Preplant Treatments Research Articles

Weed density and biomass are reduced and plant growth and seed yield increased in common bean after solarisation with clear and black plastic

Common bean is highly sensitive to early weed competition, which severely reduces growth and yield. An experiment was carried out in Zimbabwe in the 2002/03 and 2003/04 seasons to assess the effectiveness of solarisation in controlling weeds in beans. Four pre-planting treatments, viz. covering plots with (1) clear plastic and (2) black plastic for eight weeks from September to November, (3) fumigation with methyl bromide and (4) an untreated control, were laid out in a randomised complete block design with four replicates. Soil temperature at 5 cm depth was significantly (p < 0.05) higher in the clear plastic treatment (39–55 °C) than the black plastic (30–43 °C), fumigated (37–41 °C) and uncovered treatments (30–40 °C). Mean weed emergence and biomass significantly (p < 0.001) increased in the order clear plastic < black plastic < fumigated < uncovered in the bean crop at 5 weeks after emergence. Number of flowers and pods plant−1 (p < 0.001) increased by 30% and 44% in the black plastic and clear plastic solarised treatments. Bean seed yield (p < 0.001) increased by 13%, 68% and 86% (2002/03 season) and by 27%, 77% and 83% (2003/04 season) in the fumigated, black plastic and clear plastic solarised treatments, respectively. The increased bean growth and seed yield is a result of solarisation reducing weed density and inducing beneficial soil amendments.

Effect on storage behaviour of elephant foot yam under the influence of different pre-planting treatments

Effect on storage behaviour of elephant foot yam under the influence of different pre-planting treatments

INFLUENCE OF BOTANICALS ON SOIL FERTILITY POTENTIALS, SEED GERMINATION AND PERFORMANCE OF MAIZE (ZEA MAYS) VARIETIES UNDER LOW FERTILE CONTINUOUSLY-CROPPED SOIL CONDITIONS

It is not unreasonable to state that, even before the introduction of organic agriculture, African local farmers have numerous of undocumented environment-friendly, nature-inclined indigenous techniques for boosting soil fertility and enhancing crop yield. However, despite the versatility of indigenous knowledge, setback is always experienced from western science, which tags such knowledge as being non-scientific and not worthy of scholarly engagements. A field experiment was carried out in the year 2013, at the Teaching and Research Farms, LadokeAkintola University of Technology, Ogbomoso, to assess the soil fertility and yield promoting potentials of some indigenous plant species’ botanicals used as pre-planting treatments on different maize varieties. It was a 3 by 5 factorial experiment. The treatments introduced were: Three (3) maize varieties (V1 = ACR-DMR-SR-Y, V2 = Local EM-W and V3 = Suwan Solo Yellow and five (5) other treatments (comprising pre-sowing botanical treatments of: Kigeliaafricana only, Glyphea brevis only, combination of Kigeliaafricana and Glyphea brevis only, NPK fertilizer application (as a reference) and the control (treated with ordinary water only). The trial was laid out in Split Plot in Randomized Complete Block Design (RCBD), replicated three times. Data were collected on growth and yield parameters, and the data collected were analysed using analysis of variance (ANOVA). Means were compared using Duncan Multiple Range Test (DMRT). All the botanical treatments significantly influenced germination, growth, yield and nutrient uptakes of maize, compared to the control. Either of the botanicals tested (with ordinary basal manure application of the pre-existing plant residues on the field), competed effectively with NPK fertilized plants. Hence, since maize responded better to sole treatments of either Kigeliaafricana or Glyphea brevis extracts, irrespective of varieties than the combined treatment of the two botanicals, any of the maize varieties is therefore recommended as being suitably compatible with either of the sole botanical treatments, in the study area. Thus, this research is reasonable, particularly in the aspects of fertilizer economy, environment-friendliness, organic farming and more profitable crop production in the tropics, where soils are continuously cropped and marginal.

