Browsing by Subject "Fertilization"

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Bedarfsgerechte Stickstoffernährung von Hopfen (Humulus lupulus L.) durch Düngesysteme mit Fertigation
(2021) Stampfl, Johannes; Ebertseder, Thomas
In terms of quantity, nitrogen is the most important and most yield limiting plant nutrient in hops (Humulus lupulus L.), whereby excess nitrogen not taken up by the hop plant is subject to various loss processes. Despite that, little is known about the exact effects of an N supply varying in rate and timing for the hop varieties and cultivation systems currently used in the Hallertau, the worlds most important hop-growing region. In the Hallertau, the required amount of nitrogen is largely supplied by surface spreading of granulated N fertilizers, whereas in semi-arid growing regions, high proportions are applied via irrigation water (fertigation). The aim of this thesis was to examine nitrogen fertilization systems with fertigation under the conditions in the Hallertau region with regard to a nitrogen nutrition that is based on the hop plant’s needs. Therefore, four research questions with different sub-aspects have been formulated, as explained below. From 2017 to 2019 the experimental research and the acquisition of empirical data has been conducted in various field trials consisting of three trial series examining the most important hop varieties at different locations. Apart from a variation in rate and timing of N fertilization, different fertilizer application forms (surface application of granulated fertilizer and above- or below-ground fertigation) have also been examined. In addition to the determination of yield, quality and N-uptake at the time of harvest, further analysis methods such as the 15N-Tracer-Technique, chlorophyll value measurements (SPAD-Meter) or passive reflection measurements were used in individual field trials to depict the N-uptake and N-distribution in different parts of the plant. a) Which effects have different nitrogen treatments varied in rate and timing? These studies found that the hop plant absorbs more than two thirds of the total amount of nitrogen over a period of 7 to 8 weeks between early June and end of July - during formation of main biomass. Despite the fact that only a low amount of nitrogen is accumulated in the plant prior to this stage, the varieties Perle and Tradition showed that a nitrogen deficit in early growth stages until end of May already leads to a decrease of yield potential. This is due to a change in the variety-characteristic formation of lateral shoots (side arms) - the later the application of nitrogen, the greater the formation of side arms was reduced, starting from the bottom to higher plant sections. Consequently, a nitrogen fertilization solely based on the hop plant’s N uptake curve cannot be recommended, neither regarding yield formation nor nitrogen utilization. Instead, an early application of the first nitrogen treatment in April is of vital importance for early maturing varieties such as Perle and Tradition. Late maturing varieties like Herkules show a higher potential of compensation due to prolonged growth phases which enables a higher adaption of N-Fertilization to the plant’s N uptake curve. The ideal amount of nitrogen fertilization with regard to yield optimization has been determined by the growth pattern - depending on variety, weather conditions and location - and therefore by the N uptake, the supply of mineral nitrogen in the soil as well as the location-specific N mineralization potential. A reduction of the nitrogen fertilization to a level significantly below the plant’s N uptake not necessarily led to a limitation of biomass and yield formation in the same year, however, it resulted in an accelerated ripening and a negative impact on external cone quality. Furthermore, it showed that the storage of nitrogen in specific storage roots declines if N levels are significantly reduced, leading to lower vitality as well as limited plant development and yield formation in the following year. With regard to the hop plant’s perennial properties as well as the goal to achieve a demand-oriented nitrogen nutrition of the hop plant it is also necessary to supply the storage roots with enough nitrogen. With respect to valuable contents of alpha acid it has been found that high N supply levels during the stage of alpha acid synthesis (starting from early August) can result in a reduction of alpha acid concentration in the variety Herkules. This decrease can be caused by late and excessive N fertilization as well as by high mineral N contents in the soil. However, this effect has not been observed in the aroma varieties Perle and Tradition. b) Is it possible to determine the current nitrogen nutritional status through non-invasive methods? The measurement of the chlorophyll value with a SPAD-Meter on the lower leaves of the main shoot generally reflected the N content and N supply status of the hop plant. However, short-term changes in the N nutritional status could not be recorded with sufficient accuracy at this measuring point, especially not during the stage of main biomass formation, since increased proportions of the applied nitrogen were transported to higher plant sections, as was shown by the use of 15N. Regarding the determination of