La gestion des biosolides de papetières au Québec : quelle serait la meilleure option pour réduire les émissions de gaz à effet de serre? (Pulp and paper mill sludge management in Quebec: what should be the best option to reduce greenhouse gas emissions?)

Les biosolides de papetières (BP) sont des matières organiques résiduelles provenant du processus d’épuration des effluents de l’industrie des pâtes et papiers. Le gouvernement québécois vise à réduire de 20 % les émissions de gaz à effet de serre (GES) par rapport au niveau de 1990 et à bannir la matière organique des lieux d’élimination d’ici 2020, ce qui affectera probablement la gestion des BP. Cette étude vise à quantifier les émissions de GES provenant des trois principales filières de gestion des BP : l’enfouissement, l’épandage sur sol agricole et la combustion avec récupération de chaleur. Les émissions de GES de l’enfouissement ont été mesurées à l’échelle pilote et celles de l’épandage, l’ont été pour des doses respectant les recommandations agronomiques. Les émissions de la combustion ont été mesurées à la cheminée de chaudières à biomasse utilisant entre 10 et 40 % de BP mélangés aux combustibles. L’enfouissement était la filière la plus émettrice de GES (0,90 t éq. CO2 t-1 BP secs), alors que les émissions étaient inférieures pour l’épandage (0,12 t éq. CO2 t-1 BP secs) et la combustion (0,00057-0,13 t éq. CO2 t-1 BP secs). L’épandage agricole et la combustion seraient de bonnes alternatives à l’enfouissement pour atténuer les émissions de GES. Toutefois, il serait nécessaire de multiplier les mesures d’émissions pour en augmenter la précision et assurer des scénarios robustes si l’on vise à initier l’élaboration d’un nouveau protocole d’obtention de crédits compensatoires pour le système de plafonnement et d’échange de droits d’émission de GES au Québec. Pulp and paper mill sludge (PPMS) is an organic residual generated from the paper mill wastewater treatments. The Quebec’s government policies aim to reduce the greenhouse gas emissions (GHG) by 20% below the level of 1990 and to ban disposal (landfilling and incineration without energy recovery) of organic material by 2020, which will likely affect PPMS management. This study aims at quantifying GHG emissions from the three main practices currently used to manage PPMS: landfilling, land application in agriculture and combustion for energy recovery. GHG emissions from landfilling were measured at the pilot-scale and those from land were measured following PPMS application at rates based on local agronomic recommendations. GHG emissions from combustion were measured at the chimney of biomass boilers using 10 to 40% PPMS in the fuel. Landfilling had the highest GHG emissions (0.90 t CO2e t-1 dry PPMS) whereas those from land application (0.12 t CO2e t-1 dry PPMS) and combustion (0.00057-0.13 t CO2e t-1 dry PPMS) were lower. Application of PPMS to agricultural land and combustion would therefore be good alternatives to landfilling to abate GHG emissions. However, more measurements would be required to increase the accuracy on the emission quantifications and start building a new offset credit protocol to be used in the Quebec cap-and-trade system for GHG emission allowances applied bylaw

Conditioning machine learning models to adjust lowbush blueberry crop management to the local agroecosystem

Agroecosystem conditions limit the productivity of lowbush blueberry. Our objectives were to investigate the effects on berry yield of agroecosystem and crop management variables, then to develop a recommendation system to adjust nutrient and soil management of lowbush blueberry to given local meteorological conditions. We collected 1504 observations from N-P-K fertilizer trials conducted in Quebec, Canada. The data set, that comprised soil, tissue, and meteorological data, was processed by Bayesian mixed models, machine learning, compositional data analysis, and Markov chains. Our investigative statistical models showed that meteorological indices had the greatest impact on yield. High mean temperature at flower bud opening and after fruit maturation, and total precipitation at flowering stage showed positive effects. Low mean temperature and low total precipitation before bud opening, at flowering, and by fruit maturity, as well as number of freezing days (<−5 °C) before flower bud opening, showed negative effects. Soil and tissue tests, and N-P-K fertilization showed smaller effects. Gaussian processes predicted yields from historical weather data, soil test, fertilizer dosage, and tissue test with a root-mean-square-error of 1447 kg ha−1. An in-house Markov chain algorithm optimized yields modelled by Gaussian processes from tissue test, soil test, and fertilizer dosage as conditioned to specified historical meteorological features, potentially increasing yield by a median factor of 1.5. Machine learning, compositional data analysis, and Markov chains allowed customizing nutrient management of lowbush blueberry at local scale

