Einfluß der N-Düngung auf Ertragsentwicklung landwirtschaftlicher Kulturen und Veränderung des mineralischen N-Gehaltes im Boden bei achtjährigen Dauerversuchen

Influence of long-time Nitrogen-fertilizing on yield response of agricultural crops and mineralized Nitrogen in soil
In the years 1979–1986 a fertilizer trial with increasing Nitrogen amount was performed in order to prove the N_min-method according to S charpf and W ehrmann . The N_min-method regards the mineralized N in soil (N_min) for optimizing the N-fertilizer amount at the begin of vegetation, could be confirmed. The optimal N-rate (including N_min) was for winter wheat and winter barley 120 kg/ha, winter rye 100 kg/ha and sugar beet 200 kg/ha. For cereals additional N-rates were given at the end of tillering 20 kg/ha N and at ear emergency 60 kg/ha N. For the optimal N-fertilizing system we found a positive N-balance (input-output) in a range of 10–25 kg/ha. The influence of N-fertilizing on the mineralized N-amount in soil was very small comparing to influence of weather, soil type or crops. Only at one location a little increase of N_min (10–15 kg/ha) could be observed after a positive N-balance (50 kg/ha).     

N-Dynamik des Bodens, Ertragsbildung und Stickstoffentzug von Winterweizen bei unterschiedlicher Höhe und Verteilung der mineralischen N-Düngung

NO₃ dynamics in the soil, yield formation and N uptake of winter wheat as influenced by dosage and distribution effects of N-fertilizer application
In a 4 year series of field trials carried out with 9 regimes of nitrogen fertilizer application at two trial sites with rather shallow top soil layers but large deviations in soil characteristics, grain yield varied between 50 dt/ ha and 120 dt/ha with nitrogen doses from 0–170 kg N/ha. Soil nitrogen supply for wheat grain formation on unfertilized plots reached 80 kg N/ha/year within the narrow range of 75–95 kg N/ha in different years at both sites which amounts to 1.5 % and 0.5 % of the highly different N-content of the trial sites.
The most successful nitrogen application regimes are characterized by modest fertilizer doses in early spring and the delay of supplemental fertilizer doses until growth stage EC 32. They resulted into modest NO) soil content from EC 29 to EC 32 and/or a noticable decrease of soil NO₃ content during growth stage EC 30–32, which seems to be responsible for the development of only modest stand densities and reduced straw yield, while the delayed supplementation with nitrogen fertilizer overcompensated these effects mainly by increased grain numbers/ear and a remarkable improvement of harvest index.
The contribution of soil borne nitrogen to kernel yield formation started to decrease with even low dosages of supplemental nitrogen fertilization with the exception of the highest yielding season 1987/88. Top levels of grain yield have been regularly obtained with supplemental nitrogen fertilizer dosages about 40 kg N/ha below grain yield nitrogen extraction if they were added within favorable application regimes.     

Auswirkungen eines 10-jährigen Miscanthusanbaus auf ausgewählte Eigenschaften eines Mineralbodens in Nordostdeutschland

Effects of 10 years of Miscanthus cultivation on different properties of mineral soil in North-east Germany
The effects of 4–10 years of Miscanthus cultivation on different soil properties was investigated at Klein Markow (Mecklenburg-Pommerania, Germany) in variants with and without Miscanthus between 1994 and 2000. Soil containing Miscanthus showed higher concentrations of organic carbon (C_org) (+0,29 %) and total nitrogen (N_t) (+0,03 %) and consequently an increased storage of soil organic matter (SOM) (+15,5 t ha^–1) as a result of high amounts of leaves, roots and rhizomes. With regard to concentrations of C_org, cation exchange capacity, porosity and water retention significantly increased, while the wet and bulk density decreased in Miscanthus variants. The concentration of C_org and storage of SOM were increased significantly during the experimental period of Miscanthus treatments. The mineralization of the organic soil compounds which developed was comparable with those of the SOM. The reintegration of the Miscanthus area into a crop rotation system was possible only after the last harvest in February and seed of winter rape in August of the same year. The application of Glyphosat and the later shading by rape stands led to failure of the Miscanthus cultivations.     

