Browsing by Subject "Konservierende Bodenbearbeitung"

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Development of management strategies to control soil erosion in field grown vegetables with a focus on white cabbage (Brassica oleracea convar. capitata var. alba L.)
(2014) Übelhör, Annegret; Claupein, Wilhelm
Soil erosion by wind and water is a widely recognized problem throughout the world. Field grown vegetables, such as white cabbage (Brassica oleracea convar. capitata var. alba L.), are particularly endangered by soil erosion because of high disturbance tillage, including deep inversion tillage by the mouldboard plough. Furthermore, wide row spacing and late soil covering by leaves intensify the problem. In light of this, field experiments were conducted from 2011 to 2013 in southwest Germany to investigate, develop and adapt soil erosion control strategies, in particular for field grown vegetables, with white cabbage as a model crop. Focus was placed first, on the use of row covers (fleece and nets), which are usually used as frost protection or for pest control in organic farming, and second, on the development and adoption of strip-tillage for field grown vegetables, which combine the benefits from conventional tillage (high yields) and no-tillage (erosion control). Artificial rainfall simulations demonstrated a high erosion control by row covers. Soil loss under fleece cover was reduced on average by 76% and under net cover by 48% compared to the uncovered control treatment. In 2012, fresh matter head yield was significantly higher under fleece (80 t ha-1) than control treatment (66 t ha1). The opposite was found in 2013, with highest yield under the non-covered control (64 t ha-1) and lowest under fleece cover (53 t ha-1). A higher prevalence of diseases under row covers compared to the control was only found in 2012 with Sclerotinia sclerotiorum on 4% of cabbage heads under fleece cover. Soil loss under strip-tillage during artificial rainfall simulations in 2011 was reduced by an average of 80% compared to conventional tillage (512 g m-2). In 2012, soil losses were reduced by an average of 90% under non-intensive strip-tillage and by 48% under intensive strip-tillage compared to conventional tillage (210 g m-2). The fresh matter head yield in 2011 and 2013 under strip-tillage (58 t ha-1 and 57 t ha-1, respectively) was similar to conventional tillage (59 t ha-1 and 58 t ha-1, respectively). In 2012, cabbage yield was significantly higher under strip-tillage (74 t ha-1) than under conventional tillage (65 t ha-1). The intensive strip-tillage treatments with broadcast and band-placed nitrogen fertilization did not show a yield increase. Yield potential under band-placed fertilized strip-tillage was, at 67 t ha 1 (2012) and 50 t ha-1 (2013), the lowest within the strip-tillage treatments. The CROPGRO cabbage model was evaluated for cabbage production under temperate European climate conditions. After calibration of main parameters of phenology and plant growth, the model showed a high accuracy with indices of agreement mostly above d=0.94. Observed dry matter cabbage head yields of the different years and different locations ranged between 6574 kg ha-1 and 11926 kg ha 1 which were predicted by the model with an accuracy of R2=0.98. Also the sensitivity analysis, conducted under different nitrogen fertilizer amounts and different fertilizer application strategies, generated realistic values from an agronomic point of view. Overall, row covers and strip-tillage seem to be suitable for minimizing the erosion risk in vegetable production. The hypotheses of high erosion control under row covers and strip tillage can be accepted. Due to the modified microclimate under row covers, the infestation with pests and diseases can increase and the influence on cabbage growth can result in either a yield increase or decrease. Based on the study results, there is no evidence that the intensive, double-tilled strip-tillage treatment or the band-placed nitrogen fertilization lead to a yield increase. The non-intensive strip-tillage with only soil preparation in autumn showed the highest yield potential within the strip-tillage treatments, with similar or even higher yields than under conventional tillage. Furthermore, the CROPGRO cabbage model is suitable to simulate growth parameters and yield potential of white cabbage under temperate European climate conditions. For the future, due to the prediction of increased frequency of heavy rainfall events, soil conservation will focus increasingly on intensive crop production and farmers, particularly vegetables growers, will be increasingly dependent on erosion control strategies. For this reason, the approaches presented in this thesis can contribute significantly to produce field grown vegetables in a sustainable way that promotes soil protection.
