Legume Cover Crops Research Articles

Cover crop farming system affects macroarthropods community diversity in Regosol of Caatinga, Brazil

The influence of a 3-years cultivation of legumes on macroarthropod community composition was investigated. Soil samples were taken from a field experiment which was conducted for three years to characterize the agronomic characteristics of eight cover crops: Crotalaria juncea L., Crotalaria spectabilis Roth, Crotalaria ochroleuca G. Don., Canavalia ensiformis (L.) DC., Mucuna pruriens (L.) DC., Dolichos lablab L., Neonotonia wightii (Wight & Arn.) J.A. Lackey, and Brachiaria decumbens Stapf. cv. Basilisk. The highest values of diversity in the macroarthropod community were found on the plot where M. pruriens was cultivated. Brachiaria decumbens cultivation showed lower values of species richness, Shannon’s diversity index and Simpson’s dominance index compared to the other studied plant species. Our findings suggest that the cultivation of legume cover crops can change positively the macroarthropod community composition. The results highlight the importance of considering the effects of legumes on the diversity of this biological component and their effect on plant growth and soil organic carbon contents. Thus, legumes may exploit positive feedback in semiarid conditions on a Regosol.

Perbandingan Arachis pintoi dengan Tanaman Kacang-kacangan Penutup Tanah Lain dalam Menekan Laju Erosi pada Lahan Kelapa Sawit Berbukit

Land preparation of oil palm plantation in hilly areas is vulnerable to environmental degradation. Legume cover crops can be used in vegetation system for soil conservation to control erotion. Arachis pintoi is a legume potential for cover crop. The objective of the research was to study the role of A. pintoi in suppressing soil erosion rate in oil palm land with the topography of hilly land. The research was conducted on the land of Bukit Kemuning farmer group, Mersam, Batanghari, Jambi with an average slope of 22.8% from September 2017 to March 2018. The experimental design used was a single-factor randomized complete block design with five treatments and four replications. The treatment consisted of natural vegetation, Arachis pintoi, Centrosema pubescens, Pueraria javanica and Calopogonium mucunoides. The results showed that the rate of increased leaf number of A. pintoi was 13.6 pieces per week and could cover the ground surface 100% at 20 weeks after planting (WAP). The dry weight of A. pintoi biomass was 496.08 g m-2 at 20 WAP. A. pintoi suppressed soil erosion by 80.45% as compared to natural vegetation treatment. However, it was not significantly different on suppression rates to other biomulch treatments.Keywords: biomass, Calopogonium mucunoides, Centrosema pubescens, land cover crop, Pueraria javanica

Effects of compost, olive mill wastewater and legume cover cropson soil characteristics, tree performance and oil quality of olive trees cv.Chemlali grown under organic farming system

Utilisation of compost, olive mill wastewater and legume cover crops in an organic mature olive grove cv Chemlali was tested from 2013 to 2015 cropping seasons. Olive trees were subjected to one of the following treatments: TC: control, no amendment; TP: olive trees amended with compost, TM: olive trees amended with organic olive mill wastewater and TF: olive trees intercropped with legumes (Fava bean). The effectsof these treatments on soil characteristics, physiological traits, nutritional status,growth and oil yield and also the quality of the olive oil were evaluated at the end of the experiment and compared to the control. The most important effects on soil characteristics included a significant increasein the N, P, K availability and an increase of soil organic matter content. The compost amendment resulted tothe most significant increase in the soil water content and olive tree performance, mainly maximum yield of photosystem II (Fv/Fm) and the stimulation of olive tree growth and yield. The use of olive mill wastewater (OMW) increased the leaf Na+ concentration and reduced significantly the electron transport rate (ETR) of olive trees. Compared to TC, all organic amendments improved significantly the oil yield by about 55, 70 and 100% inTM, TF and TP plots, respectively, however oilquality still within the threshold limits set for an ‘Extra virgin’classified olive oil.

