Preplant Soil Research Articles

Ecotoxicity of 1,3-dichloropropene, metam sodium, and dazomet on the earthworm Eisenia fetida with modified artificial soil test and natural soil test

1,3-Dichloropropene (1,3-D), metam sodium (MS), and dazomet (DZ) are widely used as preplant soil fumigants to solve soilborne problems. To provide a more scientific and accurate evaluation of 1,3-D, MS, and DZ toxicity to the earthworm Eisenia fetida, modified artificial soil test and natural soil test were studied. The suitable soil moisture to maintain over 90% survival of the earthworms after 4weeks of treatment in an enclosed system for modified artificial soil test and natural soil test were 26.9 to 86.4% of water-holding capacity (WHC) and 66.2 to 84.3% of WHC, respectively. The optimal soil moisture levels for modified artificial soil test and natural soil test (75 and 55% of WHC, respectively) were finally used to evaluate the toxicity of 1,3-D, MS, and DZ on earthworms. Each desiccator with 10 earthworms and natural or artificial soil was stored at 20±1°C under constant light of 400 to 800lx for 2weeks. The modified artificial soil test showed LC50 values for 1,3-D, MS, and DZ of 3.60, 1.69, and 5.41mg a.i. kg-1 soil, respectively. The modified natural soil test of the fumigants showed similar LC50 values of 2.77 and 0.65mg a.i. kg-1 soil, except for DZ at 0.98mg a.i. kg-1 soil. The present study confirms that both modified artificial soil test and modified natural soil test offer standard methods for acute toxicity test of 1,3-D, MS, and DZ on the earthworms and scientific evidences for assessing the effects of soil fumigants on non-target organisms in the soils. Graphical Abstract Two novel acute toxicity test methods for soil fumigants on the earthworm Eisenia fetida.

Soil persistence of dimethyl disulfide combined with chloropicrin after repeated applications

Applying pre-plant soil fumigation is a commonly used practice in plasticulture production systems to control some weed species, bacteria, and pathogenic fungi that can cause damage to high value crops such as cut flowers and vegetables. Since the phasing out of methyl bromide, growers have been seeking an alternative that has similar broad spectrum efficacy. Dimethyl disulfide (DMDS) alone or combined with chloropicrin (Pic) has proven to be effective against pathogens and has the potential to become a widely used pre-plant soil fumigant. The results show that the addition of Pic significantly increases the soil persistence of DMDS when compared to pure DMDS under totally impermeable film (TIF). Dissipation of pure DMDS during the fall application was quicker during the spring application. The dissipation curve exhibited by DMDS:Pic in the fall was not typical of this mixture. It is unclear if this trend is a result of the sequential applications.

Economic Viability of Steam as an Alternative to Preplant Soil Fumigation in California Strawberry Production

One challenge of conducting research regarding agricultural production systems is that field trials are time consuming and expensive, limiting their scale and scope. Thus, policymakers and producers benefit from researchers extracting as much information as possible from each trial. We used the Monte Carlo techniques and the sensitivity analyses to enhance our analysis of the competitiveness of steam as an alternative to fumigation for preplant soil disinfestation in California strawberry production. Chloropicrin + 1,3-dichloropropene 59.6:39 (CP + 1,3-D) resulted in higher mean net returns than did steam. However, the Monte Carlo analysis showed that in one field trial there was a high probability that steam would be more profitable, whereas in the other it was quite unlikely. We also assessed the change in economic performance of steam when it was applied combined with soil amendments of mustard seed meal (MSM). Switching from steam to steam + MSM would have reduced mean net returns. The Monte Carlo results showed that steam + MSM performed at least as well as steam alone around half the time. We evaluated factors that were likely to affect the net returns, defined as total returns minus treatment, weeding, and harvest labor costs, of using steam in the near future. Reductions in application time increased net returns. A decrease in the price of propane increased net returns.

