Crotolaria Juncea Research Articles

Tillage and cover crops effects on crop yield in wheat double‐cropping systems

AbstractThe United States is experiencing longer crop growing season in most states, which could afford producers the opportunity to diversify into double‐cropping (DC) and cover crop systems rather than the predominant summer and winter fallow systems. Thus, this study evaluated DC and cover crops effects on wheat (Triticum aestivum L.), cotton (Gossypium hirsutum L.), and soybean (Glycine max) yield under conventional tillage (CT) and no‐tillage (NT). Summer cover crops (SCCs) were sunn hemp (Crotolaria juncea L.) and sorghum sudangrass (Sorghum bicolor), while winter cover crops (WCCs) were Austrian winter pea (Pisum sativum) and wheat. Cropping systems were wheat‐fallow (W‐F), wheat‐cotton (W‐C), wheat‐soybean (W‐S), W‐SCC, WCC‐C, F‐C, WCC‐S, and F‐S. Tillage effect on crop yields varied across years. In 2021, wheat yield in CT of W‐C, W‐F, and W‐SCC (2831, 2689, and 2646 kg ha−1) significantly differed from NT of W‐S (1720 kg ha−1). No significant tillage effect was observed on cotton lint yield between W‐C and WCC‐C. For soybean, in 2020, the CT of W‐S and WCC‐S significantly outyielded the NT of W‐S and WCC‐S. Cropping system effect on wheat yield between W‐S and W‐SCC (1419 and 1987 kg ha−1) was significant in 2020 due to low stand counts in W‐SCC arising from the thick SCC biomass. Cotton lint yield in WCC‐C outyielded W‐C in all 3 years but was not significant. Soybean grain yield in W‐S was consistently higher than in WCC‐S, though not significant. Cotton lint and soybean grain yield in the fallow systems were the least. Overall, in a short term, crop yield in DC and cover crop systems were similar.

Identifying optimal early‐season harvest timing in annual fall forages

AbstractFall forage production in the northeastern United States is complicated by early onset of cool temperatures, limiting forage availability in cool‐season perennials. Annual forages planted in late summer as cover crops or supplemental forage crops may fill this niche; however, data on their nutritive value over the short fall harvest window is lacking. This study compared six annual forage crops for their forage mass and nutritive value and identified optimal harvest times based on changes between forage mass and digestibility. Monocultures of canola (Brassica napus L.), forage radish (Raphanus sativus L.), oat (Avena sativa L.), spring triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum]), spring wheat (Triticum aestivum L.), sunn hemp (Crotolaria juncea L.), and a mixture of all six species were sown in August of 2015 and 2016 then harvested at three time points (6, 8, and 10 weeks after planting [WAP]) over the fall (September–November). Canola, oat, and spring wheat had the greatest forage mass, while sunn hemp had the least across all harvests. Canola and forage radish had the lowest neutral detergent fiber (NDF) and acid detergent fiber (ADF) and greatest in vitro true dry matter digestibilities (IVTDMd) across all harvests, while sunn hemp and the grasses declined in IVTDMd after first and second harvest. Forage mass of the fall mix was comparable to the highest yielding monoculture at third harvest only. Results suggest that forage brassicas can be harvested without compromising mass or nutritive value, while cereal grasses gained forage mass at the expense of nutritive value.

Intercropping and mulching in rain-dependent cotton can improve soil structure and reduce erosion

Transgenic Bt (Bacillus thuringiensis) cotton (Gossypium spp.) hybrids are grown at wide-row spacing in India. Farmers practice traditional methods of cultivation that involve excessive inter-row cultivations. These practices exacerbate soil erosion and run-off ultimately leading to land degradation. Growing a cover crop between the cotton rows and retaining its residues in situ can reduce erosion and runoff, and improve soil productivity. We compared the effects of growing an intercrop {sorghum (Sorghum bicolor), sunnhemp (Crotolaria juncea) or sesame (Sesamum indicum)} in between the cotton rows and retaining its residues as in situ mulch, vis-à-vis plastic, newspaper mulch and the traditional farmers’ practice (FP) on the soil physical properties (soil microstructure, porosity, water stable aggregates, infiltration rate, soil erosion and soil loss) of a Vertisol near Nagpur in central India. Digital image analysis of the micrographs obtained by a scanning electron microscope indicated porosities were highest with intercropping (53–58%) and the least with the FP and plastic mulching (35–36%). Infiltration rate was in the order of intercropping (19.4–22.6 mm h−1) > newspaper mulch (14.5 mm h−1) > FP (13.8 mm h−1) > plastic mulch (12.3 mm h−1); while the reverse occurred with respect to run-off. Although run-off was the greatest (577 mm) in the plastic mulched plots, soil loss was negligible (0.58 Mg ha−1). Intercropping resulted in 35% less soil loss than FP (6.7 Mg ha−1). This study pointed out that growing an intercrop and retaining its residues as in situ mulch between the cotton rows can improve soil condition by increasing soil microstructure, water stable aggregation and infiltration rate, and reducing run-off and soil loss.

