Untersuchungen zum Einfluß von Konkurrenz auf die Bestandesentwicklung von Sommerraps bei unterschiedlicher Gunst der Umweltbedingungen

Investigations on the effect of competition with regard to the stand development of spring oilseed rape as dependent on environmental conditions
Field experiments were conducted to investigate the frequency distribution in spring oilseed rape as dependent on environmental growing conditions and plant density. As measures for frequency distribution skewness and kurtosis were estimated. The plant character determined was single plant dry matter. To understand the changes in the stand structure, samples were taken at the following developmental stages: rosette, begin of flowering, end of flowering and ripeness (harvest). Plant densities ranged from 60 plants/m², 90 plants/m² till 120 plants/m²
The results show that under unfavourable growing conditions, generally speaking, the values of (positive) skewness and kurtosis increase with the development of the plants; under favourable growing conditions, however, the values of skewness and kurtosis decrease from rosette till harvest.
Under unfavourable growing conditions as well as favourable ones, the values of skewness and kurtosis increase with strengthening of plant competition as consequence of increasing plant density. However, the trend during development and the height of the values as well as the quantitative relationships are strongly controlled by the general growing conditions. Frequency distribution, therefore, is not only a result of plant competition but also of differences in resources due to the general conditions of the location.     

Untersuchungen zum Einfluß von Standort, Saatstärke, N-Düngung, Sorte und Erntezeitpunkt auf den Ertrag und die Inhaltsstoffe von Zuckerhirse

Investigations into the effect of location, planting density, N-fertilization, variety and harvest date on yield and contents of sweet sorghum
Looking for high yielding plant species as renewable resources, sweet sorghum ( Sorghum bicolor [L.] Moench) seems to be an interesting crop.
In field trials at three locations in the south-west of Germany in 1983 and 1984 should be investigated the effect of N-fertilization, planting density, variety and harvest date on yield, different morphological characteristics and contents of sweet sorghum.
The results indicate that yields of 15-20 t DM/ha are only feasible when the given temperature sum is higher than 2000 °C (> 5°C). The maximum yield of 22.7 t DM/ha resp. 6.5 t/ha "Free Fermentable Sugar" (FFZ) was realized when a sufficient water supply and N-fertilization had been guaranteed.
The different possibilities of utilization of sweet sorghum e.g. as sugar crop, agricultural raw material for combustion or as forage crop urge the plant breeder to intensify the breeding efforts adapting this crop at the climatic conditions of Germany.     

Futterqualität und Leistung von Napier-und Paragras (Pennisetum purpureum bzw. Brachiaria mutica) unter Schnittnutzung und Beweidung mit Sahiwal-und Kreuzungsrindern auf "upland" im District Dacca/Bangladesh

Forage quality and performance of Napier and Para grass ( Pennisetum purpureum and Brachiaria mutica , resp.) cut or grazed with Sahiwal and crossed cattle on upland in the Dacca district, Bangladesh
Napier and Para grass were compared with respect to important quality parameters for two years and in a rotational grazing experiment using 30 two-years-old heifers.
Napier grass had a higher in-vitro-digestibility of organic matter (IVDOM) than Para grass. 77% of IVDOM variance was explained by the lignin contents, 88 % by lignin and ash contents. Accordingly a high correlation existed between lignin contents and IVDOM (r =−0.86; p 0,001).
The estimation of starch units resulted in higher precision by including the lignin contents in the regression equations compared with crude fibre contents alone.
Crude protein, crude fibre and magnesium contents were similar, while Napier grass contained substantially more P, K and Ca, but far less Na.
In the grazing experiment on average of both years Napier grass produced 64 % of the plant yield of Para grass, but reached 80 % of the animal production. Of the forage offered by Napier grass and Para grass 85 and 67,5 %, respectively, was converted into animal production. Therefore the weight increase (kg/ha) produced by Napier grass amounted to 90 % of the groups grazing Para grass. Daily gain averaged over both grass species and experimental years reached 440 g/heifer in the Holstein-Friesian group, 410 g with Sahiwal and 370 g with Jersey cattle.     