Post-plant strategies for management of black root rot-related decline of perennial strawberry fields

Perennial strawberries affected with black root rot generally decline in runner production, yield, and overall plant vigor over time. Several plant pathogens have been implicated in black root rot, including plant-parasitic nematodes, Pythium and Rhizoctonia spp. Pre-plant treatments such as a 3- to 5-year crop rotation or chemical fumigation are the main means of disease management. During 2007 and 2008, five post-plant treatments were evaluated for mitigation of strawberry black root rot in a naturally declining site in Ottawa County in Michigan. Fungicides and nutritional amendments were applied as drenches or foliar sprays. Most treatments increased runner establishment, yield, and overall plant vigor, particularly azoxystrobin and azoxystrobin + potassium phosphite. Root necrosis and incidence of root infection by binucleate Rhizoctonia spp. were reduced. Results were more apparent and significant in 2008 than in 2007, indicating cumulative effects over the 2 years of the trial. During 2008 and 2009, a large-scale demonstration trial was conducted with these treatments in a strawberry field with a history of black root rot in Leelanau County, MI. Improvements in bed fill and average plant weight and reductions in root necrosis and Rhizoctonia isolations were noted. This research represents the first post-plant chemical management strategy capable of slowing or even reversing the decline due to black root rot in established strawberry fields.

The Effect of Fraze Mowing on Overseed Establishment in Cynodon dactylon Turf

Cynodon spp. (bermudagrass) golf courses and athletic fields in warm‐humid and warm‐arid regions are often annually overseeded with a cool‐season grass to improve turf performance during autumn and winter. Previous research has shown that preplant cultivation treatments to the C. dactylon base typically results in improved overseed establishment. Fraze mowing is a relatively new turf maintenance technique in which thatch and grass verdure is aggressively removed by blades attached to a revolving rotor. Because fraze mowers can significantly reduce C. dactylon competition for the overseed, a study was devised to determine the effectiveness of fraze mowing as a preplant technique prior to overseeding. The study was conducted in Lexington, KY, and Knoxville, TN, during the fall and winter of 2015–2016. Treatments were applied on 17 September and consisted of an untreated control, vertical mowing (one direction, 7.5 mm deep, 2.5‐cm spacing), and fraze mowing at 0.6‐, 1.2‐, and 2.5‐cm depths. Response variables included percentage cover, germination rating, surface hardness, and percentage cover the following spring and summer. Results showed no differences between preplant treatments for germination and percentage cover the following year. However, the fraze mowing treatments resulted in reduced percentage cover for 2 to 3 wk after treatment (WAT) compared with vertical mowing and the untreated control. By 3 WAT, the overseed had established and all plots had &gt;90% cover. Surface hardness was only slightly affected by preplant treatment at just one location, and results were not consistent.

Evaluating Soil Solarization for Weed Control and Strawberry (Fragariaxananassa) Yield in Annual Plasticulture Production

Field studies were initiated in the 2013-14 and 2014-15 growing seasons to evaluate the potential of soil solarization (SS) treatments for their efficacy on weed control and crop yields and to compare SS to 1,3-dichloropropene (1,3-D)+chloropicrin (Pic) fumigation. Each replicate was a bed with dimension 10.6 m long by 0.8 m wide on top. The center 4.6 m length of each bed, referred to as plots, was used for strawberry plug transplanting and data collection. Treatments included: i) 1,3-D+Pic (39% 1,3-dichloropropene+59.6% chloropicrin) that was shank-fumigated in beds at 157 kg ha−1and covered with VIF on August 30 in both seasons; ii) SS for a 6 wk duration initiated on August 15, 2013 and August 21, 2014 by covering the bed with 1 mil clear polyethylene tarp; iii) SS for a 4wk duration initiated on September 6, 2013 and September 3, 2014; iv) SS 4 wk treatment initiated September 6, 2013 and September 3, 2014 and replaced with black VIF on October 4, 2013 and October 1, 2014 and v) a nontreated control covered with black VIF on October 4, 2013 and October 1, 2014. In both seasons, following completion of the preplant treatments, ‘Chandler’ strawberry was planted in two rows at a 36 cm in-row spacing in plots during the first wk of October. Over both seasons, the 6 wk SS treatment consistently lowered the weed density compared to the nontreated control. Weed density in the 6wk SS treatment was not statistically different from the 4wk SS treatments in the 2013-14 growing season. In both seasons, crop yield in the 4 wk SS was significantly lower than other treatments.