Effects of the planting of legume species and soil conditions on the recovery of a sand and pebble mining area

AbstractExtensive areas have been degraded worldwide through mineral extraction. Mining class II, especially sand and pebble mining (gravel extraction), has grown significantly in Brazilian Amazonia mainly in the State of Pará. In this context, the development of suitable and efficient recovery techniques is necessary to ensure mined land restoration. The objective of this study was to evaluate the effects of different types of management and green manure methods to recover degraded soil after the mining of pebbles and sand. The experiment was implemented in the northern region of the municipality of Capitão Poço, State of Pará. The procedures we used were: a randomized block design experiment, with a 4 × 3 factorial arrangement. Four legume species were tested: Cajanus cajan (L.), Canavalia ensiformis (L.) DC, Crotolaria juncea (L.), and Mucuna pruriens (L.); in addition, three soil conditions were also tested: exposed soil, topsoil, and hydrogel. Results of the analyses showed how the root collar diameter, stem length, fertility, germination, green and dry biomass varied; the variable topsoil had better results when compared to the samples that used hydrogel and those established on exposed soil in practically all the mean comparisons for isolated factors. Besides this, C. ensiformis (L.) DC and M. pruriens (L.) showed a better development, especially when grown in soils with topsoil deposition as a reconformed substrate. From these studies we conclude that the use of this substrate is to be recommended. C. ensiformis (L.) DC and M. pruriens (L.) are also recommended for restoration.

Soil aggregation and potential carbon and nitrogen mineralization with cover crops under tropical no-till

Sustainability of agriculture with no-tillage (NT) production requires appropriate cover cropping and not a simple and random approach of any cover crop species. However, relatively little is known of the long-term soil surface impacts of different cover crops in rotation with soybean (Glycine max) under NT in the tropics. We evaluated the impacts of different cover crops on soil aggregation, soil organic carbon (C) and nitrogen (N) fractions, and soil microbial activity of a Typic Rhodudalf at the end of 12 years under NT in Sao Paulo state of Brazil. Treatments included main plots during the winter dry season (triticale [× Triticosecale] and sunflower [Helianthus annuus]) and subplots during the spring cover crop season (pearl millet [Pennisetum glaucum], sunn hemp [Crotolaria juncea], forage sorghum [Sorghum bicolor], and fallow with occasional chiseling). All eight of these treatments followed soybean in summer. Winter crop treatments had no effect on soil aggregation, but total organic C and N concentrations were greater (p

Stamen elongation in sunn hemp appears to allow delayed self-pollination in the absence of pollinators – A case of bet-hedging?

Sunn hemp, Crotolaria juncea L., is an important green manure crop in the tropics. In this species, flowers are hermaphrodite, self-compatible, but herkogamous with the stigma located well above the anthers, and thus appear to be cross-pollinated. Anthers are dimorphic (5 stamens with short and 5 stamens with long filaments) and hidden beneath keel petals. The longevity of flowers was three days. Of the 16 species of bees that visited flowers of sunn hemp, four species of Megachile (M. lanata, M. bicolor, M. disjuncta and M. anthracina) and one species of Xylocopa (X. fenestrata) were effective pollinators and constituted more than 75% of visits. Species of Apis never came in contact with stigma or anther lobes and were not involved in pollination. Open pollination resulted in 78% pod set. However, when flowers were prevented from pollinator visitation, the pod set was still 62%. In the absence of pollinators, filaments of long stamens elongated and reached the level of stigma which presumably led to delayed autonomous self-pollination, a bet-hedging strategy by the plant to set seeds in the absence of pollinators.