Land Preparation Methods and Soil Quality of a Vertisol Area in the Central Highlands of Ethiopia
(2005) Jijo, Teklu Erkossa; Stahr, Karl
The industrialization of agriculture led to societal concerns for environmental protection and food quality in developed countries. On the other hand, the need for increased agricultural productivity to address the persistent poverty and food insecurity in developing countries is intensified. Thus, improved management systems to meet the double objectives of increased productivity and sustained environmental quality are increasingly required. The assessment of soil quality and productivity are among the means of monitoring the various management systems to achieve the goals. Among the interrelated definitions formulated for soil quality, a committee established by Soil Science Society of America for the same purpose defined it as the capacity of soil to function within natural and managed ecosystem boundaries to sustain plant and animal productivity, maintain or enhance soil, water and air quality and support human health and habitation. The central idea in most of the definitions is the capacity of the soil to function. The capacity of a soil to function depends on its inherent properties derived from its genesis and the dynamic properties resulting from the prevailing management systems. Most of the hitherto soil quality assessments considered agricultural production as the major management goal. As this study was conducted in the highlands of Ethiopia where food security remains a basic challenge, the primary management goal could not be different. Shortage and fragmentation of land driven by population pressure have become issues of concern in the area. With a continually dwindling national land-holding average of only one ha per household, farmers struggle to produce enough to feed their families. Since the possibility of expanding agricultural land is limited, increased production is realistic only from higher productivity per unit land per unit time. Covering about 8 million ha, Vertisols are among the high potential soils, where significant increase in productivity is likely. However, their productivity is constrained by their physical and hydrological properties, manifested by their hardness when dry and their stickiness when wet, impeding land preparation. The traditional management systems led neither to increased productivity nor to enhanced soil quality. Thus, the need for alternative technologies is paramount. Despite a concerted effort during the last two decades to develop improved technologies for the soils, land preparation for agricultural productivity and sustaiability remains a major challenge. In addition to technical difficulties associated with their nature and deep-rooted poverty and illiteracy, lack of farmers? participation is believed to have hampered the development and adoption of robust technologies. The challenge facing the soil management research in Ethiopia is thus double fold: development of technologies that swiftly increase agricultural production and ensure judicious use of the land resources. Farmers are the ultimate decision makers on their plots, at least in Ethiopia, often irrespective of the consequences of their decisions. Simple technologies are required to manipulate their decisions in favour of the desired goals. This requires development of technologies that fit into their aspiration, tradition and socio-cultural values with their participation in the generation and evaluation of the technologies. This study was to identify alternative land preparation methods for increased productivity and economic profitability, while maintaining or enhancing the soil quality of the Vertisols. The hypothesis tested was that the alternative land preparation methods improve soil productivity and maintain or enhance soil quality. Three alternatives, Broad Bed and Furrow (BBF), Green Manure (GM) and Reduced Tillage (RT) with the traditional method, Ridge and Furrow (RF) were compared for 6 years, setting crop yield, economic profitability, and soil erosion and soil quality as performance indicators. This on station experiment was complemented by a participatory assessment at a small watershed scale. The objectives of the latter were identification of local soil functions, definition of soil quality concepts, and identification of soil quality indicators and evaluation of the soils for the major functions. Land preparation methods influence soil functions through their effects on soils qualities. Among the soil physical quality indicators considered, GM increased aggregate stability and reduced surface crust strength due to its increased OM content and microbial activities. While RT led to least penetration resistance, infiltration, water-holding capacity, and moisture content were less sensitive to the treatments. The chemical characteristics and plant nutrients response was not consistent indicating the need of longer time for the effects to show a clear trend. Organic carbon and MBC content of the soil increased due to RT and GM, but the increment was not proportional leading to lower microbial quotient. This indicates SOM build up with a long-term soil quality improvement. The effect on runoff was inconsistent during the first three years (1998-2000), but BBF and RT slightly increased. In 2001 and 2002, BBF drained 67% and 54 %, respectively, of the seasonal rainfall as runoff while RT routed 61% and 53%. There is a non significant tendency of increased soil and nutrient losses from BBF and RT due to the increased runoff. BBF significantly increased the grain yield of lentils by 59% (1.03 t ha-1 to 1.63 t ha-1) compared to the control. Similarly, RT resulted in the highest grain yield of wheat (1.86 t ha-1) and tef (1.34 