Soil Temperature Simulation with Varying Residue Management

Maintaining crop residue on the soil surface is an important part of conservation tillage. Although broad effects of residues on soil temperature (T_s) are well documented, the methods to predict soil temperatures under various surface residues and tillage conditions are limited. Using the T_s at 0-, 0.05-, 0.10-, and 0.30-m depths, we developed a simplified model to predict T_s for a uniform soil from air temperature (T_a) data. Data were collected under various tillage and surface residue conditions after wheat ( Triticum aestivum L.) harvest. Residue management treatments were disk, sweep, and no-tillage (with standing or shredded residues). The model predicts maximum and minimum T_s at 0-, 0.05-, 0.10-, and 0.30-m depths using maximum and minimum T_s measured at 2-m above the soil surface, residue mass, apparent thermal diffusivity, and initial Ts profiles. Mean absolute deviation between simulated and measured maximum and minimum surface T_s were 0.53 and 0.44 °C or less, respectively. Root zone maximum and minimum T, were simulated within 0.14 to 0.91 and 0.27 to 0.95 °C, respectively, of the measured T_s. Greater precision of maximum and minimum soil temperature predictions with depth was obtained by using apparent thermal diffusivity calculated from initial T_s profiles. The proposed model can be useful in predicting T_s profiles required for crop growth modeling.     

Irrigation Scheduling and Watermelon Yield Model for the Jordan Valley

A crop yield and soil water management simulation model (CRPSM) developed at Utah State University was modified, calibrated and tested using local weather data and field results from a trickle irrigation experiment with different mulching on watermelon ( Citrullus lanatus ), carried out at the University of Jordan Research Station, in the Jordan Valley.
Simulated irrigation schedules were then applied with some of the four options provided by the model. The water yield index, WYI, introduced by B attikhi and H ill (1985) to select the most efficient schedule as based on yield and water use efficiency, was then determined. WYI ranged from 27 to 87. The field schedule, WM₂, had a WYI of 62. Whereas, the model provided a much better schedule, WM₇ (WYI = 86). WM₇ requires 17 irrigations of 2.0 cm per irrigation totaling a water supply of 44.1 cm with an irrigation season starting on April 7 to give a yield equivalent to the potential yield, 80.0 MT/ha. On the other hand, the best field schedule, WM₂ under transparent mulch, required 14 irrigations to provide 45.9 cm (including rainfall and soil moisture change), with a season starting on April 28 resulted in a yield of 68.8 MT/ha. So we can see that by using the same amounts of total water supply but with different schedule we can get the potential yield. The model has, therefore, provided few better schedules that can be tested in the field at lower costs before final recommendations are made.     

Studies on Plant Type of Certain Forage Crops

A field experiment was conducted at Indian Grassland and Fodder Research Institute, Jhansi to study the plant type of certain forage crops (G uar — GL 7, GL-8, HFG-119, IGFRI-212 and Guar-80; Dinanath grass — P₁ and P₂; Pigeonpea — 3029, 6986, 7086; Bajra — rajko; Sunhemp-1; M. P. Chari; Sesbania egyptica ; Sesbania annuals) on the basis of their growth behaviour, plant canopy, bare length in monoculture at two stages of crop growth, so that these results may be critically assessed and incorporated while formulating the forage system sysnthesis for reaping high biomass produce per unit area. It was noted that growth rate and bare length were initially lower which markedly increased at second stage of crop growth except guar. Growth rate und bare length were in the order of M. P. C hari > Sunhemp > Sesbania annuals > Dinanath grass — P₁; while this order was reverse for growth rate. Among legume crops the plant type sunhemp was superior over pigeon pea and guar. Pigeon pea had highest growth rate and low bare length as compared to guar except the variety Guar-80. In view of achieving potential biomass production these data may be computed in formulation of various system where C₄ plants — bajra-rajko/M. P. C hari (characterised with maximum bare length and poor canopy) and dinanath grass (minimum bare length and thick canopy) is essential; and legumes which showing associative effects find its place in between the crops.     

