Spectral reflection and crop parameters: can the disentanglement of primary and secondary traits lead to more robust and extensible prediction models?

Recently the application of spectral reflection data for the prediction of crop parameters for applications in precision agriculture, such as green area index (GAI), total aboveground dry matter (DM), and total aboveground nitrogen content (N content) increases. However, the usability of vegetation indices (VI) for the prediction of crop parameters is strongly limited by the fact that most VI calibrations are only valid for specific crops and growth periods. The results of the presented study based on the differentiation of primary (main driver of the reflectance signal) and secondary (not directly related to reflectance signal) crop parameters. For GAI prediction, a universal (without crop-specific parametrization) simple ratio vegetation index (SR) provided good calibration (R2 adj. = 0.90, MAE = 0.32, rMAE = 22%) and evaluation results (MAE = 0.33, rMAE = 18%). The disentanglement of primary and secondary traits allowed the development of a functional two-step model for the estimation of the N content during vegetative growth (MAE = 19.2 g N m−1, rMAE = 44%). This model was based on fundamental, crop-specific relationships between the crop parameters GAI and N content. Additionally, an advanced functional approach was tested enabling the whole-season prediction of DM and confirming a reliable GAI estimation throughout the whole growing season (R2 = 0.89–0.93)

Klimawirkung unterschiedlicher Winterzwischenfrüchte in typischen Fruchtfolgesequenzen

Aus Klimaschutzperspektive gilt es die Trade-Offs im Zwischenfruchtanbau zu quantifizieren und standortangepasse Strategien zur Minimierung der Treibhausgasemissionen abzuleiten. Aus 3-jährigen Feldversuchen an 4 Standorten wurden typische Fruchtfolgesequenzen intensitäts-abhängig bewertet

Estimation of Biomass and N Uptake in Different Winter Cover Crops from UAV-Based Multispectral Canopy Reflectance Data

Cover crops are known to provide beneficial effects to agricultural systems such as a reduction in nitrate leaching, erosion control, and an increase in soil organic matter. The monitoring of cover crops’ growth (e.g., green area index (GAI), nitrogen (N) uptake, or dry matter (DM)) using remote sensing techniques allows us to identify the physiological processes involved and to optimise management decisions. Based on the data of a two-year trial (2018, 2019) in Kiel, Northern Germany, the multispectral sensor Sequoia (Parrot) was calibrated to the selected parameters of the winter cover crops oilseed radish, saia oat, spring vetch, and winter rye as sole cover crops and combined in mixtures. Two simple ratios (SRred, SRred edge) and two normalised difference indices (NDred, NDred edge) were calculated and tested for their predicting power. Furthermore, the advantage of the species/mixture–individual compared to the universal models was analysed. SRred best predicted GAI, DM, and N uptake (R2: 0.60, 0.53, 0.45, respectively) in a universal model approach. The canopy parameters of saia oat and spring vetch were estimated by species–individual models, achieving a higher R2 than with the universal model. Comparing mixture–individual models to the universal model revealed low relative error differences below 3%. The findings of the current study serve as a tool for the rapid and inexpensive estimation of cover crops’ canopy parameters that determine environmental services