t ha-1). Economically, BBF is the most profitable option for lentils with 65% increase in total gross margin while RT resulted in 11% and 8% increase in gross margin of wheat and tef, respectively, as compared to the control. The soil quality index was not significantly affected by the land preparation methods. Nevertheless, GM has shown a slight enhancement with the highest SQI, followed by BBF and RT. Thus, the land preparation methods are favoured in order of GM> BBF> RT> RF, for soil quality. The relative enhancement of soil quality by GM was linked mainly to its increased Corg content. The performance indicators (productivity, economic profitability, soil conservation and soil quality) are also affected differently. A matrix ranking of the effects on the indicators showed that none of treatments is superior for all the indicators. The average of the ranks (no weight attached) showed that BBF was the most favourable followed by RT. Therefore, the methods are preferred in the order of BBF> RT>GM=RF considering the overall indicators. The superiority of BBF and RT corresponds to their productivity and economic benefits. For soil quality and erosion control, GM is a favourable option. However, as its economic benefit was low, further improvement is required. In addition, lack of fast growing legumes tolerant to both shortage and excess water, failure of the short rain for planting, cost of chopping and incorporating the cover crops and the possible need of special equipment for incorporating may hinder its wider application and hence need further investigation. The success of the alternatives depends on the farmers? capacity and willingness to invest. As the issues of soil quality and land degradation are more of societal concerns than of the individual farmers, external technical and financial incentives are desirable to enhance their capacity and to initiate their interest. Institutional and policy issues influencing agriculture and natural resource management and uncertainties like variation in weather deserve judicious consideration.
Die Ökobilanz zur Abschätzung von Umweltwirkungen in der Pflanzenproduktion - dargestellt anhand von Praxisversuchen zur konservierenden Bodenbearbeitung und von unterschiedlich intensiv wirtschaftenden konventionellen Betrieben
(2003) Arman, Beate; Claupein, Wilhelm
In the agricultural field difficulties in life-cycle assessment result from the fact that the methods of life-cycle assessment were developed in techno-industrial production. Agricultural production, however, differs from industrial production in that it depends more strongly on natural resources and, moreover, has a direct influence on them. Hence, apart from preparing data for the used production goods, the expansion of environmental impact categories to include specific effects from agriculture is focused on in the adaptation of ecobalances as an agricultural method. Among others deficiencies here include the balancing of effects in agriculturally utilized soil. The ecobalances at hand were carried out with two different goals in mind. For one, the impact of conventional and conservational cultivation methods were to be balanced. The goal of this ecobalance was to show whether life-cycle assessment have adequate selective power in order to be used as a decision criterion in the optimisation of cultural methods and their environmental impact. For another, the intensity of cultivation of three agricultural enterprises was compared. It was to be shown here whether life-cycle assessment can provide transparency as to the environmental effects of various production methods, which would enable the consumer to obtain information on the environmental relevance of these methods. A further goal of this work was the development of a method for the recording of effects on the soil in life-cycle assessment. The examined farms are situated in the Hohenlohe region and were integrated in the subproject "Conservation Tillage" of the "Cultural Landscape Hohenlohe" project group. In order to balance soil working methods, the three methods plow, cultivator and mulch sowing were examined. The data was obtained from two test fields with the same crop rotation on one of the farms. Balancing of the intensity of cultivation was carried out on three conventionally working farms using varying levels of fertilizer, crop protectants and tillage. The balanced crop rotation of the three farms did not vary (sugar-beets, winter wheat, winter barley). When developing methods for balancing environmental effects on agriculturally utilized soil three aspects were decisive in the selection of balanced effects: 1. What soil properties are there? 2. Which of these properties are influenced directly by cultivation measures? 3. For which properties are relevant negative effects caused by agriculture known? Based on the indicated methods the impact was assessed for the following soil properties: - Soil depth is influenced by soil loss. Soil loss was calculated with the universal soil loss equation. - Impact on the nutrient content was assessed with the help of a nutrient field balance, humus content with the help of a humus balance. - Variations in soil density caused by loading were assessed with the help of the weighted soil load. - Soil life is affected by pollutant input, modelling of the effect potential was carried out with the help of the Critical-Surface-Time model. All in all the results show that in order to differentiate between the tillage variants with respect to their environmental impact, it is necessary to also consider effects on the soil. Comparison of the farms showed that life-cycle assessment can reflect the environmental relevance of different cultivation intensities and can make them visible for the consumer.