Cumulative Effects of Pre-sowing Seed Treatment and Foliar Application of Salts in Improving Biomass and Grain Yield of Soybean in Moderate Saline/alkaline Soil

Field trial studies were carried out to find out whether performance of soybean could be improved as a result of pre-sowing soaking treatment of seeds. Comparatively pre-sowing seed treatment with KNO₃, NaNO₃, NaCl, thiourea and di-Ammonium phosphate (DAP) resulted in better development of the root and shoot system than the control. As a result of pre sowing seed treatment, there was an increase in dry matter production by 44, 27 and 32 % over the control in KNO₃, NaNO₃ and DAP treatments respectively. Similarly increase in seed yield was noticed in NaNO₃ (45 %), KNO₃ (40 %) and DAP (50 %) pretreated plants. The number of existing nodules was reduced both in the control and treated plants due to pH (8.4) of the soil.
To investigate the cumulative effects of foliar spray on plants raised from pre-sowing seed treatment, salt solutions (NaCl, KNO₃, NaNO₃, thiourea, DAP) at optimal level were sprayed separately three times at three different stages of development. As a result of foliar spray moderate increase in growth in KNO₃ (20 %), thiourea (29 %) and DAP (25 %) treatment was observed over the control. Seed yield increased significantly (56–70 %) in all treatments except NaCl spray, due to increase in the number of pods (41–63 %) per plant. Foliar spray of nutrients increased protein yield without affecting the oil content. It is suggested that a considerable fertilizer economy may be effected by coupling pre-sowing seed treatment with foliar fertilization.     

Effects of the Application of Amorphous Silica on Transpiration and Photosynthesis of Soybean Plants Under Varied Soil and Relative Air Humidity Conditions

In epidermal cell walls of soybean leaves treated with amorphous silica accumulation of silica could be detected by means of electron microscopy and electron probe microanalysis. This changed the physical properties of the cell wall and affected the cuticular transpiration and uptake of CO₂: When the soil in which the plants were grown was dry (60% of the field capacity) and relative air humidity was below 50 %, the loss of water through the cuticle was smaller than the loss of CO₂ uptake. This caused a higher grain yield under the conditions of temporarily restricted low air humidity.     

Water Stress, Water Use Efficiency, Carbon Isotope Discrimination and Leaf Gas Exchange Relationships of the Bush Bean

Water use efficiencies for the whole plant (WUE₁) and single leaves (WUE₁) were studied in a greenhouse as a function of soil moisture during four phenological stages of bush bean growth. WUE₁ increased significantly with soil moisture stress and attained its maximum value before the flowering stage. WUE₁ and WUE₁ were linearly related ( r = 0.92), and WUE₁ was correlated with the transpiration rate ( r = -0.87), stomatal conductance ( r = -0.80) and photosynthetic rate ( r = 0.81). Carbon isotope discrimination.), decreased as soil moisture decreased, and) was negatively correlated with both WUE₁ ( r = -0.92) and WUE₁ ( r = -0.88). There were significant differences in leaf N among water regimes.     

A Rapid Method for Measuring Freezing Resistance in Crop Plants

The objective of this study was to develop a technique based on chlorophyll fluorescence to assess freezing injury and resistance of leaves. Optimization was done with faba bean leaves and applicability to other crops was examined at winter and spring with types of barley, oats, rape and faba beans. Selected leaves from young hardened beans were subjected to standardized freezing tests with different minimum temperatures ( T _min) and fluorescence was monitored. After a dark period basic fluorescence ( F _O was induced by 0.2 μmol m⁻² s⁻¹ pulsed red light and maximum fluorescence ( F _m) was assayed at different light intensities. 1500 μmol m⁻² s⁻¹ rendered to give the maximum possible output of Fm and best differentiation of differently damaged leaves by F _n= F _m - F _O. Leaf temperature during measurement and during a short storage (± 2 h) should be kept at about 0°C to avoid biases between differently damaged leaves. The measuring spot on the leaf must be standardized since fluorescence response differed at the tip and base of a leaflet, but not between the two leaflets of a faba bean leaf. The applicability of F _rr (ratio of F _r of stressed to unstressed leaves) as a measure of resistance was demonstrated by comparison of winter hardiness of cultivars with freezing resistance calculated from the relationship of F _vr and the T _min used in freezing tests.     