threshold values a classification of the plant development into before, during and after main biomass formation independent of the measuring point, is considered appropriate, since the chlorophyll value correlates with the plant’s development stage. Vegetation indices, calculated on the basis of reflectance spectra, represent not only the N content but also the actual N uptake of the crop, which is why passive reflectance measurement methods have a higher informative value with regard to the current N supply status of the plant compared to chlorophyll value measurements. Therefore, this technology could be used to achieve a site-specific optimization of rate and timing of N fertilization and thus a more demand-oriented nitrogen nutrition of the hop plant in the future. c) What are the effects of surface and subsurface drip irrigation? In the period from 2017 to 2019, additional irrigation of the aroma variety Perle on sandy soil led to a stabilization of the agronomic parameters cone yield and alpha acid content every year. In addition, irrigation also achieved an improvement of nitrogen utilization. Compared to subsurface systems, surface drip irrigation achieved a higher efficiency if the horizontal water distribution was limited by hydraulic soil properties. It was shown that this is due to the fact that the majority of the hop plant’s fine root system is located in the hill formed along the hop rows and the soil layers beneath it. d) What are the effects of a nitrogen nutrition via irrigation water? A system comparison was made between N fertilization systems with fertigation and a solely granulated N application. The use of fertigation resulted not only in an improvement of cone yield and alpha acid content, but also in an increase of the plants nitrogen uptake and a reduction of Nmin content in the soil, which is also associated with a reduction of the risk of nitrate leaching into the groundwater. Fertilization systems with fertigation achieved a higher nitrogen utilization especially at low N-fertilization rates. If two thirds of the total amount of nitrogen were applied via irrigation water, the concentration over a 6-week period proved to have a positive impact on all analyzed varieties, especially under conditions of a limited N supply, since a higher proportion of N has been applied during main biomass formation and the stage of lateral shoot growth. For an efficient N-fertilization with fertigation the application should take place between mid-June and late July while no significant amounts of nitrogen should be applied after early August. For early maturing varieties such as Perle and Tradition, there is a risk of a late N application as it is hardly possible to lay out the drip tubes before the 25th week of the year. Therefore, in early maturing varieties, a higher proportion of N should be applied in earlier growth stages while the amount of N applied via fertigation should be less than two-thirds of the total amount of N fertilizer. A substantial advantage of fertilization systems with fertigation is that nitrogen applied via the irrigation water is immediately absorbed by the plants, which allows an effective short-term intervention in the plant’s nitrogen nutrition. On the basis of a reliable recording of the current N supply status with sensors during the main growth stage, fertigation could be used to adjust the N fertilization in order to achieve a site-specific and demand-oriented nitrogen nutrition of the hop plant.
The effects of leguminous living mulch intercropping and its growth management on organic cabbage yield and biological nitrogen fixation
(2022) Stein, Sophie; Hartung, Jens; Möller, Kurt; Zikeli, Sabine
In organic horticulture, living mulches (LM) are used for weed suppression and erosion prevention. In addition, leguminous LM can contribute to higher nitrogen (N) import into vegetable cultivation systems via biological N2 fixation (BNF). In order to investigate the effect of LM systems, a two- as well as three-year field experiment was conducted between 2019 and 2021 at two locations in Southwest Germany. White cabbage was intercropped with two different clover varieties (Trifolium repens cv. ‘Rivendel’, with regular growth and T. repens cv. ‘Pipolina’, a micro clover) and perennial ryegrass (Lolium perenne cv. ‘Premium’). Bare soil (with spontaneous vegetation) without intercropping was the control treatment. The second factor was the growth management of the LM: incorporation by rototilling before planting the cabbage, intercropping with the cabbage and no LM growth management, and intercropping with mulching of the LM during the cabbage growing. The results show that rototilling LM before planting the cabbage did not lead to higher weight of cabbage residues or differences in total head yield among the treatments for growth management. Intercropping without further LM growth management did not result in a reduced total head yield of cabbage compared to mulching. The micro clover ‘Pipolina’ showed no reduced competition with cabbage compared to the regular-growing white clover ‘Rivendel’. Therefore, we conclude that leguminous LM systems, regardless of growth management, can achieve high yields with sufficient irrigation and additional fertilization while increasing the inputs of N via BNF into the entire cropping system.