Effect of Green Manuring Crops on Carbon Mineralization, Dehydrogenase and β-Glucosidase Activities in Inceptisols

Pot culture and incubation studies were conducted to assess the carbon mineralization and soil enzyme activities with green manure crop residue in Inceptisols. The studies were undertaken with six green manure crop residues viz., sunhemp (Crotolaria juncea), cluster bean (Cymopsis tetragonaloba), cow pea (Vigna unguiculata), mutant dhaincha (Sesbania rostrata), green gram (Vigna mungo) and soybean (Glycine max L. Merrill) which were grown up to 50 per cent flowering in the pot along with control at Division of Soil Science and Agricultural Chemistry, College of Agriculture, Pune during 2020-21 in completely randomized design with three replications. Carbon mineralization and soil enzyme activities i.e. dehydrogenase and β- glucosidase were studied by incorporating green manure crop residues in soil. In the incubation study, the mutant dhaincha recorded significantly higher release of CO2-C throughout the incubation period than othertreatments. The rate of release of CO2-C was slow at 0 and 15 days after incubation but increased at 45 days after incubation and thereafter, gradual decline in all green manures incorporated treatments was observed. Higher dehydrogenase and β- glucosidase activity were recorded in sun hemp treated pots.

Using the cover crop N calculator for adaptive nitrogen fertilizer management: a proof of concept

AbstractLegume cover crops can supply a significant amount of nitrogen (N) for cash crops, which is particularly important for organic farmers. Because N mineralization from cover crop residue depends on the amount of biomass, cover crop quality, as well as environmental conditions such as soil moisture and temperature, predicting the amount of N mineralized and the timing of release has been difficult. We have developed a Cover Crop Nitrogen Calculator based on the N subroutine of the CERES crop model and evaluated the use of the predicted N credits on yields of fall broccoli [Brassica oleracea L. (Italica group)] at a research farm and two working farms. Research farm trials consisted of a cowpea (Vigna unguiculata L. Walp.) cover crop and no cover crop treatments, each at four N rates (0N, 0.5N, 1N and 1.5N, with 1N the target N rate of 112 kg N ha−1 in 2013 and 168 kg N ha−1 in 2014 and 2015) in a randomized complete block design. On-farm trials consisted of a cowpea or sunn hemp (Crotolaria juncea L.) cover crop at four N rates (0N, 0.5N, 1N and 1.5N) and no cover crop treatment at the 1N rate in a completely randomized design. Cover crop biomass and quality (N%, carbohydrates%, cellulose% and lignin%) were measured and used with a 5-yr average soil moisture and soil temperature from a local weather station to predict an N credit. In the cover crop treatments, the N rate was modified by the predicted credit, while the no cover crop treatment received the full N fertilizer rate either as feathermeal (certified organic fields) or as urea (conventional field). At the research farm, broccoli yield increased up to the 0.5N rate, and there was no difference in yield between the no cover 0.5N rate and the cover crop 0.5N rate in 2013, 2014 and 2105. On-farm, we saw an N response in two site-years. In these site-years, there was no difference between the no cover 1N rate and the cover crop 1N rate. At the third site-year, no N response was seen. Overall, our results showed using the cover crop credit predicted by the Calculator did not reduce yields. The use of a decision support tool such as the Calculator may help farmers better manage N fertilizer when cover crops are used, and increase cover crop adoption.

Purification, characterization and retting of Crotolaria juncea fibres by an alkaline pectin lyase from Fusarium oxysporum MTCC 1755

Using solid-state fermentation, production of an industrially important pectin lyase from a fungal strain Fusarium oxysporum MTCC 1755 was attempted, which was further subjected to purification and characterization. The enzyme was purified by three steps, namely ammonium sulfate fractionation, cation-exchange chromatography on CM cellulose followed by gel filtration chromatography using Sephadex G-100 column. A 16-fold purification with 31.2% yield and 3.2 U/mg specific activity was achieved. The optimum pH of the purified enzyme was 9.0 and stability ranged from pH 5.0–7.0 for 24 h. Optimum temperature of purified enzyme was found to be 40 °C while temperature stability ranged from 10 to 50 °C for 30 min. The Km and kcat of the enzyme was 1.75 mg/ml and 83.3 s−1, respectively. The purified enzyme was found to be highly stimulated by Ca2+ ions while sugars like mannitol and sorbitol, and salts like NaCl and CaCl2 enhanced the thermostability. The purified pectin lyase was found suitable for retting of Crotolaria juncea fiber.