Yield trend of winter wheat with varying N fertilization

Dauerversuche können helfen, langfristige Entwicklungen zu identifizieren und zu quantifizieren. In einem Stickstoff-(N)-Steigerungsversuch, der seit 1974 auf dem Versuchsgut Hohenschulen im Östlichen Hügelland Schleswig-Holsteins durchgeführt wird, wurde Winterweizen zu den 3 Terminen Vegetationsbeginn, Schossbeginn EC 30 und Ährenschieben EC 50/51 mit jeweils 0, 40, 80 und 120 kg N ha–1 in allen Kombinationen gedüngt (4*4*4 = 64 N-Varianten, 0–360 kg N ha–1), um ex post das jahresspezifische N-Optimum abschätzen zu können. Die Sorte Diplomat wurde als Standardsorte durchgehend von Versuchsbeginn bis 2002 angebaut, während als zweite, jeweils neuere Sorte Kanzler (1983–1991), Orestis (1992–1995), Ritmo (1996–2004) und Tommi (ab 2005) geprüft wurden. Aus den jahres- und sortenspezifischen Ertragsfunktionen (basierend auf einem quadratischen Ansatz mit der N-Gesamtmenge) wurden der Ertrag in der ungedüngten Variante, die optimale N-Düngung und der entsprechende optimale Ertrag abgeleitet. Daraufhin wurde durch lineare Regression geprüft, ob Ertrags­trends vorlagen. Der Ertrag in der ungedüngten Kontrolle veränderte sich im Zeitablauf nicht signifikant. Dem­gegenüber stieg der Ertrag bei optimaler N-Düngung bei allen Sorten um 0,63 dt ha–1 a–1, allerdings auf unterschiedlichem absoluten Niveau, signifikant während der Versuchsdauer an, wobei sich jedoch die Höhe der optimalen N-Düngung nicht veränderte. Mit steigenden Erträgen sank die Rohproteinkonzentration. Ein statistisch absicherbarer Zusammenhang zwischen der jahresspezifisch optimalen N-Düngermenge und dem entsprechenden Ertragsniveau konnte nicht beobachtet werden. Als mögliche Ursachen für die steigenden Erträge bei opti­maler N-Düngung werden Veränderungen der Produk­tionstechnik, der Jahrestemperatur oder der CO2-Konzentration der Atmosphäre diskutiert.    Long-term field experiments allow identifying and quantifying trends. A field trial was set up in 1974 at the Hohenschulen Experimental Farm in Schleswig-Holstein (Northern Germany) to test different nitrogen (N) treatments in wheat. N fertilization varied in timing and total amount. 0, 40, 80 or 120 kg N ha–1 were applied each at the beginning of spring growth, at stem elongation (GS 30) and at ear emergence (GS 50/51) in any possible combination resulting in 64 (4*4*4) N treatments ranging from 0 to 320 kg N ha–1. The cultivar Diplomat was grown from the trial set up until 2002, whereas Kanzler (1983–1991), Orestis (1992–1995), Ritmo (1996–2004) und Tommi (since 2005) were parallelly tested as newer genotypes. Yield in the unfertilized control, optimal N amount and the respective grain yield were estimated from the year and genotype specific N response curves (quadratic polynomial function based on the total N amount). Linear regression was used to test for trends in these coefficients. Grain yield without N fertilization showed no trend. However, yield of the optimal fertilized treatment increased by 0.063 t ha–1 a–1. Yield trend was similar in all varieties, but at different levels indicating genetic improvements. In contrast, the optimal N amount was not affected. Grain protein concentration correlated negatively with the yield level, whereas only a poor relationship between optimal N amount and the respective yield occurred. As causes for the trend in the optimal yield changes in crop management, average mean temperature or CO2 concentration in the atmosphere are discussed.   &nbsp

Intensitäts- und standortdifferenziertes Klimaschutzpotential von Leguminosen in Anbausystemen mit N-effizienter Düngung (Projekt ISLAND)

Der aktuelle Kenntnisstand zu N2O-Emissionen der Leguminosenbestände in der Literatur ist nicht einheitlich. Im Projekt ISLAND wird das Potential von Fruchtfolgen und der Beitrag von Leguminosen zu klimaschonendem N-Management in Produktionssystemen unterschiedlicher Intensität utersucht

N-Umsatz, Spurengasemissionen und Produktivität von Fruchtfolgen zur Biogasproduktion in einer Kalkmarsch Schleswig-Holsteins