Soil disinfestation with dimethyl disulfide for management of Fusarium wilt on lettuce in Italy

The efficacy of dimethyl disulfide (DMDS) applied in pre-planting treatment by shank injection was investigated on the lettuce Fusarium oxysporum f.sp. lactucae (FOL) pathosystem in Northern Italy (Piedmont), in three experimental trials. DMDS was tested alone or in combination with metham sodium at 35.9 g/m2, on lettuce cultivars showing different levels of susceptibility to the pathogen. DMDS, at 60 g/m2, reduced FOL symptoms on the highly susceptible butterhead type of 70, 97 and 99%, and of 87, 97 and 100% on the moderately susceptible cultivar, respectively. DMDS at 30 and 40 g/m2 showed a only partial efficacy on both lettuce types used in naturally infested soil, with a disease reduction from 30.3 to 64.5%, significantly comparable with dazomet. The results provided by DMDS at 40 g/m2 plus metham sodium at 35.9 g/m2 were statistically similar to those obtained with DMDS alone at 60 g/m2, and better than those provided by dazomet alone. A positive effect on lettuce yield and weed control by DMDS, at the highest dosage tested and by DMDS plus metham sodium, was also observed.

Adaptation of primocane fruiting raspberry plants to environmental factors under the influence of Bacillus strains in Western Siberia.

In geographical locations with a short vegetative season and continental climate that include Western Siberia, growing primocane fruiting raspberry varieties becomes very important. However, it is necessary to help the plants to overcome the environmental stress factors. This study aimed to evaluate the impact of the pre-planting treatment of primocane fruiting raspberry root system with Bacillus strains on the following plant development under variable environmental conditions. In 2012, Bacillus subtilis RCAM В-10641, Bacillus amyloliquefaciens RCAM В-10642, and Bacillus licheniformis RCAM В-10562 were used for inoculating the root system of primocane fruiting raspberry cultivar Nedosyagaemaya before planting. The test suspensions were 105CFU/ml for each bacterial strains. The effects of this treatment on plant growth and crop productivity were estimated in 2012-2015 growing seasons differed by environmental conditions. The pre-planting treatment by the bacterial strains increased the number of new raspberry canes and the number of plant generative organs as well as crop productivity compared to control. In addition, these bacilli acted as the standard humic fertilizer. Variable environmental factors such as air temperature, relative humidity, and winter and spring frosts seriously influenced the plant biological parameters and crop productivity of control plants. At the same time, the pre-planting primocane fruiting root treatment by Bacillus strains decreased the negative effects of abiotic stresses on plants in all years of the research. Of the three strains studied, B. subtilis was shown to reveal the best results in adaptation of primocane fruiting raspberry plants to environmental factors in Western Siberia. For the first time, the role of Bacillus strains in enhancing frost resistance in primocane fruiting raspberry plants was shown. These bacilli are capable of being the basis of multifunctional biological formulations for effective plant and environmental health management in growing primocane fruiting raspberry.

Impacts of Variable Rate Nitrogen (VRN) on Nitrate-N Losses from Tile Drained Maize in Minnesota, USA

Little is known about the effectiveness of sensor-based variable rate nitrogen (VRN) fertilizer application at reducing nitrate-N losses. A variable rate in-season nitrogen (VRN) treatment was compared to a conventional pre-plant uniform rate nitrogen treatment in eight Minnesota, USA sub-fields. Water samples collected weekly during 2016 were analyzed for nitrate-N. The Drainmod model was able to accurately represent measured tile discharge and nitrate-N concentration data. Modeled nitrate-N losses in tile discharge were 16% lower in VRN than uniform treatments. These results show that in-season VRN fertilizer N management can significantly reduce nitrate-N loads from tile drained maize fields.