Einfluß der Erosion auf die Standortproduktivität im Silomaisanbau

Influence of erosion on productivity of maize ( Zea mays L.) cultivation
Accelerated erosion was monitored in Eastern Schleswig-Holstein (F.R.G.) during the last decades. The objective of this study was to compare agricultural productivity of upper, middle and base slope segments to the respective soil parameters, reflecting results of long-term erosion.
Five soil catenas were surveyed. Each catena was divided into three segments representing an eroded area (upper segment), an area with an equilibrium between erosion, accumulation and soil development (middle segment) and an area with accumulation (base slope segment).
In 1986 soil qualities, growth characters and yield components of maize were analysed for each slope segment. At eroded slope segments vegetation cover and yield were significantly lower than at middle and base slope segments. Middle slope segments (equilibrium between erosion, accumulation and soil development) snowed balanced soil quality parameters and high maize yields with a desired combination of yield components.     

Effekte der Sorten- (Weizen)und der Arten- (Weizen, Roggen) Mischung auf die Ertragsleistung krankheitsfreier Bestände

Effects of cultivar (wheat) and species (wheat, rye) mixtures on grain yield of desease-free stands
Cultivar mixtures (winter wheat) and species mixtures (winter wheat/winter rye) grown free from pests and diseases in different environments are compared to pure stands and analyzed with respect to inter-component relationships relevant for yield. All mixtures consisted from two components which were planted 1:1. Mixing effects (i.e. deviations from arithmetic mean of respective components grown in pure stands) on grain yield/ha and yield structure were dependent on components and growing conditions, particularly nitrogen availability. Under conditions suboptimal for one component, ontogenetic differences between components resulted in positive mixing effects on grain yield since the yield proportion of the accompanying partner increased more than proportionally. In several instances, yield proportions shitted without leading to mixing effects. In some experiments and/or mixtures mixing effects could not be observed at all.     

Untersuchungen zum Einfluß von Konkurrenzbedingungen auf die Entwicklung der Bestandesstruktur von Sommerraps

Investigations on the effect of competition on stand structure of spring oilseed rape
On the basis of a field experiment with spring oilseed rape, frequency distributions of plant dry matter and plant height were investigated. Samples were taken at four developmental stages: rosette, begin of flowering, end of flowering, ripeness (harvest). To understand the effect of competition in a plant population on frequency distribution, distance of rows (16 cm, 32 cm) and number of plants (60, 90 and 120 plants/m²) were varied. Differences in frequency distribution were estimated by skewness and kurtosis.
The results show that with age of the plant population the skewness of the plant character dry matter decreases from a high positive value till ripeness to a low positive value; kurtosis also decreases during development and tends to a value of 0 at ripeness. The effect of competition as produced by number of plants for area is mirrored by a positive skewness increasing with increasing number of plants per area. The value for kurtosis also increases with the stronger competition as consequence of plant density. Row distance did not show specific effects of frequency distribution. Plant height did, generally speaking, not react to competition.     

Einfluß des Lichtangebotes auf das Wachstum und die biologische Stickstoff-Fixierung von Weißklee (Trifolium repens L.)

