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.     

A Quantitative Method to Assess Freezing Resistance in Faba Beans

In order to quantify freezing resistance (R₅₀) of winter faba beans from a limited number of plants, leaves were exposed to artificial freezing stresses with different test temperatures (TT_i). Injury (I_i) was assessed by rating (score: 0—8) and by conductivity measurements. The basic assumption that I_i depends almost linearly on TT_i over a sufficiently broad range with a constant ΔI/ΔTT could be verified and hence a formula is presented to compute freezing resistance R₅₀= (I_i—I₅₀) ×ΔTT/ΔI + TT_i with I₅₀ being a medium injury. This formula allows to quantify resistance by assessing I_i after freezing test(s) with definite TT_i. About 25 leaves are required. Rating appeared preferable to conductivity measurements because of easier and quicker performance and a slightly better discrimination between samples of different resistance. Based on a standardized freezing test, ΔI/ΔTT was determined. Application of the formula with ΔI/ΔTT = 2.5 units/°C for unhardened and hardened leaves, restrictions and experiences are discussed.     

Gaswechselmessungen an Fababohnen-Blättern (Vicia faba L.)

Measurement of gas exchange in faba-bean leaves ( Vida faba L.)
By means of gas-exchange measurements (minicuvette system and porometer), photosynthesis and its light dependence was investigated on attached leaves of different varieties of faba beans. The results showed no relevant difference in photosynthetic capacity for the varieties. This is true also for parameters calculated from light dependence, i.e. light compensation point, light saturation, and quantum yield. Generally, the light compensation point lay under 50 μE PAR/m²/s and light saturation was reached at about 1400 μE PAR/m²/ s. Photosynthesis was strongly dependent on leaf age and difference in photosynthetic capacity due to different varieties could be excluded as an essential reason for different rates of flowers dropping and pod dropping in faba beans.     

Some Agronomic and Physiological Aspects of Salt Tolerance in Cotton (Gossypium hirsutum L.)

Evaluation of commonly grown cotton (Gossypium hir-sutum L.) genotypes under saline environment may help to cope with the venture of the crop failure in salt-affected soils. In a pot experiment, four cotton genotypes (MNH-93, NIAB-78. S-12, and B-557) were grown to compare their relative performance on a sandy clay loam soil (original ECe = 1.9 dS m⁻¹) salinized with a salt mixture (Na₂SO₄, NaCl, CaCl₂, MgSO₄ in the ratio of 9:5:5:1 on equivalent basis) to EQ levels of 10 and 20 dS m⁻¹. The crop was raised to the flower initiation stage. The imposed salinity stress exhibited deleterious effect on the germination and vegetative growth with significant differences among the genotypes. Leaf area, stem thickness, shoot (stem + leaves) and root weights decreased with the increase in substrate salinity. NIAB-78 showed the least decline followed by MNH-93. Leaf thickness showed an opposite trend as an increase in this parameter was observed with the rising salinity, the maximum increase being in the case of NIAB-78. Analysis of the leaf sap showed increased Na⁺ and Cl⁻ concentrations and decreased K⁺ concentration with the increase in substrate salinity. A better osmotic adjustment, a lower Na⁺/K⁺ ratio and a lower Cl concentration were found in the leaves of NIAB-78 followed by MNH-93. This contributed towards their better growth performance under saline conditions.     

Influence of Oil Seed Rape and Faba Bean as Green Manure on Nitrogen Utilization in a Spring Cereal Rotation

A lysimeter study was conducted to investigate how nitrogen uptake of spring wheat and oats and N leaching losses are differing when either oilseed rape or faba bean are grown as green manure. The experiment was conducted during 1982–1988, and fertilizer applied to the cereals was either farmyard manure, FYM, (6 and 12 g N/m²/year) or mineral fertilizer, MiF, at a rate of 6 g N/m². On average of the 7 year period faba bean increased N uptake of the cereals fertilized with FYM at harvest by 3–4 g/m². Differences between the two application rates were negligible. N-leaching losses increased twofold when faba bean was grown instead of oilseed rape. Growing faba bean after cereals supplied with MiF, too, increased N uptake of the cereals and significantly increased leaching losses.     

N2-Fixierung und Ertragsstruktur der Weißen Lupine (Lupinus albus L.) im Vergleich zu Vicia faba L. und Glycine max (L.) Merr. auf verschiedenen Standorten

N₂-Fixation and Yield Structure of White Lupin ( Lupinus albus L.) in Comparison to Vicia faba L. and Glycine max (L.) Merr. on Different Sites
In field studies white lupin ( Lupinus albus L., Eldo ) was compared with faba bean ( Vicia faba L., Herz Freya ) in 1986 and soybean ( Glycine max [L.] Merr., Gambit ) in 1988 on five sites respectively. Total N₂-fixation, which was determined by the extended difference method, and yield components were correlated to weather and soil conditions:
1. While faba bean responded to low pH with delayed nodulation, white lupin showed no decrease in N₂-fixation at pH less than 5.5 as far as soil was not calcareous.
2. The white lupin developed its root system most quickly into further soil depths and produced a root dry weight six times as large as that of faba bean in the soil layer 60-90 cm until the end of July (Bayreuth).
3. Despite on the calcareous sites the white lupin showed the highest total-N₂-fixation (max. 36 g N/m²) throughout, the N-gain for the succeeding crop was up to 8 g N/m² for white lupin and faba bean as well. In contrast the N-balance of soybean was mostly negative.
4. Seed yields of white lupin (48-450 g/m²) ranged between those of faba bean (145-549 g/m²) and of soybean (89-290 g/m²); its raw protein yields were the highest found (max. 158 g/m²) though.     