The Effects of Intercrop Spacing Patterns on the Silage Yield of Maize and Soybean

The effects of intercrop spacing patterns on the silage yields of both maize (lea mays L.) and soybean (Glycine max [L.] Merr.) were examined from 1985 to 1987. Dwarf maize was intercropped with nonnodulatmg or nodulating soybean in the spacing patterns, S_40same (two crops in the same row, 40 cm row width) and S_20ait or S_40ak (two crops in alternate rows, 20 cm or 40 cm row width, respectively). Tall maize was intercropped with nodulating soybean in S_40sames S_40alt and S_40pair (maize in 40 cm paired rows, soybean rows 20 cm outside each maize row and 80 cm from the next set of four rows) at 0 or 60 kg N ha⁻¹ and at population densities of 67% maize: 67% soybean or 50 % maize: 50% soybean. Maize and soybean were also intercropped and stripcropped on a farm-scale. The only difference between intercrops arranged in the same rows versus those in alternate rows was that the average soybean protein yields were higher in S_40same than in S_40alt. In 1986, the S_40alt maize-soybean intercrops produced higher maize yields, total biomass yields and Land Equivalent Ratios (LERs) than in S_40pirs, and in 1987, these responses were higher in intercrops than in stripcrops. In 1986, at 0 kg N ha⁻¹, the soybean biomass and protein yields were lower in S_40alt, than in S_40pairs and in 1987, these responses were lower in intercrops than in stripcrops.     

Infiltration of Simulated Rainfall: Dry Aggregate Size Effects

Water conservation often is limited by soil conditions that cause runoff, even from small rainstorms. This study evaluated the influence of tillage-induced aggregates on infiltration into Pullman soil (Torrertic Paleustoll). Tillage methods were PLOW (plowing and disking), ROTO (rotary), SWEEP (sweep), or NOTILL (no-tillage). Aggregate sizes were <0.42, 0.42—0.84, 0.84—2.0, 2.0—6.4, and 6.4—18.3mm. Rainwater was applied until runoff and percolation became constant. Final infiltration (I_f) rates differed due to tillage, aggregate size, and interaction effects, but maximum difference was only 8.1 mm h⁻¹, suggesting that If rate differences have little significance from a water conservation viewpoint during intense, short-duration rainstorms that occur in semiarid regions. Cumulative infiltration (I_c) apparently is of greater significance; it was greatest for large aggregates. The PLOW treatment resulted in most large aggregates and presumably would result in greatest I_c. However, under field conditions, I_c was similar for PLOW and SWEEP treatments. For the SWEEP treatment, tillage undercut the surface and retained more residues, thus negating the advantage of larger, but apparently less stable, aggregates with the PLOW treatment with respect to I_c.     

Das optimale N-Angebot im Frühjahr bei unterschiedlicher Keimdichte von Winterweizen

The optimal N-supply in spring for different plant densities of winter wheat
The influence of plant density (plt./m²) on the optimal N-supply in spring (N_min-content + N-fertilization) has been tested at three sites. The different plant density was produced by different seed rates in autumn of about 150, 250, 350, 450 and 550 grains/m². The N-supply in spring was - apart from a non-fertilized field (N_min-content) 80, 100, 120, 140 and 160 kg N/ha. Additionally, 80 kg N/ha were applicated as N-topdressing. Moreover the optimal N-supply in spring has been tested on a winter wheat field thinned out due to winterkilling. In detail we got the following results:
1. The reduction of the N_min-content due to the N-uptake by the plants slowed down in accordance with minor plant density.
2. The same N-supply in the soil produced a higher N-supply per individual plant in accordance with decreasing plant density and lead to a considerable increase of N-nutrition.
3. Thin crops showed a higher tillering. The differences in plant density between 150 and 550 plt./m² in spring diminished to about 90 ears/m² at harvest.
4. Independently of plant density the maximum yield was obtained by a N-supply (N_min+ N-fertilization) in spring of about 120 kg/ha N. Due to the abundant N-nutrition of the individual plants and the minor increase of yield a higher N-supply is not necessary with a minor plant density.
5. Essentially the yield level was only diminished with the lowest plant density (100-140 plt./m²).     