Re-plant problems in long-term no-tillage cropping systems : causal analysis and mitigation strategies
(2016) Afzal; Neumann, Günter
No-tillage is considered as a promising alternative for tillage-based conventional farming, by saving energy-input and time, reducing groundwater pollution and counteracting soil erosion and losses of the soil-organic matter. However, in the recent past, no-tillage farmers in Southwest Germany repeatedly reported problems particularly in winter wheat production, characterized by stunted plant growth in early spring, chlorosis, impaired fine root development and increased disease susceptibility. These symptoms were particularly apparent on field sites with long-term (≥ 10 years) no-tillage history (LT) but not on adjacent short-term (≤ 2 years) no-tillage plots (ST). The effects could be reproduced in pot experiments under controlled conditions, with soils collected from the respective field sites in five different locations, providing a basis for causal analysis. The expression of damage symptoms in pot experiments with sieved soils, excluded differences in soil compaction, induced by long-term no-tillage farming as a potential cause. Soil analysis revealed higher levels of soil organic matter in the topsoil, as expected for LT field sites and no apparent mineral nutrient deficiencies, both, on LT and ST soils. However, phosphate (P) deficiency was characteristic for plants grown on LT soils. Obviously, this was caused by the limited acquisition of sparingly soluble soil P, due to impaired root development but not by low P availability on LT soils. In four out of five cases, gamma-ray soil sterilization did not affect the expression of plant damage symptoms on LT soils, excluding pathogen effects as a major cause. Soil application of biochar, at a rate of 5% (v/v), rapidly restored plant growth on LT soils, detectable already during the first week after sowing. This finding points to the presence of a phytotoxic compound since binding of soil xenobiotics by biochar is well documented. Accumulation of allelopathic compounds, originating from crop residues and root exudates remaining in the topsoil, is a problem related to no-tillage farming, particularly in cases of limited crop rotations or in monocultures, which also applied to the investigated field sites. However, a specific wheat auto-allelopathic effect is unlikely, since similar crop damage was also observed in soybean, sunflower, oilseed rape and various cover crops. Typical for allelopathic effects, in the pot experiments, plant damage symptoms in winter wheat appeared rapidly during emergence and early seedling development. However, under field conditions, germination and early growth were usually not affected, and symptoms were first detectable during re-growth in early spring. Moreover, damage symptoms disappeared when soil sampling was performed in summer instead of early spring, suggesting degradation of the toxic compound, which is also not compatible with the hypothesis of long-term accumulation of allelopathic compounds. The observed temporal pattern of plant damage rather resembled residual effects, occasionally observed after application of certain herbicides with soil activity (e.g., sulfonylureas, propyzamide). Therefore, a systematic survey of herbicide residues was conducted for topsoils on six pairs of LT and ST-field sites. Characteristic for no-tillage farming, glyphosate was the only herbicide, commonly and regularly used on all investigated field sites. The soil analysis revealed higher levels of glyphosate residues on all investigated LT, soils as compared with directly neighboured ST plots. Particularly on LT plots with strong expression of plant damage symptoms, high concentrations of glyphosate (2-4 mg kg-1 soil), and of its metabolite AMPA were detected in the 10 cm topsoil layer. This concentration range is characteristic for residual levels, usually observed several days after glyphosate applications but was still detectable in early spring, six months after the last glyphosate treatment, while only trace concentrations below the detection limit (0.05 mg kg-1 soil) were found in ST soils. Coinciding with the declining plant damage potential, residual glyphosate and AMPA concentrations on LT plots declined during the vegetation period until early summer. No comparable pattern was detectable