Variability in Harvest Index of Grain Crops and Potential Significance for Carbon Accounting

Unkovich, M.; Baldock, J. A.; Forbes, Matthew

doi:10.1016/s0065-2113(10)05005-4

Cited by 176 publications

(114 citation statements)

References 126 publications

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“…Furthermore, the simulated HI in the distant future under RCP8.5 was the lowest, this being the scenario in which higher temperatures are projected. High temperatures put stress on seed filling during the reproductive stage of many crops and thus usually reduce the HI (Porter and Semenov, 2005;Unkovich et al, 2010). A growth chamber experiment for canola indicates that high temperature during the reproductive phase significantly reduces the HI (Angadi et al, 2000), and that is consistent with a field experiment that showed that HI decreased with high temperature during the seed filling of canola (Faraji et al, 2009).…”

Section: Discussion Heat Stress and Changes In Crop Harvest Index Wasupporting

confidence: 67%

Simulated Canola Yield Responses to Climate Change and Adaptation in Canada

et al. 2018

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A projected future warmer climate implies signifi cant impacts on canola (Brassica napus L.) production in Canada. We aimed to use a modeling approach to simulate climate change impacts on canola yield in Canada and to evaluate potential adaptation measures. Th e CSM-CROPGRO-Canola model was used to simulate the responses of canola to the projected climate change at Brandon on the Prairies, and West Nipissing and Normandin in eastern Canada. Future climate scenarios for the near (2041-2070) and distant (2071-2100) future under two representative concentration pathways (RCP4.5 and RCP8.5) were developed based on climate change simulations by a regional climate model CanRCM4. Seeding dates were estimated from air temperature, precipitation, and soil moisture to account for the potential of earlier seeding as an adaptation measure. Compared to the baseline climate, simulated seed yield reduction was 42, 21, and 24% in the near future and of 37, 27, and 23% in the distant future, under RCP4.5, respectively for Brandon, West Nipissing, and Normandin. A larger reduction was simulated under RCP8.5, especially in the distant future at Brandon and West Nipissing. Th e simulated seed yield reduction was associated with increases in heat and water stresses under rainfed conditions with current N fertilizer application rates. Coping with heat and water stresses is a big challenge for canola production in Canada under the projected climate change, especially on the Canadian Prairies.

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Section: Discussion Heat Stress and Changes In Crop Harvest Index Wasupporting

confidence: 67%

Simulated Canola Yield Responses to Climate Change and Adaptation in Canada

et al. 2018

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“…Further interrogation of the historic rainfall records showed that the pattern of rainfall distribution used for the drier treatment in this study was not necessarily typical of all other years within that decile, highlighting the extremely variable distribution of rainfall across seasons in these environments and thus the difficulty in developing strategies to manage N inputs. The HI values attained in this study can be considered good for semi-arid conditions (Passioura and Angus 2010), although glasshouse trials do commonly have higher HI values than field trials (Unkovich et al 2010).…”

Section: Fate Of Urea Fertiliser N and Efficiency Of Sowing Versus Lamentioning

confidence: 72%

Fate of fertiliser N applied to wheat on a coarse textured highly calcareous soil under simulated semi-arid conditions

et al. 2011

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Background and Aims Quantitative information on the fate and efficiency of nitrogen (N) fertiliser applied to coarse textured highly calcareous soils in semi-arid farming systems is scarce but, as systems intensify, is essential to support sustainable agronomic management decisions Method A glasshouse study was undertaken to trace the fate of N fertiliser applied to wheat (Triticum aestivum L. cv Yitpi) grown on a reconstructed profile (0 to 600 mm) of a grey highly calcareous (>35% CaCO 3 ) sandy loam soil. Two watering treatments were applied (drier and wetter) equivalent to low (decile 2, 179 mm) and medium (decile 5, 234 mm) growing season rainfall for a location with typical semi-arid environment in southern Australia. 15 N-labelled urea fertiliser (35.4 mg N/pot) was applied in a split application -at sowing and 70 days after sowing, followed by immediate watering or watering after delay of 1 week.Results Recovery of N fertiliser in grain (30 to 52%) was greater for the wetter treatment, and when water was applied immediately following fertiliser application. It was also similar for N applied at sowing and N applied during crop growth. Overall, more than 40% of the urea fertiliser N remained in the soil at anthesis, largely in the top 100 mm, indicating little movement of fertiliser N down the profile even with application of water. Losses of urea fertiliser N (13-24%) were considered relatively small given the highly calcareous nature of the soil; and were significantly greater from N applied during growth compared to at sowing, particularly where watering did not immediately follow application. There was no effect of fertiliser N on grain yield due to sufficient available N in soil at sowing (139mgN/pot), but N concentration and DM of stubbles was increased. Watering treatment did not affect shoot dry matter production up to anthesis, although root weight was higher in the wetter treatment, and grain yield was 9% greater. Conclusions It is concluded that the potential for N losses from urea applied to highly calcareous coarse textured soils in semi-arid agricultural areas appears relatively low. Further, where there are relatively large amounts of plant available N present at sowing, a strategy of delayed or withheld applications of N to manage economic risk may have minimal effects on grain production in seasons with drier than average rainfall.

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“…In addition to the C added by the cover crops, the total amount of C added to each plot was estimated assuming that the harvest index for grain crops (the ratio of harvested grain to the total aboveground biological yield) is approximately 50% (Unkovich et al, 2010), i.e., for each megagram of grain yield, 1 Mg of shoot dry matter is produced, and assuming that the shoot/root ratio in soils for cereal crops is 30% (Balesdent and Balabane, 1996;Bolinder et al, 1997;Kisselle et al, 2001). Based on these assumptions and the total grain production data (Table 1), it can be estimated that 4.4 to 125 Mg ha −1 of crop residues (leaves, stems, and roots) was added to the soil during the 12 or 17 yr since the beginning of the experiments.…”

Section: Soil Organic Carbon and Relative Cumulative Yieldmentioning

confidence: 99%