Phosphorus mobility in acidic wild blueberry soils in Québec, Canada

In the province of Québec, about 35,000 ha of land are devoted to growing wild lowbush blueberry (Vaccinium angustifolium Ait.). Blueberry fields are located on acidic, well-drained soils with low nutrient levels. To ensure high crop productivity, fertilizers are applied in the spring of the sprout year. The objective of this study was to determine the effect of phosphorus (P) fertilizer applications on soil P mobility under field conditions. Experiments were conducted in commercial stands of wild blueberries between 2004 and 2008 in the Lake St. Jean area, Québec, Canada. Four P rates (0 to 90 kg P2O5 ha-1) were applied in May of the sprout year. Soil P was determined in the 0–5, 5–15 and 15–30 cm soil layers after Mehlich 3 (PM3) extraction. Following P application, soil PM3 increased significantly in the surface soil layer and in the 5–15 cm soil layer in both the sprout and production years. Phosphorus addition had no significant effect on the 15–30 cm soil layer. The P/(Al+Fe)M3 molar ratio reached 10.7% in the soil surface with the highest P application rate. In the other soil layers, the molar ratio was below 3.10%. Under field conditions, P leaching was limited to the 5–15 cm soil layer but a P build-up occurred in the soil surface. Furthermore, the P/(Al+Fe)M3 molar ratio that was measured in the surface soil layer was very close to the critical value (11.3%) beyond which there is a risk of surface water contamination

Paper Mill Biosolids and Forest-Derived Liming Materials Applied on Cropland: Residual Effects on Soil Properties and Metal Availability

Combined paper mill biosolids (PB) and forest-derived liming by-products improve soil properties, but their residual effects following several years of application have hardly been investigated. A 13-year (2009–2021) field study was initiated at Yamachiche, QC, Canada, to assess the residual effects of PB and liming materials on the properties of a loamy soil. The PB was applied during nine consecutive years (2000–2008) at 0, 30, 60, and 90 Mg wet·ha−1, whereas the 30 Mg PB·ha−1 rate also received one of three liming materials (calcitic lime, lime mud, wood ash) at 3 Mg wet·ha−1. No amendment was applied during residual years. Past liming materials continued to increase soil pH but their effect decreased over time; meanwhile, past PB applications caused a low increase in residual soil NO3-N. Soil total C, which represented 40% of added organic C when PB applications ceased, stabilized to 15% after six years. Soil Mehlich-3-extractable contents declined over the thirteen residual years to be not significant for P, K, and Cu, while they reached half the values of the application years for Zn and Cd. Conversely, Mehlich-3 Ca was little affected by time. Therefore, land PB and liming material applications benefited soil properties several years after their cessation

Refine phosphorus stratification caused by long-term tillage and P fertilisation in maize -soybean rotation in eastern Canada

International audienc

Tillage practice and phosphorus fertilization effects on the distribution and morphology of corn roots

International audienceNo-tillage (NT) is agricultural practice recommended in context of conservation agriculture. Consequently, the NT management systems often cause the stratification of phosphorus (P) with depth with high concentrations of P at the upper soil profile depending on the rate of P fertilization, as well as the alteration of soil properties. As a result, corn roots distribution and morphology could be modified. However, little is known about how the root system in soil profile responds to different combinations of tillage and P supply. A study was conducted at L’Acadie (Québec, Canada), on a clay loam soil in 2014 to quantify the effects of different tillages and P fertilization rates on corn (Zea mays, L.) root distribution and morphology. This long term field experiment, initiated in 1992, is a split-plot device with principal factor of tillage (mouldboard plow (CT) and no-till (NT)) and sub-plot factor of P fertilization (0, 17.5 and 35 kg P ha-1 biennially applied) under a corn-soybean rotation (Ziadi et al. 2014). Root samples were collected at R1 (silking) stage by 8 cm diameter soil cores. Cores were taken up to a depth of 40 cm at 5 cm, 15 cm and 25 cm perpendicularly to the corn row and were cut out at 5 depths: 0-5cm, 5-10 cm, 10-20 cm, 20-30 cm and 30-40 cm. After washing and sieving, root length and surface area of 1st order (diameter >0.08 cm), 2nd order (diameter range from 0.02 to 0.08 cm) and 3rd order (diameter < 0.02 cm) roots were measured on scanned image with the software WinRHIZO (Regent Instruments Inc., Quebec, Canada). The root distribution and morphology pattern in the soil profile showed no significant differences between NT and CT. The 35 kg P ha-1, biennially applied, tends to increase RLD by 27% and 43% to the fertilization of 0 and 17.5 kg P ha-1 as well as the root surface area (27% and 49%, respectively)