Aufgrund des bisher wenig untersuchten Agrarlandschaftsraumes als auch neuartiger Biogasgärreste ist der Effekt der Biogasnutzung auf den Stoffhaushalt von Marschstandorten schwer zu quantifizieren. Auf einem noch nicht entkalkten Marschstandort Nordfries-lands, Schleswig-Holstein, wurden in einem Parzellenversuch mehrjährige Untersuchungen zur N-Düngewirksamkeit und Spurengasemissionen (N2O, NH3) bei Düngung mit Mineraldünger (KAS) und Biogasgärresten durchgeführt. Die N-Dünger wurden zur Produktion von Silomais, Weidelgras und GPS-Weizen als Biogassubstrat genutzt. Biogas-gärreste wurden mit Schleppschläuchen ausgebracht. Bei Verwendung des Mineraldüngers erzielten Maismonokultur, Ackergras sowie eine Fruchtfolge (Mais-Weizen-Welsches Weidelgras) etwa gleich hohe Erträge (ca. 30 t TM ha 1 2a-1). Bei Weizen und Ackergras führte die Düngung mit Biogasgärresten zu deutlich reduzierten Erträgen. NH3-Emissionen lagen aufgrund hoher Windgeschwin- digkeiten höher als in anderen Regionen Schleswig-Holsteins, wobei Ackergras bei weitem die höchsten (80 kg N ha-1 2a-1) und Maismonokultur die geringsten (20 kg N ha-1 2a-1) kumulierten Verluste aufwies. Ohne signifikante Unterschiede zwischen den N-Düngern lagen kumulierte N2O-Emissionen mit 1–5 kg N ha-1 a-1 trotz beträchtlicher N-Aufwand-mengen und des tonreichen Bodens relativ niedrig

Induced Arp2/3 Complex Depletion Increases FMNL2/3 Formin Expression and Filopodia Formation.

The Arp2/3 complex generates branched actin filament networks operating in cell edge protrusion and vesicle trafficking. Here we employ a conditional knockout mouse model permitting tissue- or cell-type specific deletion of the murine Actr3 gene (encoding Arp3). A functional Actr3 gene appeared essential for fibroblast viability and growth. Thus, we developed cell lines for exploring the consequences of acute, tamoxifen-induced Actr3 deletion causing near-complete loss of functional Arp2/3 complex expression as well as abolished lamellipodia formation and membrane ruffling, as expected. Interestingly, Arp3-depleted cells displayed enhanced rather than reduced cell spreading, employing numerous filopodia, and showed little defects in the rates of random cell migration. However, both exploration of new space by individual cells and collective migration were clearly compromised by the incapability to efficiently maintain directionality of migration, while the principal ability to chemotax was only moderately affected. Examination of actin remodeling at the cell periphery revealed reduced actin turnover rates in Arp2/3-deficient cells, clearly deviating from previous sequestration approaches. Most surprisingly, induced removal of Arp2/3 complexes reproducibly increased FMNL formin expression, which correlated with the explosive induction of filopodia formation. Our results thus highlight both direct and indirect effects of acute Arp2/3 complex removal on actin cytoskeleton regulation

Nitrous oxide emissions from winter oilseed rape cultivation

Winter oilseed rape (Brassica napus L., WOSR) is the major oil crop cultivated in Europe. Rapeseed oil is predominantly used for production of biodiesel. The framework of the European Renewable Energy Directive requires that use of biofuels achieves GHG savings of at least 50% compared to use of fossil fuel starting in 2018. However, N2O field emissions are estimated using emission factors that are not specific for the crop and associated with strong uncertainty. N2O field emissions are controlled by N fertilization and dominate the GHG balance of WOSR cropping due to the high global warming potential of N2O. Thus, field experiments were conducted to increase the data basis and subsequently derive a new WOSR-specific emission factor. N2O emissions and crop yields were monitored for three years over a range of N fertilization intensities at five study sites representative of German WOSR production. N2O fluxes exhibited the typical high spatial and temporal variability in dependence on soil texture, weather and nitrogen availability. The annual N2O emissions ranged between 0.24 kg and 5.48 kg N2O-N ha−1 a−1. N fertilization increased N2O emissions, particularly with the highest N treatment (240 kg N ha−1). Oil yield increased up to a fertilizer amount of 120 kg N ha−1, higher N-doses increased grain yield but decreased oil concentrations in the seeds. Consequently oil yield remained constant at higher N fertilization. Since, yield-related emission also increased exponentially with N surpluses, there is potential for reduction of the N fertilizer rate, which offers perspectives for the mitigation of GHG emissions. Our measurements double the published data basis of annual N2O flux measurements in WOSR. Based on this extended dataset we modeled the relationship between N2O emissions and fertilizer N input using an exponential model. The corresponding new N2O emission factor was 0.6% of applied fertilizer N for a common N fertilizer amount under best management practice in WOSR production (200 kg N ha−1 a−1). This factor is substantially lower than the linear IPCC Tier 1 factor (EF1) of 1.0% and other models that have been proposed. © 201