Evaluation and improvement of N fertilization strategies in the wheat/maize double-cropping system of the North China Plain
(2015) Hartmann, Tobias Edward; Müller, Torsten
The North China Plain (NCP) is the main production area of cereal crops in China. The intensification of agricultural systems and the increased use of chemical N fertilizers are contributing to environmental pollution. One of the objectives of this thesis was to apply an Nmin based approach for the calculation of N application rates to a previously over-fertilized farmers field of the NCP and to evaluate the potential of reducing N inputs while maintaining the grain yield of a summer-maize/winter-wheat double-cropping system; and to evaluate fertilizer strategies, aiming to reduce N inputs and loss. Using an Nmin based approach for the calculation of fertilizer application rates, a reduction of fertilizer input by up to 50% compared to farmers practice (550 kg N ha-1 a-1) is possible without negatively affecting the grain yield of a wheat / maize double cropping system. The extreme re-supply of N during the summer-vegetation periods of maize in the first two experimental seasons resulted in high yields of the control treatment (CK: 2009: 5.7 and 2010: 5.9 Mg ha-1), which did not significantly differ from the fertilized treatments. This resulted in a reduced recovery efficiency of N (REN: 0.09 kg kg-1 – 0.30 kg kg-1). According to the results of this field experiment there was no agronomic justification for the application of fertilizer N. The grain yield of maize of the control treatment finally decreased in the third vegetation period of summer-maize. While maintaining the yield level, the optimized application of N increased REN (0.37 – 0.58 kg kg-1) significantly compared to farmers practice (0.21 kg kg-1) in this final vegetation period of maize. Wheat, in contrast to maize, is dependent on the application of fertilizer N for yield formation. In both vegetation periods of wheat, REN of the reduced treatments (0.34 – 1.0 kg kg-1) was significantly higher compared to FP (0.26 and 0.27 kg kg-1). The highest cumulated (5 vegetation periods) agronomic efficiency of N, as well as cumulated grain yield of the wheat/maize double-cropping system was observed when ammoniumsulphate-nitrate was applied in combination with the nitrification inhibitor 3,4-dimethylpyrazolephosphate (ASNDMPP: AEN: 19 kg kg-1, yield: 35 Mg ha-1) and according to crop N demand and residual soil mineral N. The highest REN was observed when urea ammonium nitrate was applied in a shallow, banded depot (UANDEP: 40 kg kg-1). The results of this field experiment further show that the N surplus (fertilized N - grain N) as well as the N balance (N Input - N output) after harvest are significantly lower when an optimized approach to fertilizer application is followed. The over-application of N for an optimized application of urea or ASNDMPP (Surplus: -25kg to 98 kg N ha-1; Balance: -36 to 102 kg N ha-1) was significantly reduced compared to current farmers practice (Surplus: 156kg to 187 kg N ha-1; Balance: 56 to 262 kg N ha-1). This leads to lower residual N in the soil horizon from 0 - 90 cm in the reduced treatments (113 kg N ha-1 at end of experiment) compared to FP (293 kg N ha-1). The results of this experiment indicate that N contained in the residues of maize is available only to the subsequent summer-crop and may sufficiently supply N for the yield formation of maize. Should the over-application of N be effectively reduced in the cropping systems of the NCP it is therefore necessary to take the N mineralization potential of soils into account. Based on the results of this field experiment and others, a crop-soil interface model (HERMES) was calibrated and validated to the conditions of the NCP. Finally, this research observed the effect of wheat straw and the urease inhibitor (UI) N-(n-buthyl) thiophosphoric triamide (nBPT) on the turnover of urea, as well as the loss of ammonia and nitrous oxide from an alkaline soil of the NCP. UI inhibit or reduce the appearance of ammonia after the application of urea and almost completely prevent the loss of N as ammonia (urea: 12 – 14% loss). nBPT effectively reduces the rate of urea hydrolysis but does not down-regulate the process enough to completely inhibit nitrification, thereby maintaining the availability of N from urea for plants. Further, the addition of wheat straw prolongs the appearance of ammonium after the application of urea while the appearance of nitrate is reduced. Wheat straw may therefore either act as a stimulant of hydrolysis or as an inhibitor of nitrification. The addition of urea increases soil respiration and the emission of N2O drastically, possibly acting as a C and N source for microbial organisms and causing a priming effect on microbial activity in soils. This effect was increased further when wheat straw as well as urea were added to soil. nBPT, in contrast, prevents a significant increase in CO2-respiration and N2O-emission. The urease inhibitor may therefore generally restrict microbial activity or shift nitrification/denitrification processes towards the emission of N2.