A Nodulation-Proficient Nonrhizobial Inhabitant of Pueraria phaseoloides.

Pueraria phaseoloides is a legume cover crop, found chiefly in the wet zone of Sri Lanka. Nitrogen fixation is performed by nodular inhabitants of this cover crop, comparable to the nodule-dwelling bacteria of most other legume plants. We isolated a bacterium (Sub1) from Pueraria phaseoloides, of coccobacillus cell shape, that showed nodulation, when assessed by hydroponics, showing nodules as early as 3 weeks after reinfection. When a nifH fragment from the genome of this bacterium was amplified using a pair of nifH primers, it yielded an amplicon of 360 bp that, when sequenced, helped us identify the bacterium, as belonging to a species of Pseudacidovorax intermedius, at 99% sequence identity. When we constructed a phylogenetic tree with neighboring sequences, we encountered nifH sequences of Pseudacidovorax, forming a monophyletic cluster, which too contained a single Azospirillum species. The genus Pseudacidovorax is a bacterium that, so far, has not been associated with legume nodules. Sub1 secreted a pair of enzymes to the extracellular medium to degrade cellulose and milk proteins. The Sub1 bacterium showed biofilm formation and secreted into the extracellular medium, indole acetic acid. Sub1 also showed a “bulls eye” swarming pattern for the chemoattractant proline, while showing no significant chemotaxis movement, for naringenin, quercetin, and glutamate. Sub1 too possesses the basic genetic foundation (nifH and nifD) to produce a molybdenum-dependent nitrogenase enzyme. We finally show that this rare nonrhizobial bacterium is able to impact, positively, nodulation and shoot length of Pueraria plants, demonstrating that this beta-proteobacterium can abet the biological vigor of this legume cover crop.

Maize and Weed Response to Legume Cover Short Fallow and Fertilizer in Port Harcourt South Eastern Nigeria

Field experiment was conducted in Faculty of Agriculture Teaching and Research Farm University of Port Harcourt, Port Harcourt, Rivers State, South Eastern Region of Nigeria between March and September 2017; to evaluate the effect of planted short fallow legume cover crop on maize performance and weed growth. The experimental design was a 5 x 2 factorial in randomized complete block design (RCBD) in a plot size of 4 m x 4 m with four replicates. The treatments consisted of four different legumes cover species fallow and a natural fallow as follows: Mucuna [Velvet bean (Mucuna pruriens (L.) DC var. utilis), Lablab (Lablab purpureus (L.) Sweet), Pigeon pea (Cajanus cajan (L.) Mill spp)], Centrosema (Centrosema pascuorum (L.) and a natural fallow (No Legume Cover) and two levels of inorganic fertilizer as NPK 15: 15: 15 (0 and 15 Kg ha-1 NPK). All legume cover growth characteristics were negatively correlated with weed cover and weed dry weight (r = -0.58 and r = -0.59 at P=0.0001). Legume dry weight had a positive correlation with all maize parameter (r =0.64 at P=0.0001) except for stem diameter (r = -0.43 at P=0.0051). Similarly, all weed attributes were negatively correlated to maize parameters. Maize height was better in plots that received short fallow legumes than natural fallow. There was increase in soil Nitrogen level after 10 weeks of fallow. Legume cover crop short fallow has the potentials for weed suppression, soil fertility and productivity improvement in maize culture.