The impact of legume and cereal cover crops on rhizosphere microbial communities of subsequent vegetable crops for contrasting crop decline

Crop decline is a progressive soil health reduction commonly associated to the specialized cultivations. As a series of biotic factors are involved in this phenomenon, it can be controlled with essentially agronomic methods, the impact of winter cover crops on early growth at subsequent vegetable crops was investigated in a two-year field study. Barley and hairy vetch were incorporated into the soil following two mechanical terminations of cover crops (green manure and green mulching). Immediately after, tomato and zucchini seedlings were transplanted and grown for 28days. The above-ground biomass of the vegetables was taken as indicator of crop response to pre-plant treatments, whilst root colonizing fungi and rhizosphere bacteria were the two analyzed soil microbial components. Root-colonizing fungi were evaluated using culture-based methods, bacteria were analyzed by amplification of rhizosphere soil DNA with 16S rDNA, then processed with PCR-DGGE. Tomato and zucchini growth response after vetch was always significantly higher than after barley regardless of mechanical termination. Rhizosphere bacterial communities differed significantly between cover crops and this differences was maintained also in the subsequent vegetable crops. Root-colonizing fungi differed between barley and vetch, although they shared most species (70%) such as Pythium spp., binucleate Rhizoctonia AG-A and several Fusarium spp. The latter three fungal groups were also found most abundant in tomato and zucchini roots. Pathogenicity test showed that tomato was more susceptible than zucchini to Pythium, Rhizoctonia solani, Fusarium oxysporum and Fusarium spp. and that their relationship with vegetable plants varied from pathogenic to neutral, up to mutualistic in the case of Rhizoctonia AG-A. These findings indicate difficulty to identify specific biotic agents responsible of crop decline. Tomato and zucchini showed an undoubted growth improvement after legume; however, a certain specificity of Cylindrocarpon-like fungi and Phoma spp. to hairy vetch suggests that, when exploiting benefit of this cover crop for mitigating yield decline of vegetable crops, legume should alternate cereal and other botanically distant genera in rotation.

THE DEVELOPMENT OF BIOLOGICAL PRODUCT FOR PLANT GROWING ON THE BASIS OF STREPTOMYCES ALBUS

In this work the influence of experimental forms of biological product from Streptomyces albus UN44 on the growth processes of agricultural plants (wheat, peas, corn) was studied. The advantages of the preparation are demonstrated, which contains not only antibiotic and enzymatic complexes, synthesized by the producer, but also its biomass for the stimulation of seed germination processes, growth and development of the said plants seedlings. The proposed process description of biological product Streptofungin-Phyto production in two forms is the basis for engineering development and operating regulations. The preparation can be developed as a suspension with a cell titer of 109 CFU/cm3 in PET-containers (2 – 5 l) or as a dried mass in plastic bags (1 – 2 kg). The biological product can be recommended for use on the stage of pre-planting treatment of seeds by soaking, as well as deep root watering and irrigation. The remedy is safe for humans, animals and plants and can be used together with other microbial mass-based biofertilizers.

Sprouting, yield and economics of elephant foot yam (Amorphophallus paeoniifolius Dennst.) under the influence of different pre-planting treatments with organic and inorganic substances

The aim of this study was to evaluate the sprouting, yield and economics of elephant foot yam under the influence of different pre-planting treatments using organic and inorganic substances. The pre-planting treatment of minisetts with thiourea at 400 ppm resulted in maximum sprouting percentage (97.22%). This treatment also recorded highest corm yield (12.57 t ha -1 ) and showed maximum increase in corm yield (31.07%) over the control treatment. The economics over two years showed that among the different pre-planting treatments, the thiourea at 400 ppm stood as the best treatment which gave maximum net return of Rs. 91851 with a B: C ratio of 2.71 followed by thiourea at 300 ppm (net return Rs. 90651 and B: C ratio 2.69), thiourea at 200 ppm (net return Rs. 88951 and B: C ratio 2.66) and KNO 3 at 250 ppm (net return Rs. 88021 and B: C ratio 2.66).

