well as their effectiveness to nodulate legumes such as soybeans. Factors such as soil properties and legume species influence the volume and symbiotic effectiveness of native rhizobia to nodulate crop legumes. To investigate the abundance of rhizobia isolates, legume crops were uprooted to obtain nodules for most probable number (MPN) determination of rhizobia isolates, and soybean (Glycine max.) was used to verify the presence of suitable and efficient rhizobia strains for nitrogen fixation. Soil samples were obtained from the holes out of which nodules were collected, and the laboratory analysis included pH, Mg, K, available P, organic C, Ca, and N to establish the correlation between the soil status and number of rhizobia isolates' cells. Significant variations (p‐value <.05) were observed in the cell counts of Rhizobia isolates from Glycine max, Phaseolus vulgaris, Pisum sativum, and Vigna unguiculata, particularly when compared to Arachis hypogaea isolates under acidic conditions. Notably, Pisum sativum and Vigna unguiculata showed consistent performance across all pH conditions. The number of rhizobia isolates was found to be significantly linked to total N and P deficiencies (p < .05). It was also established that total N was dependent on the number of rhizobia cells and that there is a strong correlation between organic carbon and N content. This study highlights the crucial role of understanding and optimizing conditions for rhizobia nodulation in diverse soil environments, emphasizing its potential impact on enhancing biological nitrogen fixation in legumes.

A study was conducted in Northern Province of Rwanda, from the College of Agriculture and Veterinary Medicine, Busogo Campus located in Musanze district to evaluate the effect of feed type on rabbit growth in rabbit intensification systems in Rwanda. The Complete Randomized Design (CRD) was used and data were collected on rabbit growth weekly for a period of 12 weeks. The experiment was composed of three treatments replicated ten times. The treatments included three types of feeds namely; cabbage combined with Mucuna pruriens added to local forage (I), cabbages combined with Leucaena leucocephala added to local forage (II) and a control composed of other varieties of locally available forage, such as Bidens pilosa, Crassocephalum vitellium and Galinsoga parviflora (III) which was considered as the control (Farmers practice). The feeds were given to ten rabbits separated in individual cages, and each rabbit was considered a replicate. Water was given ad libitum. One month old rabbits (weaners) were used and data were collected after one week of adaptation for 12 weeks. The results showed that the mean of weight gain after 12 weeks was 783.3 g, 760.7 g and 705.7 g for feed type I, II and III respectively. The difference between means of feed types after 12 weeks was not significant (p > 0.5), which implied that rabbit growth did not depend on the feed type. The mean weight gain after 8 weeks was 707.5 g, 661.4 g and 577.1 g for feed type I, II and III respectively. At 8 weeks, the difference between means of feed types was significant (p Mucuna pruriens combined with cabbage and local forage were growing faster than rabbits from other treatments at 8 weeks. The researchers recommended that farmers should be facilitated with feeding materials by the concerned institutions. Training of rabbit farmers and further researches on locally available feeding materials were also given as recommendations at the end of this study.

Adept use of fertilizers is critical if sustainable development goal two of zero hunger and agroecosystem resilience are to be achieved for African smallholder agroecosystems. These heterogeneous systems are characterized by poor soil health mainly attributed to soil nutrient depletion. However, conventional methods do not take into account spatial patterns across geographies within agroecosystems, which poses great challenges for targeted interventions of nutrient management. This study aimed to develop a novel population-based farm survey approach for diagnosing soil nutrient deficiencies. The approach embraces principles of land health surveillance of problem definition and rigorous sampling scheme. The advent of rapid soil testing techniques, like infrared spectroscopy, offers opportune avenues for high-density soil and plant characterization. A farm survey was conducted on 64 maize fields, to collect data on soil and plant tissue nutrient concentration and grain yield (GY) for maize crops, using hierarchical and purposive sampling. Correlations between soil test values with GY and biomass were established. The relationship between GY, soil NPK, and the tissue nutrient concentrations was evaluated to guide the setting up of localized critical soil test values. Diagnosis Recommendation Integrated System (DRIS) indices for total nitrogen (N), total phosphorus (P), and total potassium (K) were used to rank and map the prevalence of nutrient limitations. A positive correlation existed between plant tissue nutrient concentration with GY with R2 values of 0.089, 0.033, and 0.001 for NPK, respectively. Soil test cut-off values were 0.01%, 12 mg kg-1, 4.5 cmolc kg-1 for NPK, respectively, which varied slightly from established soil critical values for soil nutrient diagnostics. N and K were the most limiting nutrients for maize production in 67% of sampled fields. The study demonstrates that a population-based farm survey of crop fields can be a useful tool in nutrient diagnostics and setting priorities for site-specific fertilizer recommendations. A larger-scale application of the approach is warranted.