Soil coverage, phytomass production and nutrient accumulation at intercropping maize and legumes system

Intercropping of maize and legume cover crop is currently usual at low technological areas, due to some high benefits and potential such as suppressing weeds, recycling nutrients and coverage of the soil. Suppression of weed is important due to its huge competitory impact on the commercial crops. The nutrient recycling is also important becuase it reduces usage of fertilizers on low technological agriculture. The soil coverage is important to prevent the erosion and reduce the nutrient leaching. All those positive effects can be influenced by type of cultivated species on the intercropping consortium. This study aimed to evaluate the soil coverage, phytomass production and accumulation of nutrients by plants in a maize and legume intercropping system. The experiment consisted of rustic maize “Caiano de Sobrália” variety, intercropped with Brazilian velvet bean, black mucuna, lablab-bean and pigeon pea, whereas a control treatment (sole maize culture) was also added. First, the maize was sown on the experiment. 64 days after emergence (DAE) the legumes were sown. The soil cover rates were evaluated at 0, 64, 84, 120, and 144 DAE. The corn grains were harvested at 120 DAE to obtain the corn grain yield. The remaining portion of maize and entire legume plants were sampled at 144 DAE, when the accumulation of dry mass and nutrient were measured. The intercropping system did not affect the corn grain yield and the soil cover rate provided by maize plants. The black mucuna had the greatest weeds suppression and nutrient accumulation among the legumes cover crops evaluated.

Legume cover crops under no-tillage favor organomineral association in microaggregates and soil C accumulation

Both no-tillage and legume cover crops have been shown to increase soil organic carbon (SOC) in subtropical soils. However, the mechanisms underpinning management system effects on SOC accumulation are still not well understood. We used a combination of aggregate size and density fractionation to elucidate these mechanisms at a 30-year old experiment on an Acrisol in southern Brazil. The effects of two tillage systems [conventional system (CT) and no-tillage (NT)] combined with three cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] were evaluated in the top 20 cm soil layer. Overall, macroaggregation (>0.25 mm) was significantly influenced by tillage with NT showing values 14% greater than CT in the 0–5 cm soil depth. On average, the occluded light fraction-C content in macroaggregates was more than twice as high under NT compared to CT (4.4 vs. 1.8 g kg−1). This effect was more pronounced when legume cover crops were grown. However, the most significant effect of cover crops was observed in the organomineral fraction of microaggregates, especially under NT (12.1 under O/M and 19.8 g kg−1 under OV/MC). Our results suggest that, although NT increased the occluded light fraction-C compared to CT, this effect was smaller than the gains that legume cover crops offered in organomineral association.

Cover Crop Species and Cultivars for Drill‐Interseeding in Mid‐Atlantic Corn and Soybean

Core Ideas Annual ryegrass and orchardgrass performed similarly in field corn. Medium red clover was the most consistent legume species in field corn. No effect of annual ryegrass cultivar was observed in field corn. Annual ryegrass was the most consistent species in soybean. ABSTRACTDrill‐interseeding is becoming a viable method for integrating cover crops in no‐till corn (Zea mays L.) production in the Mid‐Atlantic region. Development of best management practices for drill‐interseeding cover crops into no‐till grain crops requires greater understanding of cover crop performance at the species and cultivar level. Experiments were conducted at multiple Mid‐Atlantic locations (Maryland, Pennsylvania, New York) in two consecutive growing seasons (2013–2014, 2014–2015) to evaluate establishment and performance of drill‐interseeded: (i) grass and legume cover crop species (n = 8) and annual ryegrass [Lolium perenne L. spp. multiflorum (Lam.) Husnot] cultivars (n = 10) in field corn, and (ii) grass and legume cover crop species (n = 6) in soybean [Glycine max (L.) Merr]. Fall biomass production of drill‐interseeded cover crops was higher and less variable among locations in field corn than soybean. Annual ryegrass, orchardgrass (Dactylis glomerata L.), medium red clover (Trifolium pratense L.), and crimson clover (Trifolium incarntum L.) produced greater mean fall biomass than other species in field corn, but variable winter hardiness of crimson clover resulted in less spring biomass than alternative species. No differences were observed among annual ryegrass cultivars. Annual ryegrass, medium red clover, and crimson clover produced greater mean fall biomass than other species in soybean across locations. Our results highlight the viability of a narrow suite of cover crop species for interseeding in Mid‐Atlantic no‐till grain systems and point to the need for development of agronomic practices that facilitate greater niche complementarity between cover and cash crops.