Influence of light quantity on growth and biological nitrogen fixation of white clover ( Trifolium repens L.)
The influence of photon irradiance (E_p; 100 to 500 μmol m⁻² s⁻¹) and of the photoperiod (16 or 11 h) on growth and nitrogenase activity of nodulated white clover plants was studied in growth chambers at two nitrate levels (1.0 and 7.5 mM NO₃⁻).
Total dry mass production, the root proportion and nitrogenase activity increased with increasing E_p and photoperiod. Nitrogenase activity generally increased proportionally to root mass. Only at low E_p (100 μmol m⁻² s⁻¹) and under a short photoperiod (11 h) was the specific nitrogenase activity per unit root mass reduced. An abrupt change in E_p led to a rapid and parallel change in nitrogenase activity and relative growth rate.
A higher NO₃⁻ concentration in the nutrient solution (7.5 mM) led to a marked decrease in specific nitrogenase activity, but increased growth between 200 and 500 μmol m⁻² s⁻¹ during early development only. At 100 μmol m⁻² s⁻¹, there was no growth response to nitrate, although its effect on nitrogenase activity was more marked than at a higher E_p.
The results show that with changing light quantity, biological nitrogen fixation of white clover adapts to the existing demand for nitrogen and does not limit growth except during early development, even when light supply is low.     

Einfluß eines Wachstumsregulators auf die 'Sink'-Kapazität von Raps (Brassica napus L.)

Influence of a Plant Growth Regulator on the 'Sink' Capacity of Oilseed Rape ( Brassica napus L. )
A pot experiment was carried out to examine the effect of the plant growth regulator Triapenthenol (RSW) on the apical dominance of oilseed rape and its corresponding effect on the plant's 'sink' capacity. RSW's influence on the number of flower primordia, flowers, pods, yield and yield structure of the whole plant and of different fractions of the plant (main shoot, lateral shoots 1–3, lateral shoots >3; 1st, 2nd and 3rd-order lateral shoots) and its effect on gibberellin content and shoot height was measured.
RSW diminished dominance of the main shoot and of 1st-order lateral shoots: the initiation of flower primordia was increased to about 34% and 116%, respectively, in fraction lateral shoots higher than 3 and 3rd-order lateral shoots. Buds developed in a more synchronized pattern leading to a significantly improved number of flowers and pods in fraction lateral shoots higher than 3. Despite an increased number of pods per plant, grain yield remained unchanged because of a decrease in the number of seeds per pod and an unaffected thousand-kernel weight.
A decreased content of gibberelhn A19 (GA19), GA20, GA1 and GA8 was evident after application of RSW, and a correlation between gibberellin-content and shoot height was found.
The results of this study suggest that high levels of such GAs, that primarily promote shoot elongation and strengthen the apical dominance within the plant, limit the plant's 'sink' capacity. These effects may be due to a gibberellin-promoted auxin-synthesis.     

Einfluß eines variierten N-Angebots auf α-Amylase-Aktivität, primäre Dormanz und Auswuchsresistenz von Weichweizen (Triticum aestivum L.), Roggen (Secale cereale L.) und Triticale (X Triticosecale Wittmack)

Influence of Varying N-Fertilization Rates on α-Amylase Activity, Primary Dormancy and Resistance to Pre-Harvest Sprouting in Wheat ( Triticum aestivum L.), Rye ( Secale cereale L.) and Triticale (X Triticosecale Wittmack)
Pre-harvest sprouting, induced by unfavourable ecological conditions, can affect the grain growers success considerably. Positive correlations are reported between resistance to pre-harvest sprouting and primary dormancy. Genotypes with a short dormancy period have a high pre-harvest sprouting risk. In the case of a premature germination of caryopses in the head of grain a hydrolysis of intact starch granules caused by the endoenzyme α-amylase takes place in the endosperm.
Negative correlations between falling number and protein content are reported, however, it is unknown, if a varying N-application influences pre-harvest sprouting rates, dormancy periods and amylase activity. For this reason, both greenhouse and field trials were conducted with different N-fertilization rates and (additional in the greenhouse) a rain simulation treatment.
High amounts of α-amylase a few days post anthesis are opposed to small enzyme activities in mature kernels. Stratificating temperatures and germination inducing precipitations at the same time are inducing pre-harvest sprouting and a high α-amylase activity especially in rye and triticale. It seems as if N-deficiency reduces the possibility of pre-harvest sprouting, on the other hand high N-rates increase the enzymes' activity and promote germination processes in the kernel. Effects of N-fertilization on dormancy are not known.
In the discussion of reasons for an increase of α-amylase activity in sprouted grain caryopses, changes in the relation of the phytohormones gibberellic acid (promoter of enzyme activities) and abscisine acid are mainly presumed.     