Optimizing anaerobic soil disinfestation for fresh market tomato production: Nematode and weed control, yield, and fruit quality

Anaerobic soil disinfestation (ASD) has potential as an alternative to chemical-fumigation for controlling soilborne pathogens and pests. Previously, control of nutsedge was sub-optimal and the quantity of inputs for commercial production was an impediment to adoption. Field studies were conducted in Citra and Immokalee, Florida to assess the effects of ASD with reduced amendments and inclusion of a pre-emergent herbicide on weed and nematode populations, tomato yield, and fruit quality. Pre-plant soil treatments included ASD with 6.9m3ha−1 of molasses and 11Mgha−1 of composted poultry litter (CPL) (ASD0.5), ASD with 13.9m3ha−1 of molasses and 22Mgha−1 of CPL (ASD1.0), and chemical soil fumigation using Pic-Clor 60 (CSF). Subplot treatments were halosulfuron-methyl (Sandea®) herbicide and no herbicide application. ASD0.5 reached high and equivalent accumulation of anaerobic conditions as ASD1.0 during the three-week soil treatment in both locations. Root galling and plant-parasitic nematode population at harvest in ASD treatments were similar in nematode suppression to CSF in both locations, while ASD1.0 resulted in higher non-parasitic nematode populations in soil compared to CSF in Citra. In Citra, ASD treatments did not differ from CSF in total marketable fruit yield; however, ASD0.5 resulted in higher total yield of extra-large fruit than CSF and ASD1.0. In Immokalee, no difference was observed in total marketable yield between ASD0.5 and CSF, whereas ASD1.0 produced 26.3% and 20.4% higher total marketable yield than that of CSF and ASD0.5, respectively. ASD treatments had no impact on fruit quality attributes including color, firmness, pH, total soluble solids, and dry matter content. Herbicide application improved nutsedge control and had no negative impact on the development of anaerobicity in ASD-treated plots, while total marketable yield and fruit quality were not impacted by herbicide treatment in either location. Despite some variations between the two locations, reduced application rates of CPL and molasses produced results similar to the full rates of amendment as well as the fumigation treatment. Overall, combining ASD with an herbicide had no negative impacts on crop production and resulted in improved weed control.

Effects of Two Types of Fertilizer and <i>Arbuscular Mycorrhiza</i> on Damping off Disease (<i>Macrophomina phaseolina</i>) of Cowpea (<i>Vigna uniguiculata</i> L. Walp)

A screen house experiment was carried out to determine the effect of organic fertilizer, compost, inorganic fertilizer, and single super phosphate and <i>Arbuscular mycorrhiza</i> on damping-off disease of cowpea. The experimental design used was completely randomized design (CRD). There were fifteen treatments which were replicated three times. 2g of <i>Macrophomina phaseolina</i> (damping off disease) was infested on 10kg of soil sample in each pot with (30 by 75) cm spacing. <i>Arbuscular mycorrhiza</i>, compost (poultry based) and single super phosphate (SSP) were applied at the rate of 2250kg/ha, 1670kg/ha and 676kg/ha respectively. Three seeds of cowpea were sown into each pot, but later thinned into two plants per pot. Data on germination percentage at 7, 14, 21 and 28 days, number of leaves of cowpea at 2, 4, 6 and 8 weeks after planting, weight of pods per plant, incidence and severity at which pathogens affected the cowpea plant per treatment and growth yield of each treatment were collected and analyzed using analysis of variance (ANOVA) and means separated using the Duncan multiple range test. The plants that were treated with 676kg/ha single super phosphate produced higher cumulative weight of harvested fruits per plant followed by <i>Arbuscular mycorrhiza</i>, which did not have any negative effect on environment. The values of phosphorus in the post harvest soil analysis revealed that lower values of phosphorus were recorded in Single Super Phosphate treated pots, while plants treated with <i>Arbuscular mycorrhiza</i> at 500kgha^-1 produced higher P value than the pre-planting soil analysis indicating the absorption of large amount of the elements. It was therefore recommended that <i>Arbuscular mycorrhiza</i> could be used to optimize seed yield in cowpea.