The effect of legume cover crop Mucuna bracteata on soil physical properties, runoff and erosion in three slopes of immature oil palm plantation

This study determined the effect of legume cover crop Mucuna bracteata (MB) on soil physical properties, runoff and erosion on three slopes of immature oil palm plantation. This research used split plot design with three slopes as main plot consisted of: S1=slope 0-8%, S2=slope 8-15% and S3=slope 15-25%. The use of MB as subplot consisted of: M0=unovergrown with MB and M1=overgrown with MB. The measuring runoff and erosion used small plot method. The research showed that the oil palm plantation which overgrown by MB had the soil physical properties such as field moisture content, bulk density, total pore space, permeability, infiltration and organic matter better than without MB. The higher slope level decreased the soil physical properties; (2) the use of MB decreased the runoff and erosion compared to the unovergrown MB. The higher level of the slope induced the greater runoff and erosion; (3) the combination of slope with the MB resulted the lower runoff and erosion even at the steeper slope; (4) There is a positive correlation between rainfall intensity and runoff, and runoff with erosion. Thereby, the more rainfall intensity, more runoff as well, and the increase of runoff followed by the increased erosion.

Earthworm Fauna in Citrus Orchards by Legume Cover Crop Culture in Jeju Island

Earthworm Fauna in Citrus Orchards by Legume Cover Crop Culture in Jeju Island

Legume nitrogen credits for sugarcane production: implications for soil N availability and ratoon yield

One of the steps needed to achieve sustainable bioenergy is to reduce our reliance on synthetic nitrogen (N). Despite the fact that legume cover crops have the potential to increase soil quality and sugarcane (Saccharum spp.) yield, much information is still needed to determine amount of N available from cover crops to sequential ratoon cycles. This study was designed to assess the impacts of sunn hemp (Crotalaria spectabilis) cover crop on soil N dynamics and sugarcane ratoon response to N fertilization during two harvest seasons across three contrasting soil and climatic conditions in southern Brazil. The treatments consisted of cover crop and fallow established prior to sugarcane replanting; in addition to three N-fertilizer rates 60, 120 and 180 kg N ha−1 and a 0-N control applied during the first and second ratoons. Although there was increased sugarcane yield (8–13 Mg ha−1 in first ratoon and 10–16 Mg ha−1 in second ratoon) in plots planted with cover crop, it was not possible to detect significant increases in soil inorganic N, microbial biomass C and Illinois Soil N Test content under cover crop compared with fallow. Cover crop with sunn hemp increased the accumulated two-year yields by 14–25 Mg ha−1 at all sites and NUE (Mg stalks kg−1 N) across all N rates at two sites. Our findings support the conclusion that cover crop did not change the N requirement of succeeding ratoon crops but increases the yield, thereby improving NUE in sugarcane systems.

Biomass Production and Potential Fixed Nitrogen Inputs from Leguminous Cover Crops in Subtropical Avocado Plantations