Crop residues and mulches release phytotoxic substances into the soil that affect plant growth. An experiment was conducted at the Uganda National Crop Resources Research Institute, Namulonge during 2016, to identify compounds in the stover of potted Cymbopogon nardus, Desmodium uncinatum, Oryza sativa, (NERICA 1), Mucuna pruriens and Zea mays (LONGE 6H) at fourty five days after germination. This marked near the average stationary phase for test crops’ growth when secondary metabolites are maximum. Organic compounds in the stover were extracted using solid phase micro-extraction. Samples were subjected to analysis using a 7890A Gas Chromatography system. Data files were transferred into a distinct folder and data was uploaded onto XCMS online platform for pair wise comparison and other related statistical analysis in the National institute of Science and Technology library. Ten terpenoids and one ester were identified in cymbopogon stover. Desmodium stover released six terpenoids and three phenols. Rice stover produced six terpenoids, three phenolic compounds and one ester. Mucuna stover released two terpenoids and four phenols. The maize stover produced five terpenoids and four phenolic compounds. Profiled compounds from cymbopogon, desmodium, rice, mucuna and maize could be responsible for the reported negative allelopathic effects such as auto-toxicity and suppression of companion crops expressed in agricultural ecosystems. Allelopathic activity of the profiled compounds should be confirmed through bioassays extracts and residues studies. The development and incorporation of the profiled metabolites into agricultural management system may lead to the production of bio-herbicides that reduce environmental degradation and increase crop productivity.

Allelochemicals cause yield differences under various ecosystems worldwide. Studies were conducted at the National Crops Resources Research Institute, Namulonge, Uganda during 2016 to investigate allelopathic properties of bioactive compounds in upland rice (NERICA 1), Desmodium uncinatum, Zea mays (LONGE 6H) and Mucuna pruriens root leachates. Studies involved pot screening, equal compartment agar experiments, germination tests and growth of potted plants. Results under the pot study indicated that maize, rice and mucuna leachates significantly (P ≤ 0.05), reduced root lengths (49%-63%), plant heights (48%-66%) and biomass (63%-75%) for Ageratum conyzoides, Bidens pilosa and Gallinsoga. parviflora weeds. G. parviflora root growth was reduced (20%-41%) and stem growth declined (19%-42%) when maize, rice and mucuna leachates were applied in the equal compartment agar study. Increased leachate concentrations (25%-75%) significantly (P ≤ 0.05), increased the mean germination time (0.4-2.8 days) for mucuna, desmodium, rice and maize as seed germination indices (SGI) were reduced (1.3%-49%). Potted mucuna, maize and desmodium reduced (1.3%-49%) rice root length. Potting mucuna with maize reduced (32%) mucuna leaf width while desmodium growth parameters were reduced (49%-64%) when potted with maize and mucuna. Potting maize with mucuna or desmodium increased the maize leaf length (18%) and SGI (25). Application of higher (25%-75%) rice/maize leachate concentrations similarly increased the maize leaf length (31%) and SGI (119). Allelopathic properties affect seed germination, crop growth and development, and characterise ecosystems age structures. Strategic management of crops under allelopathic ecosystems is critical.

Allelochemicals regulate the productivity of crop ecosystems. A screen house experiment was conducted (2016) at the National Crops Resources Research Institute, Namulonge, Uganda to determine the effects of NERICA 1 rice (an interspecific hybrid between Oryza sativa and O. glaberrima species), Cymbopogon nardus (C), Desmodium uncinatum (D), Mucuna pruriens (Mc) and LONGE 6H, Zea mays (Mz) on crop relative growth rates (RGR), nitrogen (N), phosphorus (P) and potassium (K) nutrient levels. One field study was conducted on a farm (2017) to establish the allelopathic interactive effects of RCDMcMz on Striga hermonthica (a parasitic weed), crop competition and productivity. Data was collected on striga, RMz growth, nutrient levels and yield. Potted rice reduced (30%-47%) in root length but Mz leaf length increased (31% & 15%) with Mc & D. RMc reduced (73%) striga and increased rice RGR (14-42 days). RD similarly reduced (67%) striga. RC increased (96%, 44% & 73%) rice NPK uptake, RGR (14-42 days), reduced (57%) striga and increased (1.56) the combined land equivalent ratio (CLER) and rice grain yields. RMz reduced (16%, 38% & 38%) rice NPK reserves, RGR (14-42 days), CLER (1.0), grain yields and increased (36%) striga. RD recorded higher CLER (1.56). MzMc reduced (15% & 27%) maize P uptake and NP uptake increased (42% & 9.3%) under MzC & MzD (73% & 29%). RMc increased rice RGR (14-42 days). Maize RGR (14-28 days) increased under MzD, MzMc & MzC and reduced (28-42 days) under MzD, RC & MzMc.. The ecosystems’ productivity was attributed to allelopathy.