Soil tillage and P fertilization efects on root distribution and morphology of corn (Zea mays, L.) and soybean (Glycin max, L.)

In context of conservation agriculture, various soil properties modifications including phosphorus (P) stratification along soil profile induced by no-till practice (NT) might affect crop root development. This study aimed to investigate tillage and P fertilization effects on root distribution and morphology of corn and soybean. A field corn-soybean rotation experiment established in 1992 at l’Acadie is a split-plot design (4 replicates) with tillage (moldboard plough (MP) and NT) and P fertilization (0 (0P), 17.5 (0.5P) and 35 (1P) kg P·ha-1 every two years) as main and sub-plot factors. Soils and corn roots were sampled in 2014 at silking stage by collecting soil cores to 60-cm depth (0-5, 5-10, and every 10 cm) at 5, 15 and 25 cm perpendicularly to the row. Soybean roots were sampled in 2015 at flowering stage. Root length (RL) was determined with WinRHIZO. Corn root length density (RLD) was higher in MP (1.48 cm·cm-3) than in NT (1.28 cm·cm-3). 0P and 0.5P treatments (1.29 and 1.23 cm·cm-3, respectively) significantly reduced RLD compared to 1P (1.62 cm·cm-3). Corn roots mostly accumulated at 0-5 and 5-10 cm. Tillage and P fertilization had no effect on corn root vertical distribution. However, tillage had significant effects on soybean root vertical partition. Soybean in NT had a RLD of 1.95 cm·cm-3 on average; and roots mostly accumulated at 0-10 cm with 44% of total RL. MP had lower RLD (1.55 cm·cm-3), with the highest RL proportion (36%) at 10-20 cm. Additionally, soybean had relatively higher RLDs in 0P and 0.5P than 1P.Compared to corn, the higher proportion of soybean roots in top layers in NT might indicate a higher sensibility of soybean roots to the soil P stratification. While the reduction of corn roots in NT could be more related to a higher weed competition

Simplified measurment based simplified model of soil-plant phosphorus cycles in log-term agrosystems

International audienc

Simplified measurment based simplified model of soil-plant phosphorus cycles in log-term agrosystems

International audienc

Simplified measurement-based simulation model of soil-plant phosphorus cycles in long-term agro-systems

Actual phosphorus models are created in conventional tillage system. In addition, most simulation models are process-based, which need mathematical descriptions of fundamental physio-chemical mechanisms. The small time-step e.g. daily might not fit long-term simulation. In this study, a P model based on measured data was created to simulate the evolution of soil P status along soil profile in long-term. In P model, a soil zone was divided into 30 grids according to vertical (0-5, 5-10, 10-20, 20-30 and 30-40 cm) and lateral (0-10, 10-20 and 20-30 cm for two sides into inter-row) coordinates. For each grid, P stock was defined as total amount of phosphate ions in solid and liquid phases. The P inputs and P outputs of each grid such as fertilizer, uptake, runoff and leaching were estimated with measured data in every time-step (yearly). The P status (phosphate ion concentration in soil solution) was calculated from P stock and P budget in each time step. The simulation was conducted with two tillage systems [moldboard plough (MP) and no-till (NT)].The P model managed to simulate the evolution of P status along soil profile in MP and NT during 25 years; while it was a homogenous distribution of soil P within 0-20 cm in MP. The simulated results indicated that higher accumulation of soil P in upper layers might lead to a lower use of soil P stocked in sub-soil by crop uptake. However, the model still needs validation and adjustment of parameters to form more accurate results