Efficacy of Virus Inhibitory Agent (VIA), Isolated from Host Plants Treated with Purified Clerodendrum aculeatum Phytoprotein Alone and in Combination with Bioenhancers

It was revealed that the effectiveness of VIAs, obtained from source hosts, pretreated either with purified CA phytoprotein alone or in combination with a few bioenhancers, was variable. Out of all those used, VIA isolated from the leaves of Crotolaria juncea (CT-VIA), pretreated with purified phytoprotein, isolated from the leaves of Clerodendrum aculeatum plants (CA-phytoprotein), along withbioenhancer (L-Lysine monohydro Chloride - CA+M9), gave best response, when mixed with an inoculum of Sunnhemp Rosette Virus, incubated in-vitro before inoculation and then assayed for its antiviral efficacy on the leaves of Cyamopsis tetragonoloba plants. The VIA, at a concentration of 1:10, was found to be optimum and further increase in its strength did not show any considerable effect on ex vivo inactivation of Virus. Local lesions appeared, on the leaves of treated and untreated (control) plants of Cyamopsis tetragonoloba 4-6 days following virus inoculation, exhibited significant reduction of 88%, 95%, 90% and 93% by CT-VIA isolated from the leaves treated with CA alone, CA+M9, CA+M3 and CA+M9+M3 respectively.

Effect of different mulching materials on maize growth and yield in conservation agriculture systems of sub-humid Zimbabwe

The introduction of conservation agriculture (CA) for smallholders increased the competition for crop residues between crop and livestock enterprises of the mixed smallholder farming system. Smallholders practicing CA have resorted to using grass and leaf litter in addition to available crop residues. The effect of these different mulching materials on maize (Zea mays L.) growth and yield is not well documented in smallholder CA systems of southern Africa. A two-year experiment was run in 2012/13 and 2013/14 seasons to evaluate the effect of maize residues, grass (Hyparrhenia filipendula (L.) Stapf.) and leaf litter that farmers are currently using and residues from leguminous species, sunhemp (Crotolaria juncea L.) and Tephrosia (Tephrosia vogelii ((Hook) f.)) on maize nitrogen (N) uptake, growth and yield. Significant differences in soil water content across treatments were only observed during March in 2012/13 season. Maize residues retained more soil water and Tephrosia had the lowest soil water content when seasonal rainfall pattern was erratic. Grass and Tephrosia treatments had the lowest chlorophyll content. Conventional ploughing, maize residues and leaf litter had similar chlorophyll content which was significantly higher than grass and Tephrosia treatments. At a site with higher initial soil fertility conventional ploughing treatment out yielded the other treatments by 727–1265 kg ha−1. With more degraded sandy soil conventional practice had 119–430 kg ha−1 more maize grain than the CA treatments. With adequate fertilization, the mulching materials have a similar effect on maize growth in basins and direct seeding. Further studies on different application rates of mulching materials and mineral N fertilizer, and nutrient release patterns of these residues are critical in order to better understand soil fertility management under smallholder CA systems.

Environmental and economic impacts of different sugarcane production systems in the ethanol biorefinery

AbstractEconomic and environmental impacts of ethanol biorefineries with different sugarcane (Saccharum spp.) production technologies are evaluated with a focus on harvesting systems, reduced tillage, controlled traffic farming to reduce soil compaction, and alternatives of sugarcane rotation. Results showed that scenarios with sunn hemp (Crotolaria juncea) as a rotation crop in the sugarcane cycle present great potential to decrease environmental impacts of sugarcane biorefineries. Although reduced tillage promotes a reduction in sugarcane production costs in comparison to conventional tillage, it only cause a slightly decrease (less than 5%) on ethanol environmental impacts. Use of soybean (Glycine max) as a rotation crop yields an extra source of income, increasing the net agricultural revenues by 15% compared to scenario with sunn hemp. However, better economic and environmental impacts for sugarcane biorefinery are obtained with use of sunn hemp in the crop rotation and controlled traffic farming. Sugarcane production using controlled traffic farming allows an increased number of harvesters, with consequent reduction of 43% in greenhouse gases emissions, 24% in fossil depletion, and 44% in acidification potential when compared to burned cane scenario. These results reinforce that better agricultural management practices should be used to maximize number of cuts in the sugarcane cycle. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Effects of Interplanting Flowering Plants on the Biological Control of Corn Earworm (Lepidoptera: Noctuidae) and Thrips (Thysanoptera: Thripidae) in Sweet Corn.