Competition between Canada Thistle [Cirsium arvense (L.) Scop.] and Faba Bean (Vicia faba L.)

This study was conducted to investigate whether density, above-ground biomass and nitrogen (N) concentration of Cirsium arvense (L.) Scop. cause serious reductions in faba bean ( Vicia faba L.) yield. A 2-year field experiment (1991–93) with four Cirsium densities (0, 4, 16, 64 plants m^–2) was carried out. Statistical analysis showed a significant effect of Cirsium density on faba bean yield. Multiple regression analysis showed that the main factors causing faba bean yield losses were the density and above-ground biomass of Cirsium . The results of this study demonstrate that Cirsium competition reduces faba bean yield. The mean faba bean yield losses over the 2 years were 10, 12 and 8% for above-ground biomass, seed and stem, respectively, for a Cirsium density of 16 plants m^–2.     

Optimum Seed Rate and Nitrogen Fertilizer Requirement of Rice Under Semi-deepwater Ecosystem

The effect of varying seed rates (100–1000 seeds m⁻²) and nitrogen fertilizer (0–60 kg N ha_-1) applied either in a single basal dose or in splits was investigated on a tall elongating, photosensitive rice variety, Nalini, under semi-deepwater conditions (0–100cm) during 1993 and 1994 at Cuttack, India. Seedling emergence was higher in 1993 (53.9 %) than in 1994 (44.1 %) and it increased proportionately with increasing seed rate, Increase in the number of tillers and panicles m⁻² at higher seed rates was associated with a corresponding decrease in panicle weight. Regression analysis indicated a decrease of 0.91–1.28g in panicle weight for an increase of 100 panicles m⁻². The grain yield of rice was significantly higher at 400 seeds m⁻² in 1993 and at 600 seeds m⁻² in 1994 than at low seed rates but further increase in seed rate did not increase the yield. Application of N fertilizer increased the panicle number and thereby grain yield significantly. The effect of basal and split applied N at active or maximum tillering stages as well as between 30 and 60 kg N ha⁻¹ was not significant on the grain yield. The results suggest that a basal dose of 30kg N ha⁻¹ and seeding density of 400–600 seeds m⁻², resulting in 40–50 % seedling emergence and 150–200 panicles m⁻², each with 2.0–2.5 g weight, may be adequate for optimum productivity of rice under semideepwater conditions.     

Studies on Sowing Depth for Chickpea (Cicer arietinum L.), Faba Bean(Vicia faba L.) and Lentil (Lens culinaris Medik) in a Mediterranean-type Environment of South-western Australia

Pulses such as chickpea, faba bean and lentil have hypogeal emergence and their cotyledons remain where the seed is sown, while only the shoot emerges from the soil surface. The effect of three sowing depths (2.5, 5 and 10 cm) on the growth and yield of these pulses was studied at three locations across three seasons in the cropping regions of south-western Australia, with a Mediterranean-type environment. There was no effect of sowing depth on crop phenology, nodulation or dry matter production for any species. Mean seed yields across sites ranged from 810 to 2073 kg ha⁻¹ for chickpea, 817–3381 kg ha⁻¹ for faba bean, and 1173–2024 kg ha⁻¹ for lentil. In general, deep sowing did not reduce seed yields, and in some instances, seed yield was greater at the deeper sowings for chickpea and faba bean. We conclude that the optimum sowing depth for chickpea and faba bean is 5–8 cm, and for lentil 4–6 cm. Sowing at depth may also improve crop establishment where moisture from summer and autumn rainfall is stored in the subsoil below 5 cm, by reducing damage from herbicides applied immediately before or after sowing, and by improving the survival of Rhizobium inoculated on the seed due to more favourable soil conditions at depth.     

Effect of Some Growth Factors and Glyphosate Herbicide on Pigments and Protein in Faba Beans (Vicia faba L.)

Two field experiments were carried out during 1982/83 and 1983/84 seasons at Experimental Farm of National Research Centre at Shalakan, Kalubia Governorate, Egypt, to study the effects of supplemental growth factors on the reversal of glyphosate-induced inhibition in photosynthetic pigments and protein in faba beans. A split plot design with four replications was used in both seasons. Glyphosate at 0,312 and 468 g.a.i./ha as well as the untreated treatment, arranged at random in main plots while, the growth factors, i.e., growth regulators, amino acids and nutrient elements at different concentrations distributed randomly in the sub plots. The results could be summarized as follows:
1. Glyphosate decreased chlorophyll a, b and carotenoides content and the total pigments content in the leaves of faba bean plants, as well as, the protein content of seeds and protein yield per hectare.
2. The treatments of phenylalanine at 500 ppm, urea at 1 %, cytolinin at 4/1000 and tryptophan at 500 ppm, reversed the glyphosate-induced-phytotoxicity on decreasing the chlorophyll a, b content and total pigments content in faba bean leaves. The same treatments, as well as, zinc sulfate at 1 %, reversed the glyphosate-induced-phytotoxicity on decreasing the carotenoids content in faba bean leaves.
3. The treatment of G a ₃ at 100 ppm gave the highest percentage of crude protein in seeds, while the lowest value was obtained from cytokinin at 4/1000, in both seasons.
4. The treatments of cytokinin at 4/1000, phenylalanine at 500 ppm and tryptophan at both levels, reversed the glyphosate-induced-phytotoxicity on decreasing the protein yield per h.