NEW RESOURCE-SAVING TECHNOLOGY OF POTATO CULTIVATION ON SLOPE LANDS OF MOUNTAIN PROVINCE IN DAGESTAN

The potato is grown in all natural environment and climatic zones, along from high-mountain slope lands, situated up to 2500 meters above sea level to Pricaspian plains, situated under sea level. The total area of planted potato in the Republic is 22 thousand hectares, where potato producing takes more than half of mountain region. The mountain area occupies 2.04 million hectares, which is 38.3% of total area of Dagestan with highest peaks over 1000 meters above the sea. There are some methods of potato growing that are nearly effective in all climatic conditions, and improve yield and tuber quality. The proposed resource-saving technology enables to reduce expenses by 50 % for ploughing, soil preparation after ploughing, pre-planting soil preparation, preserving soil fertility and decreasing erosion processes. The results based on experimental data presented were to show the influence of resource-saving technology on growth, development and yield augmentation when growing on slope lands of mountain province of Dagestan. Advantages of this resource-saving technology and its economic efficiency were shown as well.

Alternatives to Current Fumigation Practices in Western States Raspberry

Red raspberry production in the western United States is heavily reliant on preplant soil fumigation to ensure the successful establishment and productivity of a planting. However, due to issues related to the regulation, availability, and economics of soil fumigation, alternatives are needed for current fumigation practices. Trials were conducted in commercial raspberry fields in California and Washington to evaluate alternatives to current fumigation practices in each region. In Washington, tarped bed fumigation with 1,3-dichlorpropene (1,3-D):chloropicrin (Telone C-35) performed as well as, and sometimes better than, the industry standard nontarped broadcast fumigation with Telone C-35 for the control of the soilborne pathogen Phytophthora rubi and the plant-parasitic nematode Pratylenchus penetrans. In one of the Washington trials, yield of raspberry grown in tarped bed-fumigated areas was 47% greater than the yield of plants grown in nontarped broadcast-fumigated areas. In California, a combination of chloropicrin:1,3-D (Pic-Clor 60) performed as well as the industry standard of methyl bromide:chloropicrin. Raspberry plants grown in soil fumigated with either of these fumigants were approximately 26% taller than plants grown in nonfumigated soil. Our results indicate that there are viable fumigation alternatives to the current fumigation systems used in Washington and California raspberry production systems.

English

Leguminous crops play an important role in developing sustainable and low input crop production system and have shown good potential for inclusion in alley cropping systems. Hence, a study was carried out at the Teaching and Research Farm of the Faculty of Agriculture, Chukwuemeka Odumegwu Ojukwu University to evaluate the productivity of an impaired ultisol under cassava/maize for over six years planted with different legumes. The experiment was laid out in a randomized complete block design. The treatments studied were, cowpea, groundnut, bambara groundnut, pigeon pea and control which is maize. Data collected was subjected to an analysis of variance test based on randomized complete block design (RCBD) and treatment means were separated using least significant difference (LSD&lt;0.05). The findings from the study showed that there were significant (P&lt;0.05) differences among the treatments in growth, yield and soil chemical parameters assessed as well as the texture of the studied soil. The legume crops planted on the impaired soil had good nodulation which helped to replenish soil nutrient lost and good yield of pigeon pea (0.34 tha-1), Bambara groundnut (0.17 tha-1) cowpea (0.12 tha-1), Groundnut (0.10 tha-1), respectively. The result of the soil chemical parameters assessed from post harvest soil analysis indicated that the nutrient content of the studied soil increased except for exchangeable acidity (EA), K and effective cation exchange capacity which generally reduced in all the plots planted with leguminous crop. The plots planted with Bambara groundnut and groundnut showed a slight reduction in exchangeable Mg2+ relative to pre planting soil analysis which was 50% reduction relative to the control, while exchangeable Na+ content reduced in plots planted with Bambara groundnut. Evidence from this study, then showed that leguminous crop can be used to reclaim an impaired soil and improve the fertility status of the soil. Key words: Chemical properties, growth, legume crops, ultisol, yield.