Natural enemy exploitation of food resources and alternative hosts in noncrop vegetation has been shown to be an effective means of enhancing natural enemy populations in diversified agro-ecosystem. Field trials were conducted in Hawaii to examine effects of interplanting flowering plants on 1) parasitism of corn earworm, Helicoverpa zea (Boddie) eggs by Trichogramma spp., and 2) abundance of Orius spp. in relation to prey (H. zea eggs and thrips [primarily, Frankliniella occidentalis (Pergande) and Frankliniella williamsi Hood]). Sweet corn (maize), Zea mays L., was interplanted with three flowering plants, buckwheat, Fagopyrum esculentum Moench, cowpea, Vigna unguiculata (L.), and sunn hemp, Crotolaria juncea L., at 2:1 and 4:1 (corn: flowering plant) ratios in 2009 and 2010, respectively. In 2009, the abundance of Orius spp. was significantly greater in the buckwheat-interplanted treatment compared to the monocrop control at similar levels of prey availability, indicating buckwheat flowers might have provided both prey and nectar resources. In 2010, cowpea and sunn hemp flowering plants provided a source of an alternate host insect's eggs for Trichogramma spp. oviposition, resulting in significantly higher parasitism of H. zea eggs in the cowpea- and sunn hemp-interplanted treatments compared to the monocrop control. Despite of differences in pest and natural enemy interactions in two field trials, our findings suggested that provisioning of an alternate host insect's eggs through flowering plants is an effective means for enhancing Trichogramma spp. and provisioning of both nectar and prey resources through flowering plants is important for enhancing predation by Orius spp.

Assessment of in vitro antipsoriatic activity of selected Indian medicinal plants

Context: Phyllanthus simplex Retz. (Phyllanthaceae), Crotolaria juncea Linn. (Leguminosae), Leucas aspera Linn. (Lamiaceae), and Vitex glabrata R.Br. (Verbenaceae) are well-known Indian medicinal plants. Different parts of these plants are used for healing purposes traditionally in the treatment of psoriasis and various other disorders. This prompted us to assess the antipsoriatic activities of these plants.Objectives: Petroleum ether and ethanol extracts of the selected plants, i.e., P. simplex (whole plant), C. juncea (seeds), L. aspera (aerial parts), and V. glabrata (leaves) were investigated for their in vitro antipsoriatic activity.Materials and methods: Antipsoriatic activity of the extracts was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, using HaCaT cells. About 200 µl of different concentrations (25, 50, 100, 200, and 400 µg/ml) of test samples were prepared in the cell culture medium and incubated for 24 h before MTT assay to determine the viable cells. The effect of these extracts on nitric oxide (NO) production and lipid peroxidation was also evaluated.Results: Our findings revealed that these plants showed promising skin keratinocyte antiproliferative activity. However, the petroleum ether extract of C. juncea (CJPE) and ethanol extract of L. aspera (LAEE) were found to exhibit significant activity (IC50 value = 45.45 and 55.36 µg/ml, respectively).Discussion and conclusions: The inhibitory action against NO production and lipid peroxidation in HaCaT cells suggested that the antipsoriatic activity of the extracts was mediated by an antioxidant mechanism. These findings validate the claims of the use of these plants in the treatment of psoriasis.

Management of Meloidogyne incognita in yam-based cropping systems with cover crops

The effect of intercropping cover crops was with yam was assessed for nematode management both in pot and field conditions in Nigeria. The cover crops were sown with yams in pots containing sterile soil and inoculated with 5000 eggs of Meloidogyne incognita. In the field, each cover crop was separately intercropped with yams inoculated with 10,000 nematodes. From both pot and field experiments, no nematode damage was observed on yam tubers that were intercropped with Aeschynomene histrix, Crotolaria juncea, and Tagetes erecta. Damage in intercropped tubers was reduced by 72.7% with Mucuna pruriens, Centrosema pubescens, and Pueraria phaseoloides and by 58.3% with Stylosanthes guianensis compared to yams planted without cover crops; they also had lower (p ≤ 0.05) nematode populations. Cajanus cajan, Lablab purpureus and Vigna unguiculata however, supported high nematode populations and led to nematode damage in intercropped yams. Tubers from M. incognita-inoculated plants were more damaged and lost 42% more weight (p ≤ 0.05) following three months of storage than tubers from uninoculated plants. Intercropping yams with selected cover crops can be useful in managing M. incognita without reducing yam yields.