Nitrogen (N) fertiliser is applied to perennial horticultural crops to increase yields, but subsequent N losses in subtropical plantations may be high due to intense rainfall and warmer temperatures. While legume cover crops could potentially contribute N to the tree crops and reduce fertiliser-N requirements, few studies have quantified potential fixed-N inputs from cover crops legumes in tropical or subtropical tree crop systems. To address this, we investigated growth and N fixation of summer-growing Pinto peanut (Arachis pintoi Krapov. & W. C. Greg cv. Amarillo) and winter/spring dominant white clover (Trifolium repens L. cv. Haifa) grown as a mixed species cover crop in two commercial subtropical avocado (Persea americana Mill. cv. Hass) plantations. Legume biomass was assessed prior to mowing of the inter-row (fortnightly in summer and every 6–8 weeks over winter) and N fixation was estimated using the 15N natural abundance technique. Biomass production was 7377 kg ha−1 (930 kg ha−1 for white clover and 6447 kg ha−1 for Pinto peanut) at the first site over the 14-month period from December 2014 to January 2016, and 4467 kg ha−1 (1114 kg ha−1 for white clover and 3353 kg ha−1 for Pinto peanut) at the second site over the same period. Estimation of N fixation was not possible at the first site, due to a lack of difference in isotopic discrimination between the legume shoots and the reference plant (kikuyu (Pennisetum clandestinum Chiov.)) material. While legume shoots accumulated 157 kg N ha−1 (38 kg ha−1 for white clover and 119 kg ha−1 for Pinto peanut) across the season at site 1, the % N derived from atmosphere (%Ndfa) in legumes was relatively low (50–60% in Pinto peanut during the warmer months and around 30% in autumn and early spring, and from 13 % in April to 69% in September for white clover). The low %Ndfa in the legumes may have been due to low rainfall or molybdenum (Mo) deficiency. Ultimately the legume cover crops contributed an estimated 50 kg fixed N ha−1, which could partially offset fertiliser N requirements of the tree crop. Our results demonstrate the need to quantify N fixation in legume cover crops to assess potential N benefits as opposed to relying on typical measurements of legume biomass and N accumulation.

Urea and legume residues as 15N-N2O sources in a subtropical soil

In this work, we used the 15N labelling technique to identify the sources of N2O emitted by a subtropical soil following application of mineral nitrogen (N) fertiliser (urea) and residues of a legume cover crop (cowpea). For this purpose, a 45-day incubation experiment was conducted by subjecting undisturbed soil cores from a subtropical Acrisol to five different treatments: (1) control (no crop residue or fertiliser-N application); (2) 15N-labelled cowpea residue (200 μg N g–1 soil); (3) 15N-labelled urea (200 μg N g–1 soil); (4) 15N-labelled cowpea residue (100 μg N g–1 soil) + unlabelled urea (100 μg N g–1 soil); and (5) unlabelled cowpea residue (100 μg N g–1 soil) + 15N-labelled urea (100 μg N g–1 soil). Cores were analysed for total N2O formation, δ15N-N2O and δ18O-N2O by continuous flow isotope ratio mass spectrometry, as well as for total NO3–-N and NH4+-N. Legume crop residues and mineral fertiliser increased N2O emissions from soil to 10.5 and 9.7 µg N2O-N cm–2 respectively, which was roughly six times the value for control (1.5 µg N2O-N cm–2). The amount of 15N2O emitted from labelled 15N-urea (0.40–0.45% of 15N applied) was greater than from 15N-cowpea residues (0.013–0.015% of 15N applied). Unlike N-poor crop residues, urea in combination with N-rich residues (cowpea) failed to reduce N2O emissions relative to urea alone. Legume cover crops thus provide an effective mitigation strategy for N2O emissions in relation to mineral N fertilisation in climate-smart agriculture. Judging by our inconclusive results, however, using urea in combination with N-rich residues provides no clear-cut environmental advantage.

Cover Crops Impacts on Louisiana Corn Production and Soil Properties

Core Ideas Combination of cover crops with conservation tillage increased soil C. Cover crops significantly reduced nitrate‐N levels during the fallow season. Legume cover crops reduced N requirements when compared with non‐legumes. Conventionally managed, continuous monoculture row‐crop production has depleted the soil of nutrients, organic matter, and overall productivity. This has increased the need for external inputs, specifically N, to meet crop demand. Despite the growing interest in conservation practices, including minimal tillage and cover crops, little work has been reported in the Mid‐South region. Cereal rye (Secale cereal L.), forage radish (Raphanus sativus var. longipinnatus L.), berseem clover (Trifolium alexandrinum L.), crimson clover (Trifolium incarnatum L), winter pea (Pisium sativum L), hairy vetch (Vicia villosa Roth), and a cereal rye–forage radish mix were seeded in discrete blocks in October 2014, 2015, and 2016 along with a non‐cover fallow. Each block was divided into 16 sub‐plots to which one of four N fertilizer rates (0, 235, 268, and 302 kg N ha−1) were applied. Corn (Zea mays L.) grain yields increased with additions of N fertilizer; however, no difference was observed between the three fertilizer rates in 2 of 3 yr. Cover crops aided in the uptake and recycling of inorganic N, potentially reducing losses and providing N for subsequent cash crops. Following legume cover crops, corn grain yields were maximized with the addition of 235 kg N ha−1. Inclusion of grass and brassicas with no additional N input reduced corn grain yield, which remained lower than yield measured following legumes up to the 302 kg N ha−1 rate. Secondary benefits of cover crops included increased soil C (36%) and N (22%), and N cycling over a 2‐yr period.

