Oilseed rape (OSR, Brassica napus L.) is an important feedstock for biodiesel; hence, carbon dioxide (CO2), methane (CH4) and particularly fertilizer‐derived nitrous oxide (N2O) emissions during cultivation must be quantified to assess putative greenhouse gas (GHG) savings, thus creating an urgent and increasing need for such data. Substrates of nitrification [ammonium (NH4)] and denitrification [nitrate (NO3)], the predominant N2O production pathways, were supplied separately and in combination to OSR in a UK field trial aiming to: (i) produce an accurate GHG budget of fertilizer application; (ii) characterize short‐ to medium‐term variation in GHG fluxes; (iii) establish the processes driving N2O emission. Three treatments were applied twice, 1 week apart: ammonium nitrate fertilizer (NH4NO3, 69 kg‐N ha−1) mimicking the farm management, ammonium chloride (NH4Cl, 34.4 kg‐N ha−1) and sodium nitrate (NaNO3, 34.6 kg‐N ha−1). We deployed SkyLine2D for the very first time, a novel automated chamber system to measure CO2, CH4 and N2O fluxes at unprecedented high temporal and spatial resolution from OSR. During 3 weeks following the fertilizer application, CH4 fluxes were negligible, but all treatments were a net sink for CO2 (ca. 100 g CO2 m−2). Cumulative N2O emissions (ca. 120 g CO2‐eq m−2) from NH4NO3 were significantly greater (P < 0.04) than from NaNO3 (ca. 80 g CO2‐eq m−2), but did not differ from NH4Cl (ca. 100 g CO2‐eq m−2) and reduced the carbon sink of photosynthesis so that OSR was a net GHG source in the fertilizer treatment. Diurnal variation in N2O emissions, peaking in the afternoon, was more strongly associated with photosynthetically active radiation (PAR) than temperature. This suggests that the supply of carbon (C) from photosynthate may have been the key driver of the observed diurnal pattern in N2O emission and thus should be considered in future process‐based models of GHG emissions.

Decision Support Tools (DSTs) and models are becoming increasingly important to make informed decisions. The aim of this review was to understand how the scientific assumptions behind related pasture-based DSTs used in New Zealand interrelate. Using modelled feed intake of grazing sheep as a case study, we reviewed the metabolisable energy (ME) assumptions of relevant New Zealand models. Although the DSTs were largely dependent on a common model, there were some discrepancies between them. We raise two concerns: 1. In New Zealand, pasture-based livestock models to predict ME intake are highly dependent on equations developed in Australia, not validated in New Zealand. 2. The minor discrepancies between models make collaboration difficult - this is particularly pertinent to farmer-targeted DSTs. Closer collaboration between DST companies and research institutions is required to agree on consistent, robust equations aligned with the latest scientific knowledge.

&lt;p&gt;Nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O) is a potent greenhouse gas (GHG) with a global warming potential 265 times that of carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) over 100 years. Contributing approximately 70% of global anthropogenic N&lt;sub&gt;2&lt;/sub&gt;O emissions, agriculture represents the largest area of uncertainty for GHG reporting and the most challenging sector for emissions reduction: global N&lt;sub&gt;2&lt;/sub&gt;O emissions are increasing at double the rate estimated by the Intergovernmental Panel on Climate Change (IPCC). The largest source of agricultural N&lt;sub&gt;2&lt;/sub&gt;O emissions is from application of inorganic-N fertilisers, the manufacture of which produces more than 1% of global CO&lt;sub&gt;2&lt;/sub&gt; emissions and consumes 1% of global energy output.&lt;/p&gt; &lt;p&gt;However, typical crop N uptake efficiency (NupE) means approximately half the fertiliser doesn&amp;#8217;t reach the target plant, causing further ecological problems, such as biodiversity loss from eutrophication and atmospheric deposition. The extent to which microbial immobilisation of fertiliser N contributes to the NupE value of ca. 60% is currently unknown.&lt;strong&gt; &lt;/strong&gt;If N immobilisation is found to be a large contributor to reducing N available to crops, this offers new opportunities to better manage fertiliser N inputs. Critically, with a growing global population, it is vital that we can increase food crop yields, and more efficient use of water and nutrients could help close the 70% &amp;#8216;yield gap&amp;#8217; between potential and actual crop yields. Finally, inorganic N is the largest single cost in gross margins for wheat production and prices are rising. Increased NupE therefore represents a key opportunity for farmers to increase their financial sustainability.&amp;#160;&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt; &lt;p&gt;We hypothesised that under the conventional management of three applications of inorganic N in the spring, crops do not have the ability to outcompete the fast-growing soil microbial community for N, and that by supplying N to the crop in a &amp;#8216;little and often&amp;#8217; approach, we could increase NupE by reducing immobilisation, and consequentially reduce N&lt;sub&gt;2&lt;/sub&gt;O emissions. We conducted a field study of a winter wheat crop on a northern UK farm to investigate this, which compared conventional N fertiliser management (220 kg N ha&lt;sup&gt;-1&lt;/sup&gt; over three applications) of ammonium nitrate, to a little and often approach (220 kg N ha&lt;sup&gt;-1&lt;/sup&gt; over six applications) and an untreated (0 kg N ha&lt;sup&gt;-1&lt;/sup&gt;) control. We followed the crop until harvest, and continuously measured N&lt;sub&gt;2&lt;/sub&gt;O emissions and net ecosystem exchange of CO&lt;sub&gt;2&lt;/sub&gt; using a skyline2D automated flux system and also measured C and N pools in soil, plants and microbial biomass to assess changes in N uptake and allocation.&lt;/p&gt; &lt;p&gt;We will present data which shows the outcome of plant-microbe competition for N in our agricultural system, and discuss the implications of different N fertiliser management for yield, profitability and GHG mitigation.&lt;/p&gt;

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Deferred grazing is a common management practice in which pastures are rested from grazing between mid-spring and the end of summer/early autumn. It has been used to rejuvenate pastures and better manage the spring pasture surplus although its impact on farm profitability is unknown. FARMAX was used to explore the impact of deferred grazing on profitability on a north-western Waikato beef and sheep hill country farm based on experimental data and likely management responses. The Base Scenario modelled farm profitability assuming spring surplus in a typical year. When 15% of the farm was deferred and it was assumed that the increased grazing pressure on the rest of the farm led to greater control of the spring feed surplus and improved pasture quality, there was an increase in ewe performance and the number lambs sold at target weight. Per head and total farm gross margins increased by 8%. Results demonstrate how the use of deferred grazing as a pasture management tool to increase resilience can also enhance livestock performance and profitability at the whole-farm level.