Browsing by Subject "Tillage"

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Einfluss der Bearbeitungsintensität beim Umbruch von Luzerne-Kleegras auf die Stickstoffmineralisation zur Folgefrucht Winterweizen im organischen Landbau
(2003) Wald, Fabian; Claupein, Wilhelm
In the crop rotation of organic farming grass-legume mixtures play an important role due to the legumes´ ability to assimilate N. Ploughing-in of established grass-legume mixtures results in releasing the assimilated N by mineralisation of organic matter. In practice the mineralisation can only be controlled by means of soil cultivation. The aim of the present study is to analyse the relations between different intensities of soil cultivation and N-mineralisation. The data were used to test the simulation model CANDY. The field experiment of each 0.1 ha was set up at three sites in two different locations, which were cultivated from 1999 to 2001: Hohenheim (with trials 610 and 611) and Kleinhohenheim (with trial 660). In the beginning all sites had a three-year old grass-clover-alfalfa mixture, which was ploughed-in for trial 610 and 660 in the late summer of 1999 and in the year 2000 for trial 611. The factor soil tillage was varied in three stages as follows: RT+RT+plough: double rototill cultivation (RT, 10 cm deep) in intervals of approx. 2 weeks, followed by ploughing (plough, 25 cm deep); RT+plough: single rototill cultivation, followed by ploughing (depths as mentioned above); Plough: ploughing without any preceding cultivation (depth 25 cm). After uniform seedbed preparation with a rotary harrow, wheat was sown on all trial sites in autumn, and in trials 610 and 660 it was followed by oat in 2001. Nitrogen content in the soil was determined by repeated sampling at a depths of 0-10, 10-20, 20-30, 30-60 and 60-90 cm. Monitoring boxes were installed in 1 m depth in an undisturbed soil body from September 2000 until April 2001 to record nitrate leaching. Ploughing-in of the grass-clover-alfalfa by means of rototiller cultivation (treatments RT+RT+plough and RT+plough) was followed by a significant increase of mineralisation, which in case of the plough treatment was less pronounced. In this case the date of cultivation, 6 weeks after the rototilling, may have had an influence. Nmin-contents in autumn 1999 were higher after RT+RT+plough than after RT+plough. It has to be taken into consideration that there was a time gap between both treatments of 9 days. But also in the following year (611), when both treatments were cultivated the same date, there was a significant, slight difference of the Nmin values depending on the treatment. Nitrate leaching was only measured in trial 611. Quantities of 86, 84 and 64 kg N/ha were observed in treatments RT+RT+plough, RT+plough and plough, respectively during winter. Due to high Nmin-contents in autumn, for the rototill treatments higher nitrate losses can be assumed compared to the plough treatment for both years of experiment. Depending on the location, nitrogen uptake and yields of wheat turned out to be different. In Kleinhohenheim they were lower in treatments RT+RT+plough and RT+plough than in the plough treatment. It was the other way round in Hohenheim on a higher production level. Due to strong hail impact, this relation between the treatments was not to be proved in trial 611. Oat was the second crop. In this case no effects of intensity of soil cultivation on nitrogen uptake and yield could be observed between treatments and locations. The CANDY model was used for simulating the results of trials 610 and 611. First, the model seemed to be inadequate because it could not model the N-dynamic after soil cultivation. Adding fictitious organic material to the system helped to overcome this problem and then, on average, the N-dynamic model fit was satisfying. An estimate to overcome the general insufficient fit of the model could be mineralisation of parts of the physically protected organic matter (SOS), which is already implemented in the model, right at the moment of cultivation. Data of soil moisture of trial 611 served to calibrate the model successfully. With amended soil parameters the model was then easily applied to the corresponding data of trial 610. In contrast, CANDY did not predict well the nitrate leaching - possibly because the model did not consider preferential flow.
Facilitation of weed seed predation by living mulch and cover crops
(2022) Schumacher, Matthias; Gerhards, Roland
Weed seed predation (WSP) is an important agro‐ecosystem service that naturally suppresses weed populations. Disturbances directly interfere with the activity of the seed predators, for example, harvest and soil tillage during a peak in weed seed availability (around cereal harvest). Plant soil cover and reduced soil tillage are factors that might positively affect WSP. We investigated cover crops and living mulch along with soil disturbance (no‐till and conventional seeding) in comparison to a fallow and repeated stubble tillage with a chisel plough in terms of WSP, activity‐density of carabid beetles and soil cover. A field experiment with a randomised complete block design and four replications was conducted at two sites from 2017 until 2019. WSP rates were assessed with seed cards and exclosure cages from July until November during a period of eight consecutive days each month. Living mulch exhibited the highest WSP rates of 72% with a maximum of 95% immediately following cereal harvest in August and September of 2017 and 2019, while the remainder of the treatments ranged from 2% to 5% WSP. In October and November mustard showed on average twice as high WSP rates compared to the other treatments (50% vs. 10%–25%). Seeding and soil tillage did not significantly influence carabid beetle activity‐density and WSP, except for living mulch. Predator groups (invertebrates and vertebrates) were not influenced by the various treatments, rather year and month determined the predator groups dominance. Besides their weed suppressive effects, living mulches and cover crops also facilitate WSP.