Cropping systems including legume cover crops favour mineral–organic associations enriched with microbial metabolites in no-till soil

Long-term carbon (C) stabilisation in tropical and subtropical soils under no-tillage (NT) rests on the formation of mineral–organic associations (MOAs) that can be enriched with microbial metabolites. In this work, we assessed the role of long-term tillage and cropping systems and mineral N fertilisation in enriching MOAs with microbial metabolites in a subtropical soil. For this purpose, we sampled a sandy clay loam Acrisol up to 1 m depth involved in an ongoing 30-year-old experiment under two different tillage systems (conventional tillage and NT) in the presence and absence of legume cover crops and mineral nitrogen (N) fertilisation. The soil samples were subjected to particle size fractionation and n-alkane analysis. The NT and the presence of legume cover crops in the surface soil layer (0−5 cm) increased the abundance of plant-derived lipids (i.e. compounds with n-alkane chains of 25−33 C atoms) in the whole soil. Microbial-derived lipids (i.e. compounds with shorter n-alkane chains (15−24 C atoms)) were more abundant in the clay fraction of the surface (0−5 cm) and sub-surface soil layers (20−30 and 75−100 cm) in NT soil receiving high-quality residues of legume cover crops. However, N fertilisation decreased the abundance of microbial-derived lipids in the clay fraction of the 0−5 and 20−30 cm soil layers. Our findings highlight the role of N-rich residues of legume cover crops, but not of mineral N fertilisation, in the long-term stabilisation of C in MOAs in NT soils through the action of microbial residues.

Influence of Contrasting Soil Moisture Conditions on Carbon Dioxide and Nitrous Oxide Emissions from Terminated Green Manures

Core Ideas Impacts of soil moisture at incorporation of two legumes on the CO2 and N2O emissions were studied. Availability of soil moisture led to rapid mineralization of biomass C and N. Legume incorporation based on short‐term rainfall forecast did not avoid large N2O emissions. Carbon dioxide (CO2) and nitrous oxide (N2O) emissions from decomposing legume green manures largely depend on soil moisture. A potential management to mitigate N2O emissions could be to incorporate legumes during dry periods based on the short‐term rainfall forecast. The present mesocosm study was designed to examine the impact of soil moisture due to different timing of rainfall after incorporation of legume cover crops on CO2 and N2O emissions. Two timings of rainfall were simulated as early and late rainfall that received 80 mm deionized water at or 1 wk after incorporation of the legumes. An additional 20 mm water was added after 2 wk of the first simulated rainfalls. Gas fluxes of CO2 and N2O were measured using closed chamber method for 28 d incubation assay. Soil concentrations of NH4+ and NO3–, concentrations of N in undecomposed biomass, and abundances of denitrifier bacterial genes (nirK, nirS, and nosZ) and arbuscular mycorrhiza fungi (AMF) were determined at weekly intervals. Carbon dioxide emissions increased immediately after the first simulated rainfall events and peaked around Day 2 to 3, whereas N2O emissions reached peak level around Day 8 to 10 from both legume treatments. After the first rainfall simulations, soil NH4+ and NO3– concentrations increased, whereas biomass N concentrations decreased rapidly. Abundance of nirK, nosZ, and AMF was positively correlated (P < 0.05) to N2O emissions. Dynamics and magnitude of emissions after first rainfall events remained similar irrespective of the timing of simulated rainfall. In conclusion, our results indicated that soil incorporation of legumes based on a short‐term rainfall forecast may not be an effective tool to avoid large N2O emissions.