Root growth potential, water relations and carbohydrate status of ash alternative species following pre-plant storage

The catastrophic loss of ash (Fraxinus spp.) trees in the midwestern United States due to emerald ash borer has emphasized the need for greater diversity in urban and community forests. However, the availability of some important Fraxinus alternative species may be limited due to difficulties in nursery production. We conducted two trials to examine growth and physiological responses of bare-root tree liners to pre-plant storage and handling. In both trials, bare-root liners were given one of four treatments for three weeks prior to planting: 1) control, 2) cold storage (4°C), 3) sweating (warm, moist storage), or 4) heeled-in (outdoor storage). Subjecting trees to a warm, moist environment before planting (sweating) increased shoot dieback of Celtic occidentalis trees. Root growth potential was very low for Quercus spp. trees and varied by treatment for Celtis occidentalis trees. Taxodium distichum trees had a relatively high root growth potential in all treatments. Stem water potential measured immediately before and after pre-plant treatments indicated that Quercus spp. trees and T. distichum trees were able to rehydrate during sweating while water stress in C. occidentalis trees remained high (stem water potential <−2.0MPa). The results suggest that poor transplanting success reported for Quercus spp. trees may be related to low root growth potential, whereas poor establishment of Celtis occidentalis trees is related to a combination of factors including desiccation, poor root regeneration and poor carbohydrate status. None of the pre-plant treatments reduced shoot dieback compared to control trees that were not stored prior to planting.

Effects of mulching on above and below ground pests and beneficials in a green onion agroecosystem

In 2013 and 2014, different mulching systems were investigated for their potential to suppress above and below ground pests, and enhance beneficial arthropods and soil health in green onion (Allium cepa) plantings. Three types of mulch systems (organic, living and solarization mulch) were evaluated and compared. Green onions were grown in four pre-plant treatments: (1) organic mulch generated by flail mowing a sunn hemp (Crotalaria juncea) cover crop (SH) followed by a no-till cropping system, (2) soil solarization (Sol), (3) sunn hemp-solarization mulch in which the sunn hemp was incorporated into the soil followed by soil solarization (SHSol), and (4) bare ground with insecticides (BG). Sol, SHSol and BG were practiced in conventional tilled system. SH (in 2013 and 2014) and SHSol (in 2014) treatments included strips of buckwheat and cowpea along the crop border to serve as living mulch or insectary plants. Green onion plants in SH had lower thrips and leaf miners damage than other treatments in both study years. When insectary borders were added to SHSol in 2014, thrips and leaf miners damages were also reduced in SHSol compared to Sol and BG. Incidence of purple blotch was reduced in SH and SHSol treatments in 2014. The SH treatment contained an increased abundance and richness of detritivores, predatory arthropods, parasitoids and beneficial free-living nematodes (particularly bacterivores and fungivores). Although weeds and initial populations of plant-parasitic nematodes were lower in solarization (Sol, SHSol) than other treatments, green onion yield was greatest in SH organic mulch systems in both study years. Overall, the integration of surface organic, living and solarization mulches into a green onion agroecosystem provided multiple ecosystem services including suppression of above and below ground pest organisms.

Integrated Management of Glyphosate-Resistant Giant Ragweed (Ambrosia trifida) with Tillage and Herbicides in Soybean

Giant ragweed is one of the most competitive annual broadleaf weeds in soybean production fields in the midwestern United States and eastern Canada because of its early emergence, rapid growth rate, high plasticity, and resistance to glyphosate and acetolactate synthase inhibitors. Therefore, early-season management of giant ragweed is critical to avoid yield loss. The objectives of this study were to evaluate control of glyphosate-resistant giant ragweed through the integration of preplant tillage or 2,4-D; PRE or early POST (EPOST) followed by (fb) late POST (LPOST) herbicide programs with or without preplant tillage or 2,4-D; and their effect on soybean injury and yield. A field study was conducted in 2013 and 2014 in David City, NE in a field infested with glyphosate-resistant giant ragweed. Preplant tillage or 2,4-D application provided &gt; 90% control of glyphosate-resistant giant ragweed 14 d after preplant treatment. Giant ragweed control and biomass reduction were consistently &gt; 90% with preplant tillage or 2,4-D fb sulfentrazone plus cloransulam PRE or glyphosate plus cloransulam EPOST fb glyphosate plus fomesafen or lactofen LPOST compared with ≤ 86% control with same treatments without preplant tillage or 2,4-D. PRE or EPOST fb LPOST herbicide programs preceded by preplant treatments resulted in giant ragweed density &lt; 2 plants m−2and soybean yield &gt; 2,400 kg ha−1compared with the density of ≥ 2 plants m−2and soybean yield &lt; 1,800 kg ha−1under PRE or EPOST fb LPOST herbicide programs. The contrast analysis also indicated that preplant tillage or 2,4-D fb a PRE or POST program was more effective for giant ragweed management compared with PRE fb POST herbicide programs. Integration of preplant tillage would provide an alternative method for early-season control of giant ragweed; however, a follow up application of herbicides is needed for season-long control in soybean.

