Soils under irrigated agriculture are a significant source of nitrous oxide (N2O) owing to high inputs of nitrogen (N) fertiliser and water. This study investigated the potential for N2O mitigation by manipulating the soil moisture deficit through irrigation scheduling in combination with, and in comparison to, using the nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP). Lysimeter cores planted with wheat were fitted with automated chambers for continuous measurements of N2O fluxes. Treatments included conventional irrigation (CONV), reduced deficit irrigation (RED), CONV-DMPP and RED-DMPP. The total seasonal volume of irrigation water applied was constant for all treatments but the timing and quantity in individual irrigation applications varied among treatments. 15N-labelled urea was used to track the source of N2O emissions and plant N uptake. The majority of N2O emissions occurred immediately after irrigations began on 1 September 2014. Applying RED and DMPP individually slightly decreased N2O emissions but when applied in combination (RED-DMPP) the greatest reductions in N2O emissions were observed. There was no effect of treatments on plant N uptake, 15N recovery or yield possibly because the system was not N limited. Half of the plant N and 53% to 87% of N2O was derived from non-fertiliser sources in soil, highlighting the opportunity to further exploit this valuable N pool.

Fertilization is an effective agronomic management technique for increasing crop production. However, the overuse of chemical fertilizer stimulates energy consumption and greenhouse gas (GHG) emissions, which are antagonistic to sustainable wheat production. In this study, we estimated the energy and GHG performances of different fertilization regimes based on a 32−year fertilization experiment. In this long−term experiment, there are five treatments: CK (no fertilizer with wheat residue removal), NPK (chemical fertilizer with wheat residue removal), NPKPM (chemical fertilizer and pig manure with wheat residue removal), NPKCM (chemical fertilizer and cattle manure with wheat residue removal), and NPKWS (chemical fertilizer with wheat residue retention). The results indicated that NPKCM and NPKPM consumed higher total energy than NPK and NPKWS, which was attributed to the extra energy usage of farmyard manure. Although NPKCM and NPKPM increased energy output by 4.7 and 2.8%, NPKWS stood out by delivering the highest energy use efficiency (EUE) of 6.66, energy productivity of 0.26 kg MJ⁻¹, energy profitability of 5.66, net return of 1799.82 US$ ha⁻¹ and lower specific energy of 3.84 MJ kg⁻¹. Moreover, the yield scale carbon footprint of NPKWS decreased by 66.7 and 52.3% compared with NPKCM and NPKPM, respectively. This study shows that the application of chemical fertilizer in combination with wheat residue retention is a good strategy to increase EUE and economic benefits while decreasing the carbon footprint of wheat production.

Soil compaction commonly impacts productivity in Australian cotton production systems. A field experiment conducted during the 2019–2020 season showed that compaction decreased lint yield by 27%. The objective of this study is to evaluate the legacy effect of soil compaction on subsequent crop yields (wheat [ Triticum aestivum L.] in 2020 and 2022 and cotton [ Gossypium hirsutum L.] in 2021–2022). Wheat and cotton yields, cotton biomass, Verticillium wilt incidence in cotton, soil water, and soil strength were assessed. There was no legacy effect of soil compaction on the wheat grain yields in the 2020 and 2022 seasons. The lack of difference in wheat yields is the result of sufficient rainfall recharging the soil profile during the growing season to overcome compaction limitations of deeper soil water extraction. Similarly, there was no legacy effect of soil compaction on cotton lint yield or fiber quality in the 2021–2022 crop. We found no difference in soil strength (penetrometer resistance) or soil water use by cotton during the 2021–2022 season. These results suggest, indirectly, that cotton root systems were not constrained from extracting water from lower depths of the soil. Verticillium wilt was absent in the compacted plots, and its incidence reached 15.3% in the uncompacted plots during the 2021–2022 season. The legacy effect of soil compaction may not impact subsequent crop yields under the right climatic conditions. However, a study conducted during dry years could offer further insights into its long‐term impact. Future research should be expanded to explore the relationship between disease incidence and soil compaction.

The average lint yield of irrigated cotton in Australia ranges from 2270 to 3700 kg/ha, but yields vary substantially between farms and also between fields on the same farm. Differences in soil properties may cause these yield variations. Identifying which factors are causal and what management can be implemented to mitigate the impacts should help optimize inputs and improve profits. During the 2018–2019 summer cotton‐growing season, a paired‐field comparison approach was used to investigate and improve the understanding of soil property‐induced irrigated cotton yield differences within five farms across three regions of NSW, Australia. The paired fields at each farm recorded an average lint yield difference of >284 kg/ha (measured in 2018–2019 or 5‐year average lint yield). Several soil properties differed between the paired fields at each farm comparison. The soil organic carbon stocks were higher in the higher‐yielding fields at all the farm comparisons and the normalized lint yield percentage was positively correlated with soil organic carbon stocks. Soil sodicity was higher in the lower‐yielding fields at 3 of the 5 comparisons. Results for most soil nutrient tests were above the recommended critical concentrations for Australian cotton production. A stepwise linear regression excluding soil nutrients that were above soil test critical values for crop response and below crop toxicity levels indicated the lint yield was positively correlated with SOC stocks and negatively correlated with sodicity and bulk density. No earthworms were detected during visual soil assessment or soil sampling across all the sites. Visual soil assessment was not a sensitive predictor of cotton crop performance. Comparing soil properties using a paired field approach may assist cotton growers in understanding the factors behind yield differences. A similar strip comparison approach could be adopted for within‐field variability by dividing the fields into discrete performance zones and assessing the soil properties of each zone separately.