Effect of Biofumigation on Population Densities of Pratylenchus spp. and Verticillium spp. and Potato Yield in Eastern Canada.

Biofumigation has been proposed as an alternative to soil fumigation to manage soil-borne diseases including potato early dying disease complex (PED). This study examined the potential of using brown mustard (Mustard juncea) biofumigation to manage PED under rain-fed potato production in New Brunswick, Canada in two trials between 2017 and 2020 in comparison with chloropicrin fumigation and a conventional barley rotation. Biofumigation increased yield in one trial, but not in a second trial where the potato crop experienced severe drought, whereas chloropicrin fumigation increased yield in both trials. Biofumigation was effective in suppressing root-lesion nematode (RLN, Pratylenchus spp.) counts in both trials, but was ineffective in suppressing V. dahliae population density. Chloropicrin fumigation was effective in suppressing RLN counts and V. dahliae population density only in the hill where injected, but the effect was short-lived as the population density of V. dahliae in the hill increased to the level of the control in one potato growing season. Biofumigation may be an alternative to chloropicrin fumigation in managing PED, particularly in fields with high RLN population but relatively low Verticillium population density. However, neither biofumigation nor fumigation used alone may be sustainable in the short-term potato rotations commonly used in New Brunswick, and additional beneficial practices are required to sustain productivity in the long-term.

La biofumigación se ha propuesto como una alternativa a la fumigación del suelo para manejar las enfermedades transmitidas por el suelo, incluido el complejo de enfermedades de muerte prematura de la papa (PED). Este estudio examinó el potencial del uso de la biofumigación de mostaza marrón (Mustard juncea) para manejar la PED bajo la producción de papa de secano en New Brunswick, Canadá, en dos ensayos entre 2017 y 2020 en comparación con la fumigación con cloropicrina y una rotación de cebada convencional. La biofumigación aumentó el rendimiento en un ensayo, pero no en un segundo ensayo en el que el cultivo de papa experimentó una sequía severa, mientras que la fumigación con cloropicrina aumentó el rendimiento en ambos ensayos. La biofumigación fue efectiva para suprimir los conteos del nematodo lesionador de la raíz (RLN, Pratylenchus spp.) en ambos ensayos, pero fue ineficaz para suprimir la densidad de población de V. dahliae. La fumigación con cloropicrina fue efectiva para suprimir los conteos de RLN y la densidad de población de V. dahliae solo en el lomo del surco donde se inyectó, pero el efecto fue de corta duración ya que la densidad de población de V. dahliae en el surco aumentó al nivel del testigo en un ciclo de cultivo de papa. La biofumigación puede ser una alternativa a la fumigación con cloropicrina en el manejo de la PED, particularmente en campos con alta población de RLN pero densidad de población de Verticillium relativamente baja. Sin embargo, ni la biofumigación ni la fumigación utilizadas por sí solas pueden ser sustentables en las rotaciones de papa a corto plazo comúnmente utilizadas en New Brunswick, y se requieren prácticas benéficas adicionales para mantener la productividad a largo plazo.

Drainage increases CO2 and N2 O emissions from tropical peat soils.

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO2 respiration rates, CH4 and N2 O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO2  ha-1  year-1 ) than in natural forest (median = 35.9 Mg CO2  ha-1  year-1 ). Groundwater level had a stronger effect on soil CO2 emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO2  ha-1  year-1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N2 O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha-1  year-1 ). Deeper groundwater levels induced high N2 O emissions, which constitute about 15% of total GHG emissions. CH4 emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO2 emissions. Surprisingly, the CO2 emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively.

Dataset on soil carbon dioxide fluxes from an incubation with tropical peat from three different land-uses in Jambi Sumatra Indonesia.