Anaerobic soil disinfestation reduces survival and infectivity of Phytophthora nicotianae chlamydospores in pepper

Phytophthora nicotianae is the principal causal agent of root and crown rot disease of pepper plants in Extremadura (western Spain), a spring-summer crop in this region. Preplant soil treatment by anaerobic soil disinfestation (ASD) may effectively control plant pathogens in many crop production systems, but field conditions and availability of C sources can limit its practical application. A laboratory experiment was conducted to study P. nicotianae control by ASD with low temperatures and several carbon (C) sources: rice bran, rapeseed cake, grape pomace and brewer’s spent grain. Survival and infectivity of pepper by P. nicotianae chlamydospores were reduced with all C sources assayed and redox potential in all ASD treatments indicated that reductive soil conditions were achieved. Rice bran (20tonsha−1); rapeseed cake (20tonsha−1), and grape pomace (40tonsha−1) were also assayed in a field experiment in early spring. Survival and infectivity of P. nicotianae were also reduced with all C sources. An increase of dehydrogenase and urease activities and a strong pH decline were observed with rice bran and rapeseed cake, probably related to an increase of anaerobic bacterial populations in soil. Application of ASD with high C source rates may be effective in control of P. nicotianae under low temperature conditions.

Засоренность озимой тритикале в зависимости от агротехнических приемов возделывания

The investigations were carried out in 2014-2015, on a light gray forest heavy loamy soil. The humus content in the arable layer was 5.9%. The mobile phosphorus was 162 and exchangeable potassium was 172 mg per kilogram, respectively, pH of salt extract was 5.6. The total area of the plot was 200 m2, the discount area - 150 m2. Replication - fourfold, placing of plots was successive. Experience scheme: Factor A - preplant soil tillage: 1. Cultivation - 10-12 cm. 2. Milling – 10-12 cm. Factor B – fertilizers: 1. Without fertilizers (control). 2. Fertilizers, aimed to 4.0 tons per hectare (N120P75K90). The following varieties were used as the object of the study: Kornet, Kristal and Nemchinovskaya 56. The norms of fertilizers is calculated by the balance method, based on their removal from the crop and in the soil. The options, treated with a cultivator, were the most clogged. There are no significant difference among tested varieties of Kornet, Nemchinovskaya 56 and Kristal, but Nemchinovskaya 56 was the most clogged - 36 units per square meter, and less weedy was Cornet. When milling , the most clogged was Nemchinovskaya 56 variety - 30 units per square meter. In the way of without fertilization (control), Kristal variety was the most clogged - 21 units per square meter. The weed infestation of winter triticale at the beginning of growing season of Kristal variety was more to 21.3%, Nemchinovskaya 56 variety to 17% and Kristal to 21.6% more, than in milling. At the end of the growing season of winter triticale during cultivation the weeds increased by 71% and 74%. The same pattern was preserved debris perennial weeds early in the growing season 2.4-4.2 units per square meter, at the end of the growing season 4.6-4.7 units per square meter. The most clogged varieties were Nemchinovskaya 56 – 2.8-4.6 units per square meter and Kristal 2.7-4.7 units per square meter.&#x0D;

Do a native and two exotic grasses respond differently in soils conditioned by native vegetation versus an exotic grass?

Invasion by the exotic annual grass Bromus tectorum often increases soil nutrient availability. It is unclear, however, if other grasses benefit from this higher nutrient status. Soil from three sites in the northern Great Basin U.S.A. conditioned by B. tectorum invasion (BTCS=B. tectorum conditioned soil), paired with adjacent areas conditioned by native vegetation (NCS=native conditioned soil), were freshly-collected. Replicates were sown to B. tectorum, Elymus wawawaiensis (native perennial grass), and Agropyron cristatum (exotic perennial grass) and grown for 70 days. Above-ground biomass of the exotics B. tectorum and A. cristatum averaged over 2 times greater in BTCS relative to their growth in NCS. Above-ground biomass of the native E. wawawaiensis was statistically similar whether grown in BTCS or NCS. Overall, plants grown in BTCS had statistically similar tissue N and significantly greater tissue P concentrations compared to plants grown in NCS. The native perennial grass had significantly more negative ∂15N values when grown in BTCS relative to NCS suggesting it is accessing isotopically different N sources between the two substrates that B. tectorum or A. cristatum do not sense. Post-harvest soil mineral N was significantly greater for BTCS compared with NCS. Grown in BTCS, both exotic grasses significantly reduced soil mineral N relative to unplanted controls, but the native grass did not. The variable with the strongest explanatory power for above-ground plant mass was % utilization of the pre-plant soil pool of bicarbonate-extractable P. For the two exotics tested, BTCS is a superior growth medium than NCS. The native E. wawawaiensis may not benefit from growth in BTCS because it has slower nutrient uptake kinetics and growth to efficiently utilize greater N and P availability.