Management effect on the weed control efficiency in double cropping systems
(2023) Schmidt, Fruzsina; Böhm, Herwart; Graß, Rüdiger; Wachendorf, Michael; Piepho, Hans-Peter
There are often negative side-effects associated with the traditional (silage) maize cropping system related to the unprotected soil surface. Reducing soil disturbance could enhance system sustainability. Yet, increased weed pressure and decreased nitrogen availability, particularly in organic agriculture, may limit the implementation of alternative management methods. Therefore, a field experiment was conducted at two distinct locations to evaluate the weed control efficiency of 18 organically managed silage maize cropping systems. Examined parameters were relative weed groundcover (GCweed) and its correlation with maize dry matter yield (DMY), relative proportion of dominant weed species (DWS) and their groups by life form (DWSgroup). Treatment factors comprised first crop (FC—winter pea, hairy vetch, and their mixtures with rye, control (sole silage maize cropping system—SCS)), management—incorporating FC use and tillage (double cropping system no-till (DCS NT), double cropping system reduced till (DCS RT), double cropped, mulched system (DCMS Roll) and SCS control), fertilization, mechanical weed control and row width (75 cm and 50 cm). The variation among environments was high, but similar patterns occurred across locations: Generally low GCweed occurred (below 28%) and, therefore, typically no correlation to maize DMY was observed. The number of crops (system), system:management and occasionally management:FC (group) influenced GCweed and DWS(group). Row width had inconsistent and/or marginal effects. Results suggest differences related to the successful inclusion of DCS and DCMS into the rotation, and to the altered soil conditions, additional physical destruction by shallow tillage operations, especially in the early season, which possibly acts through soil thermal and chemical properties, as well as light conditions. DCS RT could successfully reduce GCweed below 5%, whereas DCS NT and particularly DCMS (Mix) suffered from inadequate FC management. Improvements in DCMS may comprise the use of earlier maturing legumes, especially hairy vetch varieties, further reduction/omission of the cereal companion in the mixture and/or more destructive termination of the FC.
Nitrous oxide emissions and mitigation strategies in winter oilseed rape cultivation
(2019) Kesenheimer, Katharina Anne; Müller, Torsten
After carbon dioxide and methane, nitrous oxide, is the third most important greenhouse gas in the atmosphere. Nitrous oxide contributes to the greenhouse gas effect as well as to ozone depletion. The major portion of anthropogenic N2O emissions are stimulated by the use of nitrogen fertilizers in agriculture. The main processes for N2O production in soils are nitrification and denitrification. Various environmental and management factors such as precipitation, soil type, tillage, and crop residues affect these processes. N2O emissions can occur substantially in the post-harvest period. In Germany, approximately 50 % of the annual N2O emissions can occur during winter. This exhibits the importance and necessity of annual data sets which prevent misinterpretations instigated by investigations limited to the vegetation period. Winter oilseed rape is the most important raw material for biodiesel in Germany. As of 2018, the framework of the European Renewable Energy Directive requires that the use of biofuels achieve GHG savings of at least 50 % compared to fossil fuels. Feedstock production for biodiesel contributes more than half of the total GHG emissions. To close the nutrient cycle with renewable energy, digestate from biogas plants can be used as a substitute for mineral N fertilizer permitting the reduction of GHG emissions in the production process of synthetic fertilizers. When compared to other crops, OSR has a high N demand. The low N removal by the seeds results in inefficient use of nitrogen and therefore a high N surplus in the soil which is susceptible to gaseous or leaching losses to the environment. Another potential risk for N2O losses are crop residues after harvest. The type of soil cultivation can have both positive and negative implications on N2O emissions which depend, among other things, on tillage depth, soil type and moisture. Results from studies measuring N2O emissions from different tillage systems are contradicting and site dependent. This study aims to investigate the effect of (a) N fertilization (mineral and organic), (b) nitrification inhibitors, (c) crop residues and (d) tillage on direct N2O emissions and, inter alia, yield and soil nitrogen dynamics in OSR production. N2O emissions were monitored for three years over a range of N fertilization levels at five study sites chosen so as to best represent typical winter oilseed rape production in Germany. Furthermore, the effect of the nitrification inhibitor (NI) TZ+MP (1H-1,2,4-triazole and 3- methylpyrazole) with digestate is investigated. Additional experiments for 15N labelled crop residues, nitrification inhibitor DMPP (3,4-dimethylepyrazole phosphate) with mineral fertilizer and soil tillage were implemented. A high spatial and temporal variability in N2O fluxes over all sites was observed. At each site, increased N2O fluxes were often detected after N fertilization in conjunction with rainfall events. During the first six weeks after harvest we frequently observed increased N2O fluxes following rainfall. In this postharvest period of winter oilseed rape, nitrate contents in the top soil were generally elevated. There were no considerable N2O pulses observed during thawing of frozen soil. Winters were mild without any severe frost periods in all three surveyed years which could be a reason for the generally low N2O winter fluxes observed in this study. On all examined sites, increasing N fertilization significantly enhanced N2O flux rates. Data obtained during the study were used to augment an existing model, wherefrom a new emission factor for OSR can be calculated. Assuming a quantity of 200 kg N ha-1 the global fertilizer-related emission factor derived from the exponential model was 0.6 %. This factor is within the uncertainty range of the EF1 IPCC emission factor (0.3 % – 3.0 %), but about 40 % lower than the 1 % IPCC default. The nitrification inhibitor (NI) TZ+MP combined with digestate mitigated the N2O fluxes significantly across all study sites and experimental years. As already noted in the fertilizer experiment, a high spatial and temporal variability in N2O fluxes over all sites was observed. The magnitudes of the N2O fluxes also showed similar trends. Over the entire investigation, the application of the NI significantly reduced annual N2O emission by a factor of three. During the fertilization period this mitigation effect was six times significant. This clearly emphasizes the importance of annual data sets to avoid overestimating NI effects.