Arbuscular Mycorhizal Fungi (AMF) occur naturally in agroecosystems and interact symbiotically with crops, facilitating nutrition. This study aimed at assessing the occurrence, abundance and diversity of AMF communities in the maize cropping system and their relation to soils properties in two agroecological zones in South Kivu, eastern DR Congo. Soil samples were collected from eight sites, with 4 sites in highland at 1400 to 2000 m altitude above sea level (in Katana, Kavumu, Mulamba and Mugogo) and four in the lowland at <1000 m (in Luberizi, Bwegera, Luvungi and Kamaniola). Spores were extracted from the field soils, morphologically identified and counted. AMF spores occurrence, abundances, species richness, and diversity were determined. A total of 38 AMF morphotypes distributed in 11 genera were obtained with the majority being from Gigasporaceae, Acaulosporaceae, and Glomeraceae families. This is the first report on the occurrence of these species in the eastern of DR Congo. Acaulospopra excavata, Acaulospopra bireticulata, Densitscutata erythropa, Funneliformis mosseae and Scutellospora pellucida were ubiquitous in all the agroecologies. Spores densities were higher in the highland with the highest recorded in Mulamba. Soil pH and phosphorus content influenced AMF distribution. The many different ubiquitous species indicate adaptation to a wide range of physicochemical environments and could reduce the cost of AMF inoculants production for the region. Maize agroecosystems are rich in AMF diversity and selection of appropriate fungal species from the Gigasporaceae, Acaulosporaceae and Glomeraceae as biofertilizer could contribute in improving crops production. Key words: Arbuscular mycorrhizal fungi, diversity, occurence, agroecological zones, maize, South Kivu.

The objective of this study was to assess the impact of climate change on intercrops of maize and improved pigeonpea varieties developed. Future climate data for Katumani were downscaled from the National Meteorological Research Centre (CNRM) and Commonwealth Scientific and Industrial Research Organization (CSIRO) climate models using the Statistical Downscaling Model (SDSM) version 4.2. Both models predicted that Katumani will be warmer by 2°C and wetter by 11% by 2100. Agricultural Production Systems Simulator (APSIM) model version 7.3 was used to assess the impact of both increase in temperature and rainfall on maize and pigeonpea yield in Katumani. Maize crop will increase by 141–-150% and 10–-23 % in 2050 and 2100, respectively. Intercropping maize with pigeonpea will give mixed maize yield results. Pigeonpea yields will decline by 10–20 and 4–9% by 2100 under CSIRO and CNRM models, respectively. Intercropping short and medium duration pigeonpea varieties with maize will reduce pigeonpea yields by 60–80 and 70–90% under the CSIRO and CNRM model, respectively. There is a need to develop heat and waterlogging-tolerant pigeonpea varieties to help farmers adapt to climate change and to protect the huge pigeonpea export market currently enjoyed by Kenya.

Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.

Conversion of forests to cultivated farms through slash-and-burn or chop-and-char practices often results in rapid loss of soil organic matter (SOM) or conversion of inherent SOM into pyrogenic organic matter (PyOM). However, there is little knowledge about the short-term changes in soil macrofauna that may occur when large amount of biochar are added to the soil. A thirty-day microcosm study was conducted to assess effects of biochar derived from two trees, Croton megalocarpus Hutch. and Zanthoxylum gilletii (De Wild.) P.G.Waterman, on the activity of a geophagous earthworm, Pontoscolex corethrurus. A portion of the biochar was leached with either acetone or 2 M HC1, to remove easily mineralizable organic matter and ash contents, respectively. Each of the biochar types was mixed with soil at a rate equivalent to 5, 10 and 25 Mg ha(-1). Casts were collected after 30 days and used as a measure of earthworms' activity. Casts dry weight was affected more by amount than the type of biochar. The highest cast weight (188.1 g and 176.5 g) was recorded in microcosm that received 5 Mg ha(-1)- of C. megalocarpus and Z. gilletii biochar, respectively. Notably, the weight decreased with increasing biochar additions. Cast weight decreased by 4% in microcosms that received 10 Mg of C. megalocarpus biochar ha(-1)-and by 15% in microcosms that received the same biochar type at a rate of 25 Mg ha(-1). Similarly, there was a 6% decline in cast weight in microcosms that received 10 Mg of Z. gilletii biochar ha(-1)-and an 8% decline in microcosms amended with 25 Mg ha(-1)- of the same biochar type. Easily mineralizable organic matter or nutrients were not responsible for the observed differences in cast production since leaching with acetone or HC1 did not change the effects. The C and N content in casts and bulk soil were not significantly different, an indication that earthworms did not seek out biochar, but rather indiscriminately utilised the soil rich in biochar.