Revised chloropicrin use requirements impact strawberry growers unequally

Buffer zone requirements are by nature spatial and their effects are site-specific, with some fields — because of their location — more impacted than others. Using a set of strawberry fields in Ventura County that were preplant soil fumigated in 2013 as a baseline, we examined how much acreage eligible for chloropicrin fumigation would have been lost if either of two buffer zone distance regulations had been in effect: any one of the four sets of alternative distances proposed in May 2013 by the California Department of Pesticide Regulation (DPR) or the buffer zone distances DPR released in January 2015. Buffer zone distances are based on several factors including the anticipated protection of human health, referred to as the percentile of protection. We find that the effects are highly dependent on the percentile of protection. From 4% to 29% of the fumigated blocks analyzed would have had an increase in buffer zone acreage depending on the percentile of protection. In those blocks, the share of total acreage that would no longer have been eligible for fumigation with chloropicrin varied from 3% to 45%. We also identify strategies that growers employed to reduce required buffer zone distances under use requirements in effect in 2013. The most frequently used strategies were using a tarp type with the lowest buffer zone requirements (“60% tarp”), extending a buffer onto a neighboring property, road and/or farm path, and reducing application rates. The results have an important policy implication: spatially defined use regulations have very different effects for different fields; aggregated industry-level analyses will miss the range of impacts on growers.

Growing for the future: Collective action, land stewardship and soilborne pathogens in California strawberry production

Outlook Growing for the future: Collective action, land stewardship and soilborne pathogens in California strawberry production Margaret Lloyd, UC Cooperative Extension Farm Advisor, Yolo, Solano and Sacramento counties Tom Gordon, Professor, Department of Plant Pathology, UC Davis Sustaining high strawberry yields will require an integrated approach that includes collaborative management of fields to limit the spread of soilborne pathogens. required, one that integrates advances in disease resistance through breeding with closer attention to the factors that influence the survival, activity and spread of pathogen populations in soil. Many of the latter, such as rotating crops and cleaning equipment, frequently involve multiple operators. As a result, there is a need to recognize that patho- gen-free soil is effectively a common-pool resource and that protecting it will require collective action. The end of methyl bromide Since the early 1950s, diseases caused by soilborne pathogens have been managed primarily through the use of preplant soil fumigation. Before that time, Verticillium wilt, caused by Verticillium dahliae, imposed a major limitation on strawberry production. Recognition of the fungicidal prop- erties of chloropicrin and the enhanced efficacy achieved by addition of methyl bromide lifted this http://calag.ucanr.edu • JULY–SEPTEMBER 2016 101 Jack Kelly Clark C alifornia accounts for more than 80% of U.S. strawberry production, a harvest worth $2.5 billion in 2014. Fertile soils and the prevail- ing climate on the Central Coast support per acre yields twice that of Florida, the second largest pro- ducer, and 10 times more than most other states. Yet California strawberry growers face sig- nificant challenges. Among the most important is the declining availability of suitable land. The potential for a given field to produce an acceptable yield depends not only on physical and chemical characteristics of the soil but also, critically, on the presence or absence of soil dwelling pathogens that can infect strawberry roots and cause diseases that limit fruit production. As described below, effec- tive control of soilborne pathogens of strawberries was once readily achieved by means that are no longer available to strawberry growers. It now seems likely that no single measure will suffice to meet the challenge of soilborne patho- gens. Rather, a multi-faceted approach will be