for residues of other herbicides, such as pendimethalin and propyzamide. Degradation of glyphosate residues in soils correlates with microbial activity. Accordingly, reduced soil respiration as an indicator for microbial activity was detected in four out of five cases in soil samples collected from LT field sites, suggesting delayed glyphosate degradation as compared with ST plots. Due to rapid adsorption, glyphosate usually exhibits extremely limited soil activity. However, at least trace concentrations of glyphosate and AMPA (1.5-3.5 µg L-1) were detectable also in the potentially plant-available, water-soluble phase in spring samples, collected from LT field plots with high potential for plant damage. Nutrient solution experiments, with 3-6 weeks exposure of winter wheat to the residual herbicide concentrations detected in the LT soil solution, revealed the development of chlorosis and similar to soil experiments, a 30%-50% reduction in fine root production, which surprisingly was mainly induced by AMPA and to a lesser extent by glyphosate itself. Accordingly, both, in hydroponics and LT soil experiments, the plant damage symptoms were not associated with shikimate accumulation in the root tissue as a physiological indicator for glyphosate but not for AMPA toxicity. The dominant role of AMPA toxicity also became apparent by the fact that, both, glyphosate resistant (GR) and non-resistant (NR) soybean plants were affected on LT no-tillage soils since transgenic GR plants are not resistant to AMPA. A preliminary RNAseq gene expression analysis of the root tissue just prior to the appearance of visible plant damage symptoms, revealed down-regulation of genes involved in general stress responses, down-regulation of aquaporin genes (PIPs and TIPs) with functions in water uptake and root elongation, down-regulation of ethylene-related genes but up-regulation of cytokinin-related gene expression indicating interferences with hormonal balances. These changes in gene expression patterns relative to the untreated control were detected in plants treated with AMPA and glyphosate+AMPA but not with glyphosate alone. The findings suggest that long-term exposure to subtoxic levels of AMPA, as major glyphosate metabolite temporally accumulated in LT no-tillage soils, can finally interfere with metabolic processes essential for normal root development. A series of pot and field experiments were initiated to test the potential of selected commercial formulations of plant growth-promoting microorganisms, based on strains of Pseudomonas sp., Bacillus amyloliquefaciens, and Trichoderma harzianum, for mitigation of plant stress symptoms, expressed on LT no-tillage field sites in spring. For members of the selected microbial genera, root growth-promoting effects, pathogen suppression, and glyphosate degradation potential have been reported. Unfortunately, plant growth promotion was detectable only on ST soils but was not successful on LT plots, both, in pot and field experiments, probably related to limited root development for microbial colonization and early summer drought under field conditions. As an alternative approach, incorporation of pyrolysis biochar from woody substrates at a rate of 5 % (v/v) to the top 10 cm soil layer of LT soils, equivalent to approx. 35 t ha-1, were able to restore plant growth completely in pot experiments and protected wheat plants from glyphosate overdose applications (up to 8 L Roundup Ultramax® ha-1), even on artificial substrates with low potential for glyphosate adsorption. As a short-term mitigation strategy, field-testing with different biochar concentrations is recommended. During the last two years, farmers also modified their no-tillage management strategies on the investigated field sites by introducing more variable crop rotations including, winter wheat, winter rape, maize and soybean and using mustard, pea, and Crotalaria as cover crops. Despite further annual applications of glyphosate (3 L ha-1 of a 360 g ai L-1 formulation), plant performance on the respective field sites was significantly improved. These observations suggest that limited crop rotation favored the development of a soil microflora with low degradation potential for glyphosate, leading to a decline in degradation rates of glyphosate soil residues and underline the importance of crop diversity management.