Ongoing research on organic growing media for greenhouse tomato production is driven by the constant changes in the quality, stability, and form of the organic byproducts used in the manufacturing of these media. This study was undertaken to determine appropriate irrigation set points for a sawdust–peat mix (SP) under development given that the performance of this substrate appeared to be strongly dependent on appropriate irrigation management. A greenhouse tomato experiment was conducted to compare different irrigation management approaches for a SP substrate in the spring and summer. Using preliminary measurements from an initial experiment (Expt. 1), different irrigation strategies for the SP substrate were compared in a second experiment (Expt. 2): 1) a variable irrigation regime using a timer control (with frequency adjusted as a function of irradiance); 2) tensiometer control at –1.5 kPa; and 3) two constant substrate water potential devices: –1.1 kPa and –0.9 kPa. An irrigation timer/controller using solar radiation input was used with a rockwool control (RC) substrate. Measurements of plant activity [photosynthesis rate and stomatal conductance ( g _S )], substrate physical and chemical properties, biomass, and yield were obtained. For all irrigation strategies, results indicated that 10% to 20% higher photosynthesis rates and g _S values were obtained with the SP substrate compared with RC. Data indicated that moderate drying conditions (matric potential ranging from –2.2 kPa to –1.5 kPa in Expt. 1 and Expt. 2, respectively) relative to container capacity (–0.6 kPa) were beneficial for improving plant photosynthetic activity and allowed the highest yields for the SP substrate. Variable irrigation management showed higher levels of plant activity than constant watering and increased the oxygen concentration in the substrate by ≈2% in absolute value relative to the constant water potential device. Lower CO ₂ and N ₂ O levels were also observed with the variable irrigation strategy. On the other hand, maximum nutrient solution savings were achieved with the constant matric potential devices (8% to 31% relative to the RC). This study showed high productivity potential for the SP substrate with suitable irrigation management. Replacing conventional growing media with organic waste-based products using an appropriate irrigation strategy may help to increase the sustainability of the greenhouse industry.

Water table control has been successfully tested to improve the sustainability of water management in cranberry production. In the province of Québec (Canada), three sites were investigated to determine the optimum water table depth below soil surface (WTD) using three criteria: (1) increasing yield without decreasing fruit quality; (2) minimizing the amount of water needed by the sprinkler system; and (3) avoiding hypoxic stresses in the rhizosphere. Our results show that the final yield, the berry sugar content, the total number of berries, the number of berries per upright, and the fruit set were maximized when the WTD was 60 cm. Sprinkler water savings of 77% were obtained where the WTD was shallower than 66 cm. In order to avoid hypoxic conditions due to poor drainage, the water level in the canals surrounding the beds should be lowered to 80 cm when a rainfall or a frost protection irrigation is anticipated. All sides of a block of beds must be surrounded by canals to ensure a uniform WTD and to avoid lateral hydraulic gradients that could cause peripheral seepage losses.

Subsidence, erosion, and degradation in agricultural peatlands are leading to the disappearance of highly fertile farmland. This study investigated two strategies aimed at extending the lifespan of cultivated peat soils: the application of straw and wood chips to compensate for soil losses and the application of copper (Cu) to slow peat decomposition, based on previous recommendations. Peat soil samples (270 g) were amended with 11 t ha ^–1 of biomass materials (14.8 g kg ^–1 ) and 235.6 mg Cu kg ^–1 and incubated in glass jars at constant temperature and water content. Thirty chemical parameters were then monitored over a 56‐d period through repeated soil sampling. Discriminant analysis showed that the addition of biomass had the greatest affect on nitrogen (N) availability, immobilizing 7.8 to 12.1 kg of inorganic N per metric ton of incorporated biomass. Considering that peat soils may require from 4 to 40 t biomass ha ^–1 yr ^–1 to reach carbon equilibrium, the tested biomass materials could immobilize from 34 to 500 kg ha ^–1 of N if confirmed at the field scale. This may help capture excess N but may also limit crop growth. Alternatively, slowing decomposition could reduce both biomass requirements and N immobilization. However, the results show that Cu had little effect on parameters linked to organic matter decomposition. Indeed, dissolved organic carbon was decreased by 11% in Cu‐treated soils. A longer‐term study should be conducted to confirm these observations at the field scale, thus helping to develop conservation strategies suitable for agricultural production.

Improvements in water productivity are of primary importance for maintaining agricultural productivity and sustainability. Water potential-based irrigation management has proven effective for this purpose with many different crops, including strawberries. However, problems related to spatial variability of soil properties and irrigation efficiency were reported when applying this management method to strawberries in soils with rock fragments. In this study, a field-scale experiment was performed to evaluate the impacts of three irrigation management scales and a pulsed water application method on strawberry yield and water productivity. An analytical solution to Richards’ equation was also used to establish critical soil water potentials for this crop and evaluate the effects of the variability in the soil properties. Results showed that spatial variability of soil properties at the experimental site was important but not enough to influence crop response to irrigation practices. The studied properties did not present any spatial structure that could allow establishing specific management zones. A four-fold reduction in the size of the irrigation management zones had no effect on yield and increased the water applications. Pulsed application led to significant yield (22%) and water productivity (36%) increases compared with the standard water application method used by the producer at the experimental site.