Production and Nitrogen Use Efficiency of Oat Forages Receiving Slurry or Urea

Although fall‐grown oat (Avena sativa L.) has potential for use as supplementary fall forage throughout the north‐central United States, one additional benefit is the option for summer manure distribution that is not possible within a conventional corn (Zea mays L.) cropping program. ‘ForagePlus’ oat was seeded into replicated plots fertilized with urea at rates of 0, 20, 40, 60, or 100 kg N ha−1 or with dairy slurry applied at approximately 42,300 and 84,600 L ha−1 (105 and 209 kg N ha−1, respectively). Apparent N recovery from fall‐grown oat plots fertilized with urea ranged from 65.8 to 89.8%. This suggested aggressive scavenging of N, but calculation of these high apparent N recovery rates was dependent on relatively low preplanting soil NO3–N concentrations, as well as a good dry matter (DM) yield response to N fertilization (y = −0.114x2 + 29.9x + 2130; R2 = 0.982). For this study, applications of high and low rates of dairy slurry yielded respective N fertilizer equivalencies of 38 and 45 kg N ha−1 for fall‐grown oat, which are roughly equivalent to Wisconsin recommendations for cereal grains (45 kg N ha−1). Apparent N recovery following application of the high and low rates of dairy slurry was 18.1 and 25.5%, respectively; however, when expressed on the basis of NH4–N applied, apparent N recovery for fall‐grown oat averaged 53.5% and did not differ among slurry application rate treatments. Fall‐grown oat appears to be an effective scavenger of N applied as NH4–N from dairy slurry.Core Ideas Fall‐grown oat possesses unique forage quality characteristics. Fall‐grown oat can serve as attractive emergency fall forage. Use of fall‐grown oat allows for summer manure application that is decoupled from corn production. Fall‐grown oat is an effective scavenger of NH4–N applied from dairy slurry. Fall‐grown oat may be a useful tool in managing N from dairy manures.

Management of ACCase-Inhibiting Herbicide-Resistant Smooth Barley (Hordeum glaucum) in Field Pea with Alternative Herbicides

Smooth barley is an annual weed species that is infesting crops and pastures in South Australia. Complicating control options is the presence of herbicide-resistant biotypes. A field trial was conducted to identify alternative herbicides for the management of acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide-resistant smooth barley in field pea. Preplant (PP) soil applications of pyroxasulfone; prosulfocarb plus S-metolachlor; dimethenamid-P; propyzamide; trifluralin alone or with triallate or with diuron; or imazamox applied POST were evaluated for their effectiveness and crop safety. Propyzamide, pyroxasulfone, or imazamox applied POST provided a high level of smooth barley control, did not cause any crop injury, and increased field pea grain or forage yield compared with the nontreated. Furthermore, propyzamide or pyroxasulfone reduced panicle density and seed production in smooth barley, whereas the effectiveness of POST imazamox varied over the two seasons. Dimethenamid-P reduced the impact of smooth barley on field pea yield, but cause stunting, and was less effective than propyzamide, pyroxasulfone, and imazamox in reducing smooth barley seed production. Negative relationship between field pea yield and smooth barley panicle density indicated that smooth barley is highly competitive in field pea crops and can cause large yield losses. The results of this investigation suggest that propyzamide or pyroxasulfone applied PP and imazamox applied POST could be used effectively in the field for the management of ACCase-inhibiting herbicide-resistant smooth barley in South Australia.

Influence of brassicaceous soil amendments on potentially beneficial and pathogenic soil microorganisms and seedling growth in Douglas-fir nurseries

