Institut für Pflanzenbau und Grünland (bis 2010)

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/42

Nachfolgeinstitut ab 2011: Institut für Landschafts- und Pflanzenökologie

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Die Auswirkungen einer einmalig variierten Bodenbearbeitung auf Ertragsbildung, Verunkrautung und Bodennitratgehalt unter ökologischen Produktionsbedingungen
(2007) Häberle, Annette; Claupein, Wilhelm
Although organic farming is a very non-polluting kind of agriculture, nitrate leachate losses can also be found under this management. Restrictions in organic fertilization have the purpose to keep the nitrate leachate with soil tillage and crop rotation on a low level. Due to this aim field experiments were conducted to investigate the short-term effect of timing and method of cultivation after the harvest of legumes and crops with high-N crop residues on N mineralization, nitrate leaching, crop growth, diseases and weeds in wheat crops. The study was designed to compare the effects of the ?Schutz- und Ausgleichsverordnung? (SchALVO) in Baden-Württemberg and tillage strategies which are normally used in practice, like reduced and conventional tillage in autumn and to compare different times of conventional tillage in winter and spring in three different areas of Baden-Württemberg with typically soil types. The areas were located in the Main-Tauber-Kreis with soils from Keuper and shell lime, in the Gäu-Region with soils from löss and the Schwäbische Alb with soils of limestone. Especially organic farms use, for the admancement of yield und for the regulation of weed population, a timely and increased requirement of soil tillage. In the results of October 2002 till summer 2005 there was no significant influence of timing and method of cultivation, for example reduced tillage in autumn or tillage in winter or spring, on the productivity of organic farms. In the most cases the conditions on the experimental fields were very good resulting of a low weed density and a good farming management. On fields with a high density of perennial weeds the risk of multiplication of weed population persists even after a short-term variation of tillage. There were only a few, not significant differences in the development of wheat growth because of different soil tillage. The most differences were seen between the growth of winter wheat and summer wheat. The yield of summer wheat was not significantly lower than the yield of winter wheat. Summer wheat reached nearly the same yield potential with higher amounts of crude protein. Especially in areas with strong winters and low N-input the yield of summer wheat was higher than the yield of winter wheat. Because of a second peak of mineralization in spring there was a better adaptation of NO3-release to the growth of summer wheat after soil tillage in November, December and February. Because of the better utilization of soil-N from summer wheat the lower yield potential in comparison to winter wheat was relativised in the most areas. With regard to N mineralization a time displacement of soil tillage in winter or spring didnt reduce the N-mineralization before winter in all cases. But in this time displaced treatments there was a second peak in N-mineralization additional to the first peak in autumn. Short-term practice of reduced soil tillage did not reduce N-release in the field experiments. Altogether a time displaced soil tillage in winter or spring could be, based on the experiments, a practical alternative for N-conservation through winter with regard to N-mineralization as well as with regard to corn yield. With the cultivation of a fast-growing catch crop farmers could reach an additional reduction of mineralised N amount over winter. In the farming practice a well timed sowing of catch crops is not always possible, like it is shown in the experiments, but it should be kept in mind for N conservation.
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.
Pflanzenbauliche Untersuchungen zum ökologischen Anbau von Körnerleguminosen an sommertrockenen Standorten Südwestdeutschlands
(2007) Poetsch, Jens; Claupein, Wilhelm
Grain legumes, as nitrogen fixing crop, protein rich animal feed and marketable product are of great importance for organic agriculture. Due to staged abolition of the possibility to add non-organic products in organic animal feeding, the EU?s demand for organically produced protein feed is further increasing. Field bean (Vicia faba) and field pea (Pisum sativum) are large-scale crops but feature a limited feeding value. Lupin species (Lupinus spp.) excel by protein contents of up to 40% in the seed and higher protein value. At warmth favoured locations in southwestern Germany the valuable soybean (Glycine max) can be grown successfully and obtain above-average proceeds in natural food industry. Constraints of yield stability of grain legumes result amongst other things from frequently high weed infestation in organic cropping systems and suboptimal water supply at summer-dry locations. For lupins, moreover, particular soil requirements and the seed-borne fungal disease anthracnosis are problematic. Nitrogen residues after harvest are relevant for subsequent crop as well as groundwater protection. The presented work aimed at defining preconditions and developing cropping strategies to optimise yield stability and level of organically grown grain legumes with a main focus on summer-dry locations, to