Purification and biochemical characterization of an alkaline pectin lyase from Fusarium decemcellulare MTCC 2079 suitable for Crotalaria juncea fiber retting.

An extracellular pectin lyase secreted by Fusarium decemcellulare MTCC 2079 under solid state fermentation condition has been purified to electrophoretic homogeniety by using ammonium sulfate fractionation, carboxymethyl cellulose and gel filtration (Sephadex G-100) column chromatographies. The purified enzyme showed single protein band corresponding to molecular mass 45 ± 01 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme had maximum activity at pH 9.0 and showed maximum stability in the pH range of 9.0-12.0. The optimum temperature of the purified enzyme was 50 °C and it showed maximum stability upto 40 °C. The energy of activation for the thermal denaturation (Ea ) was 59.06 kJ mol(-1) K(-1). The Km and kcat values using citrus pectin as the substrate were 0.125 mg ml(-1) and 72.9 s(-1) in 100 mM sodium carbonate buffer pH 9.0 at 50 °C. The biophysical studies on pectin lyase showed that its secondary structure belongs to α + β class of protein with comparatively less of β-sheets. Purified pectin lyase showed efficient retting of Crotolaria juncea fibers.

Effect of different mulching materials on weed dynamics and yield of direct seeded rice in Chitwan, Nepal

An experiment was carried out at farmers' field to compare the effects of live mulches and herbicide on weed growth and dynamics, yield, and economic performance of direct seeded rice under humid sub-tropical condition at Phulbari, Chitwan in 2009. The experiment was conducted in Randomized Complete Block Design with eight treatments and three replications. The treatments consisted of i) control, ii) three hand weeding, iii) herbicide application (bispyribac sodium @ 80 ml/ha) + one hand weeding, iv) wheat straw mulch @ 5t/ha + one hand weeding, v) Eupatorium mulch @ 5t/ha + one hand weeding, vi) brown manuring with Sesbania aculeata @ 30 kg/ha, vii) brown manuring with Sesamum indicum @ 2kg/ha, and viii) brown manuring with Crotolaria juncea @ 30 kg/ha. Weed dry matter accumulation was significantly lower with herbicide application (1.15 g/m2) than wheat straw mulch (6.75 g/m2). The treatments with brown manuring and Eupatorium mulch were found to be equally effective in suppressing the weed growth by reducing both dry matter content and weed density. Application of Eupatorium mulch one day after sowing produced significantly higher grain yield (3.5 t/ha) than control (1.77 t/ha), Sesamum brown manuring (2.97 t/ha) and wheat straw mulch (2.83 t/ha). Yield attributes like effective tillers/m2, panicle length and panicle weight were positively correlated with grain yield (r = 0.540, 0.705, 0.531 and 0.613 respectively). The net profit (Rs. 63.17 x 1000/ha) obtained from the treatment with Eupatorium mulch was higher than other tested treatments. Eupatorium mulch and herbicide application recorded equal benefit cost ratio of 2.4. Cultivation of direct seeded rice with the application of Eupatorium mulch or brown manuring (BM) of Sesamum was found effective for increasing yield and net returns in humid subtropical condition of Chitwan. Live mulching could be an eco-friendly weed control options in DSR. The BM option also provides crop residue for the addition of organic matter. This result suggests that BM is a potential alternative of herbicide application. Either mulching with Eupatorium and wheat straw or growing of Sesbania and Crotolaria as BM with rice up to 30 DAS are advisable to increase productivity with reduced cost of production at Chitwan and similar condition. Agronomy Journal of Nepal (Agron JN) Vol. 3. 2013, Page 73-81 DOI: http://dx.doi.org/10.3126/ajn.v3i0.9008

Heavy Metal Phytoremediation Potential of a Heavy Metal Resistant Soil Bacterial Isolate, Achromobacter sp. Strain AO22