ABSTRACT The role of below-ground interactions between microbial biocontrol agents and soil fauna for combatting soil-borne plant diseases have not been studied sufficiently. This study tested the hypothesis that the beneficial bacterium Bacillus velezensis UCMB5113 and the anecic earthworm Lumbricus terrestris positively influence health and growth of peas (Pisum sativum L.) infested with the pathogen Aphanomyces euteiches causing root-rot disease. A greenhouse fully factorial experiment studied the effects of A. euteches, B. velezensis and L. terrestris on the emergence, growth and health of pea plants. The factors B. velezensis and L. terrestris resulted in taller plants (p = .003 and p = .030). B. velezensis treatment resulted in a higher biomass of shoots and roots (p ≤ .001 and p = .005). The effects increased with the presence of both factors (p = .036). Earthworms reduced the disease symptoms significantly (p = .032). The decreased disease symptoms caused by the earthworms might be due to the consumption of A. euteiches (direct effect) as well as soil disturbance (indirect effect). Interactions between the microorganisms added and the earthworms were shown. B. velezensis and L. terrestris can be useful for enhancement of plant growth and for biological control of root-rot in peas.

Use of inorganic fertilizers in smallholder cropping systems in Africa is often becoming inefficient due to increasing unresponsiveness to fertilizer application. A study was conducted for 2 years (four seasons) to assess the effects of biochar made from Prosopis juliflora (Sw.) DC. biomass on nutrients, fauna abundance and subsequent influence on maize planted in a nitisol. There were 12 amendments comprising: (i) biochar applied alone at a rate of 5 and 10 Mg ha−1; (ii) three fertilizer types applied separately (di-ammonium phosphate (18:46:0), urea (46:0:0) and composite NPK (23:23:0)); (iii) six fertilizer + biochar blends of the three fertilizer types and two biochar rates (0.05 and 0.1 Mg ha−1); and (iv) a control with no inputs. Treatments were replicated four times in a randomized complete block design. The amendments were applied in the first two seasons, while the last two were used to assess residual effects. At the end of the first two seasons, total C and N were higher in soils where biochar or fertilizer + biochar was applied, with more than 15.0 g C and 1.9 g N kg−1, compared to 10.4 g C and 1.0 g N kg−1 in control plots. Available P and exchangeable K were over 200% and 100% higher in biochar or fertilizer + biochar amended than control soils, respectively. Application of biochar had no effects on macrofauna such as beetles, centipedes, millipedes, termites and ants, but attracted earthworms. Soil that received 10 Mg biochar ha−1 recorded twice the number of earthworms (207 individuals m−2) compared to soil with 5 Mg biochar ha−1 (105 individuals m−2) and control (97 individuals m−2). Soils which received biochar, with or without fertilizer, had higher taxonomic richness (7.0 species) compared to soils which received DAP (2.8) or NPK (3.8). Nematodes, particularly bacterivorous groups, decreased by more than eight times with biochar application. In the first and second seasons, 5.6 Mg maize grain yield ha−1 was obtained from plots amended with biochar (without fertilizer), which was about six times higher than that harvested from unfertilised control at 0.9 Mg ha−1. Yield differences in plots where fertilizer was applied with or without biochar were not significant. Yield in the third and fourth seasons declined to 3.2 and 1.5 Mg ha−1, irrespective of fertilizer type or biochar amounts.