ISOLATION, CHARACTERIZATION AND INOCULUM FORMULATION OF NODULE FORMING BACTERIA OF KUDZU (Pueraria phaseoloides (Roxb.)Benth.) FOR COASTAL SANDY LAND CONSERVATION

Kudzu plantation (Pueraria phaseoloides) as legume cover crop is one of alternatives in coastal sandy land conservation. The crops are known to associate with a root nodule-forming bacteria (Rhizobium sp.) which give some benefits to nutrient cycling i.e. : atmospheric N2 fixing and play role as soil conditioner; soil Nitrogen enrichment; nutrient cycling; and increasing other nutrients availability. A research to study the isolation dan bacterial inoculum multiplication from wild kudzu root nodules, compatible isolates screening and selected isolates multiplication, and examining the form, amounts and most proper inoculum application method was conducted in Greenhouse and Laboratory of Microbiology in Yogyakarta province.The research were held in four phases : (1) isolation, purification and characterization of isolates; (2) reinoculation dan compatibility testing of isolates to kudzu seeds; (3) inoculum multiplication; and (4) examination of the form, amounts and most proper inoculum application method. Physical and biochemical properties of the isolates were observed during the isolation phase. Infection and nodulation activity were observed during the reinoculation phase. Indirectly counting of the microbial numbers to obtain the cell numbers was conducted during the inoculum multiplication. While infection and nodulation activity and plant growth were observed during the inoculum testing phase.Isolates purification on Yeast Mannitol Agar + congo-red media gave 5 different isolates named RP-Etp1, RP-Etp2, RP-Etp3, RP-Etp4, RP-Etp5. The RP-Etp4 isolate had the highest compatibility to the kudzu seeds (number of effective nodules >100 per plant), followed by RP-Etp5 (medium compatibility, number of effective nodules 50–100 per plant), RP-Etp1 and RP-Etp3 (low compatibility, number of effective nodules < 10). Isolate RP-Etp2 was incompatible to the kudzu.Optimum cell numbers was reached in 48 hours incubation time. Application of broth/liquid inoculum of Rhizobium sp. has advantages over solid inoculum (in peat) as it gives the highest number of nodules, and the optimum dosage was 2 – 4 ml per plant. The highest infection-nodulation activity and plant growth were reached in 4 ml inoculum per plant (direct application) or 2 ml inoculum per plant (weekly applied in two weeks).

Nitrous oxide emissions increase exponentially with organic N rate from cover crops and applied poultry litter