Studies on the Effect of Pre-planting Treatments of Corms (Minisetts) with Different Organic and Inorganic Substances on Growth and Yield of Elephant Foot Yam under Agro-climatic Condition of Chhattisgarh Plains

In the present study, the maximum plant height at 120 days after planting was recorded under pre-planting soaking of minisetts in thiourea at 400 ppm (48.36 cm) followed by its lower concentration at 300 ppm (47.65 cm). The thiourea at 400 ppm recorded significantly maximum pseudo-stem girth (9.52 cm), number of pseudo-stems plant -1 (4.34) and average canopy spread (42.37 cm) among different pre-planting treatments. Thiourea at 400 ppm took significantly maximum number of days to first senescence, days to 50 per cent senescence and delayed maturity in elephant foot yam in comparison to rest of the treatments. Among different pre-planting treatments, the maximum diameter of corms and corm yield plant -1 were recorded under thiourea at 300 ppm (7.34 cm and 0.540 kg) followed by its higher i.e. 400 ppm (7.33 cm and 0.539 kg) and lower concentration i.e. 200 ppm (7.16 cm and 0.522 kg). The next best treatment in increasing corm yield plant-1 was found to be cow dung 50 % + cow urine 50 % (0.506 kg). The pre-planting treatment of minisetts with thiourea at 400 ppm resulted highest corm yield (12.57 t ha -1 ) and this treatment showed maximum increase in corm yield (31.07 per cent) over control treatment. The next best treatment in increasing corm yield was noted to be thiourea at 300 ppm (12.43 t ha -1 ), thiourea at 200 ppm (12.24 t ha -1 ) and KNO 3 at 250 ppm (12.11 t ha -1 ).

Influence of permafrost microorganisms on morphophysiological indicators of spring wheat

Biologically active compounds on the basis of highly efficient strains of bacteria of the genus Bacillus are currently being sought for to increase the yield of grain crops in the North. There is a number of biological products available, including those based on bacteria in the genus Bacillus (Phytosporin-M, Bactofit, Gamair, Integral, and other). However, the effectiveness of these drugs in the northern regions may be reduced, because the activity of introduced microorganisms depends on their adaptability in the rhizosphere and rhizoplane. This article describes the effect of bacteria of the genus Bacillus in permafrost on the morphological and physiological indicators of seedlings of soft spring wheat variety Irgina. These indicators are germination energy, laboratory seed germination, length and wet weight of roots and shoots of seedlings, as well as the length of coleoptile and number of chlorophylls a, b and carotenoid in the pigment extract from the plant material. It has been demonstrated that germination and morphometric parameters were significantly higher following exposure to Bacillus strains in permafrost than following treatment with the current strain of Phytosporin-M. It is likely that in the process of swelling of seeds (during their preplant treatment) Bacillus bacteria reach the caryopsis with water and begin to cleave spare nutrients actively, making them easier accessible for assimilation by seedlings. It is proposed that the increase in morphophysiological indicators of spring wheat variety Irgina is also a consequence of stimulation of the photosynthesis system and, consequently, an increased efficiency of absorption of light energy. Considering how differently different strains of bacteria isolated from permafrost influence the morphological and physiological and biochemical parameters of the plant, it appears that these strains or their combinations can be used for the development of biologics ensuring a comprehensive effect.