Assessing nitrous oxide emissions and productivity of cropping systems for biogas production using digestate and mineral fertilisation in a coastal marsh site

Significant greenhouse gas emissions during substrate cultivation reduces the potential environmental benefits of biogas production. This study investigates the productivity of different cropping systems and their environmental impact in terms of nitrous oxide (N2O) emissions under the environmental conditions of the coastal marsh regions (Northern Germany) with heavy clay soils, in a 2-year field trial (April 2009-March 2011). Treatments included four cropping systems (perennial ryegrass (Lolium perenne, PR) ley, continuous maize (Zea mays), a rotation (CR1) of spring wheat (Triticum aestivum), Italian ryegrass (Lolium multiflorum, IR) and maize, and a rotation (CR2) of maize, winter wheat and IR; two sources of N (nitrogen) fertilizers (calcium ammonium nitrate, and biogas residue (BR)), and three levels of N fertilizer applications (control, moderate, high). Nitrous oxide emissions were determined for the unfertilized and highly fertilized cropping systems comprising PR ley, CR1 and CR2. Cumulative annual N2O emissions varied across the treatments, ranging from 0.82 to 3.4 kg N2O-N ha−1 year−1. Under high N fertilizer applications, PR ley incurred higher N2O-N losses compared to other tested cropping systems, and IR cover crop caused relatively high N2O-N emissions in a short vegetation period. The study observed wide range of yield-scaled emissions (0.00–5.60 kg N2O-N (Mg DM)−1) for different crops, emphasizing the variability in N2O emissions linked to cropping systems. The N2O-N emission factors for the three cropping systems were found to be low to moderate for all treatments, ranging from 0.03% to 0.53% compared to IPCC default Tier 1 N2O-N EFs. The lower emissions in the study were associated with prolonged high soil moisture conditions (water filled pore space >70%.), indicated by its negative correlation with N2O-N fluxes. Low dry matter and N yield of PR and of the wheat-IR sequence after BR application compared to other crops indicated a low N use efficiency. The estimation of N2O-N emissions based on N surplus was not promising specifically for the coastal study site where high groundwater level and organic matter in the soils were the predominant drivers for N2O-N emissions

N-Umsatz und Spurengasemissionen typischer Biomassefruchtfolgen zur Biogaserzeugung in Norddeutschland

Im Rahmen des Verbundprojektes Biogas-Expert an der CAU-Kiel wurden an zwei Standorten Schleswig-Holsteins veschiedene Fruchtfolgen zur Bereitstellung von Biogassubstraten unter Verwendung von Biogasgüllen als N-Dünger durchgeführt. Maismonokultur wies die höchsten Trockenmasseerträge auf, wobei keine signifikanten Unterschiede in den Erträgen zwischen Biogasgärresten, organischen N-Düngern und mineralischen Düngern ermittelt wurden. Während in Bezug auf die N-Düngeform bei N2O- und Nitratauswaschungsverlusten kein Einfluss der N-Form auf die Höhe der Verluste festgestellt wurde, war die Düngung mit Biogasgüllen mit signifikant erhöhten NH3-Verlusten verknüpft. Eine abschließende Bewertung der Produktionssysteme ist erst durch Analyse der experimentellen Ergebnisse mit einem Systemmodell möglich