Effects of Interspecific Competition on the Inheritance of Quantitative Traits in White Clover *)

Analysis of a half diallel cross among four white clover cultivars, grown as monocultures and in mixtures (duocultures) with two separate perennial rye-grass cultivars, confirmed that for stolon and leaf number a higher proportion of the genetic variance in duocultures was non-additive. For canopy height and dry weight, however, this proportion was less affected by inter-specific competition. An additive-dominance model of gene action sufficed for all four characters in monocultures, but in duocultures epis-tasis was just one of the factors complicating the genetic picture. This, coupled with short-term reversals in the direction of dominance, merely illustrates the complexity of breeding white clover cultivars. Possible future developments in the breeding of white clover are discussed in the light of these results.     

Einfluß der Bestandesdichte auf Ertrags- und Qualitätskriterien sowie über mögliche Ursachen der Konkurrenz in Zuckerrübenbeständen

Influence of Plant Density on Yield and Quality and Possible Causes of Competition in Sugar Beet Crops
In trials conducted over 9 years at 1 location plant densities ranged from 35,000 to 110,000 plants/ha. Root yield, sugar yield and white sugar yield reached maximum values at 92,700, 94,700 and 96,000 plants/ha, respectively. The decrease in yield per 1,000 plants/ha was greater as the plant density fell. The quality criteria (sugar concentration, white sugar concentration and sugar gain) were at their maxima at 107,000, 104,600 and 100,000 plants/ha, respectively, and they decreased at an almost constant rate as plant density declined. The concentrations of potassium, sodium and amino-N, the main factors which determine quality in Germany, as well as the sugar loss were all minimized at about 110,000 plants/ha and they increased at a progressively-greater rate per 1,000 plants/ha as plant density declined. The maximum differences between large and small plant densities were: root yield 13.6%, sugar yield 16.7%, white sugar yield 18.6%, sugar concentration 3.7%, white sugar concentration 5.3%, sugar gain 1.7%, sugar loss 9.3%, potassium concentration 8.4%, sodium concentration 30.5% and amino-N concentration 25.4%. As well as a comparison of the yield and quality criteria, the paper considers competition within the foliage, particularly when different amounts of nitrogen are available, as the main cause for yield differences between sugar beet crops.     

Einfluß des Stickstoffangebotes auf Substanzbildung, Erntegewicht und Qualität der Zuckerrübe unter besonderer Berücksichtigung von Temperatur und Globalstrahlung in Gefäßversuchen

Influence of nitrogen supply on dry matter production, yield and quality of sugar beet with special reference to temperature and irradiance in pot experiments
The influence of nitrogen on yield and quality of sugar beet has been studied in many experiments. In comparison, little is known about the changes in sugar beet metabolism caused by increasing the nitrogen supply. The experiments described in this series of papers deal with the influence of nitrogen supply on mineral metabolism. This first paper describes the influence of nitrogen on dry matter production, yield and quality of beet with special reference to temperature and irradiance. The experiments, conducted in 1988 and 1989 using sand culture in pots, included five nitrogen levels. These treatments were sampled five times during the season and at harvest time. Overall, in 1989 sugar yield (g/pot) was 30 to 50 % greater than in 1988. In 1989 there was only a little more irradiance and duration of sunshine (7 and 11 % respectively) than in 1988, and the larger yield in 1989 was probably caused by a bright period of four weeks in May/June. Where least nitrogen was supplied, deficiency symptoms appeared in early June. When this happened an ammonium-urea solution was added to the leaves: it increased growth, but not enough to equal the white sugar yield of the treatment where the sand was given the same amount of N at the beginning of the season.