Stability Analysis of Winter-rape (Brassica napus L.) by Using Plant Density and Mean Yield per Plant

The yield F per area can be expressed multiplicatively by using yield components. For the most simple case of including only two yield components one obtains: F = X₁− X₂ with X₁= number of plants per area (= plant density) and X₂= mean yield per plant.
For normal variables X₁ and X₂ the phenotypic yield stability of F, which has been measured quantitatively by the variance V(F) of F, can be explicitly expressed dependent on 1) the component means, 2) the component variances and 3) the correlation between the two components. V(F), therefore, depends on 5 parameters.
For many applications the use of the coefficient of variation v of F instead of the variance itself may be advantageous, v can be explicitly expressed dependent on 1) the coefficients of variation of the yield components and 2) the correlation between the components, v, therefore, depends on 3 parameters.
The different conditions leading to the same phenotypic yield stability can be investigated by using these explicit expressions for V(F) and v.
The main purpose of the present paper is the application of these theoretical models and results to the data of an extensive field trial with winter-rape, which has been performed for 5 years with 4 plant densities and 3 row distances.
For the lowest plant density (40 plants/m²) there results a very good agreement between the theoretically expected and the experimentally obtained values for the phenotypic stability of yield per area. But, for the higher plant densities this result don't hold true. Possible causes and explanations are discussed in detail.     

Zum Einfluß von Untersaaten zur Begrünung von Ackerbrachen auf die Vegetationsentwicklung und die Nitratdynamik

The influence of undersown green manure crops for fallows – set-aside land – in view of vegetation-development and the dynamic of nitrate
In view of the establishment of rotational fallows - set-aside land - as well as the bridging of the vegetation-free winter period the suitability of different undersown grasses and legumes m winter cereals was investigated in field trials. Festuca rubra developed well in winter barley and winter wheat. The success of the cultivation of Lolium perenne, Trifolium pratense and Trifolium repens in winter cereals is uncertain because of the risk of light and water deficiences. Dactylis glomerata caused an negative influence on the yield of the cover crop. During the fallow period only low levels of nitrate could be found in the soil. Under fallow tilled repeatedly complete fallow- a nitrate accumulation could be observed during the fallow period. After ploughing up the fallow vegetation, nitrate concentrations - depth 0–150 cm – increased to 60 kg NO₃-N · ha^-1 after the natural fallow without seeding, between 60 and 130 kg NO₃-N · ha^-1 after Trifolium and between 160 and 210 kg NO₃-N · ha^-1 after complete fallow. Lowest nitrate levels were observed from the grass-sites. Undersown Festuca rubra seems to be the best choice in order to compete with weeds, to form a dense sod and to prevent nitrate leaching. In general a seed rate of 8 kg · ha^-1 can be recommended.     

Effects of Long-term Application of Slurry on Soil Nitrogen Mineralization

Field trials were conducted for two years on two farms which differed in long-term application of slurry in order to study the long-term effect of slurry and the effect of application time (no slurry, slurry autumn, slurry spring) on the dynamics of nitrogen in the soil.
The results can be summarized as follows:
On the farm with long-term application of slurry, ("livestock farm"), nitrate-content in the soil was markedly higher than on the farm without slurry application ("arable farm"). This is due to a more intensive N-mineralization during autumn and spring. On the livestock farm a remarkably high mineralization of nitrogen was observed at soil temperatures near 0°C, while on the "arable farm" N-mineralization started only at temperatures above +4°C.
The high N-mineralization during autumn on the "livestock farm" implies the risk of N leaching into deeper soil layers during winter.
Slurry application caused a large increase of mineralized nitrogen in soil. No site-differences in decomposition of actual slurry applications have been observed.
High N infiltration-rates may occur when slurry is applied in autumn, depending on the amount of autumn and winter rainfall. Thes risk of nitrogen leaching also persists, when slurry is applied in spring and crops with late N-uptake are cultivated (e.g. sugar beet).
The intensive leaching of nitrogen after application of slurry is caused by the fast nitrification of slurry-NH₄, which may happen even at low temperatures.     

