Potential soil organic carbon sequestration with cover crops in German croplands

<p>Cover crops have been suggested to preserve or even increase the soil organic carbon (SOC) stocks in croplands which can contribute to soil fertility and climate change mitigation. Cover crop cultivation increased in most European countries during the last years. However, it remains unquantified how many additional cover crops can be integrated into existing crop rotations. Moreover, there are no realistic quantitative estimates of the SOC sequestration potential of implementing additional cover crops in Germany.</p><p>We analyzed recent German crop rotations obtained from the first German Agricultural Soil Inventory for available cultivation windows (winter fallows) for cover crops, and we simulated the SOC sequestration potential of additional cover crops in the topsoil using a SOC model ensemble consisting of RothC and C-TOOL. In order to estimate a reasonable carbon input via the cover crops’ biomass, we developed a new allometric function which takes the effect of the weather and the seeding date on the development of the biomass into account.</p><p>Our study shows that only one third of the cultivation windows are currently used for cultivating cover crops. Thus, the cover crops’ cultivation area could be tripled with additional 2 Mio ha each year. With these additional cover crops, the annual C input could be increased by 12% from 3.68 to 4.13 Mg C ha<sup>-1</sup> a<sup>-1</sup>. Within 50 years, this would result in 35 Tg more SOC in the top 30cm of German croplands which corresponds to 2.6 Tg CO<sub>2</sub> equivalents per year. Despite the dry weather conditions, a considerably large increase in SOC can be achieved in the eastern regions of Germany due to a low current cover crop cultivation frequency. However, the limited water availability during the time of cover crop establishment may require undersowing.</p><p>We conclude that including cover crops in crop rotations and consequently avoiding bare fallow in winter is a key measure in a climate mitigation strategy for managing cropland soils, and we will discuss the benefits and barriers of growing cover crops in Germany and Europe.</p>

Effect of seeding date on winter canola (Bassica napus L.) yield and oil quality in southern Ontario

Winter canola or winter oilseed rape (Brassica napus L.) is not commonly grown in Canada. While winter oilseed rape is the dominant growth form in Europe, Canadian canola production is dominated by spring types in western Canada. Research conducted in the 1980s indicated that the environmental conditions in southern Ontario are well suited to the production of winter canola. Since then, however, interest in the crop has ebbed and little to no research has been conducted on the agronomic issues that potentially limit its adoption in the province. The objective of this research was to identify an optimal seeding date for winter canola in southern Ontario. Three winter canola hybrids were evaluated across five seeding dates ranging from early September to late October. Results established the first two weeks of September as the optimal seeding period for winter canola in southern Ontario. Seeding winter canola during this period, such that greater than 600 GDD could be accumulated before the first fall frost, not only reduced winterkill to approximately 20% but also maximized yield potential and ensured optimal oil quality. Winter canola showed great potential for production in southern Ontario and its addition to current crop rotations would diversify and enhance crop production practices in this portion of the province.

Season, sowing date, and row cover influences the production of cool season vegetables in movable high tunnels

Moveable high tunnels offer the possibility of increasing the number of crops harvested from a given piece of ground in northern latitudes where there is a short growing season. In an effort to expand crop scheduling options, three leafy greens and three root vegetables were grown in the spring in a movable high tunnel, and in the fall were sown outside and the tunnel was moved over the crops in late September. The effects of seeding date and addition of row cover were further explored on fresh weight and days to harvest. Using row cover within the high tunnel increased growing degree hours (GDH) by an average of 29% in the spring and 17% in the fall over a high tunnel without row cover. Soil degree hours (SDH) in the high tunnel with row cover increased an average of 9% in the spring and 12% in the fall over the high tunnel without row cover. The addition of row cover increased yield of leafy greens and turnip by an average of 35% in spring 2018 when the outside air temperature was considerably below average. Early-seeded fall leafy greens out-yielded late-seeded by 52% due to the ability to make a second harvest. Using row cover within the high tunnel increased GDH and SDH during both spring and fall seasons and increased the yield of cool season vegetables when outside air temperatures were considerably below average.