Organic Nitrogen in Soy Nutrition

The article aims at finding ways to control the symbiotic fixation and study methods for activating legumes-rhizobia symbiosis. The article provides the results of studies on the effect of bacterial fertilizers, micronutrients, growth regulators and planting date on the activity of the biological fixation of soybeans. The article shows the effect of pre-planting treatment and different planting dates for the duration of symbiosis, symbiotic organs sizes, and the amount of fixed air nitrogen. It is found that inoculation of soybean seeds with active rhizobia strains, especially together with micronutrients and growth regulators, significantly increases the proportion of fixed nitrogen in its total consumption to 40–49% for the UAI 6 variety and up to 34–38% for the Mageva variety. The obtained data give reason to believe that the use of active rhizobia strains, bacterial fertilizers, micronutrients and growth regulators in soybean cultivation can be an essential tool for agriculture biologization.

Impact of cover crop in pre-plant of apple orchards: relationship between crop health, root inhabiting fungi and rhizospheric bacteria

Manici, L. M., Kelderer, M., Caputo, F., Nicoletti, F., De Luca Picione, F. and Topp A. R. 2015. Impact of cover crop in pre-plant of apple orchards: relationship between crop health, root inhabiting fungi and rhizospheric bacteria. Can. J. Plant Sci. 95: 947–958. Replant disease of fruit tree orchards has a multifactorial etiology, mainly due to the decline in soil biodiversity along with an increase in root rot pathogens, which can be principally countered with appropriate cropping practices. Therefore, a study on the impact of cover crops on plant health of young fruit trees in long-term orchards was performed. Bioassays were performed over two consecutive growing cycles using soil from a multigeneration apple orchard affected by replant disease. First, a cycle was performed with three cover crops (alfalfa, barley, marigold) and apple rootstock plantlets; at the end, the above-ground part of the plant was removed and root residues left in the soil. In the second cycle, an apple orchard planting was simulated upon the first experimental design. Changes of diversity and composition of root inhabiting fungi and rhizospheric bacteria were evaluated as well as apple plant growth response to the pre-plant treatments. Results suggest that one cycle with alternate plants was sufficient to induce changes at the rhizosphere level, despite soil microbial resilience caused by the same long-term soil management. Rhizospheric bacteria were generally affected by plant genotype. Findings suggest that all three different cover crops can harbor almost all fungal species that colonize apple in replanted orchards (Fusarium spp., Pythum spp., binucleate Rhizoctonia sp., Cylindrocarpon-like-fungi and a several nonpathogenic saprophytic fungi named “other”), but their infection frequency varied according to the host plant. A single pre-plant break treatment did not overall differ significantly in plant growth of subsequent apple tree; however, break with marigold, which increased abundance of nonpathogenic root inhabiting fungi more than other cover crops, gave significantly higher plant growth than obtained after barley. This study provides evidence about cover-crop potential to increase soil diversity in long-term permanent cropping systems and to manipulate root colonizing fungi involved in crop health.

Vegetative propagation of African walnut (&lt;i&gt;Plukenetia conophora&lt;/i&gt;) using pre-treated stem cuttings of varied physiological ages

The effect of physiological age of stem cuttings and pre-planting treatment on adventitious root and shoot growth of stem cuttings of African walnut (Plukenetia conophora) were investigated at Nsukka, Nigeria in 2012. Nodal cuttings of semi-hardwood and softwood categories were dipped in water and coconut water for 30 minutes before planting. Cuttings used as control treatment were neither dipped in water nor coconut water. Factorial combinations of age of stem cutting and pre-planting treatment were arranged in completely randomized design (CRD) and replicated three times. Results of analysis of variance (ANOVA) indicated a non-significant main effect of age of stem cutting and pre-planting treatment on number of days to breaking of dormancy and shoot formation. Physiological age of cuttings significantly (p &lt; 0.05) influenced number of shoots formed, length of vine and number of leaves in favour of the semi-hardwood cuttings. Significant interaction between age of cuttings and pre-planting treatment was observed on percentage of cuttings with shoot and number of shoots per cutting. While semi-hardwood cuttings gave higher number of shoot when dipped in water, softwood cuttings (at 2- 4WAP) did better when dipped in coconut water. Available data suggest that softwood cuttings of this species are more amenable to clonal propagation. However, if semi-hardwood cuttings must be used, then dipping in water becomes a necessity. Evidences from this study affirm the practicability of clonal propagation of P. conophora via stem cuttings.Key words: African walnut, Pre-treatment, Vegetative propagation, Stem cuttings.