Fusarium, Cylindrocarpon and Pythium spp. are the major soil-borne pathogens of conifer seedlings. Soil fumigation with methyl bromide and chloropicrin has been the most effective method for reducing the population density and disease pressure of these organisms. Due to safety and environmental concerns, use of methyl bromide as a pre-plant soil fumigant has been abolished in the majority of cropping systems. However, the conifer seedling industry continues to use methyl bromide under a quarantine pre-shipment exemption due to a lack of effective alternatives. Toward identifying alternatives to methyl bromide for management of soil microbial populations, a three-year field study was conducted in northwest USA. The objective of this study was to examine the effects of brassica seed meals and green manures on potentially pathogenic and beneficial microorganisms, soil health, and seedling growth in conifer nursery fields. The study treatments were Brassica juncea seed meal, B. carinata seed meal, Sinapis alba seed meal, B. juncea green manure, methyl bromide/chloropicrin fumigation, and a non-treated control, with four replications in a randomized complete block design. The treatments were incorporated into soil in autumn or early spring, and Douglas-fir (Pseudotsuga menziesii) seedlings were transplanted into plots in late spring. Population densities of Fusarium, Cylindrocarpon, Pythium, actinomycetes, and Trichoderma; mineralizable nitrogen; and dehydrogenase enzyme activity in soil were assessed at pre-transplant, post-transplant, and seedling harvest. The pre-treatment soil pathogen count was similar among study plots. At transplant time, Fusarium spp. densities in soil were generally similar among most brassica treatments but fumigated plots generally had less Fusarium. Treatment with S. alba, however, increased soil densities of Fusarium spp. In 2012, Fusarium spp. density was significantly lower after B. juncea green manure incorporation [1.8 log CFU (colony forming units)] than after chemical fumigation (2.4 log CFU) or in the untreated control (2.6 log CFU); whereas the soil density of potentially antagonist Trichoderma spp. was significantly greater in fumigated plots (3.7 log CFU) followed by B. juncea green manure (3.4 log CFU) and lowest in control (3.2 log CFU). Fumigation produced the largest seedlings but B. juncea green manure also produced significantly larger seedlings than control. Dehydrogenase activity, an indicator of soil microbial activity, was greatest with B. juncea green manure and lowest in fumigated soil. Mineralizable nitrogen in soil followed the same trend. These results suggest that B. juncea green manure may have a suppressive effect on soil-borne pathogens, and maintain or improve soil and seedling health.

Efficacy of reduced rate fumigant alternatives and methyl bromide against soilborne pathogens and weeds in western forest nurseries

Preplant soil fumigation is commonly used to control soilborne pathogens and weeds in forest seedling nurseries of Oregon and Washington. However, lower chemical inputs are desired to meet state and federal application regulations, to minimize buffer zone size requirements, and to help protect the environment. Therefore, the objectives of this research were to evaluate the efficacy of three reduced rate soil fumigants under totally impermeable film (TIF) in managing soilborne diseases and weeds, and to determine if combined applications of up to four biocontrol agents improved soilborne disease control. Reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene, all applied in combination with chloropicrin, were effective in decreasing soil populations of Pythium and Fusarium as well as the presence of Pythium in root debris from the previous crop. The roots of Douglas-fir (Pseudotsuga menziesii) seedlings transplanted into each fumigant treatment were also colonized less by Pythium and Fusarium than those transplanted into nonfumigated control plots. However, biocontrol treatments were not effective against either pathogen. Weed biomass and weeding times were also significantly reduced by fumigation. Application costs were similar for all three fumigant treatments, but seedling size was largest from the methyl bromide and metam sodium treatments followed by the 1,3-dichloropropene treatment. Based on the results of this study, reduced rates of methyl bromide, metam sodium, and 1,3-dichloropropene show promise in managing soilborne diseases and weeds in forest nurseries.

Compost and poultry manure as preplant soil amendments for red raspberry: Comparative effects on root lesion nematodes, soil quality and risk of nitrate leaching