Best management practices to reduce nitrous oxide (N2O) emissions following application of organic sources of N to soils are poorly developed. For example, while cover crops are promoted for their conservation benefits, their impact on N2O emissions varies considerably. Subsurface banding of animal manures is promoted to reduce nitrogen losses through ammonia volatilization, but the impact on soil N2O emissions is uncertain. To assess the interactive effects of cover crops and subsurface banded poultry litter (SSB PL), we measured annual N2O emissions for three years in a field trial of corn (Zea mays L.) in Beltsville, MD, following either winter fallow or mulched cover crops (cereal rye [Secale cereale L.], hairy vetch [Vicia villosa Roth.], or a mixture of both species), with four rates of SSB PL (9276 kg plant available N (PAN) ha-1) and selected contrasts with surface banded urea-ammonium nitrate (UAN, 150 kg N ha-1) or broadcast incorporated PL (67 kg PAN ha-1). N2O emissions increased exponentially with total N input from organic sources (SSB PL + cover crop residue). This relationship differed by cover crop treatment, with lowest emissions following cereal rye, and highest emissions following hairy vetch. The model intercept ranged from 0.3061.371 kg N2O-N ha-1 (cereal rye < bare ground = mixture < hairy vetch; p = 0.03, 0.24, 0.01), and the exponential coefficient ranged from 0.003000.00603 kg N2O-N kg-1 N (hairy vetch < cereal rye = bare ground = mixture; p = 0.02, p > 0.10). Corn grain yield was similar (mean, 13.8 Mg ha−1) for all cover crops when PL was applied at 135 kg PAN ha−1. SSB PL increased N2O emissions relative to tillage-incorporated PL at an equivalent rate following hairy vetch or cover crop mixture (by 76% or 60%, respectively; p < 0.001) while increasing corn yield by 32% or 16%, respectively. SSB PL decreased emissions relative to surface banded UAN at an equivalent rate following the cover crop mixture, but increased emissions following bare ground (by 34% and 45%, respectively; p = 0.002) while having no influence on corn grain yield, which averaged 13.7 Mg ha−1. Our results indicate that grass:legume cover crop mixtures with SSB PL can lower N2O emissions compared to legume monoculture with SSB PL while maintaining comparable N inputs and corn grain yields.

Pinto peanut cover crop nitrogen contributions and potential to mitigate nitrous oxide emissions in subtropical coffee plantations

Many coffee (Coffea arabica L) production systems are characterised by high use of nitrogen (N) fertilisers, which can result in N leaching and emissions of nitrous oxide (N2O). We investigated the potential for legume cover crops grown inter-row to provide N for coffee trees and lower seasonal N2O emissions compared to poultry litter amendment at two subtropical field sites over 12 months, with unfertilised traditional grass groundcover used as a control treatment. Groundcovers (legume and grass treatments) were slashed from the inter-row into the tree line every 2–6 weeks as per normal farming operations. The prostrate ground cover legume Pinto peanut (Arachis pintoi) produced 4–5 t ha−1 biomass at both sites over the 12 month period, and fixed 146 kg N ha−1 year−1 at one site as estimated using the 15N natural abundance method. Background emissions from soil were lower at site 1 (0.38 kg N2O-N ha−1 year−1) than site 2 (2.26 kg N2O-N ha−1 year−1) reflecting differences in soil N and C levels at the sites. The use of Pinto peanut residues as an N amendment didn't result in any N2O flux events beyond those observed in the traditional groundcover control treatment across the season at either site, while the application of poultry litter to match farmer practice at these sites led to a major emission event. Ultimately, the Pinto peanut cover crop treatment led to a lower emission factor than for poultry litter at both sites, and resulted in significantly lower cumulative seasonal emissions for the legume cover crop (0.34 kg N2O-N ha−1 season−1) than poultry litter amendment (0.68 kg N2O-N ha−1 season−1) at site 1 despite similar inputs of N into the system. These findings suggest cover crop legumes could be integrated into coffee plantations to offset a portion of external N inputs, while lowering N2O emissions.

Valuing the ecosystem services of cover crops: barriers and pathways forward

Apart from yield, our appreciation towards ecosystem services provided by conservation agriculture has mostly been limited to organic farming. Despite its multiple recognizable environmental benefits, cover cropping has a relatively low adoption rate, likely due to its multifaceted management requirements, implementation cost and yield variability. Although legume cover crops could increase crop productivity of low input agriculture, the potential cost savings from reduced use of synthetic agricultural inputs (relative to other management costs of cover crops) remains to be determined. To promote greater cover crop adoption, interdisciplinary research examining bundled trade-offs and/or synergies between ecosystem services and their impacts on farm economy should be prioritized. Detailed economic analyses are needed to capture the ecosystem service values of cover cropping, including those that are not easily quantifiable in monetary terms. These would heighten public awareness and help foster government support (e.g., education, incentives) for greater adoption of sustainable practice.