Soil organic matter (SOM) is considered an important determinant of soil fertility in tropical agroecosystems. While numerous studies have shown the value of agroforestry in increasing soil nutrients and improving crop yield, few have addressed the systematic impacts of duration of cultivation on soil aggregation and C storage in such systems. A study was conducted in South Nandi (Kenya) to assess spatial influence of three dominant trees (Croton megalocarpus, Eucalyptus grandis and Zanthroxylum gilletii) on soil aggregation and C content in agroforestry systems. The study was conducted in a chronosequence experimental set-up where farms were continuously cultivated for 10, 16 and 62 years since conversion from primary forest. It was hypothesized that soil aggregates and whole soil and aggregate-associated C would decrease with duration of cultivation, with the magnitude of influence being reduced by the presence of trees and abundance of earthworms and termites. Greater abundance of small macroaggregates and microaggregates were recorded in soils under the canopy of Z. gilletii with an average weight of 62.8 g and 9.4 g 100 g(-1) of soil compared to 53.9 g and 3.1 g 100 g(-1) in soils under C. megalocwpus and 48.7 g and 3.9 g 100 g(-1) in soils under E grandis, respectively. These differences could be attributed to the high number of endogeic earthworm species, Nematogenia lacuum (Ocnerodrilidae) in soils under the canopy of Z gilletii trees. Since N. lacuum is a small-sized species (40-55 mm long), it produces small faecal pellets and thus, we could infer that this species may have contributed to the fragmentation of large macroaggregates into small macroaggregates and microaggregates. The C content decreased by almost 40% in soils under longer duration of cultivation, with higher magnitude of differences associated with Z. gilletii trees. Increased microbial population in earthworms' casts can increase mineralization rates, which may explain the low aggregate-associated C content under Z. gilletii trees where high number of N. lacuum were recorded. This study shows the significance of specific trees in shaping soil aggregation process and soil C content which could have far-reaching implications for the long-term C storage in the soil and hence net contributions to climate change mitigation.

Few studies have evaluated improved pigeonpea varieties developed and released in Kenya for soil fertility improvement and contribution to the productivity of cereal-based cropping systems prevalent in marginal areas. A study comprising field and greenhouse experiments was conducted between 2009 and 2013, in order to evaluate improved pigeonpea varieties for nitrogen (N) uptake, biological nitrogen fixation (BNF), response to rhizobia inoculation and their effect on maize yields. Field experiments were conducted in Katumani Research Centre using a split-split plot design, with three pigeonpea varieties, two cropping systems and three crop residue regimes as the main plot, subplot, and sub-subplot, respectively. Greenhouse experiments were conducted at Muguga Research Centre where five pigeonpea varieties were screened for BNF and response to rhizobia inoculation in plastic pots filled with 10 kg of soil and replicated four times in a completely randomized design. Data collected on nitrogen uptake, BNF and maize and pigeonpea yields was subjected to analysis of variance using GENSTAT statistical software. Pigeonpea had significantly (p ≤ 0.05) higher nitrogen uptake compared with maize; Mbaazi II (84–114 kg N ha−1) absorbed more N, followed by Kat 60/8 (29–44 kg N ha−1) and Mbaazi I (20–37 kg N ha−1). All the three pigeonpea varieties fixed 60–70 kg N ha−1, meaning they were all good nitrogen fixers. Mbaazi II fixed significantly (p ≤ 0.05) higher N (70 kg N ha−1) compared with KAT 60/8 (66 kg N ha−1) and Mbaazi I (62 kg N ha−1) when intercropped with maize. Inoculation with rhizobia gave mixed results. Mbaazi II-maize intercrop gave the highest maize (1.9 t ha−1) and pigeonpea (1.4 t ha−1) grain yields and produced sufficient maize stover (2.1 t ha−1) and pigeonpea stalks (2.9 t ha−1).

Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.

Conservation agriculture (CA) (zero tillage + organic inputs as surface residue) is believed to improve soil nutrient status, soil structure, control soil erosion, and also enhance soil fauna diversity. Despite the widespread interest in CA, empirical evidence of the benefits of CA on soil fauna diversity is limited, especially in low-input systems of sub-Saharan Africa (SSA). Consequently, the magnitude and effect by CA on soil fauna remains unquantified. The aim of this study was to evaluate the effect of CA and associated management practices on soil fauna richness and abundance. We hypothesized that CA and mixed cropping would positively influence soil fauna richness and abundance. We compared CA with conventional till (CT: with or without residues) in sole maize and maize-bean cropping systems. Soil macrofauna and mesofauna were sampled across the treatments in medium-term (6 years) trials in Embu, Central Kenya, and Kakamega (6 years) and a long-term trial in Nyabeda (15 years) using soil monoliths and core samplers, respectively. In agreement with our hypothesis, higher macrofauna taxonomic richness and mesofauna was recorded in CA than in CT without residues. This study demonstrated that: (1) medium to long-term addition of organic residues enhances soil fauna richness and abundance, (2) CA increases soil fauna taxonomic richness and abundance compared with CT, and (3) CA under maize-bean intercropping, rotation and sole maize cropping systems promote soil fauna richness and abundance compared with sole legume (common beans). We conclude that adoption of CA is important in enhancing richness of soil fauna. Given the numerous challenges faced by smallholder farmers of SSA in the adoption of CA, who in most cases rarely practice all the three CA principles simultaneously, we propose a further study that will determine the effects and interactions between each of the CA components on soil fauna richness and abundance.