Phenotyping a Diverse Collection of Forage Sorghum Genotypes for Chilling Tolerance

Forage sorghum (FS) (Sorghum bicolor (L.) Moench) is a warm-season biomass crop used as forage for hay or silage with the potential to become a bioenergy feedstock or for dual-purpose (forage and energy). The objective of this study was to screen potential forage sorghum genotypes for increased chilling tolerance and biomass productivity. Seventy-one genotypes of FS were first ranked for high to low vigor index under controlled conditions at 24, 12, and 10 °C. Field experiments were also conducted on a subset of 12 genotypes in Fargo and Hickson, ND, USA, in 2017 and 2018, using two different seeding dates: early (10 May) and late (27 May). Field emergence index values were greater for the late-seeding compared with the early seeding date. Under field conditions, seed mortality and biomass yield were affected by the seeding date and biomass yield correlated with emergence index and normalized vegetative index. Chemical composition of forage sorghum biomass was not affected by the seeding dates. The results of this study suggest that some forage sorghum genotypes carry genetic traits for increased chilling tolerance and produce greater biomass yield when seeded earlier than normal, which could allow for breeding chilling tolerance into forage sorghum.

Estimation of corn harvest date in South Korea based on the accumulated temperature

<p>This study was estimated harvest date of corn in South Korea based on the temperature index called the accumulated temperature. The accumulated temperature was calculated using observed daily mean temperature. We assumed a unified seeding date, 5 April, across the South Korea. The daily mean temperatures from 61 weather stations provided by the Korean Meteorological Administration were obtained for the period 2009-2018 (10 years). We used 1,650℃ as the criterion of the accumulated temperature to identify harvest date of corn for early-cultivated variety. The accumulated temperature over the most areas generally meted the criterion (1,650℃) in early July. In case of 2018, 66% area of Gang-won province, major corn producer, become suitable to harvest corn in July, peaking in the middle July (51%). The harvest date has been accelerating due to increase in daily mean temperature during the recent 10 years. This study infers that changes in farming activities are needed through reflecting the environmental change.        </p><p> </p><p>Acknowledgements</p><p>: This study was carried out with the support of “Research Program for Agricultural Science & Technology Development (Project No. PJ014882)”, National Institute of Agricultural Sciences, Rural Development Administration, Republic of Korea.</p><p> </p>

Nitrogen Pulse and Competition Affects Nitrogen Metabolism in Invasive Weed (Amaranthus retroflexus) and Native Crop (Glycine max)

Nitrogen (N) pulse is a frequent event in agroecosystems caused by fertilization. Understanding the responses of nitrogen metabolisms in native crops and invasive weeds to N pulses is essential in investigating the invasive mechanism of invasive weeds. A pot experiment was carried out to study the impacts of N pulse and the interspecific competition on nitrogen metabolism of an invasive weed (Amaranthus retroflexus) and a native crop (Glycine max); the plants were applied with an equal amount of N in three N pulse treatments, i.e., sole-summit treatment (SS) with N only applied on the seeding date, double-summit treatment (DS) with twice N applied (the fertilizer was applied on both the seeding date and the flowering date), and no-summit treatment (NS) in which N was applied evenly during the experiment. The results showed that A. retroflexus increased the nitrate reductase (NR) activity more than G. max (except for the roots) in the early growing stage, and increased the glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities in stem more than G. max in SS and DS treatments during the last two growing stages, however, the advantages were far weaker in the NS treatment. Interspecific competition had negative effects on the nitrogen metabolism of the two species among most of the sample times, and the effects of interspecific competition exerted a tissue-specific influence on nitrogen metabolism in the two species. A. retroflexus switched to reproductive growth earlier in SS treatment than in the DS and NS treatments when it was grown in mixed planting, and its height was the lowest in the NS treatment, so the competitive ability of A. retroflexus was higher in the SS and DS treatments than in the NS treatment, while SS treatment was the common application method of N fertilizer in the G. max farmland in China. Thus, the results of this study suggest that, if the farmer changed the N fertilizer application mode to a constant multiple fertilization mode, the competitive capacity of A. retroflexus will be reduced.