Conversion of tropical peat swamp forests to increase and agricultural production has generated substantial peat carbon loss in the Asia-Pacific region. Different land-uses and management practices oxidize the tropical peat at diverse rates due mainly to different water table levels. In recent years, several studies have measured soil carbon dioxide emissions in-situ; however, only few studies have evaluated the effect of moisture on carbon dioxide fluxes in incubation experiments. Here, we present the dataset of an incubation performed with 360 intact peat cores from three different land-uses (i.e. 120 from intact peat swamp forest; 120 from drained logged peat forest; and 120 from oil palm plantation) collected on the peat dome of Jambi Sumatra Indonesia. Different moisture levels in the intact cores were set by either drying the intact peat cores for short period of time or by adding extra water before the incubation. Dynamic dark aerobic incubation in airtight containers coupled with carbon dioxide measurement with an infrared gas analyser and the gas fluxes was used to measure to gas fluxes. The average carbon dioxide fluxes were 5.38 ± 0.91, 4.15 ± 0.35 and 1.55 ± 0.13 µg CO2-C g-1 h-1 for the intact peat swamp forest, drained logged peat forest and oil palm plantation, respectively.

Improving Soil Quality and Potato Productivity with Manure and High-Residue Cover Crops in Eastern Canada.

Under intensive low residue agricultural systems, such as those involving potato (Solanum tuberosum L.)-based systems, stagnant crop yields and declining soil health and environmental quality are common issues. This study evaluated the effects of pen-pack cow (Bos Taurus) manure application (20 Mg·ha-1) and cover crops on nitrate dynamics and soil N supply capacity, subsequent potato yield, selected soil properties, and soil-borne disease. Eight cover crops were tested and included grasses, legumes, or a mixture of legumes and grasses, with red clover (Trifolium pratense L.) used as a control. Forage pearl millet (Pennisetum glaucum L.) was associated with highest dry matter. On average, red clover had 88% higher total N accumulation than the treatments mixing grasses and legumes, and the former was associated with higher soil nitrate in fall before residue incorporation and overwinter, but this was not translated into increased potato yields. Pearl millet and sorghum sudangrass (Sorghum bicolor × sorghum bicolor var. Sudanese) were associated with lower soil nitrate in comparison to red clover while being associated with higher total potato yield and lower numerical value of root-lesion nematodes (Pratylenchus penetrans), although this was not statistically significant at 5% probability level. Manure incorporation increased total and marketable yield by 28% and 26%, respectively, and increased soil N supply capacity by an average of 44%. Carbon dioxide released after a short incubation as a proxy of soil microbial respiration increased by an average of 27% with manure application. Our study quantified the positive effect of manure application and high-residue cover crops on soil quality and potato yield for the province of Prince Edward Island.

Soil heterotrophic respiration assessment using minimally disturbed soil microcosm cores.

Ex-situ measurement of soil respiration is usually done with highly disturbed samples that may confound the interpretation and extrapolation of results. We have developed a lab respiration assessment method that better simulates field conditions and allows efflux estimations based on soil surface area. First, intact soil cores are extracted in the field and transferred to the lab. Next, soil moisture content and bulk density are assessed in each soil core. Immediately following this the soil cores are gently broken, pooled per treatment (or plot) and the root systems removed. Subsequently the field moist, non-sieved soils are repacked into microcosm cores at their respective bulk densities. Moisture content in the microcosms is adjusted to desired levels by adding drops of deionized water or by air drying for several hours. After moisture adjustment, the cores are pre-incubated at 25 °C for two weeks. Afterwards, the microcosms are further incubated in the dark at the desired temperatures in airtight containers. At incubation times of 0, 48 and 96 h, 20 ml of gas sample is collected from each container via the septum, and then injected into pre-evacuated exetainers for CO2 determination using a gas chromatograph or an infrared gas analyzer. Finally, soil efflux is estimated based on the rate of linear CO2 increase in the container headspace. One of the advantages of this method is that results can be presented per unit of mass (e.g. mg CO2-C g soil-1 day-1) or area (e.g. g CO2-C m2 day-1). These soil microcosms can also be used to simultaneously assess emissions of CH4 and N2O during incubations. This new method uses: •Small intact soil cores collected in the field.•Soil microcosms.•Efflux calculated per unit of area.