increase diversity of cultivatable crops and provide information on disposition of nitrogen residues. For this purpose from 2003 to 2005 trials at several locations as well as in greenhouse and laboratory were accomplished. Field trials on organic weed control in soybean as well as white and narrow-leafed lupin (Lupinus albus und L. angustifolius) were conducted at organically managed commercial sites in the upper rhine valley. At the same time agronomic measures for optimisation of competitiveness and machinery implementation were varied. Early high soil coverage and crop height contributed considerably to grain legumes? competitiveness. Delayed sowing at elevated temperatures supported rapid juvenile development and allowed for pre-sowing weed control. At optimum sowing date these effects may be used without yield depression or maturity problems. Reduced row distance was beneficial for optimum space utilisation and early crop closure, but effectiveness of mechanical means was highest at high row distance and large areal proportion for interrow cultivation. As an optimum compromise for grain legumes row distances of 30 - 35 cm are recommended. Optimum impact of mechanical means against weeds was achieved by combining interrow cultivation with harrow or fingerweeder. Forgoing interrow cultivation may be considered in strongly competitive crops like field bean. Lupin species appeared rather poor in competitiveness compared to other crops. Field trials on effects of cultivar and cropping strategy on overwintering and yield performance of autumn-sown field bean, field pea and white lupin were conducted at three locations. Summer drought caused substantial yield advantages of autumn-sown compared to spring-sown cultivars due to superior water supply at earlier flowering. With sufficient water supply a head start was not yield effective. Differing coincidence with pests and diseases could account for advantages (head start on aphid infestation) or disadvantages (fungal infections during winter period) of autumn-sown cultivars. Overwintering was excellent for winter field bean and good for winter field pea. For winter white lupin further trials are required. Temperatures down to -12°C were well endured by all of the three crops. The most important cropping parameter was the sowing date. Winter field bean permitted a relatively wide sowing window. Winter white lupin required strong development before winter and preferably early sowing. Sowing date of winter field pea presented an optimisation problem, because sowing too early leads to overdevelopment and reduced cold-tolerance, while sowing too late may reduce yield potential. Optimum sowing dates for southwestern Germany according to experimental results are in the range of early September (winter white lupin), mid-October (winter field bean) and late October (winter field pea). Water use efficiency may gain significantly in importance in the future. A two-year trial on cultivation prospects and yield performance of the notably drought tolerant chickpea (Cicer arietinum) in the upper rhine valley resulted in successful crop development, but problems with empty pods and inadequate grain quality. Further trials are considered promising. A field trial with white and narrow-leafed lupin confirmed that anthracnosis of lupin spreads less rapidly and yield effectively at summer-dry locations, and narrow-leafed lupin frequently stays unaffected. Laboratory studies for optimising detection methodology of the causative organism Colletotrichum lupini showed advantages of using sectioned petri dishes (quad plates), which confined propagation of disturbing organisms. A trial on seed storage under different temperatures, seed moisture contents and CO2-atmosphere produced no distinct treatment effect, but could confirm the general decrease of seed infection by storage. According to literature hot air (approx. 4 days at 65°C) also reduces seed infection effectively. Thus, storage or hot air treatment of basic seed and propagation at summer-dry locations appear as a viable over-all strategy. Difficult soil requirements of white and narrow-leafed lupin were studied by a pot trial as well as a comprehensive literature analysis. It is concluded that the so-called lime chlorosis is caused by HCO3--induced inactivation of physiologically relevant Fe(II) in the plant. Accumulation of HCO3- is basically caused by insufficient soil aeration and promoted by the presence of lime in the clay fraction. Furthermore, especially in narrow-leafed lupin, disturbances of root development are caused by high Ca-content or high and at the same time strongly buffered pH of soil solution. These conditions are often but not necessarily caused by lime. Analyses of harvest residues and soil were consulted for estimation of nitrogen dynamics. Immobilisation due to degradation of residues with high C:N ratio as well as uptake by catch crops contributed substantially to nitrogen conservation. Risk of leaching is predominantly site dependent. The over-all nitrogen balance of grain legumes when exporting the seed may be low or even negative. In conclusion, results of the presented work indicate that site adapted cropping systems with agronomic measures in the areas of crop rotation, choice of cultivar, sowing date or space allocation can still contribute considerably to yield stability in organic cultivation of grain legumes.

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