Raspberry fields in the Pacific Northwest, USA and British Columbia, Canada are often prepared for replanting by fumigating with broad-spectrum biocides to control root-lesion nematodes, Pratylenchus penetrans. Nematode-suppressive organic amendments have been advocated as reduced risk alternatives to fumigation but may pose other risks to the environment. This study compared alternative pre-plant soil management practices with respect to their effects on plant-parasitic nematode populations, soil quality parameters and risk of nitrate leaching. In fall of 2009 and 2010, a mature raspberry field was mowed down and plowed, and replicate plots were randomly allocated to each of six treatments: (1) a non-amended control, (2) fumigation with Basamid®, (3) fall seeded barley cover crop, (4) recommended rate (20m3ha−1) and (5) historical “biofumigant” high rate (250m3ha−1) of spring incorporated poultry manure, and (6) spring incorporated compost (250m3ha−1). Raspberry cv Saanich was planted approximately one month after incorporation of amendments. Composite soil samples were taken from each plot at multiple times during two subsequent growing seasons and analyzed for nematode populations and soil chemical and physical properties. Primocane biomass was assessed at the end of each of the first two growing seasons as an index of crop vigor. The high poultry manure and compost treatments suppressed root-lesion nematode populations nearly as well as fumigation over two growing seasons. These treatments also improved soil bulk densities and aggregation relative to control, cover crop and fumigation treatments, while compost addition beneficially increased soil pH, CEC and Ca concentrations more than manure. Primocane production in the manure and compost treatments was greater than in the control and cover crop treatments, but less than in the fumigated treatment. Substantial nitrate accumulation in soil amended with the high rate of manure indicated that application of sufficient manure to suppress parasitic nematodes would pose a significant risk of nitrate leaching. In contrast, soil nitrate accumulation was not significantly increased in the compost amended plots. Overall, compost application reduced nematode populations, improved crop growth and did not increase the risk of nitrate leaching in the short term and may be a viable alternative to fumigation.

Organically acceptable practices to improve replant success of temperate tree-fruit crops

For most temperate perennial fruit crops, replanting into soil that was used previously to grow the same or a related crop species usually results in poor early growth, preventing new plantings from reaching potential levels of productivity and economic returns to growers. Increases in population densities of root pathogens along with deleterious changes in soil quality under the preceding crops are largely responsible for these replant disease complexes. Driven by the rise in organic fruit production and new restrictions on fumigants and fumigation practices in the conventional sector, considerable research has been aimed, over the past two decades, to the development of non-chemical and organically-acceptable means of managing replant disease complexes. As apple is the most widely grown temperate perennial fruit crop, the majority of this research has been directed at the apple replant disease complex. This review summarizes knowledge of the causes of replant disease complexes of temperate orchard crops, and recent applied research on organically-acceptable practices to reduce the impacts of these disease complexes. Brassica seed meal amendments and composts show considerable promise as pre-plant soil amendments to improve replanted tree establishment. Composts have the added benefit of contributing to improvements in overall soil health that may enhance productivity in the long-term. Additional research to understand better the mechanisms by which compost amendments enhance replanted tree establishment would lead to improvements in the effectiveness and reliability of their utilization to alleviate replant disease.

The effect of green manure and organic amendments on potato yield, nitrogen uptake and soil mineral nitrogen

Fertility management is challenging for organic crops with intensive nutrient demands such as potatoes (Solanum tuberosum L.). Four crop sequences varying in pre-potato green manures as main plots and four fertility treatments applied in the potato phase only [control, inorganic fertilizer (FERT), municipal solid food waste compost (MSW) and paper mill biosolid compost (PMB)] as subplots were compared in five-year organic potato rotations in Eastern Canada. Potato yields did not differ significantly between crop rotations; however, soil amendments had significant impacts on potato yields. Averaged across years, total tuber yields were in the order; FERT (34.2 Mg ha−1) > MSW (29.6 Mg ha−1) > control (26.5 Mg ha−1). Total potato N uptake (TNU) levels were 89, 115, 107 and 147 kg N ha−1, respectively, for control, MSW, PMB and FERT, and were greater when potato followed red clover (119–124 kg N ha−1) compared with oat/pea/vetch mixture (107–108 kg N ha−1). Plant N use efficiency (NUE) was 299, 263, 263 and 235, respectively, for control, MSW, PMB and FERT. Pre-plant soil mineral N (SMN) ranged between 39 and 112 kg N ha−1 among different crop rotations. During the tuber initiation stage, SMN ranged between 40 and 66 kg N ha−1 while during tuber bulking it ranged between 10 and 14 kg N ha−1 among different crop rotations and soil amendments. Post-harvest SMN ranged between 8 and 30 kg N ha−1 for all rotations and amendment treatments.