Influence of Soil Drought on Plant Growth, Assimilation and Dissimilation of CO2 and Accumulation of Photosynthates in Field Bean (Vicia faba L. minor) During Pod Formation and Rapid Pod Growth

Field bean planes cultivar Nadwiślański were submitted to soil drought (30 % of field soil water capacity) for 5 days at the stage of pod formation (A) and of rapid pod growth (B) and then exposed for 20 minutes to ¹⁴CO₂. Radioactivity of leaves, stems, roots, and pods or pod shells and seeds was measured 1, 5, 24 and 48 hours after exposition.
In both stages soil drought reduced by about five times total CO₂ assimilation, mainly owing to lower activity of the photosynthetic apparatus and also, though less so, to reduced leaf growth. Photosynthetic activity referred to the dry weight of the leaves dropped to 22-35% of controls. Accumulation of photosynthetates in generative organs was much less depressed than ¹⁴CO₂ assimilation. 48 hours after exposition to ¹⁴CO₂ of drought treated plants, the contents of ¹⁴C of pods in phase A, and seeds in phase B, amounted to respectively 24% and 36% of assimilated ¹⁴C and equalled 91.5% and 74% of the corresponding values for controls.
The progressive decline of radioactivity in leaves and stems after ¹⁴CO₂ exposition was distinctly correlated to the rise of radioactivity of generative organs both in soil drought treated plants and in controls. Slightly lower values of correlation coefficients in drought treated plants may indicate impairment under drought conditions of synchronization in processes of unloading and accumulation of assimilates.
In plants drought treated in phase A the ability to dissimilate ¹⁴C was reduced to about 59% of that in controls, but when drought was applied in phase B, dissimilation rate was about three times as high.     

Ecophysiology of the Plant–Rhizosphere System

The rhizosphere is the site of organic deposition and the generator of habitat and resource heterogeneity for soil organisms. Plants can modify their rhizosphere through nutrient, moisture and O₂ uptake from the rhizosphere, rhizo-deposition and production of root exudates. As a result, rhizosphere chemical (pH, nutrient solubility, O₂, CO₂ and other chemicals), physical (moisture and aeration), and biological (soil pathogens, beneficial microorganisms and allelopathy) characteristics will be changed or modified. Rhizosphere microorganisms have positive or negative effects on plant growth and morphology by affecting the plant hormone balance, plant enzymatic activity, nutrient availability and toxicity, and competition with other plants. Plants modify the rhizosphere and as a result will modify the community.     

Pflanzenwachstum durch CO2/HCO3-Eintrag über die Wurzel

Plant Growth after Application of CO₂/HCO₃ to the Roots
After applying H¹⁴CO₃ to the root system of summer wheat in hermetically sealed pots, absorption and incorporation of HCO₃ in the sugar-, starch-, and fibre-fraction (approximately 50 % of the absorped ¹⁴C) could be shown. This fraction reached 0.44–1.21 % of total C-assimilation of the shoot during growing stage F9/F10 on the Feeke-scala. 1/3 of the HCO₃-fraction resting in the soil was bound organically indicating that microorganisms may be able to utilize exogenous anorganic CO₂/HCO₃ for their photosynthesis.     

Stickstoffaufnahme und Stickstoffrückstände von Hauptfrucht-und Ausfallrapsbeständen

Nitrogen Uptake and Nitrogen Residuals of Winter Oil-Seed Rape and Fallout Rape
The objective of the investigation was a study of the relationship between seed dry-matter production and vegetative dry-matter production in oil-seed rape crops and their dependence on the production conditions. In addition to the relationship between the N-uptake during the vegetation period and the N-residue after harvest was of major interest. Furthermore the potential for N-uptake in fallout rape was measured. Over two vegetation periods factorial field experiments with winter oil-seed rape, cv. Lirabon, different drilling techniques and different nitrogen fertilization levels were tested. Measured traits were: the dry-matter accumulation including root mass and fall-off leaf-material mass, the N-uptake of both the oil-seed crops and the fallout rape stands, and, simultaneously, the soil NO₃-N content. Finally the harvest indices and the N-harvest indices were calculated.
Combined with a N-uptake of up to 330 kg N/ha, oil-seed rape crops produced up to 200 dt dry matter/ ha. At seed yield levels of 33dt/ha (d.m.), harvest indices varied from 0.14—0.23 and N-harvest indices varied from 0.30–0.50. As a result of the residue of vegetative plant material at harvest, leaf losses before harvest and the soil NO₃-N-contents at harvest up to 275 kg N/ha remained in the field. After the harvest of oil-seed rape, the soil NO₃-N-contents were quickly reduced by emerging and growing fallout rape stands. However, following soil-preparation measures in the autumn, a continuous rise in the soil NO₃-N-content was observed.