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Nitrogen management is central to the economic and environmental dimensions of agricultural sustainability. Yield response to nitrogen fertilisation results from multiple interacting factors. Theoretical frameworks are lagging for the interaction between nitrogen and air temperature, the focus of this study. We analyse the relation between yield response to nitrogen fertiliser and air temperature in the critical period of yield formation for spring wheat in Australia, winter wheat in the US, and maize in both the US and Argentina. Our framework assumes (i) yield response to nitrogen fertiliser is primarily related to grain number per m2, (ii) grain number is a function of three traits: the duration of the critical period, growth rate during the critical period, and reproductive allocation, and (iii) all three traits vary non-linearly with temperature. We show that “high” nitrogen supply may be positive, neutral, or negative for yield under “high” temperature, depending on the part of the response curve captured experimentally. The relationship between yield response to nitrogen and mean temperature in the critical period was strong in wheat and weak in maize. Negative associations for both spring wheat in Australia and winter wheat with low initial soil nitrogen (< 20 kg N ha-1) in the US highlight the dominant influence of a shorter critical period with higher temperature; with high initial soil nitrogen (> 120 kg N ha-1) that favoured grain number and compromised grain fill, the relation between yield response to nitrogen and temperature was positive for winter wheat. The framework is particularly insightful where data did not match predictions; a non-linear function integrating development, carbon assimilation and reproductive partitioning bounded the pooled data for maize in the US and Argentina, where water regime, previous crop, and soil nitrogen overrode the effect of temperature on yield response to nitrogen fertilisation.

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This study aims to experimentally evaluate the influence of the combination of a supply only ventilation, called here positive input ventilation, and innovative active air vents on the Indoor Air Quality of a house. The positive input ventilation draws fresh air from the outside, filters and pre-heats it before supplying it to living areas. Active air vents are small motorised dampers set up in the upper part of windows able to move according to local pollutants measurements or to the measurements of other active air vents in the house. This combination is expected to improve the Indoor Air Quality by increasing efficiently the air change rate of a room when it is too polluted. The goal of the tests presented in this paper is to evaluate quantitatively the air change rate in a real size environment. To do so, a positive input ventilation and active air vents are set up in an experimental house. The tests were carried out in 3 different rooms. For each room, the air change rate is evaluated for different configurations of the combination. CO2 is used as a trace gas to evaluate the air change rate. Results are promising and show that the studied combination allows a significant of the air change rate of each room. An appropriate Demand Control Ventilation strategy based on the sensors of each active air vents and the communication between all the devices would thus lead to an efficient while simple improvement in the use of a positive input ventilation system.