Environmental contamination by the toxic heavy metal cadmium (Cd) is a significant problem in a number of countries, as Cd accumulates in crops and causes a number of serious illnesses. This work investigated whether a heavy metal tolerant soil bacterium, Achromobacter sp. strain AO22, could affect plant growth as well as Cd and zinc (Zn) accumulation of the fibre crop plant, sunn hemp (Crotolaria juncea). Seeds of sunn hemp were either presoaked in AO22 cell suspension, or used without pretreatment (controls), and plants from both groups grown on potting mix supplied with 0, 50 and 100ppm of Cd or Zn. The plant growth parameters and total Cd/Zn were analyzed after 4 weeks. Plants from AO22-presoaked seeds and grown on Cd exhibited longer and heavier roots, higher biomass and lower levels of Cd accumulation at 50ppm Cd, compared to controls (without AO22 association). This could be due to reduced uptake, or increased efflux, of moderate amounts of Cd from plants. AO22 also seemed to moderately enhance root and shoot lengths and Zn accumulation. It thus appears that soil microbiota such as AO22 could hold the key for development of crop plants that may be safer to use and more suitable for growth on contaminated sites.

Management of the Root Knot Nematode (Meloidogyne Javanica. Treub) and Sore Shin (Rhizoctonia Solani. Kuhn) Using A Nematicide and Poor Host Crops in Rotations

In a long term study the effects of a nematicide and six rotations: root-knot-susceptible tobacco, Nicotiana tabacum L. cv.‘KM10’ grown continuously (ContKM10), root-knot-resistant tobacco cv. ‘RK8’ grown continuously (ContRK8), grass-grass-grass-KM10 (G-G-G-KM10), grass-grass-grass-RK8 (G-G-G-RK8), KM10-Crotalaria juncea (KM10-Cr) and RK8-Crotalaria juncea (RK8-Cr), on root knot nematode, Meloidogyne javanica and sore shin, Rhizoctonia solani infection were studied. The nematicide used was ethylene dibromide (EDB) and was applied to each tobacco crop, as is standard practice. Chloris gayana cv. ‘Rhodes Katambora’, presumably a poor host of nematodes, was the grass used in all the grass-grass-grass-Tobacco rotations. The treatments were arranged in a randomized complete block design. ContKM10, KM10-Cr, G-G-G-RK8, ContiRK8 and RK8-Cr reduced root knot galling while G-G-G-KM10 increased galling. Sore shin increased with every year of rotation regardless of rotation, except in the case of G-G-G-KM10 and G-G-G-RK8 which reduced infection relative to other rotations. With the exception of G-G-G-RK8, all rotations that included RK8 suppressed root knot infection but did not suppress sore shin infection. The rotations including KM10 suppressed nematodes only with EDB treatment yearly and did not suppress sore shin except the rotation G-G-G-KM10. The role of Crotolaria juncea was masked by either RK8 or EDB. Host plant resistance in the form of RK8 was effective in controlling nematodes but did not reduce sore shin except mildly when rotated with the grass. This work recommends the use of resistant cultivars with broad-spectrum resistances.

Using Protector Plants to Reduce the Incidence of Papaya Ringspot Virus-Watermelon Strain in Zucchini

The use of plant diversification (e.g., mixed cropping, cover crops, border plants, intercrops, etc. ) to protect a primary crop from insect transmitted viral diseases is often referred to as barrier cropping. Specific plants used to mitigate virus incidence in a cash crop are frequently called protector plants. The potential use of protector plants to reduce the density of aphid vectors and incidence of aphid-borne nonpersistent virus in zucchini, Cucurbita pepo L. was evaluated during 2003, 2005, and 2006 on Oahu, HI. Cover crops, buckwheat Fagopyrum esculentum Moench and white clover Trifolium repens L., or sunn hemp, Crotolaria juncea L. and an intercropped vegetable, okra Abelmonchus esculentus (L.), were evaluated for their potential use as protector plants. Results of the field experiments showed that densities of alatae aphids in water pan traps did not differ significantly among treatment habitats during three field experiments. However, the percentage of zucchini plants showing virus symptoms was significantly lower in diculture than monoculture habitat during all 3 yr. Results from field and laboratory experiments support the hypothesis that protector plants reduced the incidence of Papaya ringspot virus-watermelon strain by acting as virus sinks and that the three cover crops were more effective in reducing Papaya ringspot virus-watermelon spread than okra.