Formation of mineral‐associated organic matter in temperate soils is primarily controlled by mineral type and modified by land use and management intensity
(2023) Bramble, De Shorn E.; Ulrich, Susanne; Schöning, Ingo; Mikutta, Robert; Brandt, Luise; Poll, Christian; Kandeler, Ellen; Mikutta, Christian; Konrad, Alexander; Siemens, Jan; Yang, Yang; Polle, Andrea; Schall, Peter; Ammer, Christian; Kaiser, Klaus; Schrumpf, Marion
Formation of mineral-associated organic matter (MAOM) supports the accumulation and stabilization of carbon (C) in soil, and thus, is a key factor in the global C cycle. Little is known about the interplay of mineral type, land use and management intensity in MAOM formation, especially on subdecadal time scales. We exposed mineral containers with goethite or illite, the most abundant iron oxide and phyllosilicate clay in temperate soils, for 5 years in topsoils of 150 forest and 150 grassland sites in three regions across Germany. Results show that irrespective of land use and management intensity, more C accumulated on goethite than illite (on average 0.23 ± 0.10 and 0.06 ± 0.03 mg m−2 mineral surface respectively). Carbon accumulation across regions was consistently higher in coniferous forests than in deciduous forests and grasslands. Structural equation models further showed that thinning and harvesting reduced MAOM formation in forests. Formation of MAOM in grasslands was not affected by grazing. Fertilization had opposite effects on MAOM formation, with the positive effect being mediated by enhanced plant productivity and the negative effect by reduced plant species richness. This highlights the caveat of applying fertilizers as a strategy to increase soil C stocks in temperate grasslands. Overall, we demonstrate that the rate and amount of MAOM formation in soil is primarily driven by mineral type, and can be modulated by land use and management intensity even on subdecadal time scales. Our results suggest that temperate soils dominated by oxides have a higher capacity to accumulate and store C than those dominated by phyllosilicate clays, even under circumneutral pH conditions. Therefore, adopting land use and management practices that increase C inputs into oxide-rich soils that are under their capacity to store C may offer great potential to enhance near-term soil C sequestration.
Nutritional and climatic effects on berry shrivel of grapevines in Southern Germany
(2012) Bachteler, Kristina; Wünsche, Jens Norbert
Berry shrivel (BS) is one of the economically most important physiological disorders in grapevine, but it is also one of the least studied ones. At the beginning of the ripening process, berries stop accumulating sugars and lose their turgescence. The must weight remains low, the berries taste sour and bitter. During the last ten years, several studies were conducted to narrow eliciting factors. As a result, an unbalanced ratio of K and Mg in the soil was considered likely to induce BS. To verify this hypothesis, two fertilization trials with two different varieties each, one via the soil and one foliar fertilization trial, were initiated. Within two years, no effect on the incidence of BS was evident. In the foliar fertilization trials, Mg, K and Ca fertilizers were tested with their effect on BS. For the first year, no significant differences could be observed. In the second year, more berries were affected by BS in the plots treated with Ca fertilizer. The plots with Mg fertilizer showed significantly less berries affected by BS than the untreated control in one variety. Extensive analysis of concentrations of Ca, Mg and K in berries illustrate that berries affected by BS show significantly higher concentrations of Ca compared to healthy berries. The loss of quality of wines made of berries affected by BS was demonstrated by must and wine analysis as well as by a consumer preference analysis. Phenolic compounds (in particular resveratrol) that are often used as indicators of abiotic stress were analysed as well. It was supposed that BS is caused or increased by abiotic stress so that the concentration of resveratrol in berries affected by BS is increased as well. However, in all varieties analysed, the concentration of resveratrol was higher in healthy berries than in affected ones. A direct connection between weather condition at bloom and especially at ripening was examined. Observations at monitoring sites and reports from other countries seem to show that cool and wet weather at these phenological stages might increase the risk of BS. It was only possible to statistically prove a connection between the precipitation at bloom and the incidence of BS.